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Pumped-storage hydroelectricity

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Diagram of the TVA pumped storage facility at Raccoon Mountain Pumped-Storage Plant
Power spectrum of a pumped-storage hydroelectricity. Green represents power consumed in pumping; red is power generated.

Pumped storage hydroelectricity is a method of storing and producing electricity to supply high peak demands by moving water between reservoirs at different elevations.

Overview

At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine, generating electricity. Reversible turbine/generator assemblies act as pump and turbine (usually a Francis turbine design). Some facilities use abandoned mines as the lower reservoir, but many use the height difference between two natural bodies of water or artificial reservoirs. Pure pumped-storage plants just shift the water between reservoirs, but combined pump-storage plants also generate their own electricity like conventional hydroelectric plants through natural stream-flow. Plants that do not use pumped-storage are referred to as conventional hydroelectric plants; conventional hydroelectric plants that have significant storage capacity may be able to play a similar role in the electrical grid as pumped storage, by deferring output until needed.

Taking into account evaporation losses from the exposed water surface and conversion losses, approximately 70% to 85% of the electrical energy used to pump the water into the elevated reservoir can be regained. The technique is currently the most cost-effective means of storing large amounts of electrical energy on an operating basis, but capital costs and the presence of appropriate geography are critical decision factors.

The relatively low energy density of pumped storage systems requires either a very large body of water or a large variation in height. For example, 1000 kilograms of water (1 cubic meter) at the top of a 100 meter tower has a potential energy of about 0.277 kW·h. The only way to store a significant amount of energy is by having a large body of water located on a hill relatively near, but as high as possible above, a second body of water. In some places this occurs naturally, in others one or both bodies of water have been man-made.

This system may be economical because it flattens out load variations on the power grid, permitting thermal power stations such as coal-fired plants and nuclear power plants that provide base-load electricity to continue operating at peak efficiency (Base load power plants), while reducing the need for "peaking" power plants that use costly fuels. Capital costs for purpose-built hydrostorage are high, however.

Along with energy management, pumped storage systems help control electrical network frequency and provide reserve generation. Thermal plants are much less able to respond to sudden changes in electrical demand, potentially causing frequency and voltage instability. Pumped storage plants, like other hydroelectric plants, can respond to load changes within seconds.

The upper reservoir (Llyn Stwlan) and dam of the Ffestiniog Pumped Storage Scheme in north Wales. The lower power station has four water turbines which generate 360 MW of electricity within 60 seconds of the need arising. The size of the dam can be judged from the car parked below.

The first use of pumped storage was in the 1890s in Italy and Switzerland. In the 1930s reversible hydroelectric turbines became available. These turbines could operate as both turbine-generators and in reverse as electric motor driven pumps. The latest in large-scale engineering technology are variable speed machines for greater efficiency. These machines generate in synchronisation with the network frequency, but operate asynchronously (independent of the network frequency) as motor-pumps.

A new use for pumped storage is to level the fluctuating output of intermittent power sources. The pumped storage absorbs load at times of high output and low demand, while providing additional peak capacity. In certain jurisdictions, electricity prices may be close to zero or occasionally negative (Ontario in early September, 2006), indicating there is more generation than load available to absorb it; although at present this is rarely due to wind alone, increased wind generation may increase the likelihood of such occurrences. It is particularly likely that pumped storage will become especially important as a balance for very large scale photovoltaic generation.[1]

In 2000 the United States had 19.5 GW of pumped storage capacity, accounting for 2.5% of baseload generating capacity. PHS generated (net) -5.5 GWh of energy[2] because more energy is consumed in pumping than is generated; losses occur due to water evaporation, electric turbine/pump efficiency, and friction.

In 1999 the EU had 32 GW capacity of pumped storage out of a total of 188 GW of hydropower and representing 5.5% of total electrical capacity in the EU.

Potential technologies

The use of underground reservoirs as lower dams has been investigated. Salt mines could be used, although ongoing and unwanted dissolution of salt could be a problem. If they prove affordable, underground systems could greatly expand the number of pumped storage sites. Saturated brine is about 20% more dense than fresh water.

A new concept in pumped storage is to utilise wind turbines to drive water pumps directly, in effect an 'Energy Storing Wind Dam'. This could provide a more efficient process and usefully smooth out the variabilities of energy captured from the wind.

Worldwide list of pumped storage plants

Australia

Austria

  • Häusling (1988), 360 MW
  • Lünerseewerk (1958), 232 MW
  • Kraftwerksgruppe Fragant, 100 MW
  • Kühtai (1981), 250 MW
  • Malta-Hauptstufe (1979), 730 MW
  • Rodundwerk I (1952), 198 MW
  • Rodundwerk II (1976), 276 MW
  • Roßhag (1972), 231 MW
  • Silz (1981), 500 MW

Belgium

  • Coo, (1979), 1100 MW

Bulgaria

  • PAVEC Chaira, (1998), 800 MW

Canada

  • Sir Adam Beck Pump Generating Station, (1957) near Niagara Falls, reversible Deriaz turbines, 174 MW

China

  • Guangzhou, (2000), 2,400 MW
  • Tianhuangping (2001), 1,800 MW

Croatia

Czech Republic

France

Germany

  • Erzhausen (1964), 220 MW
  • Geesthacht (Hamburg) (1958), 120 MW
  • Goldisthal (2002), 1,060 MW
  • Happurg (1958), 160 MW
  • Hohenwarte II (1966), 320 MW
  • Koepchenwerk (1989), 153 MW
  • Langenprozelten (1976), 160 MW
  • Markersbach (1981), 1,050 MW
  • Niederwartha, Dresden (1958), 120 MW
  • Waldeck II (1973), 440 MW

India

  • Nagarjuna Sagar PH, Andhra Pradesh, 810 MW (1 x 110 MW + 7 x 100 MW)
  • Srisailam Left Bank PH, Andhra Pradesh, 900 MW (6 x 150 MW)
  • Kadamparai, Near Coimbatore, Tamil Nadu, 400 MW
  • Purulia Pumped Storage Project, Ayodhya Hills, Purulia, West Bengal, 900 MW (Under construction)
  • Tehri dam, Uttranchal, 1000 MW (under construction approach adits started)
  • Bhira(Maharashtra) pump storage unit 150 MW
  • Mettur, near Salam, Tamilnadu, 1200MW
  • Pykara ultimate stage, Hydro electric project, Near Udagamandalam, Tamilnadu (3 x 50 MW)

Iran

Ireland

Italy

  • Piastra Edolo (1982), 1,020 MW
  • Chiotas (1981), 1,184 MW
  • Presenzano (1992), 1,000 MW
  • Lago Delio (1971), 1,040 MW

Japan

  • Imaichi (1991), 1,050 MW
  • Kannagawa (2005), 2,700 MW
  • Kazunogawa (2001), 1,600 MW
  • Kisenyama, 466 MW
  • Matanoagawa (1999), 1,200 MW
  • Midono, 122 MW
  • Niikappu, 200 MW
  • Okawachi (1995), 1,280 MW
  • Okutataragi (1998), 1,932 MW
  • Okuyoshino, 1,206 MW
  • Shin-Takasegawa, 1,280 MW
  • Shiobara, 900 MW
  • Takami, 200 MW
  • Tamahara (1986), 1,200 MW
  • Yagisawa, 240 MW
  • Yanbaru, Okinawa (1999), 30 MW (First high-head seawater pumped storage in the world) [1]

Lithuania

Luxembourg

  • Vianden, (1964), 1,100 MW

Norway

Note that Norway has a high density of hydroelectric power generation, so some of the following locations are simply pumps that never generate power themselves, but transfer water to reservoirs where it can be re-used by existing hydroelectric power stations. This information comes from [2], [3], and [4]

Philippines

  • CBK, 700MW

Poland

  • Żarnowiec, 716 MW
  • Porąbka-Żar, 500 MW
  • Solina, 200 MW
  • Żydowo, 150 MW
  • Niedzica, 92.6 MW
  • Dychów, 79.5 MW

Portugal

  • Aguieira, 270MW
  • Alqueva, 260MW
  • Alto Rabagão, 72MW
  • Torrão, 144MW
  • Vilarinho II, 74MW

Russia

  • Zagorsk (1994) 1,200/1,320 MW
  • Kuban (1968) 15.9/19.2 MW
  • Zelenchuk (under construction) 140/150.6 MW

Serbia

  • Bajina Basta (1982) 614 MW

Slovakia

  • Čierny Váh 735.16 MW

Slovenija

  • Avče unknown MW

South Africa

Spain

  • La Muela (Valencia) 628 MW
  • Sallente-Estany Gento (Lleida) 451 MW [5]
  • Tajo de la Encantada (Málaga) 360 MW
  • Aguayo (Cantabria) 339 MW
  • Moralets-Llauset (Lleida/Huesca) 210 MW [6]
  • Tavascan-Montmara (Lleida) 52 MW
  • Aldeadavila (Salamanca) 422 MW (2 X 211 MW) [7]
  • Villarino (Salamanca) 810 MW (6 X 135 MW) [8]

Sweden

  • Juktan, 334 MW [5]

Taiwan

  • Minghu (1985) 1,000 MW
  • Mingtan (1994) 1,620 MW

Ukraine

  • Kyiv HPSP 235.5 MW [9]
  • Tashlyk HPSP 905 MW/-1325 MW [10]
  • Dniestr HPSP (1st construction phase completed and now provides 972 MW, next phases will give up to 2,268 MW)[11]
  • Kaniv HPSP (design stage) 1800 MW [12]

United Kingdom

United States

California
Colorado
  • Mount Elbert 200 MW, 1,212 MW
Connecticut
  • Rocky River, (1929) 31 MW
Georgia
  • Rocky Mountain Pumped Storage Station 848 MW
Hawaii
  • Koko Crater, Oahu, Hawaii (Proposed)
Massachusetts
Michigan
Missouri
New Jersey
  • Mt. Hope 2,000 MW[6]
New York
Ohio
  • Summit Pumped Water Plant 1500 MW
Pennsylvania
Tennessee
Virginia
Washington


References

  1. ^ http://www.iea-pvps.org/products/rep8_02s.htm
  2. ^ http://www.eia.doe.gov/emeu/aer/pdf/pages/sec8_8.pdf
  3. ^ http://www.hep.hr/proizvodnja/en/basicdata/hydro/west/vinodol.aspx
  4. ^ http://www.hep.hr/proizvodnja/en/basicdata/hydro/south/velebit.aspx
  5. ^ http://hem.passagen.se/kts/english/turbin/francis/francis.htm
  6. ^ Mt. Hope: The megawatt line
  7. ^ Bath County Pumped Storage Station

See also

Articles about historical mechanical engineering landmarks from ASME:

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