Drinking water – a source of clean hydropower
The drinking water hydropower plant in Mauer
The drinking water hydropower plant in Mauer - a former suburb that is now part of Vienna's 23rd district - generates electricity in an environmentally sound manner and reduces the pressure of the incoming water stream to the level required in Vienna's distribution system. In the protected mountain spring zones and along the two pipelines that transport drinking water to Vienna, the water flow drives 14 power plants, generating some 65 million kilowatt-hours of electricity p.a. - enough to meet the power requirements of a city with 50,000 inhabitants.
Almost all tap water in Vienna comes from mountain spring zones in the Alpine ranges of the provinces of Styria and Lower Austria. From the protected spring zone the water is brought to the city in two pipelines. Given the difference in elevation, no pumps are needed for the transport, which covers considerable distances - 180 kilometres in the case of water from the Styrian Hochschwab range. Under the force of gravity, the water pressure in the pipelines builds up to levels which are too high for Vienna's distribution network - hence the need to bring down pressure as the water enters the city. In the past, this used to be done at considerable expense by means of hydraulic pressure-reducing valves (Clayton valves). But in 2006, this technology was replaced by the Mauer drinking water power plant.
Austrian national legislation (Ökostromgesetz) promotes the generation of electricity from renewable sources, and a regulation of the Federal Ministry of Economy ensures that "green" electricity is purchased at a subsidised tariff. This is the legal basis that makes the operation of the drinking water power plants economically viable. Vienna Waterworks (Municipal Department 31) concluded a contract with a private partner - the Hochquellstrom-Vertriebs GmbH, a subsidiary of Siemens Austria AG - for the construction and operation of a hydropower plant in the Mauer pressure reduction chamber of the Second Vienna Mountain Spring Pipeline. Under the terms of the contract, Hochquellstrom-Vertriebs GmbH financed and built the Mauer power plant in return for the revenue generated by power sales during the first 13 years of operation. This revenue is used by the Siemens subsidiary to cover its refinancing requirements. At the end of the 13-year period, the City of Vienna will take possession of the power plant (at fair value). The heart of the power plant is a Francis turbine. Every second, about 2,000 litres of drinking water flow over it, falling some 30 metres before being fed into Vienna's distribution system. Thus, the Mauer power plant generates about three million kilowatt-hours of electricity every year without any ill effect on the quality of the drinking water. The power is used to cover the electricity needs of some 1,000 households. The Mauer power plant is an economically viable operation, the desired pressure reduction being achieved automatically without causing any additional expense.
All in all, there are 14 drinking water power plants which generate about 65 million kilowatt-hours of electricity per year; thus the Vienna Waterworks make an important contribution to the production of environment-friendly energy. Additional the City is working on producing more ecoelectricity.
Facts & Figures
Hydropower plant Mauer:
- Start of operation: 2006
- Term of the partnership contract with Siemens: until 2019
- Capital invested EUR 1.25 million
- Annual electricity generation: 3 million kWh
- Installation of a Francis turbine with 400 kW output power
- Water flow rate: 2,000 l/s
- The Vienna Waterworks run 12 drinking water power plants (one in Vienna Mauer, 7 in the Wildalpen, 4 in the Hirschwang spring zone). Two more plants are run by Wien Energie in Gaming (Lower Austria).
- Total electricity generated p.a.: approx. 65 million kWh
Drinking water in Vienna:
- Length of distribution network: more than 3,000 km of public water mains
- Building supply lines: more than 102,000
- Drinking water sources:
First Mountain Spring Pipeline:
220,000 m³ per day
Second Mountain Spring Pipeline:
217,000 m³ per day
Lobau groundwater pumping station: 80,000 m³ per day
Moosbrunn groundwater pumping station: 62,000 m³ per day
Several minor water sources: 10,000 m³ per day
- Achievable maximum supply volume: 589,000 m³ per day
- Average quantity consumed: 375,000 m³ per day
DI (FH) Volker Schaffler
Tel. +43 1 4000 84269
Fax +43 1 4000 7997