Flexibility of thermal power generation for RES supply in Germany until 2020

Abstract

EC Directives (EC in SEC 85/3, 2008; EP, EC in COM 19, 2008) give individual targets in emission reduction and renewable energy share to the member states of the European Union. Germany is obligated to reduce its green house gas emissions by 14 % until the year 2020 related to the year 2005 and to increase its share of renewable energy in the final energy consumption to 18 %. For electrical energy—which is the main topic of this paper—the portion of electricity based on renewable energy sources (RES) is projected to increased from 15 % in 2008 to 40 % until 2020 (Bundesministerium fur Umwelt, Naturschutz und Reaktorsicherheit, 2012). Because of the short period of time, this ambiguous target represents a big challenge in development of adequate renewable generation. The high shares of wind or PV in the supply system necessitates to expand the storage capacities, extend the transmission and distribution grids and improve flexible operation of the entire energy system, starting with generation and ending with demand side. Long term scenarios of electricity generation and demand in Europe until 2040 can be found in Eurel (2012). To maintain the high standard of security of supply in the German grid, a Task Force of VDE has investigated the needs to balance the German energy system under the aspect of high penetration of RES. For the analysis of the consequences for the non-renewable power generation, a simulation model of the German energy system had been elaborated, which considers the development of RES shown in the reference scenario (VDE AT40, 2012), for the following development of RES until the year 2020: wind 60 GW, PV 60 GW, run-of-river hydro 5 GW (constant) and biomass 7 GW. In total the installed power of RES might achieve 130 GW. Considering the coincidence of RES generation, it will touch the grid load many times over the year and to a small extend overshoot the existing demand. The system simulations show, that the thermal fleet will be facing load gradients of up to 15 GW/h over 1 h in the year 2020. These high gradients will need flexible thermal power plants, which will be able to respond to fast changing renewable generation. As the power plants will in future have only a capacity factor of 20 % it will be difficult to find an economic operation scheme within the existing electricity market model.