getting to large-scale solar integration
For Better Integration,
Improve the Forecast
rAnDY MonToYA/ SAnDIA nATIonAL LABorATorIES
Accurate solar irradiance forecasts will
enable power grid operators to make
better scheduling decisions about
the optimal mix of power generation
sources, and to avoid excessive back-up reserves.
Solar energy has more potential to provide power than any other known sustainable or renew- able energy source (Edenhofer, 2011; Lewis, 2007; Lewis and Nocera, 2006). As increas- ing amounts of solar power are being used to meet electricity demands, solar irradiance forecasts are becoming more important for efficient and reliable power grid operations. The most important time scales for operation of the power grid are the day-ahead,
hour-ahead and minute-ahead scales (Ihnen, 2009), though longer-term forecasts are necessary for
planning purposes. In addition to forecasts of future solar radiation, it’s valuable for grid planners to
have an analysis of current conditions. This analysis can be used to make short-term decisions about
power distribution. Such a “nowcast” can be made from ground- or satellite-based observations (e.g.,
GOES satellite radiation products) or from a 3-D cloud analysis.
Because of the variability of solar (and wind) resources, the solar industry needs more accurate
weather forecasts than have been required. The value of wind forecasts to the wind energy industry is
well established. The public and private sectors are investing in improved forecasts of winds at turbine
height to facilitate wind integration (Marquis et al., 2011). To facilitate integration of photovoltaic
(PV) and concentrating solar power (CSP) into the nation’s grid, the industry needs reliable forecasts
of clouds (cloud type, structure, optical thickness and height), water vapor and aerosols. Figure 1 shows
different types of clouds and aerosols. Accurate solar irradiance forecasts will enable power grid opera-
