Pumped-storage hydroelectricity
A pumped-storage power plant (also pumped storage plant (PSW ) or, especially in Switzerland, Umwälzwerk called ) is a special type of storage power plant and is used to store electrical energy by pumping up of water. This water is allowed to flow downhill again and later generated while using turbines and generators back electricity. The electrical energy is thus stored by the conversion into potential energy of the water and fed after conversion of potential energy into electric energy back into the network. Thus there is a close relationship to Hubspeicherkraftwerken where instead of water -resistant body be raised. Because of the limited efficiency (see below), the absorbed energy is recovered only partially. Nevertheless, pumped storage power plants are necessary and indispensable energy storage:
- Technically (see below) for the regulation of the electricity grid to accommodate an excess supply of electric power can
- Economically (see below) to achieve a more balanced utilization of other power plants that are less controllable,
In countries with a high share of hydro storage power plants (for example, Norway) pumped storage power plants are hardly needed, since excess electricity storage hydropower plants easily reduce their production or can turn it off completely, which in steam power plants, wind turbines, photovoltaic systems and most other types of power plants with larger energy losses is, respectively, higher costs possible.
Small pumped storage can help decentralized to save energy and generate flexible power production. This allows for a decentralized integration of renewable energies.
- 7.1 Germany
- 7.2 Switzerland
- 7.3 Norway
Operation
Energy conversion
Characteristics of a pumped storage power plant is the reversible system operation. A turbine, a generator and a pump mounted on a shaft and constitute a unit, that has two modes of operation: in case of power demand of the motor-generator operates as a generator and electrical power supplies driven by the turbine. The water then flows from the upper to the lower reservoir and provides the motive power. In excess of electric power in the power grid, the motor works as a generator and electric motor drives the pump which pumps the water back to the upper reservoir. When closing the shut-off valves in the pressure lines, for example, when switching from the generator to the pump operation, it comes to pressure surges. To compensate for this, there is as close to the turbine or pump a moated castle, which compensates for these fluctuations and thus prevents damage to system components.
Besides this classic design today also pump-turbine power stations are built, which are equipped instead of the turbine and the pump with so-called pump-turbines. In the pump-turbine is a fluid machine that can be flowed through in both directions and operates depending on the rotational direction of a pump or turbine.
Storage
The size of the storage capacity in megawatt hours is basically dependent storable volume of water and the usable height difference between the upper reservoir and the turbine. For pure pumped storage, the storage capacity is usually designed so that the generators at least can produce at full load current of 4 to 8 hours.
The largest pumped storage power plants have reservoirs with hundreds of millions of cubic meters and can use it to strike a balance between the seasons, pumps, for example, in the summer and produce in the winter. There are also considerations to make use of all waterways as pumped storage. Here, a dam is to be pumped up using excess water from the stream channel against the flow direction. Applied to the German inland waterways are thus pumped storage capacities of 400 megawatts conceivable.
Above-ground
In some reservoirs, the filling volume of a natural lake was enlarged by means dam or dam ( for example, when Schluchseewerk ). Some reservoirs are natural lakes without such increases; few reservoirs were created solely by humans (for example, Hornberg reservoir, Eggbergbecken, Geesthacht ).
There are upper basin filled exclusively by means of water supply by pumping, and those (also) are fed by natural inflow to.
Underground
In the 1980s, the Dutch government commissioned the TU Delft with the exploration of underground water storage in the Limburg region. 2009 known considerations, to create storage volume in former mines. Underground pumped storage offer the advantages of aboveground pumped storage, such as Be able to provide balancing energy for the fluctuating feed- in of energy sources wind energy and solar energy, the usual drawbacks, such as consumption of landscape and altitude difference depending on the geology omitted. Occasionally, of ' underground pumped storage power plant ' the speech. Such systems could also in former mines in the Ruhr area, as well as other mining regions arise, but are completely different conditions for coal as opposed to ore deposits, such as in the field of rock stability and tightness. For a reaction in Germany the direction perpendicular tunnels of many mines are considered problematic. The emerging at the corners of intersecting passages turbulence of the flow by forming water could erode the walls and bring down the ceiling. Inhibited the flow due to the flow resistance can be a loss of energy output.
Undersea
Since 2011 is working on the development of submarine pumped storage power plants. In principle, concrete hollow spheres are lowered into great depth on the seabed. In current surpluses, such as offshore wind farms, the balls are pumped out so that air displaces the water in the hollow spheres. If the energy is needed, the balls are flooded with sea water and driven turbines. This method takes advantage of the high pressure in the depth -to-use.
History of development
On a small scale modern pumped storage power plants were first implemented in the 1920s. One of the German engineers who developed the technology for large-scale pumped storage power plants as the world's pioneering achievement, Arthur Koepchen was. According to him, the 1930 went into operation PSW Koepchenwerk RWE AG was named in Herdecke on the Ruhr. Since then, many more pumped storage plants have been built, see also List of pumped-storage power plants.
However, the basic principle of storing water as potential energy already in the late phase of the solar- agrarian age - just before the beginning of industrialization - used. Windmills that were more volatile in production as water mills, pumped water into a higher ground reservoir from which, in turn, water mills were continuously fed; a process which V.A. was used in the textile industry, especially where it arrived on a finely adjustable, regular movement of the mechanically driven looms. Thus, the ability to work at this time particularly valuable and therefore heavily used water power could be increased by wind power.
Energy Economic Importance
The ability of the pumped storage power plants to include both energy and leave, is used in the power plant management. Due to the flexibility of their use, they are particularly well suited for providing control power The generating capacity as it is in storage hydropower plants as needed within minutes and can be adjusted flexibly in a wide range. Also, the pump operation can be flexibly adapted to different levels of performance surpluses over the network when two separate risers and downpipes are available ( Schluchseewerk ) applied the principle of the hydraulic short circuit is ( Kops II) or asynchronous machines, the pump drive (PSW Goldisthal ).
Thanks to their so-called black start capability pumped storage power plants can be used in total blackouts for starting other power plants.
In his special report "100% renewable electricity supply by 2050: climate-friendly, safe, affordable " from may 2010 is the appointed by the Federal Government Advisory Council on the Environment estimates that the capacity of storage power plants in particular in Norway ( alone almost 85 TWh water tank capacity of the local to pumped storage expandable storage hydropower plants ) and Sweden is nowhere near enough to compensate for fluctuations in the future fed renewable energy. However, this requires a significant extension of the north -south grid connection. The current capacity in Germany ( recent estimates related to wind, solar gas speak of about 0.6 TWh) are too low for this purpose. However, the technology of compressed air storage power plants in Germany an estimated potential of 3.5 TWh (difference between minimum and maximum memory capacity ), which can replace or delay the development of the Norwegian reserves under certain circumstances. Due to the lower efficiency of compressed air storage power plants, however, there would be greater energy losses than with pumped storage power plants. This problem is increasingly discussed since the nuclear disaster in Fukushima, since it is due to rise by the energy transition, the proportion ecologically produced electricity in Germany.
Economics
In general low energy demand and consequently low electricity prices, the generator acts as a power consuming motor and pumps water into the upper reservoir. This stream of water is produced at peak times of power consumption, which is necessary in order not to collapse the power supply and is sold expensive. A few minutes after the request from the distribution center can be as a storage power station leave for hours at full capacity. As you can see the comparison chart to energy saving, no other technically advanced storage method can even remotely compete with the performance of a pumped storage power plant.
Hydroelectric power plants and thermal power plants such as nuclear power plants or coal-fired power plants supply power as constant as possible (base load ) and can be up- and down are just a matter of hours or days. Characterized in partial load operation and they are not particularly efficient. At the same time there are in the day and week course of a highly fluctuating power consumption (peak load ). Therefore, the operation of pumped storage power plants is economically sensible. They provide a way to, for example, at night or low selling times of the day to the grid current, which is available at comparatively low prices, offset in time in much more expensive deductible current transform for peak demand. The selling price in this business can be a multiple of the purchase price. It was clear from the beginning that this system works technically, but the economic benefit was demonstrated only by the commissioning of the Koepchenwerkes.
The existence of pumped storage power plants also protects a portion of the economic risks of thermal base-load power plants, even at night so can feed practically unused power to the grid.
Is expected to increase importance of pumped storage power plants also by the further increase in the very irregular production of electricity from wind and solar energy. The problem is that lying between the optimal fields of wind power plants on the coast and the locations of potential pumped storage plants in the low mountain range some 100 km, which are currently not bridged by high-performance capillary roads.
Efficiency
Basically, more power is needed to pump than can be recovered when flowing down again in any pumped storage power plant. Losses occur during the loading and the unloading by the friction losses of the flowing water (liquids have a flow resistance, with water is also called water resistance and hydraulic losses ) by the efficiency of the pump ( charging ) or turbine ( discharge ) by the efficiency of the motor or generator as well as transformer losses and to a lesser extent, by personal use of the pumped storage plant. The overall efficiency of a pumped storage power plant is now slightly higher in the control at 75-80 % and in exceptional cases.
In addition there are transmission losses for round- trip transportation of electrical energy. These depend on the geographic distance between energy producers, pumping storage and energy consumers.
Criticism
Pumped storage plants can have a significant intervention in the ecology and represent the landscape. Since the memory pool of regular stress and erosion must withstand by fluctuating water levels, these are concreted or asphalted usually, so no natural vegetation can be formed. The frequent water changes with a complete mixing also prevents the setting of a natural Limnology in the water body. If the pools are impounded by dams, there is a small risk of a dam break. Due to the very large pipe diameter, a burst pipe can cause extensive damage and flooding.
Opponents of pumped storage power plants call these systems " Energievernichter " and keep them for a partially distinct change in landscape and nature. However, pumped storage power plants have been the large-scale method with the highest efficiency to temporarily store electrical energy in fluctuations between supply and demand.
Aboveground pumped storage power plants
Please see the list of pumped storage power plants, are listed in the located and planned plants in operation. The world's most powerful pumped storage power plant is the Bath County Pumped Storage Power Plant with a capacity of 3,003 MW.
Germany
In Germany, a pumped storage power of about 7 GW (gigawatt ) is installed (see List of pumped-storage power plants in Germany ). The power plants are designed for a power supply of 4-8 hours daily. This gives a total storage capacity of about 40 GWh ( as of 2010). In 2006, the German pumped storage power plants generated 4,042 GWh of electrical energy; which is a share of around 0.65 % of electricity generation. This was offset by a pumping work of 5,829 GWh, so the average efficiency was about 70%.
Switzerland
Most hydropower plants in Switzerland are designed as storage power plants. The above list includes those works which can also pump. Currently arise in the Swiss Alps several large power plants with underground pipes and engine nacelles.
Norway
Most hydropower plants in Norway are designed as storage power plants. Many of these plants have both an upper and a submarine, so that they could be converted relatively easily into a pumped storage power plant.