ARB Research Seminar

This page updated July 23, 2013

Optimal Investment in Wind and Solar Power in California, 2010-2025

Dr. Matthias Fripp, Research Fellow, Environmental Change Institute, Oxford University, United Kingdom

February 17, 2009
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Wind and solar power are increasingly attractive sources of electricity as their costs fall and our desire to avoid greenhouse gas emissions rises. However, these technologies generate power only when the wind and sun are available, so it is unclear how large a role they should play in California's power system in the future.

To address this question, a new model has been developed that seeks to identify the least expensive set of investments in wind, solar and conventional generators and transmission lines, to provide a reliable power supply for California in 2010–25, while accounting for the value of avoiding carbon dioxide emissions. The Switch model (a loose acronym for solar, wind, hydro, and conventional generators and transmission) optimizes future investments in generators and transmission capacity, based on a detailed representation of the hour-by-hour behavior of each of these components. Weather conditions during each hour of the study are based on historical data, so that the optimization incorporates any correlation between wind, sunshine and loads throughout the state.

This model provides a new ability to see how the optimal design of the power system changes depending on the costs that are forecast for generators, fuel and greenhouse gas emissions. This makes it possible to assess how far electricity-sector emissions can be reduced while remaining within a pre-set financial budget, or conversely, to identify the minimum cost of achieving any level of emission reductions.

The Switch model has been used to develop several outputs that are potentially useful to California policymakers. For example, a “supply curve” shows the magnitude of emission reductions that could be achieved in California's electric power system if carbon dioxide emissions are valued at various levels between $0 and $200/ton. In principle, this could be combined with similar supply curves from other sectors in order to allocate emission reduction targets efficiently among all sectors of the economy.

Economic factors have been investigated that are likely to limit the use of renewable power, as such, cost of power will rise gradually if wind and solar power are used on a larger scale: in part because these resources will need increasing amounts of backup power from other sources, but more importantly, because they will eventually begin to generate unneeded power during some hours. However, there appears to be no sharp limit to the cost-effective use of these technologies, even when providing half or more of the system’s power.

Speaker Biography

Matthias Fripp, Ph.D., is the Next Era Research Fellow in Renewable Energy at the University of Oxford, United Kingdom. Dr. Fripp's research focuses on using optimization models to assess the role that renewable energy should play in large-scale power systems in the next two decades. Dr. Fripp's dissertation research addressed this question in the State of California, and he is currently working to replicate this analysis in the United Kingdom, and to extend it to consider the potential for dramatic emission reductions if renewable resources are complemented by strong demand-side responses – e.g., well-timed charging of plug-in hybrid-electric vehicles.

Dr. Fripp holds a Ph.D. and Master’s degree from the Energy and Resources Group at the University of California, Berkeley. He has previously worked as a modeler and researcher at Lawrence Berkeley National Laboratory, Trexler Climate+Energy Services, Inc., and the Renewable Northwest Project.

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