Pumped-storage hydroelectricity, or pumped hydroelectric energy storage, is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Although the losses of the pumping process makes the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. If the upper lake collects significant rainfall or is fed by a river the plant may be a net energy producer in the manner of a traditional hydroelectric plant. Pumped-storage hydroelectricity allows energy from intermittent sources and other renewables, or excess electricity from continuous base-load sources to be saved for periods of higher demand.
The reservoirs used with pumped storage are quite small when compared to conventional hydroelectric dams of similar power capacity, generating periods are less than half a day. Pumped storage is by far the largest-capacity form of grid energy storage available, and, as of 2017, the United States Department of Energy Global Energy Storage Database reports that PSH accounts for over 95% of all active tracked storage installations worldwide, with a total installed nameplate capacity of over 184 GW, of which about 25 GW are in the United States; the round-trip energy efficiency of PSH varies between 70%–80%, with some sources claiming up to 87%. The main disadvantage of PSH is the specialist nature of the site required, needing both geographical height and water availability. Suitable sites are therefore to be in hilly or mountainous regions, in areas of outstanding natural beauty, therefore there are social and ecological issues to overcome. Many proposed projects, at least in the U. S. avoid sensitive or scenic areas, some propose to take advantage of "brownfield" locations such as disused mines.
At times of low electrical demand, excess generation capacity is used to pump water into the upper 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 a combined turbine generator unit. In micro-PSH applications, a group of pumps and Pump As Turbine could be implemented for pumping and generating phases; the same pump could be used in both modes by changing rotational direction and speed: the operation point in pumping differs by operation point in PAT mode. In open-loop systems, pure pumped-storage plants store water in an upper reservoir with no natural inflows, while pump-back plants utilize a combination of pumped storage and conventional hydroelectric plants with an upper reservoir, replenished in part by natural inflows from a stream or river. Plants that do not use pumped-storage are referred to as conventional hydroelectric plants. Taking into account evaporation losses from the exposed water surface and conversion losses, energy recovery of 70-80% or more can be achieved.
This technique is the most cost-effective means of storing large amounts of electrical energy, but capital costs and the presence of appropriate geography are critical decision factors in selecting pumped-storage plant sites. The low energy density of pumped storage systems requires either large flows and/or large differences in height between reservoirs; the only way to store a significant amount of energy is by having a large body of water located near, but as high above as possible, a second body of water. In some places this occurs in others one or both bodies of water were man-made. Projects in which both reservoirs are artificial and in which no natural inflows are involved with either reservoir are referred to as "closed loop" systems; these systems may be economical because they flatten 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, while reducing the need for "peaking" power plants that use the same fuels as many base-load thermal plants and oil, but have been designed for flexibility rather than maximal efficiency.
Hence pumped storage systems are crucial. Capital costs for pumped-storage plants are high, although this is somewhat mitigated by their long service life of up to 75 years or more, three to five times longer than utility-scale batteries. 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 causing frequency and voltage instability. Pumped storage plants, like other hydroelectric plants, can respond to load changes within seconds; the most important use for pumped storage has traditionally been to balance baseload powerplants, but may be used to abate the fluctuating output of intermittent energy sources. Pumped storage provides a load at times of high electricity output and low electricity demand, enabling additional system peak capacity. In certain jurisdictions, electricity prices may be close
Lieutenant General Sir William Cameron Moffat, KBE, FRCS was a British Army officer and doctor. He served as Director General Army Medical Services from 1984 to 1987, Surgeon General from 1985 to 1987, he served as chief medical adviser to the British Red Cross. Moffat was born in 1929. During World War II, he was evacuated to the Isle of Bute. In 1947, he matriculated in the University of Glasgow to study medicine, he graduated Bachelor of Medicine, Bachelor of Surgery in 1951. As part of National Service, Moffat was commissioned into the Royal Army Medical Corps, British Army, on 11 October 1954 as a lieutenant. On 8 December 1954, he transferred from the National Service List to a short service commission with seniority in the rank of lieutenant from 1 August 1952, he was promoted to captain on 8 December 1954 with seniority from 1 August 1953. On 1 October 1959, he transferred to a regular commission in the rank of lieutenant with seniority from 4 August 1953, he was promoted to captain on the same day with seniority in that rank from 4 August 1954.
He was promoted to major on 4 August 1961, to lieutenant colonel on 4 August 1966. He was promoted to colonel on 4 August 1975, to brigadier on 7 April 1981, he was promoted to major-general on 1 December 1983. In 1984, he was appointed Director General Army Medical Services, the head of the British Army's medical wing, he was promoted to lieutenant-general on 28 January 1985. In 1985, he was appointed Surgeon General, therefore becoming the senior medical officer of the British Armed Forces, director of the Defence Medical Services, he retired from the British Army on 27 February 1988. Moffat died on 29 June 2014. In the 1976 Queen's Birthday Honours, Moffat was appointed Officer of the Order of the British Empire, he was appointed Honorary Surgeon to The Queen on 30 November 1983. He was promoted to Knight Commander of the Order of the British Empire in the 1985 New Year Honours. In April 1985, he was appointed Commander of the Order of St John, his tenure as Honorary Surgeon to The Queen ended on 26 February 1988.
On 19 June 1991, he was awarded an honorary Doctor of Science degree by the University of Glasgow. In 1994, he was awarded the Queen's Badge of Honour, the highest honour awarded for service to the British Red Cross
Lino Liviabella was an Italian composer. Liviabella was born in Macerata. In 1936 he won a silver medal in the art competitions of the Olympic Games for his "La vittoria", he died, aged 62, in Bologna. Chamber musicSonata No. 1 in A minor for violin and piano Natale, Suite for violin and piano Sonatina per l'Elevazione for violin and harmonium Canzonetta for violin and piano Aria for violin and organ or harmonium String Quartet No. 1 Danza for violin solo Adagio for oboe and piano S. Francesco, Meditazione for viola, 2 violins, double bass and organ Due espressioni liriche for string quartet Preludio in modo minore for 2 violins and harmonium String Quartet No. 2 Bululù, Marionetta meccanica del romanzo “Eva ultima” di Massimo Bontempelli for violin and piano Canto andaluso for violin and piano Sonata ciclica for cello and piano Sonata No. 2 in One Movement for violin and piano Lento for flute, 2 violins and harp Sonata No. 3 in One Movement for violin and piano Largo for cello and piano Canto per la Prima Comunione di Laura e Lucio for violin and harmonium Pastorale for violin or oboe and piano Lucio e Renato, Marcetta for violin and piano Scherzo for oboe and piano String Quartet No. 3 in One Movement Piano Trio Sonata No. 1 in One Movement for viola and piano Divertimento for flute, viola and harp Divertimento for flute and piano String Quartet No. 4 "La melanconia" Concerto in One Movement for violin and piano Tre momenti for viola and piano Tre pezzi for flute and harp or piano Tre pezzi for flute and harp or piano Sette duetti miniatura for violin and viola Sonata No. 2 for viola and piano Quattro brani nuziali for viola and organ or harmonium OperasSantina Zanira Antigone La Conchiglia Canto di Natale "Lino Liviabella".