Emsland power plant
Lower Saxony's Lingen has three power-plant units on a natural-gas basis installed today. Units B and C were commissioned in 1974/75, and 2010 saw the combined-cycle gas turbine (CCGT) plant going on stream as unit D with a capacity of 887 MW. The Lingen gas-fired plants are thermal power plants and use natural gas to evaporate water and drive a turbine with connected generator. However, units B and C differ from unit D in one important detail: B and C produce the steam with a gas-firing system, but unit D entirely with the hot exhaust gas from the gas turbines. Due to the deterioration in prices on the wholesale market and the increasing feed-in of renewables, in particular photovoltaics, we have taken the power plant units offline for the summer months of 2014.
The units B and C – combined power
At the heart of the two 475-MW units B and C are two steam generators: In the year 2011, the gas turbines were replaced with two new Rolls Royce turbines. Total efficiency was now increased from 41 to 46%. The 200 million euro investment boosted the total efficiency of the combined-cycle units by up to 12% and lowered the CO2 emissions by over 45,000 tons a year – with the same power generation.
Unit D is setting standards worldwide in efficiency and environmental friendliness. Like the neighbouring units B and C, unit D, too, is designed for co-generation: the exhaust gases of the two gas turbines are conducted via two waste-heat boilers to a common steam turbine.
Gas and steam plant
Thanks to combined heat and power generation, up to 100 tons of process steam an hour can be extracted from the process. That means: some of the steam is withdrawn from the steam turbine and supplied to an industrial customer. CCGT technology and heat and power cogeneration add considerably to the efficiency of a natural-gas power plant, 59.2% in the case of unit D. Such an efficient use of fuel and heat also substantially reduces the CO2 emissions – for the sake of the environment and the climate.
Gas supply and gas pipe array
The Emsland natural-gas power plant benefits from its optimal linkup with the long-distance gas grid: RWE Generation obtains the fuel from five different supply grids. To further improve the gas supply of the power station, RWE Generation has in addition built a gas pipe array. This subterranean line, some 28 km long and about 1.50m thick, has been built some three kilometres distant from the power plant. It is used to stockpile fuel and can hold up to two million cubic metres of natural gas in readiness. The gas compressed to 100 bar by a compressor station on the power station grounds is equivalent to the quantity that the power plant needs for 12 hours of full-load operations. This enables short-term fluctuations in the electricity grid to be offset.