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Selected Publications

  • Energy storage deployment and innovation for the clean energy transition

    The clean energy transition requires a co-evolution of innovation, investment, and deployment strategies for emerging energy storage technologies. A deeply decarbonized energy system research platform needs materials science advances in battery technology to overcome the intermittency challenges of wind and solar electricity. Simultaneously, policies designed to build market growth and innovation in battery storage may complement cost reductions across a suite of clean energy technologies. Further integration of R&D and deployment of new storage technologies paves a clear route toward cost-eective low-carbon electricity. Here we analyse deployment and innovation using a two-factor model that integrates the value of investment in materials innovation and technology deployment over time from an empirical dataset covering battery storage technology. Complementary advances in battery storage are of utmost importance to decarbonization alongside improvements in renewable electricity sources. We find and chart a viable path to dispatchable US$1 W−1 solar with US$100 kWh−1 battery storage that enables combinations of solar, wind, and storage to compete directly with fossil-based electricity options.

  • Energy return on investment (EROI) of mini-hydro and solar PV systems designed for a mini-grid

    With dramatic cost declines and performance improvements, both mini-hydropower and solar photovoltaics (PV) now serve as core options to meet the growing demand for electricity in underserved regions worldwide. We compare the net energy return on energy invested (EROI) of mini-hydropower and solar electricity using five existing mini-hydropower installations in northern Thailand with grid-connected solar PV simulations. Both assessments use a life cycle perspective to estimate the EROI. We find that distributed mini-grids with penetrations of solar PV up to 50% of annual generation can exceed the EROI of some fossil-based traditional centralized grid systems. The analysis will help planners and engineers optimize mini-grids for energy payback and utilize local resources in their design. The results suggest higher EROI ratios for mini-hydropower plants than solar PV, though mini-hydropower plants typically yield lower EROI ratios than their large-scale hydropower counterparts.

  • Scenarios to decarbonize residential water heating in California

    This paper presents the first detailed long-term stock turnover model to investigate scenarios to decarbonize the residential water heating sector in California, which is currently dominated by natural gas. We model a mix of water heating (WH) technologies including conventional and on-demand (tank-less) natural gas heating, electric resistance, existing electric heat pumps, advanced heat pumps with low global warming refrigerants and solar thermal water heaters. Technically feasible policy scenarios are developed by considering combinations of WH technologies with efficiency gains within each technology, lowering global warming potential of refrigerants and decreasing grid carbon intensity. We then evaluate energy demand, emissions and equipment replacement costs of the pathways. We develop multiple scenarios by which the annual greenhouse gas emissions from residential water heaters in California can be reduced by over 80% from 1990 levels resulting in an annual savings of over 10 Million Metric Tons by 2050. The overall cost of transition will depend on future cost reductions in heat pump and solar thermal water heating equipment, energy costs, and hot water consumption.

  • Effective Policy for Reducing Poverty and Inequality? The Earned Income Tax Credit and the Distribution of Income

    Forthcoming, Journal of Human Resources. (Joint with Ankur Patel)

    We examine the effect of the EITC on the poverty and income of single mothers with children using a quasi-experiment approach that leverages variation in generosity due to policy expansions across tax years and family sizes. We find that the income increasing effects of the EITC are concentrated between 75% and 150% of income-to-poverty with little effect at the lowest income levels (50% poverty and below) and at levels of 250% of poverty and higher. Specifically, a policy-induced $1000 increase in the EITC leads to an 8.4 percentage point reduction in the share of families with after tax and transfer income below 100% poverty. These results are robust to a rich set of controls and whether we compare single women with and without children or compare women with one child versus women with two or more children. They are also robust to whether we limit our analysis to the sharp increase in the 1993 expansion or use the full period of policy expansion, back to the 1986 Tax Reform Act. Importantly, event study estimates show no evidence of differential pre-trends, providing strong evidence in support of our research design. We use these results to show that by capturing the indirect effects of the credit on earnings, static calculations of the anti-poverty effects of the EITC (such as those released based on the Supplemental Poverty Measure) may be underestimated by almost 50 percent. Ours is the first paper to simultaneously estimate the combined direct and indirect effects of the EITC, to quantify how much we miss by ignoring the behavior effect, and to estimate the effects across the income distribution. 

  • Pulling Out of Paris: Why the United States’ Withdrawal Will Not Much Matter

    The Article reviews the United States’ recent decision to withdraw from the Paris Accord and recounts some of the most prominent policy discussions surrounding this decision. The Article goes on to explain, that these policy discussions reject science in favor of short-term political gains. The Article reviews new scientific reports which indicates that sea level rise may be far worse than expected, due in large part to the fact that previous computer models never looked beyond the year 2100. As this Article highlights, our policy discussions have become so heavily focused on the near future that we have created a distorted perception of time that doesn’t mesh with reality. This Article urges policy-makers to take real action on climate now, before it is too late. 

  • Three years to safeguard our climate

    Christiana Figueres and colleagues set out a six-point plan for turning the tide of the world’s carbon dioxide by 2020. Three years to safeguard our climate

  • Sustainable Design of Communities

    Moving beyond a focus on solar roofs for single-family homes, ambitious projects are attempting to join blocks of buildings into sustainable units

  • Evaluation of a proposal for reliable low-cost grid power with 100% wind, water, and solar

    A number of analyses, meta-analyses, and assessments, including those performed by the Intergovernmental Panel on Climate Change, the National Oceanic and Atmospheric Administration, the National Renewable Energy Laboratory, and the International Energy Agency, have concluded that deployment of a diverse portfolio of clean energy technologies makes a transition to a low-carbon-emission energy system both more feasible and less costly than other pathways. In contrast, Jacobson et al. [Jacobson MZ, Delucchi MA, Cameron MA, Frew BA (2015) Proc Natl Acad Sci USA 112(49):15060–15065] argue that it is feasible to provide “low-cost solutions to the grid reliability problem with 100% penetration of WWS [wind, water and solar power] across all energy sectors in the continental United States between 2050 and 2055”, with only electricity and hydrogen as energy carriers. In this paper, we evaluate that study and find significant shortcomings in the analysis. In particular, we point out that this work used invalid modeling tools, contained modeling errors, and made implausible and inadequately supported assumptions. Policy makers should treat with caution any visions of a rapid, reliable, and low-cost transition to entire energy systems that relies almost exclusively on wind, solar, and hydroelectric power.