The German hydropower industry
Hydropower, which is more than one hundred years old, is the oldest technology used for generating power. Today, more than one fifth of the world’s electricity is generated from this energy source. There are three basic types of hydroelectric power plants: run-of-river, impoundment and pumped storage power plants. Hydropower plants make a substantial contribution to ensuring base load and grid stability because, as in the case of pumped storage power plants, they can store energy.
Run-of-river power plants
This type of construction is the most common. Run-of-river power plants achieve an efficiency of almost 94 % and are generally used to cover the base load. The turbines in a run-of-river power plant use the entire flow energy of the respective river or canal, whereby the plant’s capacity is determined by the flow velocity and depth of water. Some run-of-river power plants can store water when there are low energy requirements, and then use it as reserve water at times of increased electricity demand. A specific form of run-of-river power plants is the diversion hydropower plant. Here water is dammed with a weir and redirected through a separate feeder channel where it drives the turbines. Whereas with standard run-of-river power plants there is only a slight difference in height between the upper and lower water levels, diversion hydropower plants exploit the greater head created by the damming.
Run-of-river and river hydropower plants generally use Kaplan turbines, which were developed by the Austrian professor Viktor Kaplan in 1913. The runners for these turbines are similar to ship propellers, with adjustable blades. The water is swirled through a spiral and directed through a wicket gate parallel to the blade-operating rod onto the runners.
Impoundment hydropower plants
With impoundment hydropower plants, the water is stored behind a dam in a natural or artificial lake and is fed into the lower-lying power station through a penstock. The water is forced by gravity through the penstock and drives the turbines. These power plants are particularly suitable for balancing out deviations in both regional and national electricity production and consumption, since impoundment hydropower plants can function independently of natural water flows.
Pumped storage power plants
In contrast to impoundment hydropower plants, pumped storage power plants use two water reservoirs to store water, whereby there should be as great a difference in height as possible between the upper and lower reservoirs. When the electricity supply exceeds the electricity demand and there is excess capacity, the water is pumped from the lower to the upper reservoir and is stored there for generating electricity during peak load periods. Pelton turbines, which are impulse-type turbines, are generally used to drive the generators. Here one or more nozzles direct jets of water at extremely high speed against a series of blades attached to the edge of the turbine wheel.
In the case of high-pressure hydropower plants, water is fed at high speed from a dam through the penstock to the power plant below. The large head creates high pressure on the turbines that drive the alternating current generators.
Economic viability and safety
Although the construction of large-scale hydropower plants requires considerable investment, it can certainly prove to be a worthwhile undertaking. This is because hydropower plants have a very long service life, a high operational safety and an efficiency of 75 % to 90 %, with production costs only slightly above those of electricity produced from nuclear and fossil fuels. Furthermore, hydropower plants increase supply security, do not emit pollution and hardly any heat, reduce the dependence on energy imports – with its attendant risks – and form a base for development in countries without extensive energy supplies but sufficient water resources. German companies export cutting-edge technologies and comprehensive services.
Development in Germany and worldwide
In 2006, around 21.6 billion kilowatt hours of electricity were generated in Germany using hydropower. Hydropower thus meets 3.5 % of the gross electricity demand or the requirements of more than six million households.
After wind energy, hydropower generates the largest proportion of electricity from renewable energy and, thanks to the improved conditions provided by the German Renewable Energy Sources Act, its use has increased. Plants have been modernised, and previously disused plants have been reactivated. The total installed capacity in Germany at the end of 2006 stood at around 4,700 megawatts, generated from around 7,500 hydropower plants. However, thanks to the amendment to the Renewable Energy Sources Act, the German Federal Ministry for the Environment forecasts that the next few years in Germany will see a dramatic rise in the amount of electricity produced by hydropower.
Hydropower meets 17 % of the world’s electricity demand, which is about the same amount of electricity that nuclear power provides. In more than 20 countries it produces over 90 % of the electricity generated, amounting to even 95 % in Norway and Paraguay. Canada, Brazil and China are the three largest producers of electricity from hydropower.
Regulatory framework
The construction of large hydropower plants has a considerable environmental impact, particularly where the necessary head has to be created artificially. When designing hydropower plants, it is necessary to take into account legal provisions pertaining to water, the environment and nature conservation, including the duration of administrative procedures.
Both European and German legislation lay down strict requirements for constructing or expanding hydropower plants. An example of this is the EU Water Framework Directive. Both the operation of existing plants and the construction of new plants are subject to extensive restrictions. Beside secure investment conditions, the existence of long term depreciation possibilities must also be proved.
In order to tap the remaining potential in Germany, the German Federal Ministry for the Environment is promoting the construction of small hydropower plants by granting more favourable loans. The Renewable Energy Sources Act stipulates that hydropower plants with a capacity of up to five megawatts shall be paid a minimum subsidy of 6.65 cents per kilowatt hour for a duration of 30 years. Plants with a capacity of more than 5 megawatts are subsidized at a rate of almost 8 cents per kilowatt hour.
