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Title: Improved electrical load match in California by combining solar thermal power plants with wind farms

item Vick, Brian
item Clark, Ray
item Mehos, Mark

Submitted to: National Solar Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/10/2008
Publication Date: 5/3/2008
Citation: Vick, B.D., Clark, R.N., Mehos, M. 2008. Improved electrical load match in California by combining solar thermal power plants with wind farms. In: Proceedings of the SOLAR 2008 Conference, May 3-8, 2008, San Diego, California. 2008 CDROM.

Interpretive Summary: California with its hydro, geothermal, wind, and solar energy is the second largest producer of renewable electricity in the United States (Washington state is the largest producer of renewable energy electricity due to high level of hydro power). Replacing fossil fuel electrical generation with renewable energy electrical generation will decrease the release of carbon dioxide into the atmosphere which will slow down the rapid increase in global warming (a goal of the California state government). However, in order for a much larger percentage of the total electrical generation in California to be from renewable energies like wind and solar, a better match between renewable energy generation and utility electrical load is required. Using wind farm production data and predicted production from a solar thermal power plant (with and without six hours of storage), a comparison was made between the renewable energy generation and the current utility load in California. On a monthly basis, wind farm generated electricity at the three major wind farm areas in California (Altamont Pass, east of San Francisco Bay area; Tehachapi Pass in the high desert between Tehachapi and Mojave; and San Gorgonio Pass in the low desert near Palm Springs) matches the utility load well during the highest electrical load months (May through September). Prediction of solar thermal power plant output also indicates a good match with utility load during these same high load months. Unfortunately, the hourly wind farm output during the day is not a very good match to the utility electrical load (i.e. in spring and summer the lowest wind speed generally occurs during mid-day when utility load is highest). If parabolic trough solar thermal power plants are installed in the Mojave Desert (similar to the 354 MW of plants that have been operating in Mojave Desert since 1990) then the solar electrical generation will help balance out the wind farm generation since highest solar generated electricity will be during mid-day. Adding six hours of solar thermal storage improved the utility load match significantly in the evening and reliability was also improved. Storage improves reliability because electrical production can remain at a high level even when there are lulls in the wind or clouds decrease the solar energy striking the parabolic trough mirrors. The solar energy from Mojave Desert and wind energy in the major wind farm areas are not a good match to utility load during the winter in California, but if the number of wind farms were increased east of San Diego, then the utility renewable energy match would be improved (this is because the wind energy is highest during the winter in this area). Currently in California, wind electrical generation only contributes 1.8% of total electricity and solar electrical generation only contributes 0.2%. Combining wind farms and solar thermal power plants with storage would allow a large percentage of the electrical load in California to be met by wind and solar energy due to a better match with utility load than by either renewable resource separately.

Technical Abstract: The ability of wind and solar electrical energy generation to match the current utility electrical load in California was analyzed. We compared the renewable electrical generation and the utility load in California using actual hourly wind farm data at two different locations and predicted hourly parabolic trough solar thermal output at one location. Solar energy electrical generation better matched the utility load than wind energy electrical generation; but the best match to utility load is a combination of wind and solar with six hours of molten salt storage. Also, the difference in seasonal wind generation at different locations in California, when combined with solar generation, could result in a substantial amount of the California utility electrical load being met by wind and solar energy.