28
A World Bank Study
Other planning initiatives include expanding the use of electricity storage, including a dena program for using the natural gas grid. Excess electricity would be used to produce hydrogen, which can then be fed into the natural gas network or processed into synthetic gas and stored for later use. The German TSOs utilize several forecasting services at the same time and use a weighted sum of these forecasts adjusted to observed weather patterns. For example, Amprion uses 10 different wind forecasts, which are entered into a “combination tool,” which then produces an optimal forecast taking into account the weather situation. Due to the implementation of these aggregate forecasting methods, the day-ahead wind power production forecast root mean square error for Germany as a whole averages about 4.5 percent (European Wind Energy Association 2010). TSOs sell the day-ahead forecasted amount into the day-ahead spot market; they also sell the difference between the day-ahead and intraday forecast into the intraday spot market. Any remaining deviations are covered by balancing reserves. Table 1.7 provides a synopsis of wind integration in Germany.
Spain Spain has a peak demand of about 45 gigawatts and an off-peak demand ranging between 19 and 25 gigawatts. Wind energy penetration has been as high as 54 percent, occurring in August 2009 (LÛpez 2010). Nearly all of the electricity consumed in Spain is generated domestically, with less than 1 percent imported from outside the country. Generation from solar PVs has increased in Spain from 40 gigawatts-hour in 2005 to 5,347 gigawatts-hour in 2009. Only 2 percent of solar PVs are connected to the transmission grid in Spain; the remaining are connected to the distribution grid and cannot be observed by the Red Electrica de España (REE). Nearly all of the solar PVs in Spain are connected to the distribution grid, while 70 percent of the CSP in Spain is connected to the transmission grid. Lack of grid operator awareness of solar PVs is considered a problem, as the PV plants Table 1.7 Synopsis of Wind Integration in Germany Integration issue
Synopsis
Ancillary services
Variable generation imbalances shared by the four transmission system operators (TSOs). Secondary reserve system has reduced need for all reserves except for regulation, which has remained the same. Loop flows on high wind production days significant. Net transmission capacity available on interties between Germany and other countries determined in part by wind forecast TSOs use ensemble forecasting and have a 4.5 percent root square mean error rate for country as a whole. Grid codes put in place for wind in 2005 and recently extended to solar Procedures to manage unscheduled and loop flow within the country and with neighboring countries
Integration issues
Integration strategies
Source: World Bank data.