Under the Letter of Intent (LoI), the companies aim to look into the economic and technical feasibility of integrating wind and water as energy supply.
If the results of the study are positive, the detailed planning can start as early as 2011.
The wind farms and pumped storage will probably be built at the Sundern waste heap near Hamm-Pelkum, Germany.
The planned combined power plant will use wind power at times of high wind output to pump the water of the pumped-storage power plant from a low-lying reservoir to a reservoir on top of the waste heap, some 50 m higher up.
Whenever the demand for power is high, the water is discharged back into the lower reservoir through a turbine which produces electricity. The volume of the reservoir will probably be some 600,000 m3 – roughly the equivalent of the storage volume of about 75,000 car batteries (mid-range vehicles). The pumped-storage power plant will provide a capacity of 15-20 MW.
Prof. Fritz Vahrenholt, Chairman of the Board of Directors of RWE Innogy, says: “We urgently need smart schemes to balance the natural fluctuations of wind power. Otherwise we’ll soon come to our natural limits in the growth of renewables.
“Spoil heaps may prove to be really valuable in this. They are up to 100 m high and their potential wind output is excellent. Also, the gradient of a spoil heap can be used for the operation of a pumped-storage power plant – a topographical requirement which we don’t often have in northern Germany. Another important benefit is that we don’t need to interfere with any naturally grown landscape on a spoil heap so that the project should be far more acceptable to the population.”
RAG and RWE want to work together on further projects if similar integrated energy schemes turn out to be feasible on other waste heaps in North-Rhine Westphalia.