Latest Developments in the Field of Energy Storage: Isobaric Adiabatic Compressed Air Energy Storage Combined Cycle for Off/On-Shore Wind Power Storage with a High Efficiency Factor and High Peak Power

摘要

With the increasing use of renewable energy sources, which are temporally and locally only fluctuantly available like, for instance, solar or wind energy, energy storage devices gain increasing interest and even become essential with regard to higher shares of renewable power generation. The basic motivation for the large-scale storage of electrical energy is the saving of excess energy that is created in basic load power stations or through wind energy stations in times of light load, as well as through delayed dynamic dumps as high-load energy ("energy refinement") in times of increased demand. Further possible applications are secondary regulation (capacity frequency regulation) and the supply of swiftly deployable energy reserve capacities to increase the operational reliability of the electricity network. Here, the storage efficiency factor (dynamic dump energy / stored energy) is of decisive relevance and is currently highest in pumping-storage power stations at 80%. However, these require geographic altitude differences and vast storage capacities, resulting in high investment costs and long periods of planning and building. Compressed air and heat reservoirs constitute another possibility. Through the help of compressors that are driven by electric motors, compressed air is being grouted in caverns in the case of excess electricity generation and, if required, used as combustion air for a gas turbine, whereby the emitted electric power of the gas turbine is considerably higher as the gas turbine does not have to activate a compressor. Completed salt caverns possess capacities from 300,000 to 700,000 m~3 and have a depth range of 600 to 1,800 m. State of the art compressed air energy storage (CAES - Compressed Air Energy Storage) like that of E.ON Inc. in Huntorf (illustration 1) do not generally use heat reservoirs in which compression heat could be buffered. They store the compressed air by fluctuating the pressure of the air in the cavern between a multiple of the gas turbine inflow pressure (e.g. 70 bar) and a pressure level above the gas turbine inflow pressure (e.g. 40 bar) and a minimum pressure to avoid the closing of the cavern respectively (illustration 2). However, this means that, on the one hand, an unnecessarily high degree of compression power is required, which on the other hand is generally being partly dismantled in a throttle valve without being utilised.