Publications

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2018

(72) Global carbon intensity of crude oil productionMohammad S Masnadi, Hassan M El-Houjeiri, Dominik Schunack, Yunpo Li, Jacob G Englander, Alhassan Badahdah, Jean-Christophe Monfort, James E Anderson, Timothy J Wallington, Joule A Bergerson, Deborah Gordon, Jonathan Koomey, Steven Przesmitzki, Ines L Azevedo, Xiaotao T Bi, James E Duffy, Garvin A Heath, Gregory A Keoleian, Christophe McGlade, D Nathan Meehan, Sonia Ye, Fengqi You, Michael Wang, Adam R BrandtScience Magazine, Vol. 361, Issue 6405
Producing, transporting, and refining crude oil into fuels such as gasoline and diesel accounts for ∼15 to 40% of the “well-to-wheels” life-cycle greenhouse gas (GHG) emissions of transport fuels (1). Reducing emissions from petroleum production is of particular importance, as current transport fleets are almost entirely dependent on liquid petroleum products, and many uses of petroleum have limited prospects for near-term substitution (e.g., air travel). Better understanding of crude oil GHG emissions can help to quantify the benefits of alternative fuels and identify the most cost-effective opportunities for oil-sector emissions reductions (2). Yet, while regulations are beginning to address petroleum sector GHG emissions (3–5), and private investors are beginning to consider climate-related risk in oil investments (6), such efforts have generally struggled with methodological and data challenges. First, no single method exists for measuring the carbon intensity (CI) of oils. Second, there is a lack of comprehensive geographically rich datasets that would allow evaluation and monitoring of life-cycle emissions from oils. We have previously worked to address the first challenge by developing open-source oil-sector CI modeling tools [OPGEE (7, 8), supplementary materials (SM) 1.1]. Here, we address the second challenge by using these tools to model well-to-refinery CI of all major active oil fields globally—and to identify major drivers of these emissions. We estimate emissions in 2015 from 8966 on-stream oil fields in 90 countries (SM 1.4.4). These oil fields represent ∼98% of 2015 global crude oil and condensate production. This analysis includes all major resource classes (e.g., onshore/offshore and conventional/unconventional) and accounts for GHG emissions from exploration, drilling and development, production and extraction, surface processing, and transport to the refinery inlet (collectively called “upstream” hereafter). These results are based on data from nearly 800 references, including government sources, scientific literature, and public technical reports (SM 1.4.1, 1.4.4, and table S17). Proprietary databases are used to supplement these data when information is unavailable in the public domain (generally for small oil fields). The latest Intergovernmental Panel on Climate Change (IPCC) 100-year global warming potential (AR5/GWP100) factors are used in this work (SM 1.2.1).
 Online article 

(71) Understanding cumulative risk perception from judgments and choices: An application to flood risksDe La Maza, C., Davis, A., Gonzalez, C., Azevedo, I.L.Risk Analysis
Catastrophic events, such as floods, earthquakes, hurricanes, and tsunamis, are rare, yet the cumulative risk of each event occurring at least once over an extended time period can be substantial. In this work, we assess the perception of cumulative flood risks, how those perceptions affect the choice of insurance, and whether perceptions and choices are influenced by cumulative risk information. We find that participants' cumulative risk judgments are well represented by a bimodal distribution, with a group that severely underestimates the risk and a group that moderately overestimates it. Individuals who underestimate cumulative risks make more risk‐seeking choices compared to those who overestimate cumulative risks. Providing explicit cumulative risk information for relevant time periods, as opposed to annual probabilities, is an inexpensive and effective way to improve both the perception of cumulative risk and the choices people make to protect against that risk.
 Online article 

(70) Should we build a national infrastructure to refuel natural gas powered trucks?Tong, F., Jaramillo, P., Azevedo, I.L.Journal of Industrial Systems

(69) Decarbonizing intraregional freight systems with a focus on modal shiftKaack, L.H., Vaishnav, P.T. Morgan, G.M. Azevedo, I.L. Rai, S.Environmental Research Letters Reviews, 13
Road freight transportation accounts for around 7% of total world energy-related carbon dioxide emissions. With the appropriate incentives, energy savings and emissions reductions can be achieved by shifting freight to rail or water modes, both of which are far more efficient than road. We briefly introduce five general strategies for decarbonizing freight transportation, and then focus on the literature and data relevant to estimating the global decarbonization potential through modal shift. We compare freight activity (in tonne-km) by mode for every country where data are available. We also describe major intraregional freight corridors, their modal structure, and their infrastructure needs. We find that the current world road and rail modal split is around 60:40. Most countries are experiencing strong growth in road freight and a shift from rail to road. Rail intermodal transportation holds great potential for replacing carbon-intense and fast-growing road freight, but it is essential to have a targeted design of freight systems, particularly in developing countries. Modal shift can be promoted by policies targeting infrastructure investments and internalizing external costs of road freight, but we find that not many countries have such policies in place. We identify research needs for decarbonizing the freight transportation sector both through improvements in the efficiency of individual modes and through new physical and institutional infrastructure that can support modal shift.
 Online article 

(68) Net-zero emissions energy systems,Davis, S. D.; Lewis, N. S.; Shaner, M.; Aggarwal, S.; Arent, D.; Azevedo, I. L. ; Benson, S. M.; Bradley, T.; Brouwer, K., Chiang, Y-M.; Clack, C. T. M.; Choen, A.; Doig, S.; Edmonds, J.; Fennell, P.; Field, C. B.; Hannegan, B.; Mathias Hodge, B.; Hoffert, M. I.; Ingersoll, E.; Jaramillo, P.; Lackner, K. S.; Lynd, L. R.; Mach, K. J.; Mastrandrea, M.; Odgen, J.; Peterson, P. F.; Sanchez, D. L.; Sperling, D.; Stagner, J.; Trancik, J. E.; Yang, C-S, Caldeira, K.,Science, 360 (6396)
Some energy services and industrial processes—such as long-distance freight transport, air travel, highly reliable electricity, and steel and cement manufacturing—are particularly difficult to provide without adding carbon dioxide (CO2) to the atmosphere. Rapidly growing demand for these services, combined with long lead times for technology development and long lifetimes of energy infrastructure, make decarbonization of these services both essential and urgent. We examine barriers and opportunities associated with these difficult-to-decarbonize services and processes, including possible technological solutions and research and development priorities. A range of existing technologies could meet future demands for these services and processes without net addition of CO2 to the atmosphere, but their use may depend on a combination of cost reductions via research and innovation, as well as coordinated deployment and integration of operations across currently discrete energy industries.
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(67) Expert assessments on the future of direct current in buildings,Glasgo, B.; Hendrickson, C.; Azevedo, I. L. Environmental Research Letters, 13 (7)
Increasing adoption of distributed generation, improving power electronics, and growing electronic loads in buildings have led researchers to propose increased use of direct current (DC) power distribution systems in buildings. As these systems have proven safe and reliable in other applications, they are now being considered for more widespread use in commercial and residential buildings. But nontechnical obstacles remain that have not been addressed in the technical engineering and economic analyses conducted thus far. In this paper, we report on an expert elicitation of 17 experts from industry, research organizations, and the implementation or operation of DC systems to better understand the biggest nontechnical challenges to deploying these systems more broadly. Because these challenges vary based on location, the focus of this study is on the United States of America. Results show that the two biggest barriers are industry professionals unfamiliar with DC and small markets for DC devices and components. To address these, experts proposed developing training programs for engineers and electricians, and developing pilot projects to prove the benefits of DC in niche applications where DC power distribution holds a clear advantage over AC Experts also identified lasting and inherent benefits of DC that make these systems better suited to serve future building loads. These include their ability to interface with distributed generation and onsite DC generation sources such as solar photovoltaics, as well as their ability to communicate and supply power over a single distribution line. Finally, experts identified research priorities to make a better case for what appears to be a promising technological solution to safely and reliably powering future buildings.
 PDF  Online article 

(66) Emissions intensity of the U.S. power system,Schivley, G.; Samaras, C.; Azevedo, I. L. Environmental Research Letters, 13 (6)
In the United States, the electricity sector is a major focus for implementing policies to meet national, state, or local mandatory or voluntary CO2 emissions reductions goals. Thus, it is important to have timely and available information on greenhouse gas emissions generated by the power sector to ensure that the policies implemented achieve intended emissions reductions. This work is the first to develop a transparent method to compute the emissions intensity for the US electricity section from 2001 through 2017 at different temporal (annual, quarterly, monthly) and regional (US, NERC, and state) levels. We find that between 2001 and 2017 the average annual CO2 emissions intensity of electricity production in the United States decreased by 30%, from 630 g CO2 kWh−1 to 439 g CO2 kWh−1. This change in CO2 intensity is attributable to an increase in generation from natural gas and wind accompanied by a reduction in coal-fired power generation. The decline in carbon intensity varies across regions, with the largest reduction between 2001 and 2017 from power plants in the Northeast (58%) and the smallest reduction from power plants in the Texas region (27%). In absolute terms the South-central region saw the largest decrease in emissions intensity (358 g CO2 kWh−1) and Texas saw the smallest (164 g CO2 kWh−1). We also find that replacing coal generation with natural gas or renewables has increased the monthly correlation of CO2 intensity between regions. At the state level, Delaware saw the largest decrease in CO2 intensity (466 g CO2 kWh−1), and Idaho is the only state that has not decreased CO2 intensity since 2001.
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(65) A sunny future: Expert elicitation of China's solar photovoltaic technologies,Lam, L.; Branstetter, L.; Azevedo, I. L. Environmental Research Letters, 13 (3)
China has emerged as the global manufacturing center for solar photovoltaic (PV) products. Chinese firms have entered all stages of the supply chain, producing most of the installed solar modules around the world. Meanwhile, production costs are at record lows. The decisions that Chinese solar producers make today will influence the path for the solar industry and its role towards de-carbonization of global energy systems in the years to come. However, to date, there have been no assessments of the future costs and efficiency of solar PV systems produced by the Chinese PV industry. We perform an expert elicitation to assess the technological and non-technological factors that led to the success of China’s silicon PV industry as well as likely future costs and performance. Experts evaluated key metrics such as efficiency, costs, and commercial viability of 17 silicon and non-silicon solar PV technologies by 2030. Silicon-based technologies will continue to be the mainstream product for large-scale electricity generation application in the near future, with module efficiency reaching as high as 23% and production cost as low as $0.24/W. The levelized cost of electricity for solar will be around $34/MWh, allowing solar PV to be competitive with traditional energy resources like coal. The industry’s future developments may be affected by overinvestment, overcapacity, and singular short-term focus.
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(64) Towards demand-side solutions for mitigating climate changeCreutzig, F.; Roy, J.; Lamb, W. F.; Azevedo, I. L. ; Bruine de Bruin, W.; Dalkmann, H.; Edelenbosch, O. Y.; Geels, F. W.; Grubler, A.; Hepburn, C.; Hertwich, E. G.; Khosla, R.; Mattauch, L.; Minx, J. C.; Ramakrishnan, A.; Rao, N. D.; Steinberger, J. K.; Tavoni, M.; Ürge-Vorsatz, D.; Weber E. W.Nature Climate Change, 8 268-271
Research on climate change mitigation tends to focus on supply-side technology solutions. A better understanding of demand-side solutions is missing. We propose a transdisciplinary approach to identify demand-side climate solutions, investigate their mitigation potential, detail policy measures and assess their implications for well-being.
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(63) Consumers' perceptions of energy use and energy savingsLescic, V.; Bruine de Bruin, W.; Davis, M.; Krishnamurti, T.; Azevedo, I. L.,Environmental Research Letters
Background. Policy makers and program managers need to better understand consumers' perceptions of their energy use and savings to design effective strategies for promoting energy savings. Methods. We reviewed 14 studies from the emerging interdisciplinary literature examining consumers' perceptions electricity use by specific appliances, and potential savings. Results. We find that: (1) electricity use is often overestimated for low-energy consuming appliances, and underestimated for high-energy consuming appliances; (2) curtailment strategies are typically preferred over energy efficiency strategies; (3) consumers lack information about how much electricity can be saved through specific strategies; (4) consumers use heuristics for assessing the electricity use of specific appliances, with some indication that more accurate judgments are made among consumers with higher numeracy and stronger pro-environmental attitudes. However, design differences between studies, such as variations in reference points, reporting units and assessed time periods, may affect consumers' reported perceptions. Moreover, studies differ with regard to whether accuracy of perceptions was evaluated through comparisons with general estimates of actual use, self-reported use, household-level meter readings, or real-time smart meter readings. Conclusion. Although emerging findings are promising, systematic variations in the measurement of perceived and actual electricity use are potential cause for concern. We propose avenues for future research, so as to better understand, and possibly inform, consumers' perceptions of their electricity use. Ultimately, this literature will have implications for the design of effective electricity feedback for consumers, and related policies.
 Online article 

(62) The effect of providing climate and health information on support for alternative electricity portfoliosSergi, B.; Davis, A.; Azevedo. I. L.,Environmental Research Letters
Support for addressing climate change and air pollution may depend on the type of information provided to the public. We conduct a discrete choice survey assessing preferences for combinations of electricity generation portfolios, electricity bills, and emissions reductions. We test how participants' preferences change when emissions information is explicitly provided to them. We find that support for climate mitigation increases when mitigation is accompanied by improvements to air quality and human health. We estimate that an average respondent would accept an increase in 19-27% in their electricity bill if shown information stating that either CO2 or SO2 emissions are reduced by 30%. Furthermore, an average respondent is willing to pay an increase in 30-40% in electricity bills when shown information stating that both pollutants are reduced by 30% simultaneously. This suggests that the type of emissions information provided to the public will affect their support for different electricity portfolios.
 Online article 

(61) Risks and hazards of induced seismicity by enhanced geothermal systems: an expert elicitation approachTrutnevyte, E.; Azevedo, I. L.,Environmental Research Letters, 2017
Induced seismicity is a concern for multiple geoenergy applications, including low-carbon Enhanced Geothermal Systems (EGS). We present results of an international expert elicitation (N=14) on EGS induced seismicity hazard and risk. Using a hypothetical scenario of an EGS plant and its geological context, we show that expert best-guess estimates of annualized exceedance probabilities of a M≥3 event range from 0.2% to 95% during reservoir stimulation and 0.2% to 100% during operation. Best-guess annualized exceedance probabilities of M≥5 event span from 0.002% to 2% during stimulation and 0.003% to 3% during operation. Assuming that tectonic M7 events could occur, some experts do not exclude induced (triggered) events of up to M7 too. If induced M=3 event happens at 5 km depth beneath a town with 10 thousand inhabitants, most experts estimate 50% probability that the loss is contained within 0.5 million USD without any injuries or fatalities. In case of induced M=5 event, there is 50% chance that the loss is below 50 million USD with the most-likely outcome of 50 injuries and 1 or no fatality. As we observe vast diversity in quantitative expert judgements and underlying mental models, we conclude with implications for induced seismicity risk governance. That is, we suggest to document individual expert judgements in induced seismicity elicitations before proceeding to consensual judgements, to convene larger expert panels in order not to cherry-pick experts, and to aim for multi-organization multi-model assessments of EGS induced seismicity hazard and risk.
 Online article 

(60) Marginal emissions factors for electricity generation in the midcontinent ISOThind, M. P. S.; Wilson, E.; Azevedo, I. L.; Marshall, J.,Environmental Science & Technology, 51 (24) 14445-14452
Environmental consequences of electricity generation are often determined using average emission factors. However, as different interventions are incrementally pursued in electricity systems, the resulting marginal change in emissions may differ from what one would predict based on system-average conditions. Here, we estimate average emission factors and marginal emission factors for CO2, SO2, and NOx from fossil and nonfossil generators in the Midcontinent Independent System Operator (MISO) region during years 2007–2016. We analyze multiple spatial scales (all MISO; each of the 11 MISO states; each utility; each generator) and use MISO data to characterize differences between the two emission factors (average; marginal). We also explore temporal trends in emissions factors by hour, day, month, and year, as well as the differences that arise from including only fossil generators versus total generation. We find, for example, that marginal emission factors are generally higher during late-night and early morning compared to afternoons. Overall, in MISO, average emission factors are generally higher than marginal estimates (typical difference: ∼20%). This means that the true environmental benefit of an energy efficiency program may be ∼20% smaller than anticipated if one were to use average emissions factors. Our analysis can usefully be extended to other regions to support effective near-term technical, policy and investment decisions based on marginal rather than only average emission factors.
 Online article 

(59) Distributional costs of wind energy production in Portugal under the liberalized Iberian Market regimePrata, R.; Carvalho, P.; Azevedo, I. L.,Energy Policy, 113, 500-512
Wind generation in Portugal and Spain has grown due to a decrease in technology cost and the availability of renewables electricity generation incentives. There is a strong interconnection between Spain's and Portugal's transmission systems, resulting in common prices in both countries. However, Portuguese and Spanish producers receive the incentives for producing wind-based electricity that are specified in their own national policies, resulting in different costs to rate-payers. In this paper, we estimate the costs to Portuguese rate-payers associated with the current market design and policy incentives. To do so, we regress hourly spot electricity market prices as a function of hourly wind generation, and estimate the resulting feed-in-tariff costs distributional effects over the various rate-payer categories. Total costs for rate payer are at the minimum level if joint wind generation in Portugal and Spain increases by 5.5% from what it is today. If wind generation increases much further, then the costs increase due to the FiT overcost increase. If wind generation decreases from current levels, then costs also increase due to the merit-order effect. Furthermore, we find that rate-payer categories will endure different portions of the costs, with an increase in wind generation penalizing predominantly ≤ 20.7 kVA rate-payers.
 Online article 

(58) Do tidal stream energy projects offer more value than offshore wind farms? A case study in the United KingdomLamy, J.; Azevedo, I. L.,Energy Policy, 113, 28-40
Marine-based renewable energy could help the United Kingdom (UK) move towards a more sustainable and low-carbon energy system. Today, offshore wind is the prevailing marine renewable technology but there is growing progress towards developing others, such as tidal stream energy (TSE) turbines which capture kinetic energy from tidal currents. Using historical operations data from 18 wind farms and simulated generation data for two TSE sites in the UK, we estimate that TSE projects offer about $10/MW h more in net social benefits than offshore wind projects. This estimate includes the value of energy generated, value of reduced marginal CO2 emissions, cost of visual changes to the landscape, and cost of energy generation forecast errors. However, relative to offshore wind, the increased cost of TSE projects far outweighs the increased social benefits. The levelized cost of energy (LCOE) of TSE projects is expected to be about $74/MW h to $330/MW h higher than offshore wind projects through 2050. Only with optimistic LCOE projections, small TSE projects (20 MW) may be competitive (when including increased net social benefits) with small offshore wind projects by 2020.
 Online article 

(57) Quantifying the capacity value of natural gas energy efficiency measures in New EnglandGilbraith, N.; Jaramillo, P.; Azevedo, I. L.,Utilities Journal, 50, 101-110
Natural gas utilities in New England face increasing natural gas transmission system congestion and volatile spot gas prices. We observe that prevailing evaluation methods for natural gas efficiency programs value avoided firm pipeline capacity based on its total (‘gross') cost. We propose, consistent with deregulated electricity markets, to value avoided firm pipeline capacity at its ‘net’ cost. Specifically, we account for revenues associated with selling excess capacity during periods when the firm capacity holder does not fully utilize its rights. Our evaluation of commercial building efficiency programs suggests that prevailing evaluation methods could over-estimate the value of efficiency programs when those programs are intended to offset new capacity investments (i.e., the utility is in need of additional firm capacity). The situation is more complex for a utility with sufficient firm pipeline capacity to meet forecast load (i.e., consumption). In this case, the prevailing evaluation methods have the potential to under- or over-estimate the value of efficiency programs. The value of avoided infrastructure investments is likely to vary with the specific circumstances of the utility and the expected revenues associated with short-term sales enabled by available capacity. In the future, we recommend that economic regulators of natural gas distribution utilities, the state public utility commissions (PUCs), value avoided infrastructure investments at the ‘net' cost of the investment instead of the ‘gross' cost.
 Online article 

(56) Estimating the quantity of wind and solar required to displace storage-induced emissionsHittinger, E.; Azevedo, I. L.,Environmental Science & Technology, 51 (21), 12988-12997
The variable and nondispatchable nature of wind and solar generation has been driving interest in energy storage as an enabling low-carbon technology that can help spur large-scale adoption of renewables. However, prior work has shown that adding energy storage alone for energy arbitrage in electricity systems across the U.S. routinely increases system emissions. While adding wind or solar reduces electricity system emissions, the emissions effect of both renewable generation and energy storage varies by location. In this work, we apply a marginal emissions approach to determine the net system CO2 emissions of colocated or electrically proximate wind/storage and solar/storage facilities across the U.S. and determine the amount of renewable energy required to offset the CO2 emissions resulting from operation of new energy storage. We find that it takes between 0.03 MW (Montana) and 4 MW (Michigan) of wind and between 0.25 MW (Alabama) and 17 MW (Michigan) of solar to offset the emissions from a 25 MW/100 MWh storage device, depending on location and operational mode. Systems with a realistic combination of renewables and storage will result in net emissions reductions compared with a grid without those systems, but the anticipated reductions are lower than a renewable-only addition.
 Online article 

(55) The US energy system has become more volatile and harder to predictSherwin, E. , Azevedo, I.L., Henrion, M.Nature Energy
Long-term projections of energy consumption, supply, and prices heavily influence decisions regarding long-lived energy infrastructure. Predicting the evolution of these quantities over multiple years to decades is a notoriously difficult task. This work provides the first effort in the literature to estimate volatility and unpredictability over multi-decade time frames for many quantities in the US energy system using historical projections. We determine the distribution over time of the most extreme projection errors (unpredictability) from 1985-2014, and the largest year-over-year changes (volatility) in the quantities themselves from 1949-2014. Critically, we find that both volatility and unpredictability have increased in the past decade, relative to prior decades. We encourage energy decision-makers to consider these findings, emphasizing robustness as they invest in and regulate long-lived energy infrastructure in a deeply uncertain world.
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2017

(54) Was it worthwhile? Where have the benefits of rooftop solar photovoltaic generation exceed the cost? Vaishnav, P., Horner, N., Azevedo, I.L.,Environmental Research Letters
We estimate the lifetime magnitude and distribution of the private and public benefits and costs of currently installed distributed solar PV systems in the United States. Using data for recently installed systems, we estimate the balance of benefits and costs associated with installing a non-utility solar PV system today. We also study the geographical distribution of the various subsidies that are made available to owners of rooftop solar PV systems, and compare it to distributions of population and income. We find that, after accounting for federal subsidies and local rebates and assuming a discount rate of 7%, the private benefits of new installations will exceed private costs only in seven of the 19 states for which we have data and only if customers can sell excess power to the electric grid at the retail price. These states are characterized by abundant sunshine (California, Texas and Nevada) or by high electricity prices (New York). Public benefits from reduced air pollution and climate change impact exceed the costs of the various subsidies offered system owners for less than 10% of the systems installed, even assuming a 2% discount rate. Subsidies flowed disproportionately to counties with higher median incomes in 2006. In 2014, the distribution of subsidies was closer to that of population income, but subsidies still flowed disproportionately to the better-off. The total, upfront, subsidy per kilowatt of installed capacity has fallen from $5200 in 2006 to $1400 in 2014, but the absolute magnitude of subsidy has soared as installed capacity has grown explosively. We see considerable differences in the balance of costs and benefits even within states, indicating that local factors such as system price and solar resource are important, and that policies (e.g. net metering) could be made more efficient by taking local conditions into account.
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(53) Perceptions of wind energy projects in two coastal Massachusetts communitiesLamy, J., Bruine de Bruin, W., Morgan, G., Azevedo, I.L., The Electricity Journal
Using 15 semi-structured interviews of residents in two neighboring coastal Massachusetts communities, one of which recently installed an onshore wind project, a study sought to identify the specific characteristics that drive perceptions about the existing project as well as hypothetical new onshore or offshore projects. It found that economic benefits and visual aspects of the project were most important to participants, followed by noise, environmental benefits, hazard to wildlife, and safety concerns.
 PDF  Online article 

(52) Assessing the value of information in residential building simulation: Comparing simulated and actual building loads at the circuit level, Glasgo, B., Hendrickson, C. Azevedo, I.L.,Applied Energy
Building energy simulation tools are now being used in a number of new roles such as building operation optimization, performance verification for efficiency programs, and – recently – building energy code analysis, design, and compliance verification in the residential sector. But increasing numbers of studies show major differences between the results of these simulations and the actual measured performance of the buildings they are intended to model. The accuracy and calibration of building simulations have been studied extensively in the commercial sector, but these new applications have created a need to better understand the performance of home energy simulations. In this paper, we assess the ability of the DOE’s EnergyPlus software to simulate the energy consumption of 106 homes using audit records, homeowner survey records, and occupancy estimates taken from monitored data. We compare the results of these simulations to device-level monitored data from the actual homes to provide a first measure of the accuracy of the EnergyPlus condensing unit, central air supply fan, and other energy consumption model estimates in a large number of homes. We then conduct sensitivity analysis to observe which physical and behavioral characteristics of the homes and homeowners most influence the accuracy of the modeling.
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(51) China's wind industry: Leading in deployment, lagging in innovationLam, L.; Branstetter, L.; Azevedo. I. L.,Energy Policy, 106, 588–599.
China's massive carbon emissions and air pollution concerns have led its government to embrace clean energy innovation as a means of transitioning to a more sustainable energy system. We address the question of whether China's wind industry has become an important source of clean energy technology innovation. We find that in terms of wind capacity expansion, China has delivered enormous progress, increasing its wind capacity from virtually no wind capacity in the early 2000s to 140 GW by 2015. However, in terms of innovation and cost competitiveness, the outcomes were more limited: Chinese wind turbine manufacturers have secured few international patents and achieved moderate learning rates compared to the global industry's historical learning rate. Leading China-based indigenous producers are likely to remain important global players for the foreseeable future, but further progress in reducing the cost of capital equipment may slow relative to the recent past. However, opportunities in lowering curtailment rates and improving turbine quality can reduce China's overall levelized cost of electricity for wind.
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(50) Consistency and robustness of forecasting and the need for technological detail: The case of Li-ion batteries for electric vehicles, Sakti, A., Azevedo, I.L., Fuchs, E.R.H., Michalek, J.J., Gallagher, K., Whitacre, J.F.,Energy Policy, 106, 415–426
There are a large number of accounts about rapidly declining costs of batteries with potentially transformative effects, but these accounts often are not based on detailed design and technical information. Using a method ideally suited for that purpose, we find that when experts are free to assume any battery pack design, a majority of the cost estimates are consistent with the ranges reported in the literature, although the range is notably large. However, we also find that 55% of relevant experts’ component-level cost projections are inconsistent with their total pack-level projections, and 55% of relevant experts’ elicited cost projections are inconsistent with the cost projections generated by putting their design- and process-level assumptions into our process-based cost model (PBCM). These results suggest a need for better understanding of the technical assumptions driving popular consensus regarding future costs. Approaches focusing on technological details first, followed by non-aggregated and systemic cost estimates while keeping the experts aware of any discrepancies, should they arise, may result in more accurate forecasts.
 PDF  Online article 

(49) Using advanced metering infrastructure to characterize residential energy useGlasgo, B. , Hendrickson, C., Azevedo, I.L.,The Electricity Journal, 30 (3), 64–70
Decades of effort have been dedicated to understanding precisely where energy is consumed in residences to help consumers, device manufacturers, utilities, and policymakers better manage this consumption. We review and classify the three most prevalent methods currently used to build this understanding. We then compare two prominent studies, and make recommendations for how existing datasets can inform estimates of device-level energy consumption in the U.S.
 PDF  Online article 

(48) Estimating the effect of multiple environmental stressors on coral bleaching and mortality, accepted, Welle, P. Azevedo, I.L., Doney, S., Small, M.,PlosOne, 2(5): e0175018
Coral cover has been declining in recent decades due to increased temperatures and environmental stressors. However, the extent to which different stressors contribute both individually and in concert to bleaching and mortality is still very uncertain. We develop and use a novel regression approach, using non-linear parametric models that control for unobserved time invariant effects to estimate the effects on coral bleaching and mortality due to temperature, solar radiation, depth, hurricanes and anthropogenic stressors using historical data from a large bleaching event in 2005 across the Caribbean. Two separate models are created, one to predict coral bleaching, and the other to predict near-term mortality. A large ensemble of supporting data is assembled to control for omitted variable bias and improve fit, and a significant improvement in fit is observed from univariate linear regression based on temperature alone. The results suggest that climate stressors (temperature and radiation) far outweighed direct anthropogenic stressors (using distance from shore and nearby human population density as a proxy for such stressors) in driving coral health outcomes during the 2005 event. Indeed, temperature was found to play a role ~4 times greater in both the bleaching and mortality response than population density across their observed ranges. The empirical models tested in this study have large advantages over ordinary-least squares–they offer unbiased estimates for censored data, correct for spatial correlation, and are capable of handling more complex relationships between dependent and independent variables. The models offer a framework for preparing for future warming events and climate change; guiding monitoring and attribution of other bleaching and mortality events regionally and around the globe; and informing adaptive management and conservation efforts.
 PDF  Online article 

(47) Air emissions implications of expanded wastewater treatment at coal-fired generators. Gingerich, D., Sun, X., Behrer, P., Azevedo, I.L., Mauter, MProceedings of the National Academy of Sciences, published ahead of print February 6, 2017, doi: 10.1073/pnas.1524396114
Coal-fired power plants (CFPPs) generate air, water, and solids emissions that impose substantial human health, environmental, and climate change (HEC) damages. This work demonstrates the importance of accounting for cross-media emissions tradeoffs, plant and regional emissions factors, and spatially variation in the marginal damages of air emissions when performing regulatory impact analyses for electric power generation. As a case study, we assess the benefits and costs of treating wet flue gas desulfurization (FGD) wastewater at US CFPPs using the two best available treatment technology options specified in the 2015 Effluent Limitation Guidelines (ELGs). We perform a life-cycle inventory of electricity and chemical inputs to FGD wastewater treatment processes and quantify the marginal HEC damages of associated air emissions. We combine these spatially resolved damage estimates with Environmental Protection Agency estimates of water quality benefits, fuel-switching benefits, and regulatory compliance costs. We estimate that the ELGs will impose average net costs of $3.01 per cubic meter for chemical precipitation and biological wastewater treatment and $11.26 per cubic meter for zero-liquid discharge wastewater treatment (expected cost-benefit ratios of 1.8 and 1.7, respectively), with damages concentrated in regions containing a high fraction of coal generation or a large chemical manufacturing industry.
 PDF  Online article 

(46) An integrated approach for estimating greenhouse gas emissions from 100 US metropolitan areas, accepted in Markolf, S. , Matthews, H.S., Azevedo, I.L., Hendrickson, C.T.,Environmental Research Letters
Cities have become key players in climate change mitigation policy. To develop their climate policies, cities need good assessments of their current and future emissions. We use publically available national datasets to develop an integrated approach for estimating GHG emissions at the metropolitan level over time, between multiple locations, and across sectors. We estimate consistent production-based GHG emissions for the 100 most populated metropolitan areas in the United States in 2014. We find that total 2014 metropolitan CO2 emissions range from 4.1 million metric tons in Lancaster, Pennsylvania to nearly 170 million metric tons in the Houston, Texas; with an overall average of 27 million metric tons. The top 20 absolute emitters and top 20 per capita emitters only overlap for 9 locations. Per capita emissions also show a wide variation: from 5 metric tons per person in the Tucson, Arizona to 65 metric tons per person in the Baton Rouge, Louisiana; with an overall average of 14 metric tons per person. We also compute estimates for 2002 and 2011 and compare to our 2014 emission estimates. Across all locations analyzed, average total emissions increased by 3% and average per capita emissions decreased by 14%. Where possible, we also compare our emission estimates to those reported by the cities in their climate action plans and find an average absolute difference between our estimates and those reported by the cities of 5.6 metric tons CO2 per person, likely due to temporal and scope differences between the two estimates. Our integrated emission estimation approach complements bottom-up approaches typically employed by municipalities and helps practitioners divert their attention and resources away from continuous emission accounting toward more impactful emission mitigation efforts.
 PDF  Online article 

(45) Lessons from wind policy in PortgualPeña, I. , Azevedo, I.L., Ferreira, L.M., Was it worth it?Energy Policy, 103, 193–202
Wind capacity and generation grew rapidly in several European countries, such as Portugal. Wind power adoption in Portugal began in the early 2000s, incentivized by a continuous feed-in tariff policy mechanism, coupled with public tenders for connection licenses in 2001, 2002, and 2005. These policies led to an enormous success in terms of having a large share of renewables providing electricity services: wind alone accounts today for ~23.5% of electricity demand in Portugal. We explain the reasons wind power became a key part of Portugal’s strategy to comply with European Commission climate and energy goals, and provide a detailed review of the wind feed-in tariff mechanism. We describe the actors involved in wind power production growth. We estimate the environmental and energy dependency gains achieved through wind power generation, and highlight the correlation between wind electricity generation and electricity exports. Finally, we compare the Portuguese wind policies with others countries’ policy designs and discuss the relevance of a feed-in tariff reform for subsequent wind power additions.
 PDF  Online article 

2016

(44) Known unknowns: indirect energy effects of information and communication technology. Horner, N., Shehabi, A., Azevedo, I.L. Environmental Research Letters, 11,10.
Background. There has been sustained and growing interest in characterizing the net energy impact of information and communication technology (ICT), which results from indirect effects offsetting (or amplifying) the energy directly consumed by ICT equipment. These indirect effects may be either positive or negative, and there is considerable disagreement as to the direction of this sign as well as the effect magnitude. Literature in this area ranges from studies focused on a single service (such as e-commerce versus traditional retail) to macroeconomic studies attempting to characterize the overall impact of ICT. Methods. We review the literature on the indirect energy effect of ICT found via Google Scholar, our own research, and input from other researchers in the field. The various studies are linked to an effect taxonomy, which is synthesized from several different hierarchies present in the literature. References are further grouped according to ICT service (e.g., e-commerce, telework) and summarized by scope, method, and quantitative and qualitative findings. Review results. Uncertainty persists in understanding the net energy effects of ICT. Results of indirect energy effect studies are highly sensitive to scoping decisions and assumptions made by the analyst. Uncertainty increases as the impact scope broadens, due to complex and interconnected effects. However, there is general agreement that ICT has large energy savings potential, but that the realization of this potential is highly dependent on deployment details and user behavior. Discussion. While the overall net effect of ICT is likely to remain unknown, this review suggests several guidelines for improving research quality in this area, including increased data collection, enhancing traditional modeling studies with sensitivity analysis, greater care in scoping, less confidence in characterizing aggregate impacts, more effort on understanding user behavior, and more contextual integration across the different levels of the effect taxonomy.
 PDF  Online article 

(43) China’s wind electricity and cost of carbon mitigation are more expensive than anticipated. Lam, L., Branstetter, L., Azevedo, I.L., Environmental Research Letters, 11, 8.
The success of China's transition to a low-carbon energy system will be key to achieve the global level of emissions reductions needed to avoid large negative consequences from climate change. China is undergoing an impressive build up of renewable capacity, in particular wind. Using data from the Clean Mechanism Development project database between 2004 and 2012, this study shows that while China made progress in bringing down the levelized cost of wind electricity and cost of carbon mitigation (CCM), serious grid-connection issues and high wind curtailment rates resulted in a levelized cost of wind electricity that is one-half to two times higher than expected, and a CCM that is four to six times higher. Sharp drop in electricity demand, utilization rate, and coal prices in recent years may lead to even higher results.
 PDF  Online article 

(42) How much electricity can we save by using direct current circuits in homes? Understanding the potential for electricity savings and assessing feasibility of a transition towards DC powered buildings. Glasgo, B., Azevedo, I.L., Hendrickson, C.,Applied Energy, 180, 66–75.
Advances in semiconductor-based power electronics and growing direct current loads in buildings have led researchers to reconsider whether buildings should be wired with DC circuits to reduce power conversions and facilitate a transition to efficient DC appliances. The feasibility, energy savings, and economics of such systems have been assessed and proven in data centers and commercial buildings, but the outcomes are still uncertain for the residential sector. In this work, we assess the technical and economic feasibility of DC circuits using data for 120 traditionally-wired AC homes in Austin, Texas to understand the effect of highly variable demand profiles on DC-powered residences, using appliance-level use and solar generation data, and performing a Monte Carlo simulation to quantify costs and benefits. Results show site energy savings between 9% and 20% when solar PV is distributed to all home appliances. When battery storage for excess solar energy is considered, these savings increase to 14–25%. At present DC equipment prices, converting all equipment to DC causes levelized annual costs of electricity to homeowners to roughly double. However, by converting only homes’ air conditioning condensing units to DC, the costs of direct-DC are greatly reduced and home site energy savings of 7–16% are generated. In addition to quantifying savings, we find major nontechnical barriers to implementing direct-DC in homes. These include a lack of standards for such systems, a relatively small market for DC appliances and components, utility programs designed for AC power, and a workforce unfamiliar with DC. Experience with DC is growing in other sectors, and with time this will be transitioned to a broader audience of engineers, electricians, and building inspectors to ensure that not only are the systems themselves safe, but that the image of direct current circuits becomes less foreign over time. Direct current may very well have a place in the residential sector, and research and development should continue to explore other potential benefits that might make a stronger case for a more widespread transition to what now appears a promising technology.
 PDF  Online article 

(41) Should we build wind farms close to load or invest in transmission to access better wind resources in remote areas? A case study in the MISO region, Lamy, J., Jaramillo, P., Azevedo, I.L., Wiser, R.,Energy Policy, 96, 341.350.
Wind speeds in remote areas are sometimes very high, but transmission costs to access these locations can be prohibitive. We present a conceptual model to estimate the economics of accessing high quality wind resources in remote areas to comply with renewable energy policy targets, and apply the model to the Midwestern grid (MISO) as a case study. We assess the goal of providing 40 TWh of new wind generation while minimizing costs, and include temporal aspects of wind power (variability costs and correlation to market prices) as well as total wind power produced from different farms. We find that building wind farms in North/South Dakota (windiest states) compared to Illinois (less windy, but close to load) would only be economical if the incremental transmission costs to access them were below $360/kW of wind capacity (break-even value). Historically, the incremental transmission costs for wind development in North/South Dakota compared to in Illinois are about twice this value. However, the break-even incremental transmission cost for wind farms in Minnesota/Iowa (also windy states) is $250/kW, which is consistent with historical costs. We conclude that wind development in Minnesota/Iowa is likely more economical to meet MISO renewable targets compared to North/South Dakota or Illinois.
 PDF  Online article 

(40) Power usage effectiveness in data centers: overloaded and underachieving, Horner, N., Azevedo, I.L.,The Electricity Journal, 29, 61-69.
The power usage effectiveness (PUE) metric has become an industry standard for reporting energy performance of data centers. However, it is an incomplete metric, failing to address hardware efficiency, energy productivity, and environmental performance. The industry should focus on adopting and systematically reporting more comprehensive metrics, which would allow more insight into data center energy performance.
 PDF  Online article 

(39) Effect of regional grid mix, driving patterns and climate on the comparative carbon footprint of gasoline and plug-in electric vehicles in the United States, accepted in Yuksel, T., Tamayao, M-A, Hendrickson, C.; Azevedo, I.L., Michalek, J.,Environmental Research Letters, 11, 044007.
We compare life cycle greenhouse gas (GHG) emissions from several light-duty passenger gasoline and plug-in electric vehicles (PEVs) across US counties by accounting for regional differences due to marginal grid mix, ambient temperature, patterns of vehicle miles traveled (VMT), and driving conditions (city versus highway). We find that PEVs can have larger or smaller carbon footprints than gasoline vehicles, depending on these regional factors and the specific vehicle models being compared. The Nissan Leaf battery electric vehicle has a smaller carbon footprint than the most efficient gasoline vehicle (the Toyota Prius) in the urban counties of California, Texas and Florida, whereas the Prius has a smaller carbon footprint in the Midwest and the South. The Leaf is lower emitting than the Mazda 3 conventional gasoline vehicle in most urban counties, but the Mazda 3 is lower emitting in rural Midwest counties. The Chevrolet Volt plug-in hybrid electric vehicle has a larger carbon footprint than the Prius throughout the continental US, though the Volt has a smaller carbon footprint than the Mazda 3 in many urban counties. Regional grid mix, temperature, driving conditions, and vehicle model all have substantial implications for identifying which technology has the lowest carbon footprint, whereas regional patterns of VMT have a much smaller effect. Given the variation in relative GHG implications, it is unlikely that blunt policy instruments that favor specific technology categories can ensure emission reductions universally.
 PDF  Online article 

(38) Alternative Fuel Vehicle Adoption Increases Fleet Gasoline Consumption and Greenhouse Gas Emissions under United States Corporate Average Fuel Economy Policy and Greenhouse Gas Emissions Standards, Jenn, A., Azevedo, I.L., Michalek, J.,Environmental science & technology,  50.5: 2165-2174.
The United States Corporate Average Fuel Economy (CAFE) standards and Greenhouse Gas (GHG) Emission standards are designed to reduce petroleum consumption and GHG emissions from light-duty passenger vehicles. They do so by requiring automakers to meet aggregate criteria for fleet fuel efficiency and carbon dioxide (CO2) emission rates. Several incentives for manufacturers to sell alternative fuel vehicles (AFVs) have been introduced in recent updates of CAFE/GHG policy for vehicles sold from 2012 through 2025 to help encourage a fleet technology transition. These incentives allow automakers that sell AFVs to meet less-stringent fleet efficiency targets, resulting in increased fleet-wide gasoline consumption and emissions. We derive a closed-form expression to quantify these effects. We find that each time an AFV is sold in place of a conventional vehicle, fleet emissions increase by 0 to 60 t of CO2 and gasoline consumption increases by 0 to 7000 gallons (26,000 L), depending on the AFV and year of sale. Using projections for vehicles sold from 2012 to 2025 from the Energy Information Administration, we estimate that the CAFE/GHG AFV incentives lead to a cumulative increase of 30 to 70 million metric tons of CO2 and 3 to 8 billion gallons (11 to 30 billion liters) of gasoline consumed over the vehicles’ lifetimes – the largest share of which is due to legacy GHG flex-fuel vehicle credits that expire in 2016. These effects may be 30–40% larger in practice than we estimate here due to optimistic laboratory vehicle efficiency tests used in policy compliance calculations.
 PDF  Online article 

(37) Forecasting light-duty vehicle demand using alternative-specific constants for endogeneity correction versus calibration, Haaf, C.G., Morrow, W.R., Azevedo, I.L., Feit, E., Michalek, J.J.,Transportation Research Part B, 84, 182–210.
We investigate parameter recovery and forecast accuracy implications of incorporating alternative-specific constants (ASCs) in the utility functions of vehicle choice models. We compare two methods of incorporating ASCs: (1) a maximum likelihood estimator that computes ASCs post-hoc as calibration constants (MLE-C) and (2) a generalized method of moments estimator that uses instrumental variables (GMM-IV) to correct for price endogeneity. In a synthetic study we observe significant coefficient bias with MLE-C when the price-ASC correlation (endogeneity) is large. GMM-IV successfully mitigates this bias given valid instruments but exacerbates the bias given invalid instruments. Despite greater coefficient bias, MLE-C yields better forecasts than GMM-IV with valid instruments in most of the cases examined, including most cases where the price-ASC correlation present in the estimation data is absent in the prediction data. In a market study of U.S. midsize sedan sales from 2002 – 2006 the GMM-IV model predicts the 1-year-forward market better, but the MLE-C model predicts the 5-year-forward market better. Including an ASC in predictions by any of the methods proposed improves share forecasts, and assuming that the ASC of each new vehicle matches that of its closest competitor vehicle yields the best long term forecasts. We find evidence that the instruments most frequently used in the automotive demand literature may be invalid.
 PDF  Online article 

2015

(36) A new approach of science, technology, engineering, and mathematics outreach in climate change, energy and environmental decision making, Faria, F., Klima, K., D.L., Posen, I.D., Azevedo, I.L.,Sustainability: The Journal of Record, 8(5): 261-271.
Preparing a literate public to critically evaluate issues related to climate change, energy, and the environment is an important pillar toward more sustainable societies. In this article, we focus on how informal education and outreach programs that have a combined focus on science, technology, engineering, and mathematics (STEM) and on climate change can improve knowledge, produce interest in STEM careers, and prepare educators to communicate and teach issues at the crossroads of STEM and climate change. The first part of this article describes the structure of STEM outreach programs for K-12 students and teachers in various parts of the United States. The second part presents, in detail, the structure and results of the outreach program SUCCEED (the Summer Center for Climate, Energy, and Environmental Decision-Making), a K-12 outreach program created by Carnegie Mellon University’s Department of Engineering and Public Policy (EPP). SUCCEED aims to 1.) improve scientific literacy through a summer program focusing on climate, energy, and environmental decision making for students entering 10th grade and K-12 teachers. 2.) encourage the pursuit of STEM-related careers, and 3.) help teachers prepare curriculum in these disciplines, to be used in their classes. This article also discusses how both the university and the local community can benefit from outreach programs like SUCCEED.
 PDF  Online article 

(35) Comparison of Life Cycle Greenhouse Gases from Natural Gas Pathways for Light-Duty Vehicles. Tong, R., Jaramillo, P., Azevedo, I.L.,Energy & Fuels
Low prices and abundant resources open new opportunities for using natural gas, one of which is the production of transportation fuels. In this study, we use a Monte Carlo analysis combined with a life cycle analysis framework to assess the greenhouse gas (GHG) implications of a transition to natural gas-powered vehicles. We consider six different natural gas fuel pathways in two representative light-duty vehicles: a passenger vehicle and a sport utility vehicle. We find that a battery electric vehicle (BEV) powered with natural gas-based electricity achieves around 40% life cycle emissions reductions when compared to conventional gasoline. Gaseous hydrogen fuel cell electric vehicles (FCEVs) and compressed natural gas (CNG) vehicles have comparable life cycle emissions with conventional gasoline, offering limited reductions with 100-year global warming potential (GWP) yet leading to increases with 20-year GWP. Other liquid fuel pathways (methanol, ethanol, and Fischer–Tropsch liquids) have larger GHG emissions than conventional gasoline even when carbon capture and storage technologies are available. Life cycle GHG emissions of natural gas pathways are sensitive to the vehicle fuel efficiency, to the methane leakage rates of natural gas systems, and to the GWP assumed. With the current vehicle technologies, the break-even methane leakage rates of CNG, gaseous hydrogen FCEV, and BEV are 0.9%/2.3%, 1.2%/2.8%, and 4.5%/10.8% (20-year GWP/100-year GWP). If the actual methane leakage rate is lower than the break-even rate of a specific natural gas pathway, that natural gas pathway reduces GHG emissions compared to conventional gasoline; otherwise, it leads to an increase in emissions.
 PDF  Online article 

(34) How to improve modelling approaches to represent the future costs of energy technologies? Reviewing the findings from learning curves from energy technologies. Rubin, E., Azevedo, I.L., Yeh, S., Jaramillo, P.,Energy Policy, 86, pp. 198-218.
A variety of mathematical models have been proposed to characterize and quantify the dependency of electricity supply technology costs on various drivers of technological change. The most prevalent model form, called a learning curve, or experience curve, is a log-linear equation relating the unit cost of a technology to its cumulative installed capacity or electricity generated. This one-factor model is also the most common method used to represent endogenous technical change in large-scale energy-economic models that inform energy planning and policy analysis. A characteristic parameter is the “learning rate,” defined as the fractional reduction in cost for each doubling of cumulative production or capacity. In this paper, a literature review of the learning rates reported for 11 power generation technologies employing an array of fossil fuels, nuclear, and renewable energy sources is presented. The review also includes multi-factor models proposed for some energy technologies, especially two-factor models relating cost to cumulative expenditures for research and development (R&D) as well as the cumulative installed capacity or electricity production of a technology. For all technologies studied, we found substantial variability (as much as an order of magnitude) in reported learning rates across different studies. Such variability is not readily explained by systematic differences in the time intervals, geographic regions, choice of independent variable, or other parameters of each study. This uncertainty in learning rates, together with other limitations of current learning curve formulations, suggests the need for much more careful and systematic examination of the influence of how different factors and assumptions affect policy-relevant outcomes related to the future choice and cost of electricity supply and other energy technologies.
 PDF  Online article 

(33) A Comparison of life cycle greenhouse gases from natural gas pathways for medium and heavy-duty vehicles. Tong, F., Azevedo, I.L., Jaramillo, P.,Environmental Science & Technology, 49, pp. 7123-7133.
The low-cost and abundant supply of shale gas in the United States has increased the interest in using natural gas for transportation. We compare the life cycle greenhouse gas (GHG) emissions from different natural gas pathways for medium and heavy-duty vehicles (MHDVs). For Class 8 tractor-trailers and refuse trucks, none of the natural gas pathways provide emissions reductions per unit of freight-distance moved compared to diesel trucks. When compared to the petroleum-based fuels currently used in these vehicles, CNG and centrally produced LNG increase emissions by 0–3% and 2–13%, respectively, for Class 8 trucks. Battery electric vehicles (BEVs) powered with natural gas-produced electricity are the only fuel-technology combination that achieves emission reductions for Class 8 transit buses (31% reduction compared to the petroleum-fueled vehicles). For non-Class 8 trucks (pick-up trucks, parcel delivery trucks, and box trucks), BEVs reduce emissions significantly (31–40%) compared to their diesel or gasoline counterparts. CNG and propane achieve relatively smaller emissions reductions (0–6% and 19%, respectively, compared to the petroleum-based fuels), while other natural gas pathways increase emissions for non-Class 8 MHDVs. While using natural gas to fuel electric vehicles could achieve large emission reductions for medium-duty trucks, the results suggest there are no great opportunities to achieve large emission reductions for Class 8 trucks through natural gas pathways with current technologies. There are strategies to reduce the carbon footprint of using natural gas for MHDVs, ranging from increasing vehicle fuel efficiency, reducing life cycle methane leakage rate, to achieving the same payloads and cargo volumes as conventional diesel trucks.
 PDF  Online article 

(32) Regional variability and uncertainty of electric vehicle life cycle CO2 emissions across the United States. Tamayao, M., Michalek, J., Hendrickson, C., Azevedo I.L.,Environmental Science and Technology, 49 (14), pp. 8844–8855.
We characterize regionally specific life cycle CO2 emissions per mile traveled for plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs) across the United States under alternative assumptions for regional electricity emission factors, regional boundaries, and charging schemes. We find that estimates based on marginal vs average grid emission factors differ by as much as 50% (using National Electricity Reliability Commission (NERC) regional boundaries). Use of state boundaries versus NERC region boundaries results in estimates that differ by as much as 120% for the same location (using average emission factors). We argue that consumption-based marginal emission factors are conceptually appropriate for evaluating the emissions implications of policies that increase electric vehicle sales or use in a region. We also examine generation-based marginal emission factors to assess robustness. Using these two estimates of NERC region marginal emission factors, we find the following: (1) delayed charging (i.e., starting at midnight) leads to higher emissions in most cases due largely to increased coal in the marginal generation mix at night; (2) the Chevrolet Volt has higher expected life cycle emissions than the Toyota Prius hybrid electric vehicle (the most efficient U.S. gasoline vehicle) across the U.S. in nearly all scenarios; (3) the Nissan Leaf BEV has lower life cycle emissions than the Prius in the western U.S. and in Texas, but the Prius has lower emissions in the northern Midwest regardless of assumed charging scheme and marginal emissions estimation method; (4) in other regions the lowest emitting vehicle depends on charge timing and emission factor estimation assumptions.
 PDF  Online article 

(31) How do we fund our roads? A case of decreasing revenue from electric vehicles. Jenn, A., Azevedo, I.L., Fischbeck, P.Journal of Transportation Research, 74, pp. 136-147.
Annual expenditures for transportation infrastructure have recently surpassed the funding available through tax and fee collection. One large source of revenue generation for transportation infrastructure is use fees that are charged through taxes on gasoline both on a federal and state level. A massive adoption of electric vehicles (EVs) in the United States would result in significantly lower gasoline consumption and thus reduce the revenue collected to maintain the U.S. transportation infrastructure. We investigate how different vehicles will change the annual fee collected on a marginal basis. In addition, we assess the effects of adoption of alternative vehicles on revenues using several projections of alternative vehicles adoption, both on a state-by-state basis and at the national level. We find that baseline midsize and compact vehicles such as the Toyota Camry and Honda Civic generate approximately $2500–$4000 in tax revenue over their lifetime. Under the current funding structure, battery-electric vehicles (BEVs) such as the Nissan Leaf generate substantially less at $400–$1300, while plug-in hybrid electric vehicles (PHEVs) such as the Chevrolet Volt generate $1500–$2700. Even in states with high lifetime fees due to fuel taxes, such as California, revenue generation can be upwards of 50% lower than in states with high registration fees such as Colorado. Total annual revenue generation decreases by about $200 million by 2025 as a result of EV adoption in our base case, but in projections with larger adoption of alternative vehicles could lead to revenue generation reductions as large as $900 million by 2025. Potential schemes that charge user fees on alternative fuel vehicles to overcome the decrease in revenue include a flat annual registration fee at 0.6% of the vehicle’s manufacturer suggested retail price (MSRP) or 2 per mile fee.
 PDF  Online article 

(30) Bulk Energy Storage Increases US Electricity System Emissions. Hittinger, E., Azevedo, I.L. Environmental Science & Technology, 49 (5), pp. 3203-3210.
Bulk energy storage is generally considered an important contributor for the transition toward a more flexible and sustainable electricity system. Although economically valuable, storage is not fundamentally a “green” technology, leading to reductions in emissions. We model the economic and emissions effects of bulk energy storage providing an energy arbitrage service. We calculate the profits under two scenarios (perfect and imperfect information about future electricity prices), and estimate the effect of bulk storage on net emissions of CO2, SO2, and NOx for 20 eGRID subregions in the United States. We find that net system CO2 emissions resulting from storage operation are nontrivial when compared to the emissions from electricity generation, ranging from 104 to 407 kg/MWh of delivered energy depending on location, storage operation mode, and assumptions regarding carbon intensity. Net NOx emissions range from −0.16 (i.e., producing net savings) to 0.49 kg/MWh, and are generally small when compared to average generation-related emissions. Net SO2 emissions from storage operation range from −0.01 to 1.7 kg/MWh, depending on location and storage operation mode.
 PDF  Online article 

(29) Changing the Renewable Fuel Standard to a Renewable Material Standard: Bio-Ethylene Case Study. Posen, I.D., Griffin, W.M., Matthews, H.S., Azevedo, I.L. Environmental Science & Technology, 49 (1), pp. 93-102.
The narrow scope of the U.S. renewable fuel standard (RFS2) is a missed opportunity to spur a wider range of biomass use. This is especially relevant as RFS2 targets are being missed due to demand-side limitations for ethanol consumption. This paper examines the greenhouse gas (GHG) implications of a more flexible policy based on RFS2, which includes credits for chemical use of bioethanol (to produce bioethylene). A Monte Carlo simulation is employed to estimate the life-cycle GHG emissions of conventional low-density polyethylene (LDPE), made from natural gas derived ethane (mean: 1.8 kg CO2e/kg LDPE). The life-cycle GHG emissions from bioethanol and bio-LDPE are examined for three biomass feedstocks: U.S. corn (mean: 97g CO2e/MJ and 2.6 kg CO2e/kg LDPE), U.S. switchgrass (mean: −18g CO2e/MJ and −2.9 kg CO2e/kg LDPE), and Brazilian sugar cane (mean: 33g CO2e/MJ and −1.3 kg CO2e/kg LDPE); bioproduct and fossil-product emissions are compared. Results suggest that neither corn product (bioethanol or bio-LDPE) can meet regulatory GHG targets, while switchgrass and sugar cane ethanol and bio-LDPE likely do. For U.S. production, bioethanol achieves slightly greater GHG reductions than bio-LDPE. For imported Brazilian products, bio-LDPE achieves greater GHG reductions than bioethanol. An expanded policy that includes bio-LDPE provides added flexibility without compromising GHG targets.
 PDF  Online article 

(28) Nonproliferation Improvements and Challenges Presented by Small Modular Reactors. Prasad, S., Abdulla, A., Morgan, M.G.M., Azevedo, I.L. Progress in Nuclear Energy, 80, pp. 102-109.
Small modular reactors (SMRs) may provide an energy option that will not emit greenhouse gases. From a commercial point-of-view, SMRs will be suitable to serve smaller energy markets with less developed infrastructure, to replace existing old nuclear and coal power plants, and to provide process heat in various industrial applications. In this paper, we examine how SMRs might challenge and improve the existing nonproliferation regime. To motivate our discussion, we first present the opinions gathered from an international group of nuclear experts at an SMR workshop. Next, various aspects of SMR designs such as: fissile material inventory, core-life, refueling, burnup, digital instrumentation and controls, underground designs, sealed designs, enrichment, breeders, excess reactivity, fuel element size, coolant opacity, and sea-based nuclear plants are discussed in the context of proliferation concerns. In doing this, we have used publicly available design information about a number of SMR designs (B&W mPower, SVBR-100, KLT-40S, Toshiba 4S, and General Atomics EM2). Finally, a number of recommendations are offered to help alleviate proliferation concerns that may arise due to SMR design features.
 PDF  Online article 

(27) Assessing regional differences in lighting heat replacement effects in residential buildings across the United States. Min, J., Azevedo, I.L., Hakkarainen, P.Applied Energy, 141, pp. 12-18.
Lighting accounts for 19% of total U.S. electricity consumption and 6% of carbon dioxide equivalent (CO2e) emissions. Existing technologies, such as compact fluorescent lamps and light emitting diodes, can substitute low-efficiency technologies such as incandescent lamps, while saving energy and reducing energy bills to consumers. For that reason, lighting efficiency goals have been emphasized in U.S. energy efficiency policies. However, incandescent bulbs release up to 95% of input energy as heat, impacting the overall building energy consumption: replacing them increases demands for heating service that needs to be provided by the heating systems and decreases demands for cooling service that needs to be provided by the cooling systems. This work investigates the net energy consumption, CO2e emissions, and savings in energy bills for single-family detached houses across the U.S. as one adopts more efficient lighting systems. In some regions, these heating and cooling effects from more efficient lighting can undermine up to 40% of originally intended primary energy savings, erode anticipated carbon savings completely, or lead to 30% less household monetary savings than intended. The size of the effect depends on regional factors such as climate, technologies used for heating and cooling, electricity fuel mix, emissions factors, and electricity prices. However, we also find that for moderate lighting efficiency interventions, the overall effect is small in magnitude, corresponding at most to 1% of either total emissions or of energy consumption by a house.
 PDF  Online article 

2014

(26) Regional energy and GHG savings from building codes across the United States. Gilbraith, N., Azevedo, I.L. Environmental Science & Technology, 48 (24), pp. 14121-14130.
The federal government has the goal of decreasing commercial building energy consumption and pollutant emissions by incentivizing the adoption of commercial building energy codes. Quantitative estimates of code benefits at the state level that can inform the size and allocation of these incentives are not available. We estimate the state-level climate, environmental, and health benefits (i.e., social benefits) and reductions in energy bills (private benefits) of a more stringent code (ASHRAE 90.1–2010) relative to a baseline code (ASHRAE 90.1–2007). We find that reductions in site energy use intensity range from 93 MJ/m2 of new construction per year (California) to 270 MJ/m2 of new construction per year (North Dakota). Total annual benefits from more stringent codes total $506 million for all states, where $372 million are from reductions in energy bills, and $134 million are from social benefits. These total benefits range from $0.6 million in Wyoming to $49 million in Texas. Private benefits range from $0.38 per square meter in Washington State to $1.06 per square meter in New Hampshire. Social benefits range from $0.2 per square meter annually in California to $2.5 per square meter in Ohio. Reductions in human/environmental damages and future climate damages account for nearly equal shares of social benefits.
 PDF  Online article 

(25) Consumer End-Use Energy Efficiency and Rebound Effects, Azevedo, I.L. Annual Reviews of Environment and Resources, 39, pp. 393-418.
Energy efficiency policies are pursued as a way to provide affordable and sustainable energy services. Efficiency measures that reduce energy service costs will free up resources that can be spent in the form of increased consumption—either of that same good or service or of other goods and services that require energy (and that have associated emissions). This is called the rebound effect. There is still significant ambiguity about how the rebound effect should be defined, how we can measure it, and how we can characterize its uncertainty. Occasionally the debate regarding its importance reemerges, in part because the existing studies are not easily comparable. The scope, region, end-uses, time period of analysis, and drivers for efficiency improvements all differ widely from study to study. As a result, listing one single number for rebound effects would be misleading. Rebound effects are likely to depend on the specific attributes of the policies that trigger the efficiency improvement, but such factors are often ignored. Implications for welfare changes resulting from rebound have also been largely ignored in the literature until recently.
 PDF  Online article 

(24) Should policy-makers allocate funding to vehicle electrification or end- use energy efficiency as a strategy for climate change mitigation and energy reductions? Rethinking electric utilities efficiency programs. Thomas, B., Azevedo, I.L. Energy Policy, 67, pp. 28-26.
In order to reduce greenhouse gas emissions in the United States by an order of magnitude, a portfolio of mitigation strategies is needed. Currently, many utilities pursue energy efficiency programs. We study a case where utilities could choose whether to allocate their energy efficiency budget to either end-use efficiency or vehicle electrification as a means to reduce CO2 emissions. We build a decision space that displays the conditions under which utilities should pursue either strategy. To build such decision space, assumptions are needed on how consumers respond to electric vehicle incentives, and what would be the baseline vehicle selected by consumers if no incentives were in place. Since these two aspects are highly uncertain, we treat them parametrically: if consumers are replacing a conventional vehicle with a PHEV, utility incentive programs to induce PHEV adoption appear to be cost-effective for a wide range of efficiency program costs and grid emissions factors.
 PDF  Online article 

(23) Economic analysis on the profitability of wind in Portugal between 1992 and 2010. Peña-Cabra, I., Azevedo, I.L.,Energy Economics, 45, pp. 353-363.
Discussions on the appropriate policy design and level of incentive to promote renewable energy adoption and meet the 20/20/20 goals have spurred recently in the European Union. These discussions are also ongoing in Portugal, namely in what concerns the level and duration of feed-in tariffs that should be provided to independent power producers. This, in turn, raises the question of whether the past feed-in tariff levels were well designed to achieve the goals of a larger penetration of renewables in the Portuguese grid. The policies to induce wind adoption have led to a growth in wind installed capacity and share of electricity generated by wind in Portugal, but questions arise on their cost-effectiveness and whether alternative policy designs would have led to the same goal. In this work, we estimate profits made by wind independent power producers for wind parks that were connected in Portugal between 1992 and 2010, and conclude that the feed-in tariffs have overcompensated some wind power producers. We also discuss the recent changes in feed-in tariff legislation published in February 2013 and estimate the expected costs of the introduced changes.
 PDF  Online article 

(22) Difusión de energÍa eólica: comparación de políticas de incentivos en Estados unidos y Europa. Peña-Cabra, I., González, E., Azevedo, I.L., Ferreira, F.,Revista Nano Ciencia Y Tecnologia
Frente al impacto ambiental por emisión de CO2 y metano asociados con la producción de energía por combustibles fósiles, la energía eólica se posiciona como una opción de mitigación, que está alcanzando importantes niveles de desarrollo y difusión.
 PDF  Online article 

(21) Comparing the magnitude of residential rebound effects from electric end-use efficiency across the United States. Thomas, B.A., Hausfather, Z., Azevedo, I.L.,Environmental Research Letters, 9 (7).
Many US states rely on energy efficiency goals as a strategy to reduce CO2e emissions and air pollution, to minimize investments in new power plants, and to create jobs. For those energy efficiency interventions that are cost-effective, i.e., saving money and reducing energy, consumers may increase their use of energy services, or re-spend cost savings on other carbon- and energy-intensive goods and services. In this paper, we simulate the magnitude of these 'rebound effects' in each of the 50 states in terms of CO2e emissions, focusing on residential electric end-uses under plausible assumptions. We find that a 10% reduction in annual electricity use by a household results in an emissions' reduction penalty ranging from 0.1 ton CO2e in California to 0.3 ton CO2e in Alabama (from potential emissions reductions of 0.3 ton CO2e and 1.6 ton CO2e, respectively, in the no rebound case). Rebound effects, percentage-wise, range from 6% in West Virginia (which has a high-carbon electricity and low electricity prices), to as high as 40% in California (which has low-carbon electricity and high electricity prices). The magnitude of rebound effects percentage-wise depends on the carbon intensity of the grid: in states with low emissions factors and higher electricity prices, such as California, the rebound effects are much larger percentage-wise than in states like Pennsylvania. Conversely, the states with larger per cent rebound effects are the ones where the implications in terms of absolute emissions changes are the smallest.
 PDF  Online article 

(20) The role of energy storage in accessing remote wind resources in the Midwest. Lamy, J., Azevedo, I.L., Jaramillo, P.Energy Policy, 68, pp. 123-131.
Replacing current generation with wind energy would help reduce the emissions associated with fossil fuel electricity generation. However, integrating wind into the electricity grid is not without cost. Wind power output is highly variable and average capacity factors from wind farms are often much lower than conventional generators. Further, the best wind resources with highest capacity factors are often located far away from load centers and accessing them therefore requires transmission investments. Energy storage capacity could be an alternative to some of the required transmission investment, thereby reducing capital costs for accessing remote wind farms. This work focuses on the trade-offs between energy storage and transmission. In a case study of a 200 MW wind farm in North Dakota to deliver power to Illinois, we estimate the size of transmission and energy storage capacity that yields the lowest average cost of generating and delivering electricity ($/MW h) from this farm. We find that transmission costs must be at least $600/MW-km and energy storage must cost at most $100/kW h in order for this application of energy storage to be economical.
 PDF  Online article 

(19) Labeling energy cost on light bulbs lowers implicit discount rates. Min, J., Azevedo, I.L., Michalek, J., Bruine de Bruin, W.Ecological Economics, 97, pp. 42-50.
Lighting accounts for nearly 20% of overall U.S. electricity consumption and 18% of U.S. residential electricity consumption. A transition to alternative energy-efficient technologies could reduce this energy consumption considerably. To quantify the influence of factors that drive consumer choices for light bulbs, we conducted a choice-based conjoint field experiment with 183 participants. We estimated discrete choice models from the data, and found that politically liberal consumers have a stronger preference for compact fluorescent lighting technology and for low energy consumption. Greater willingness to pay for lower energy consumption and longer life was observed in conditions where estimated operating cost information was provided. Providing estimated annual cost information to consumers reduced their implicit discount rate by a factor of five, lowering barriers to adoption of energy efficient alternatives with higher up-front costs; however, even with cost information provided, consumers continued to use implicit discount rates of around 100%, which is larger than that experienced for other energy technologies.
 PDF  Online article 

2013

(18) Effects of government incentives on wind innovation in the United States. Horner, N.C., Azevedo, I.L., Hounshell, D.A.Environmental Research Letters, 8 044032.
In the United States, as elsewhere, state and federal governments have considered or implemented a range of policies to create more sustainable energy generation systems in response to concerns over climate change, security of fuel supply, and environmental impacts. These policies include both regulatory instruments such as renewable portfolio standards (RPSs) and market incentives such as tax credits. While these policies are primarily geared towards increasing renewable generation capacity, they can indirectly affect innovation in associated technologies through a 'demand-pull' dynamic. Other policies, such as public research and development (R&D) funding, directly incentivize innovation through 'technology-push' means. In this letter, we examine these effects on innovation in the United States wind energy industry. We estimate a set of econometric models relating a set of US federal and state policies to patenting activity in wind technologies over the period 1974–2009. We find that RPS policies have had significant positive effects on wind innovation, whereas tax-based incentives have not been particularly effective. We also find evidence that the effects of RPS incentives differ between states. Finally, we find that public R&D funding can be a significant driver of wind innovation, though its effect in the US has been modest.
 PDF  Online article 

(17) Impact of federal incentives on the adoption of hybrid electric vehicles in the United States. Jenn, A., Azevedo, I.L., Ferreira, P.Energy Economics, 40, pp. 936-942, ISSN 0140-9883.
Starting in 2004, the federal government in the United States offered several nationwide incentives to consumers to increase the adoption of hybrid electric vehicles. This study assesses the effectiveness of the Energy Policy Act of 2005 in this regard using econometric methods and data between 2000 and 2010. Our model accounts for network externalities by using lagged sales as an independent variable. This approach helps to capture the exponential initial growth associated with the diffusion of new technologies and avoids overestimating the effect of the policy incentives. Our results show that the Energy Policy Act of 2005 increased the sales of hybrids from 3% to 20% depending on the vehicle model considered. In addition, we find that this incentive is only effective when the amount provided is sufficiently large.
 PDF  Online article 

(16) Regional variations in the health, environmental, and climate benefits from wind and solar generation. Siler-Evans, K., Azevedo, I.L., Morgan, M.G, Apt, J.PNAS, 110 (29), pp. 11768-11773.
When wind or solar energy displace conventional generation, the reduction in emissions varies dramatically across the United States. Although the Southwest has the greatest solar resource, a solar panel in New Jersey displaces significantly more sulfur dioxide, nitrogen oxides, and particulate matter than a panel in Arizona, resulting in 15 times more health and environmental benefits. A wind turbine in West Virginia displaces twice as much carbon dioxide as the same turbine in California. Depending on location, we estimate that the combined health, environmental, and climate benefits from wind or solar range from $10/MWh to $100/MWh, and the sites with the highest energy output do not yield the greatest social benefits in many cases. We estimate that the social benefits from existing wind farms are roughly 60% higher than the cost of the Production Tax Credit, an important federal subsidy for wind energy. However, that same investment could achieve greater health, environmental, and climate benefits if it were differentiated by region.
 PDF  Online article 

(15) Expert assessments of the cost of light water small modular reactors. Abdulla, A., Azevedo, I.L., Morgan, M.G.PNAS, 110 (24), pp. 9686-9691.
Analysts and decision makers frequently want estimates of the cost of technologies that have yet to be developed or deployed. Small modular reactors (SMRs), which could become part of a portfolio of carbon-free energy sources, are one such technology. Existing estimates of likely SMR costs rely on problematic top-down approaches or bottom-up assessments that are proprietary. When done properly, expert elicitations can complement these approaches. We developed detailed technical descriptions of two SMR designs and then conduced elicitation interviews in which we obtained probabilistic judgments from 16 experts who are involved in, or have access to, engineering-economic assessments of SMR projects. Here, we report estimates of the overnight cost and construction duration for five reactor-deployment scenarios that involve a large reactor and two light water SMRs. Consistent with the uncertainty introduced by past cost overruns and construction delays, median estimates of the cost of new large plants vary by more than a factor of 2.5. Expert judgments about likely SMR costs display an even wider range. Median estimates for a 45 megawatts-electric (MWe) SMR range from $4,000 to $16,300/kWe and from $3,200 to $7,100/kWe for a 225-MWe SMR. Sources of disagreement are highlighted, exposing the thought processes of experts involved with SMR design. There was consensus that SMRs could be built and brought online about 2 y faster than large reactors. Experts identify more affordable unit cost, factory fabrication, and shorter construction schedules as factors that may make light water SMRs economically viable.
 PDF  Online article 

(14) Reducing U.S. residential energy use and CO2 emissions: how much, how soon, and at what cost? Azevedo, I.L., Morgan, M.G., Palmer, K., and Lave, L.ES&T, 47, pp. 2502-2511.
There is growing interest in reducing energy use and emissions of carbon dioxide from the residential sector by deploying cost-effectiveness energy efficiency measures. However, there is still large uncertainty about the magnitude of the reductions that could be achieved by pursuing different energy efficiency measures across the nation. Using detailed estimates of the current inventory and performance of major appliances in U.S. homes, we model the cost, energy, and CO2 emissions reduction if they were replaced with alternatives that consume less energy or emit less CO2. We explore trade-offs between reducing CO2, reducing primary or final energy, or electricity consumption. We explore switching between electricity and direct fuel use, and among fuels. The trade-offs between different energy efficiency policy goals, as well as the environmental metrics used, are important but have been largely unexplored by previous energy modelers and policy-makers. We find that overnight replacement of the full stock of major residential appliances sets an upper bound of just over 710 × 106 tonnes/year of CO2 or a 56% reduction from baseline residential emissions. However, a policy designed instead to minimize primary energy consumption instead of CO2 emissions will achieve a 48% reduction in annual carbon dioxide emissions from the nine largest energy consuming residential end-uses. Thus, we explore the uncertainty regarding the main assumptions and different policy goals in a detailed sensitivity analysis.
 PDF  Online article 

(13) Estimating direct and indirect rebound effects for U.S. households with input-output analysis. Part 1: Theoretical Framework. Thomas, B.A. Azevedo, I.L.,Ecological Economics, 86, pp. 199-210.
This is the first part of a two-part paper providing an analytical model of the indirect rebound effect, given a direct rebound estimate, that integrates consumer demand theory with the embodied energy of household spending from environmentally-extended input–output analysis. The second part applies the model developed in part one to simulate the direct and indirect rebound for the average U.S. household in terms of primary energy, CO2e, NOx, and SO2 emissions and for energy efficiency investments in electricity, natural gas, or gasoline services. Part one provides a critical review of the largely independent economic and industrial ecology literatures on the indirect rebound. By studying the two-goods case and the n-goods case, we demonstrate that the indirect rebound is bounded by the consumer budget constraint, and inversely related to the direct rebound. We also compare the common proportional spending and income elasticity spending assumptions with our model of cross-price elasticities including both substitution and income effects for the indirect rebound. By assuming zero incremental capital costs and the same embodied energy as conventional technologies for efficient appliances, we model an upper bound of the indirect rebound. Future work should also consider the increase in consumer welfare possible through the rebound effect.
 PDF  Online article 

(12) Estimating direct and indirect rebound effects for U.S. households with input-output analysis. Part 2: Simulation. Thomas, B.A. Azevedo, I.L.,Ecological Economics, 86, pp. 188-198.
This is the second part of a two-part paper that integrates economic and industrial ecology methods to estimate the indirect rebound effect from residential energy efficiency investments. We apply the model developed in part one to simulate the indirect rebound, given an estimate of the direct rebound, using a 2002 environmentally-extended input–output model and the 2004 Consumer Expenditure Survey (in 2002$) for the U.S. We find an indirect rebound of 5–15% in primary energy and CO2e emissions, assuming a 10% direct rebound, depending on the fuel saved with efficiency and household income. The indirect rebound can be as high as 30–40% in NOx or SO2 emissions for efficiency in natural gas services. The substitution effect modeled in part one is small in most cases, and we discuss appropriate applications for proportional or income elasticity spending assumptions. Large indirect rebound effects occur as the U.S. electric grid becomes less-carbon intensive, in households with large transportation demands, or as energy prices increase. Even in extreme cases, there is limited evidence for backfire, or a rebound effect greater than 100%. Enacting pollution taxes or auctioned permits that internalize the externalities of energy use would ensure that rebound effects unambiguously increase consumers' welfare.
 PDF  Online article 

2012

(11) Contributing author to “Chapter 16: Transitions in Energy Systems”Global Energy AssessmentInternational Institute for Applied Systems Analysis, (IIASA)
The energy sector is evolving rapidly. This evolution is shaped by the convergence of several factors, including the realization that energy is a key enabler for achieving development goals, such as the Millennium Development Goals (MDGs). Chapters 2 and 6 of this report review the link between economic growth and energy use, while the effects of energy system operation for human health and the local & global envir-onment are reviewed in Chapters 3 and 4 respectively.
 PDF  Online article 

(10) ICT solutions in transportation systems: estimating the benefits and environmental impacts in Lisbon.Baptista, P.C., Azevedo, I.L., Farias, T.L,Procedia – Social and Behavioral Sciences, 54, pp. 716-725.
Information and communication technologies (ICT) holds the potential to dramatically change the way people drive and their mobility patterns, thus potentially reducing GHG emissions, air pollutants and fatalities. In this work, we study the potential environmental and the economic impacts of implementing ICT measures in personal transportation, for three scenarios of ICT applications. In the first application, we seek to investigate the effects of limiting driving speed. Non-compliance with speed limits accounts for a large part of fatal car accidents in Portugal, and therefore understanding the impact of such applications is crucial in the context of a national transportation safety policy. In this application, stricter speed limits can be obtained either by on-board vehicle devices influencing the driver not to exceed certain speed limits or on the road network imposing lower speed limits. In the second application, the impacts of fostering an eco-driving behavior are studied. In that case, we study the impact of a massive adhesion by the public to eco-driving using ICT to present the drivers with the results of their behavioral changes. The third case study assesses the impacts of the implementation of a taxation system based on on-board vehicle devices that indicate where and when the vehicle is being driven and rewarding or penalizing the driver for it. For this study the Lisbon region was addressed. The results show that different ICT applications can have considerable impacts in terms of energy consumption reductions: Scenario 2 (with main variable being speed limitation) reached a 12% reduction in 2020 compared to the BAU, followed by Scenario 4 (with main variable being eco-driving) with a 5.5% reduction, and the taxation Scenario 6 presented a 1.8% reduction. In terms of CO2 emissions, the avoided CO2 emissions from implementing these scenarios varies from 19 to 276 kton in Scenarios 3 (with main variable being eco-driving) and 2 respectively. In terms the avoided cost from the fuel not consumed and CO2 emissions not emitted, as well as the revenue from the taxation scheme, the scenarios results range from 9 to 134 M€ for Scenarios 3 and 2 respectively.
 PDF  Online article 

(9) Marginal emissions factors for the US electricity system. Siler-Evans. K., Azevedo, I.L., Morgan, M.G.,ES&T>, 46 (9), pp. 4742-4748.
There is growing interest in reducing emissions from electricity generation in the United States (U.S.). Renewable energy, energy efficiency, and energy conservation are all commonly suggested solutions. Both supply- and demand-side interventions will displace energy—and emissions—from conventional generators. Marginal emissions factors (MEFs) give a consistent metric for assessing the avoided emissions resulting from such interventions. This paper presents the first systematic calculation of MEFs for the U.S. electricity system. Using regressions of hourly generation and emissions data from 2006 through 2011, we estimate regional MEFs for CO2, NOx, and SO2, as well as the share of marginal generation from coal-, gas-, and oil-fired generators. Trends in MEFs with respect to system load, time of day, and month are explored. We compare marginal and average emissions factors (AEFs), finding that AEFs may grossly misestimate the avoided emissions resulting from an intervention. We find significant regional differences in the emissions benefits of avoiding one megawatt-hour of electricity: compared to the West, an equivalent energy efficiency measure in the Midwest is expected to avoid roughly 70% more CO2, 12 times more SO2, and 3 times more NOx emissions.
 PDF  Online article 

(8) The electricity consumption and energy savings potential of video game consoles in the United States. Hittinger, E., Mullins, K., Azevedo, I.L. Energy Efficiency Journal, 5 (4), pp. 531-545.
Total energy consumption of video game consoles has grown rapidly in the past few decades due to rapid increases in market penetration, power consumption of the devices, and increasing usage driven by new capabilities. Unfortunately, studies investigating the energy impacts of these devices have been limited and potential responses, such as ENERGY STAR requirements, have been difficult to define and implement. We estimate that the total electricity consumption of video game consoles in the US was around 11 TWh in 2007 and 16 TWh in 2010 (approximately 1 % of US residential electricity consumption), an increase of almost 50 % in 3 years. However, any estimate of total game console energy consumption is highly uncertain, and we have determined that the key uncertainty is the unknown consumer behavior with regards to powering down the system after use. Even under this uncertainty, we demonstrate that the most effective energy-saving modification is incorporation of a default auto power down feature, which could reduce electricity consumption of game consoles by 75 % (10 TWh reduction of electricity in 2010), saving consumers over $1 billion annually in electricity bills. We conclude that using an auto power down feature for game consoles is at least as effective for reducing energy consumption as implementing a strict set of energy efficiency improvements for the devices, is much easier to implement given the nature of the video game console industry, and could be applied retroactively to currently deployed consoles through firmware updates.
 PDF  Online article 

(7) Edison revisited: Should we use DC circuits for lighting in commercial buildings? Thomas, B., Azevedo I.L., Morgan, M.G.Energy Policy, 45, pp. 399-411.
We examine the economic feasibility of using dedicated DC circuits to operate lighting in commercial buildings. We compare light-emitting diodes (LEDs) and fluorescents that are powered by either a central DC power supply or traditional AC grid electricity, with and without solar photovoltaics (PV) and battery back-up. Using DOE performance targets for LEDs and solar PV, we find that by 2012 LEDs have the lowest levelized annualized cost (LAC). If a DC voltage standard were developed, so that each LED fixture's driver could be eliminated, LACs could decrease, on average, by 5% compared to AC LEDs with a driver in each fixture. DC circuits in grid-connected PV-powered LED lighting systems can lower the total unsubsidized capital costs by 4–21% and LACs by 2–21% compared to AC grid-connected PV LEDs. Grid-connected PV LEDs may match the LAC of grid-powered fluorescents by 2013. This outcome depends more on manufacturers' ability to produce LEDs that follow DOE's lamp production cost and efficacy targets, than on reducing power electronics costs for DC building circuits and voltage standardization. Further work is needed to better understand potential safety risks with DC distribution and to remove design, installation, permitting, and regulatory barriers.
 PDF  Online article 

(6) Distributed cogeneration for commercial buildings: Can we make the economics work? Siler-Evans, K., Morgan, M.G, Azevedo, I.L. Energy Policy, 42, pp. 580-590.
Although the benefits of distributed cogeneration are widely cited, adoption has been slow in the United States. Adoption could be encouraged by making cogeneration more economically attractive, either by increasing the expected returns or decreasing the risks of such investments. We evaluate the expected returns from demand response, capacity markets, regulation markets, accelerated depreciation, pricing CO2 emissions, and net metering. We find that (1) there is an incentive to overcommit in the capacity market due to lenient non-response penalties, (2) there is significant revenue potential in the regulation market, though demand-side resources are yet to participate, (3) a price on CO2 emissions will make cogeneration more attractive relative to conventional, utility-supplied energy, and (4) accelerated depreciation is an easy and effective mechanism for improving the economics of cogeneration. We go on to argue that uncertainty in fuel and electricity prices present a significant risk to cogeneration projects, and we evaluate the effectiveness of feed-in tariffs at mitigating these risks. We find that guaranteeing a fixed electricity payment is not effective. A two-part feed-in tariff, with an annual capacity payment and an energy payment that adjusts with fuel costs, can eliminate energy-price risks.
 PDF  Online article 

2011

(5) Designing building energy efficiency programs for greenhouse gas reductions. Blackhurst M., Azevedo, I.L., Matthews, H.S., Hendrickson, C.T.Energy Policy, 39 (9), pp. 5269-5279.
Costs and benefits of building energy efficiency are estimated as a means of reducing greenhouse gas emissions in Pittsburgh, PA and Austin, TX. The analysis includes electricity and natural gas consumption, covering 75% of building energy consumption in Pittsburgh and 85% in Austin. Two policy objectives were evaluated: maximize GHG reductions given initial budget constraints or maximize social savings given target GHG reductions. This approach evaluates the trade-offs between three primary and often conflicting program design parameters: initial capital constraints, social savings, and GHG reductions. Results suggest uncertainty in local stocks, demands, and efficiency significantly impacts anticipated outcomes. Annual GHG reductions of 1 ton CO2 eq/capita/yr in Pittsburgh could cost near nothing or over $20 per capita annually. Capital-constrained policies generate slightly less social savings (a present value of a few hundred dollars per capita) than policies that maximize social savings. However, sectors and end uses targeted for intervention vary depending on policy objectives and constraints. Optimal efficiency investment strategies for some end uses vary significantly (in excess of 100%) between Pittsburgh and Austin, suggesting that resources and guidance conducted at the national scale may mislead state and local decision-makers. Results are used to provide recommendations for efficiency program administrators.
 PDF  Online article 

(4) Preparing US community greenhouse gas inventories for climate action plans. Blackhurst, Matthews, H. S., Sharrard, A.L, Hendrickson, C.T., Azevedo, I.L. Environmental Research Letters, 6 (3), p.034003.
This study illustrates how alternative and supplemental community-level greenhouse gas (GHG) inventory techniques could improve climate action planning. Eighteen US community GHG inventories are reviewed for current practice. Inventory techniques could be improved by disaggregating the sectors reported, reporting inventory uncertainty and variability, and aligning inventories with local organizations that could facilitate emissions reductions. The potential advantages and challenges of supplementing inventories with comparative benchmarks are also discussed. While GHG inventorying and climate action planning are nascent fields, these techniques can improve CAP design, help communities set more meaningful emission reduction targets, and facilitate CAP implementation and progress monitoring.
 PDF  Online article 

(3) Residential electricity consumption in Portugal: Findings from top-down and bottom-up models. Weismann, D., Azevedo, I.L., Ferrão, P., Fernandez J.,Energy Policy, 39 (5), pp. 2772-2779.
An econometric study of the Portuguese residential electricity consumption is presented, with a focus on the influence of dwelling characteristics on consumption. The relationship between the dwelling and household characteristics on per capita residential electricity consumption is estimated at two different scales, involving two distinct databases: the first includes data at the municipality level for 2001, the second is the most recent Portuguese consumer expenditure survey that was collected in 2005 and 2006. The results of the analysis at both scales are consistent and indicate that household and dwelling characteristics have a significant influence on residential electricity consumption. Our results show that in Portugal the direct effect of income on electricity consumption is low and becomes smaller when more relevant control variables are included in the analysis. Future demand of electricity in Portugal will be significantly influenced by trends in socioeconomic factors as well as changes in the building stock. These trends should be taken in consideration in the formulation of policy measures to reduce electricity consumption.
 PDF  Online article 

(2) Residential and regional electricity consumption in the US and EU: how much will higher prices reduce CO2 emissions? Azevedo, I.L., Morgan, M. G., Lave, L.The Electricity Journal, Vol. 24, Issue 1 1040-6190 (Electricity Journal papers are not peer-reviewed).
Results of our analysis suggest that, given the price-inelastic behavior in both the U.S. and EU regions, public policies aimed at fostering a transition to a more sustainable energy system in order to address the climate change challenge will require more than an increase in electricity retail price if they are to induce needed conservation efforts and the adoption of more efficient technologies by households.
 PDF  Online article 

2009

(1) The transition to solid-state lightingAzevedo, I.L., Morgan, M. G., Morgan, F.The Proceedings of the IEEE, 97 (3), pp. 481-510. ISSN: 0018-9219.
Lighting constitutes more than 20% of total U.S. electricity consumption, a similar fraction in the European Union, and an even higher fraction in many developing countries. Because many current lighting technologies arebhighly inefficient, improved technologies for lighting hold great potential for energy savings and for reducing associated greenhouse gas emissions. Solid-state lighting shows great promise as a source of efficient, affordable, color-balanced white light. Indeed, assuming market discount rates, engineering-economic analysis demonstrates that white solidstate lighting already has a lower levelized annual cost (LAC)than incandescent bulbs. The LAC for white solid-state lighting will be lower than that of the most efficient fluorescent bulbs by the end of this decade. However, a large literature indicates that households do not make their decisions in terms of simple expected economic value. After a review of the technology, we compare the electricity consumption, carbon emissions, and cost-effectiveness of current lighting technologies, accounting for expected performance evolution through 2015. We then simulate the lighting electricity consumption and implicit greenhouse gases emissions for the U.S. residential and commercial sectors through 2015 under different policy scenarios: voluntary solid-state lighting adoption, implementation of lighting standards in new construction, and rebate programs or equivalent subsidies. Finally, we provide a measure of cost-effectiveness for solidstate lighting in the context of other climate change abatement policies.
 PDF 

Policy Briefs & Technical Reports

Against the Wind: China’s struggle to integrated wind energy into its national grid Lam, L., Branstetter, L., Azevedo, I.L. Peterson Institute for International Economics Policy Briefs

In 2004 indigenous firms and Sino-foreign joint ventures accounted for only 17 percent of national installed capacity. To take advantage of China’s ambitious wind farm development program while meeting its requirement for local manufacturing, Western firms scrambled to transfer technology to Chinese affiliates and local joint venture partners. Other Chinese government programs that subsidized research and the licensing of foreign technology supported these efforts. When the US government threatened to file a WTO case against China’s local content requirements, China quietly dropped them.1 By the time the legal requirement was formally rescinded, however, indigenous firms and Sino-foreign joint ventures dominated the Chinese market. The biggest wind farm build-out in history was supplied overwhelmingly with domestic equipment.

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United States Data Center Energy Usage Report Shehabi, A., Smith, S.J., Sartor, D.A., Brown, R.E., Herrlin, M., Koomey, J.G., Masanet, E.R., Horner, N., Azevedo, I.L., Lintner, W.

This report estimates historical data center electricity consumption back to 2000, relying on previous studies and historical shipment data, and forecasts consumption out to 2020 based on new trends and the most recent data available. Figure ES-1 provides an estimate of total U.S. data center electricity use (servers, storage, network equipment, and infrastructure) from 2000-2020. In 2014, data centers in the U.S. consumed an estimated 70 billion kWh, representing about 1.8% of total U.S. electricity consumption. Current study results show data center electricity consumption increased by about 4% from 2010-2014, a large shift from the 24% percent increase estimated from 2005-2010 and the nearly 90% increase estimated from 2000-2005. Energy use is expected to continue slightly increasing in the near future, increasing 4% from 2014-2020, the same rate as the past five years. Based on current trend estimates, U.S. data centers are projected to consume approximately 73 billion kWh in 2020.

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National Research Council report on “Assessment of Technologies for Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles” (author and committee member)

Medium- and heavy-duty trucks, motor coaches, and transit buses – collectively, “medium- and heavy-duty vehicles”, or MHDVs – are used in every sector of the economy. The fuel consumption and greenhouse gas emissions of MHDVs have become a focus of legislative and regulatory action in the past few years. Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two is a follow-on to the National Research Council’s 2010 report, Technologies and Approaches to Reducing the Fuel Consumption of Medium-and Heavy-Duty Vehicles. That report provided a series of findings and recommendations on the development of regulations for reducing fuel consumption of MHDVs.

Online article ]

Developing robust energy efficiency policies while accounting for consumer behavior Azevedo, I.L., Sonnberger, M., Thomas, B., Morgan, G., Renn, O. International Risk Governance Council (IRGC) report

In recent years, energy efficiency policies have been deployed or
suggested across the world, as part of countries’ energy policies
and/or as a way to achieve climate change mitigation goals. Drivers
for the promotion of energy efficiency policies include a desire
to reduce energy consumption and in particular dependence on foreign fuel supply, to lower greenhouse gas (GHG) emissions in order to mitigate the impacts of climate change, to reduce criteria air pollutants, and to provide affordable energy services. While it is widely acknowledged that there is still a large potential for energy
and greenhouse gas savings, the design of effective policies to
realise that potential is challenging. As consumers pursue cost-effective energy efficiency investments, they will have economic savings over the lifetime of their investment. Questions about how these economic savings are used by the consumers have led to a long debate in the energy economics and energy policy literature on whether some of the theoretically estimated gain in energy efficiency will be eroded as consumers consume additional goods and services. In this report, we summarise the findings from two workshops on the topic of “Energy Efficiency Policies and the Rebound Effect”.

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National Research Council (Committee Member). Assessment of solid-state lighting (Committee Member) Contributor to three of six chapters in this report

Solid-state lighting (SSL) is a new technology that has evolved from a few key inven- tions involving light-emitting diodes (LEDs) in the 1960s and spurred more recently by fundamental breakthroughs in LEDs made in the 1990s. As such, SSL lighting is not a re nement of an incumbent lighting technology but has evolved in parallel with, if more rapidly than, the incandescent and uorescent lamps familiar to consumers. As discussed in this report, SSL lighting not only can offer improvements in ef cacy (i.e., the ability to deliver the same amount of light using less electricity) and improved durability and the convenience of less frequent maintenance (e.g., in roadway lighting or in aviation), but also opens up the possibility of new applications owing to the technology’s high performance in cold environments, long life, and new form factors.

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Modeling technology learning for electricity supply technologies. Phase II report for the Electric Power Research Institute. Azevedo, I.L., Jaramillo, P., Rubin, E., Yeh, S. Phase II report for the Electric Power Research Institute. , 2013

This study illustrates how alternative and supplemental community-level greenhouse gas (GHG) inventory techniques could improve climate action planning. Eighteen US community GHG inventories are reviewed for current practice. Inventory techniques could be improved by disaggregating the sectors reported, reporting inventory uncertainty and variability, and aligning inventories with local organizations that could facilitate emissions reductions. The potential advantages and challenges of supplementing inventories with comparative benchmarks are also discussed. While GHG inventorying and climate action planning are nascent fields, these techniques can improve CAP design, help communities set more meaningful emission reduction targets, and facilitate CAP implementation and progress monitoring.

PDF ] [ Online article ]

Modeling technology learning for electricity supply technologies. Phase I report for the Electric Power Research Institute. Azevedo, I.L., Jaramillo, P., Rubin, E., Yeh, S. Phase I report for the Electric Power Research Institute

An econometric study of the Portuguese residential electricity consumption is presented, with a focus on the influence of dwelling characteristics on consumption. The relationship between the dwelling and household characteristics on per capita residential electricity consumption is estimated at two different scales, involving two distinct databases: the first includes data at the municipality level for 2001, the second is the most recent Portuguese consumer expenditure survey that was collected in 2005 and 2006. The results of the analysis at both scales are consistent and indicate that household and dwelling characteristics have a significant influence on residential electricity consumption. Our results show that in Portugal the direct effect of income on electricity consumption is low and becomes smaller when more relevant control variables are included in the analysis. Future demand of electricity in Portugal will be significantly influenced by trends in socioeconomic factors as well as changes in the building stock. These trends should be taken in consideration in the formulation of policy measures to reduce electricity consumption.

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Policymaker Guide: Managing Variable Energy Resources to Increase Renewable Electricity’s Contribution to the Grid

In this analysis, we projected Japan’s energy demand/supply and energy-related CO2 emissions to 2050. Our analysis of various scenarios indicated that Japan’s CO2 emissions in 2050 could be potentially reduced by 26-58% from the current level (FY 2005) (Figure 1). These results suggest that Japan could set a CO2 emission reduction target for 2050 at between 30% and 60%. In order to reduce CO2 emissions by 60% in 2050 from the present level, Japan will have to strongly promote energy conservation at the same pace as an annual rate of 1.9% after the oil crises (to cut primary energy demand per GDP (TPES/GDP) in 2050 by 60% from 2005) and expand the share of non-fossil energy sources in total primary energy supply in 2050 to 50% (to reduce CO2 emissions per primary energy demand (CO2/TPES) in 2050 by 40% from 2005). Concerning power generation mix in 2050, nuclear power will account for 60%, solar and other renewable energy sources for 20%, hydro power for 10% and fossil-fired generation for 10%, indicating substantial shift away from fossil fuel in electric power supply. Among the mitigation measures in the case of reducing CO2 emissions by 60% in 2050, energy conservation will make the greatest contribution to the emission reduction, being followed by solar power, nuclear power and other renewable energy sources (Figure 2). In order to realize this massive CO2 abatement, however, Japan will have to overcome technological and economic challenges including the large-scale deployment of nuclear power and renewable technologies.
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Japan’s long-term energy demand and supply: scenario to 2050. Institute of Energy Econ. Komiyama, R., Marnay, C., Stadler, M., Lai, J., Borgeson, S., Coffey, B., Azevedo, I. L. Japan

In this analysis, we projected Japan’s energy demand/supply and energy-related CO2 emissions to 2050. Our analysis of various scenarios indicated that Japan’s CO2 emissions in 2050 could be potentially reduced by 26-58% from the current level (FY 2005 (Figure 1). These results suggest that Japan could set a CO2 emission reduction target for 2050 at between 30% and 60%. In order to reduce CO2 emissions by 60% in 2050 from the present level, Japan will have to strongly promote energy conservation at the same pace as an annual rate of 1.9% after the oil crises (to cut primary energy demand per GDP (TPES/GDP) in 2050 by 60% from 2005) and expand the share of non-fossil energy sources in total primary energy supply in 2050 to 50 (to reduce CO2 emissions per primary energy demand (CO2/TPES) in 2050 by 40% from 2005). Concerning power generation mix in 2050, nuclear power will account for 60%, solar and other renewable energy sources for 20%, hydro power for 10% and fossil-fired generation for 10%, indicating substantial shift away from fossil fuel in electric power supply. Among the mitigation measures in the case of reducing CO2 emissions by 60% in 2050, energy conservation will make the greatest contribution to the emission reduction, being followed by solar power, nuclear power and other renewable energy sources (Figure 2). In order to realize this massive CO2 abatement, however, Japan will have to overcome technological and economic challenges including the large-scale deployment of nuclear power and renewable technologies.

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The open source stochastic building simulation tool SLBM and its capabilities to capture uncertainty of policymaking in the U.S. building sector Stadler, M., Marnay, C., Azevedo, I.L, Komiyama, R., and Lai, J. , LBNL-1884E. May 2009.

The increasing concern about climate change as well as the expected direct environmental economic impacts of global warming will put considerable constraints on the US building sector, which consumes roughly 48% of the total primary energy, making it the biggest single source of CO2 emissions. It is obvious that the battle against climate change can only be won by considering innovative building approaches and consumer behaviors and bringing new, effective low carbon technologies to the building / consumer market. However, the limited time given to mitigate climate change is unforgiving to misled research and / or policy. This is the reason why Lawrence Berkeley National Lab is working on an open source long range Stochastic Lite Building Module (SLBM) to estimate the impact of different policies and consumer behavior on the market penetration of low carbon building technologies. SLBM is designed to be a fast running, user-friendly model that analysts can readily run and modify in its entirety through a visual interface. The tool is fundamentally an engineering-economic model with technology adoption decisions based on cost and energy performance characteristics of competing technologies. It also incorporates consumer preferences and passive building systems as well as interactions between technologies (such as internal heat gains). Furthermore, everything is based on service demand, e.g. a certain temperature or luminous intensity, instead of energy intensities. The core objectives of this paper are to demonstrate the practical approach used, to start a discussion process between relevant stakeholders and to build collaborations.

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Cap and trade is not enough: Improving U.S. climate policy Samaras, C., Apt J., Azevedo, I.L., Lave, L.B., Morgan, M.G., Rubin, E.S. Department of Engineering and Public Policy, Carnegie Mellon University

A market-based mechanism (e.g. cap and trade or a carbon tax) is likely to be a key part of America’s strategy to reduce carbon dioxide (CO2) emissions. We need to do this soon so that a framework for emissions reductions is established. However, for at least the next decade, a market-based approach alone will not induce the investments in long-lived technology needed to put the nation on a track to achieve a 50 to 80% reduction in emissions of carbon dioxide by mid-century. The range of prices for CO2 being discussed will be too low to make this happen.

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