Energiewerkstatt, Imwind, WEB Windenergie and Windkraft Simonsfeld jointly own the firm PS-KW Energieoptimierung with investment company Benevento to develop hydro-pumped storage plants to stock up reserves of electricity generation capacity, thus compensating for wind power's variability and being able to supply power when needed.
The company is in the early stages of planning the plants. It has two small projects with 100-150kW capacity under development, which could be commissioned in 2017 or 2018, and one large project with 400-700MW capacity, which could be ready in 2018 or 2019. The plants will be able to supply power at maximum output for up to eight hours, says managing director Arnold Kainz.
The value of combining wind with hydro is increasingly being recognised by the wind sector. Hydropower is already commonly used in mountainous Austria, both for direct energy generation in run-of-river plants and for electricity storage in pumped storage stations.
Around 58% of the country's 64TWh annual power generation is supplied by hydropower. There are 552 run-of-river hydropower stations, 102 pumped storage power stations and another 1,500 very small hydro plants, so potential to integrate the technologies is huge.
Kainz would not reveal the exact locations of the plants, but stresses that they have been chosen in areas that are not subject to nature or other protections. The plants will each have an upper and a lower water reservoir with a 300-metre height difference or more. The upper reservoir will be filled once,over a period of several months by tapping water from a local stream or river. At least one million cubic metres will be required for each of the smaller plant reservoirs. Beyond that, water levels will only have to be topped up to compensate for evaporation.
Unlike other forms of electricity capacity storage, such as batteries or compressed air systems, hydro-pumped storage technology is mature, efficient, does not require chemicals, needs little in the way of raw materials and is a safe form of energy, states Energiewerkstatt.
Under Austria's wind energy support system, wind generation receives a premium feed-in tariff for 13 years after the wind station is commissioned. For stations brought online in 2010 the rate is EUR0.097/kWh. From the 14th year, the wind power will have to be sold on the electricity market. The market value of the wind power could be higher if its variability can be ironed out by combining it with controllable pumped storage power.
Additionally, if wind power is generated when demand is minimal and its market value low, such as at night, the surplus can be used to pump water to the upper reservoirs of the pumped storage plants. When the market price of electricity is more attractive, the water will be allowed to flow down to the lower reservoir, driving turbines to generate power. For every 100kWh of wind energy used to pump water for storage, the hydro plant will be able to later deliver 75kWh. "We need at least EUR0.04/kWh for the system to be economically feasible," says Kainz. The price looks very competitive with other forms of energy generation.
The country has 620 wind turbines with 1GW of wind energy in operation. The country's eco-electricity law foresees an addition of 700MW of wind capacity by 2015. The Austrian National Renewable Energy Action Plan, delivered to the European Commission, forecasts 1.57GW being installed over the period 2010 to 2020, expected to raise Austria's total to about 2.57GW.