The U.S. has agreed to cut its greenhouse gas emissions by 26-28 percent by 2025 and by 80 percent by 2050, compared to 2005 levels. To meet these goals, a large proportion of electricity that otherwise would have been produced from fossil fuels will need to be generated instead by low-carbon sources—most likely wind and solar power.
Because wind and solar power production depend on the weather, they are variable. This variability of wind and solar power introduces unique challenges to those who must maintain the constant balance between energy supply and demand required for a stable electric power grid. Unless and until energy storage is economical, “flexibility” in the power grid is key to its efficient operation. Improved forecasting across a range of time scales for wind and solar resources will provide critical flexibility and facilitate integration of weather-dependent renewable energy.
There are several ways forecast skill can be improved. One way is to better model atmospheric phenomena, by improving various parts of the weather models known as “schemes” and the mathematical coupling of these “schemes” to other schemes. Another way of improving forecast skill is to improve the data assimilation methods, and another approach is to improve our observations of relevant phenomena. The Earth System Research Laboratory (ESRL) is working on all of these.
ESRL has recently begun to optimize two of its numerical weather prediction (NWP) models—the Rapid Refresh and the High Resolution Rapid Refresh—for wind and solar applications. Specifically, research being done to improve forecast skill is targeting the intersection of wind and power with the atmosphere, including processes such as: turbulence, low level jets, shear, and formation and movement of clouds and aerosols.
ESRL is also performing research to determine the optimal suite of sensors in a national observation network to support integration of wind and solar into the power system. More vertical profiles of winds and more and higher-quality observations of solar irradiance (both total and direct) would support improvements in forecast skill. In the first Wind Forecast Improvement Project, ESRL and its partners were able to collect additional vertical profiles of winds with instruments that were available for the duration of the twelve-month field campaign. Several utility companies and Independent System Operators (ISOs) are helping fill the gap in observations by sharing with NOAA the meteorological measurements they collect at wind and solar plants.
Further research needs include an improved understanding of the co-variability of wind and solar resources, together with energy demand, on broader spatial and temporal scales; research to identify whether and how large-scale climate drivers, such as the El Nino Southern Oscillation and the Pacific Decadal Oscillation, affect wind and solar resources; and improved predictions at two-week, seasonal, annual, and decadal time scales.