A turbine ( / ˈ t ɜːr b aɪ n / or / ˈ t ɜːr b ɪ n / ) (from the Greek τύρβη , tyrbē , or Latin turbo , meaning vortex ) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work . The work produced can be used for generating electrical power when combined with a generator . A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor.
63-636: The Goldisthal Pumped Storage Station is a pumped-storage power station in the Thueringer Mountains at the upper run of the river Schwarza in Goldisthal , Germany. It was constructed between 1997 and 2004. It has an installed capacity of 1,060 megawatts (1,420,000 hp), the largest hydroelectric power plant in Germany and one of largest in Europe. Goldisthal Pumped Storage Station
126-607: A cost-effective solution for a water reservoir in a micro-pumped hydro energy storage. Such plants provide distributed energy storage and distributed flexible electricity production and can contribute to the decentralized integration of intermittent renewable energy technologies, such as wind power and solar power . Reservoirs that can be used for small pumped-storage hydropower plants could include natural or artificial lakes, reservoirs within other structures such as irrigation, or unused portions of mines or underground military installations. In Switzerland one study suggested that
189-436: A four-week test of a pumped storage underwater reservoir. In this configuration, a hollow sphere submerged and anchored at great depth acts as the lower reservoir, while the upper reservoir is the enclosing body of water. Electricity is created when water is let in via a reversible turbine integrated into the sphere. During off-peak hours, the turbine changes direction and pumps the water out again, using "surplus" electricity from
252-486: A hybrid system that both generates power from water naturally flowing into the reservoir as well as storing water pumped back to the reservoir from below the dam. The Grand Coulee Dam in the United States was expanded with a pump-back system in 1973. Existing dams may be repowered with reversing turbines thereby extending the length of time the plant can operate at capacity. Optionally a pump back powerhouse such as
315-404: A pump and as a turbine generator (usually Francis turbine designs). Variable speed operation further optimizes the round trip efficiency in pumped hydro storage plants. In micro-PSH applications, a group of pumps and Pump As Turbine (PAT) could be implemented respectively for pumping and generating phases. The same pump could be used in both modes by changing rotational direction and speed:
378-417: A reaction type design with the base of the blade solely impulse. The reason is due to the effect of the rotation speed for each blade. As the volume increases, the blade height increases, and the base of the blade spins at a slower speed relative to the tip. This change in speed forces a designer to change from impulse at the base, to a high reaction-style tip. Classical turbine design methods were developed in
441-591: A reservoir. The largest one, Saurdal, which is part of the Ulla-Førre complex, has four 160 MW Francis turbines , but only two are reversible. The lower reservoir is at a higher elevation than the station itself, and thus the water pumped up can only be used once before it has to flow to the next station, Kvilldal, further down the tunnel system. And in addition to the lower reservoir, it will receive water that can be pumped up from 23 river/stream and small reservoir intakes. Some of which will have already gone through
504-473: A significant amount of energy is by having a large body of water located 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 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
567-641: A similar role in the electrical grid as pumped storage if appropriately equipped. Taking into account conversion losses and evaporation losses from the exposed water surface, energy recovery of 70–80% or more can be achieved. This technique is currently the most cost-effective means of storing large amounts of electrical energy, but capital costs and the necessity of appropriate geography are critical decision factors in selecting pumped-storage plant sites. The relatively low energy density of pumped storage systems requires either large flows and/or large differences in height between reservoirs. The only way to store
630-437: A smaller power station on its way. In 2010, the United States had 21.5 GW of pumped storage generating capacity (20.6% of world capacity). PSH contributed 21,073 GWh of energy in 2020 in the United States, but −5,321 GWh (net) because more energy is consumed in pumping than is generated. Nameplate pumped storage capacity had grown to 21.6 GW by 2014, with pumped storage comprising 97% of grid-scale energy storage in
693-529: A total installed capacity of 1344 MW and an average annual production of 2247 GWh. The pumped storage hydropower in Norway is built a bit differently from the rest of the world. They are designed for seasonal pumping. Most of them can also not cycle the water endlessly, but only pump and reuse once. The reason for this is the design of the tunnels and the elevation of lower and upper reservoirs. Some, like Nygard power station, pump water from several river intakes up to
SECTION 10
#1732766160004756-518: A total installed storage capacity of over 1.6 TWh . A pumped-storage hydroelectricity generally consists of two water reservoirs at different heights, connected with each other. 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. Pumped storage plants usually use reversible turbine/generator assemblies, which can act both as
819-776: Is a type of hydroelectric energy storage used by electric power systems for load balancing . A PSH system 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 typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar , wind , and other renewables) or excess electricity from continuous base-load sources (such as coal or nuclear) to be saved for periods of higher demand. The reservoirs used with pumped storage can be quite small, when contrasted with
882-435: Is changed to velocity head by accelerating the fluid with a nozzle . Pelton wheels and de Laval turbines use this process exclusively. Impulse turbines do not require a pressure casement around the rotor since the fluid jet is created by the nozzle prior to reaching the blades on the rotor. Newton's second law describes the transfer of energy for impulse turbines. Impulse turbines are most efficient for use in cases where
945-441: Is much smaller than the land occupied by the solar and windfarms that the storage might support. Closed loop (off-river) pumped hydro storage has the smallest carbon emissions per unit of storage of all candidates for large-scale energy storage. Pumped storage plants can operate with seawater, although there are additional challenges compared to using fresh water, such as saltwater corrosion and barnacle growth. Inaugurated in 1966,
1008-489: Is necessary. Smaller pumped storage plants cannot achieve the same economies of scale as larger ones, but some do exist, including a recent 13 MW project in Germany. Shell Energy has proposed a 5 MW project in Washington State. Some have proposed small pumped storage plants in buildings, although these are not yet economical. Also, it is difficult to fit large reservoirs into the urban landscape (and
1071-505: Is normally displayed as a turbine map or characteristic. The number of blades in the rotor and the number of vanes in the stator are often two different prime numbers in order to reduce the harmonics and maximize the blade-passing frequency. A large proportion of the world's electrical power is generated by turbo generators . Turbines are used in gas turbine engines on land, sea and air. Turbochargers are used on piston engines. Gas turbines have very high power densities (i.e.
1134-459: Is owned and operated by Vattenfall (Vattenfall Wasserkraft GmbH). The upper reservoir is located at an altitude of 880 m (2,890 ft). It has an active (or usable) capacity of 12 million m³ and a surface area of 55 hectares. In order to create this basin, the mountain summit was cleared away. This stored quantity of water is enough for eight hours of operation. This corresponds to a maximally storable electric power quantity of 8.5 GWh with
1197-640: Is rarely due to wind or solar power alone, increased use of such generation will increase the likelihood of those occurrences. It is particularly likely that pumped storage will become especially important as a balance for very large-scale photovoltaic and wind generation. Increased long-distance transmission capacity combined with significant amounts of energy storage will be a crucial part of regulating any large-scale deployment of intermittent renewable power sources. The high non-firm renewable electricity penetration in some regions supplies 40% of annual output, but 60% may be reached before additional storage
1260-940: Is somewhat mitigated by their proven long service life of decades - and in some cases over a century, which is three to five times longer than utility-scale batteries. When electricity prices become negative , pumped hydro operators may earn twice - when "buying" the electricity to pump the water to the upper reservoir at negative spot prices and again when selling the electricity at a later time when prices are high. Along with energy management, pumped storage systems help stabilize electrical network frequency and provide reserve generation. Thermal plants are much less able to respond to sudden changes in electrical demand that potentially cause 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 they may also be used to abate
1323-486: Is variable speed machines for greater efficiency. These machines operate in synchronization with the network frequency when generating, but operate asynchronously (independent of the network frequency) when pumping. The first use of pumped-storage in the United States was in 1930 by the Connecticut Electric and Power Company, using a large reservoir located near New Milford, Connecticut, pumping water from
SECTION 20
#17327661600041386-531: The Russell Dam (1992) may be added to a dam for increased generating capacity. Making use of an existing dam's upper reservoir and transmission system can expedite projects and reduce costs. Turbine Gas , steam , and water turbines have a casing around the blades that contains and controls the working fluid. The word "turbine" was coined in 1822 by the French mining engineer Claude Burdin from
1449-623: The 240 MW Rance tidal power station in France can partially work as a pumped-storage station. When high tides occur at off-peak hours, the turbines can be used to pump more seawater into the reservoir than the high tide would have naturally brought in. It is the only large-scale power plant of its kind. In 1999, the 30 MW Yanbaru project in Okinawa was the first demonstration of seawater pumped storage. It has since been decommissioned. A 300 MW seawater-based Lanai Pumped Storage Project
1512-491: The 3 million abandoned wells in the US. Using hydraulic fracturing pressure can be stored underground in impermeable strata such as shale. The shale used contains no hydrocarbons. Small (or micro) applications for pumped storage could be built on streams and within infrastructures, such as drinking water networks and artificial snow-making infrastructures. In this regard, a storm-water basin has been concretely implemented as
1575-620: The EU. Japan had 25.5 GW net capacity (24.5% of world capacity). The six largest operational pumped-storage plants are listed below (for a detailed list see List of pumped-storage hydroelectric power stations ) : Australia has 15GW of pumped storage under construction or in development. Examples include: In June 2018 the Australian federal government announced that 14 sites had been identified in Tasmania for pumped storage hydro, with
1638-628: The Greek τύρβη , tyrbē , meaning " vortex " or "whirling", in a memo, "Des turbines hydrauliques ou machines rotatoires à grande vitesse", which he submitted to the Académie royale des sciences in Paris. However, it was not until 1824 that a committee of the Académie (composed of Prony, Dupin, and Girard) reported favorably on Burdin's memo. Benoit Fourneyron , a former student of Claude Burdin, built
1701-473: The Greek τύρβη , tyrbē , meaning " vortex " or "whirling". Benoit Fourneyron , a former student of Claude Burdin, built the first practical water turbine. Credit for invention of the steam turbine is given both to Anglo-Irish engineer Sir Charles Parsons (1854–1931) for invention of the reaction turbine, and to Swedish engineer Gustaf de Laval (1845–1913) for invention of the impulse turbine. Modern steam turbines frequently employ both reaction and impulse in
1764-511: The Housatonic River to the storage reservoir 70 metres (230 ft) above. In 2009, world pumped storage generating capacity was 104 GW , while other sources claim 127 GW, which comprises the vast majority of all types of utility grade electric storage. The European Union had 38.3 GW net capacity (36.8% of world capacity) out of a total of 140 GW of hydropower and representing 5% of total net electrical capacity in
1827-567: The Kidston project under construction in Australia. Water requirements for PSH are small: about 1 gigalitre of initial fill water per gigawatt-hour of storage. This water is recycled uphill and back downhill between the two reservoirs for many decades, but evaporation losses (beyond what rainfall and any inflow from local waterways provide) must be replaced. Land requirements are also small: about 10 hectares per gigawatt-hour of storage, which
1890-453: The United States. As of late 2014, there were 51 active project proposals with a total of 39 GW of new nameplate capacity across all stages of the FERC licensing process for new pumped storage hydroelectric plants in the United States, but no new plants were currently under construction in the United States at the time. Conventional hydroelectric dams may also make use of pumped storage in
1953-549: The basic performance of a turbine stage. Gas exits the stationary turbine nozzle guide vanes at absolute velocity V a1 . The rotor rotates at velocity U . Relative to the rotor, the velocity of the gas as it impinges on the rotor entrance is V r1 . The gas is turned by the rotor and exits, relative to the rotor, at velocity V r2 . However, in absolute terms the rotor exit velocity is V a2 . The velocity triangles are constructed using these various velocity vectors. Velocity triangles can be constructed at any section through
Goldisthal Pumped Storage Station - Misplaced Pages Continue
2016-498: The blading (for example: hub, tip, midsection and so on) but are usually shown at the mean stage radius. Mean performance for the stage can be calculated from the velocity triangles, at this radius, using the Euler equation : Hence: where: The turbine pressure ratio is a function of Δ h T {\displaystyle {\frac {\Delta h}{T}}} and the turbine efficiency. Modern turbine design carries
2079-444: The calculations further. Computational fluid dynamics dispenses with many of the simplifying assumptions used to derive classical formulas and computer software facilitates optimization. These tools have led to steady improvements in turbine design over the last forty years. The primary numerical classification of a turbine is its specific speed . This number describes the speed of the turbine at its maximum efficiency with respect to
2142-421: The direction of flow of a high velocity fluid or gas jet. The resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy. There is no pressure change of the fluid or gas in the turbine blades (the moving blades), as in the case of a steam or gas turbine, all the pressure drop takes place in the stationary blades (the nozzles). Before reaching the turbine, the fluid's pressure head
2205-573: The effective storage in about 2 trillion electric vehicle batteries), which is about 100 times more than needed to support 100% renewable electricity. Most are closed-loop systems away from rivers. Areas of natural beauty and new dams on rivers can be avoided because of the very large number of potential sites. Some projects utilise existing reservoirs (dubbed "bluefield") such as the 350 Gigawatt-hour Snowy 2.0 scheme under construction in Australia. Some recently proposed projects propose to take advantage of "brownfield" locations such as disused mines such as
2268-652: The efficiency of pumped storage by using fluid 2.5x denser than water ("a fine-milled suspended solid in water" ), such that "projects can be 2.5x smaller for the same power." The first use of pumped storage was in 1907 in Switzerland , at the Engeweiher pumped storage facility near Schaffhausen, Switzerland. In the 1930s reversible hydroelectric turbines became available. This apparatus could operate both as turbine generators and in reverse as electric motor-driven pumps. The latest in large-scale engineering technology
2331-419: The existing height difference between storage basins and turbines. Two 800 m long penstocks , inclined at approximately 25 degrees serve as a conduit for water transfer. The lower reservoir has a capacity of 18.9 million cubic metres (670 × 10 ^ cu ft). The power station contains four 265 MW Francis pump turbines . From the outset of planning of this power station, it met with opposition and
2394-541: The first practical water turbine. Credit for invention of the steam turbine is given both to Anglo-Irish engineer Sir Charles Parsons (1854–1931) for invention of the reaction turbine, and to Swedish engineer Gustaf de Laval (1845–1913) for invention of the impulse turbine. A working fluid contains potential energy (pressure head ) and kinetic energy (velocity head). The fluid may be compressible or incompressible . Several physical principles are employed by turbines to collect this energy: Impulse turbines change
2457-441: The flow is low and the inlet pressure is high. Reaction turbines develop torque by reacting to the gas or fluid's pressure or mass. The pressure of the gas or fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the turbine stage(s) or the turbine must be fully immersed in the fluid flow (such as with wind turbines). The casing contains and directs
2520-418: 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 to zero or occasionally negative on occasions that there is more electrical generation available than there is load available to absorb it. Although at present this
2583-402: The fluctuating water level may make them unsuitable for recreational use). Nevertheless, some authors defend the technological simplicity and security of water supply as important externalities . The main requirement for PSH is hilly country. The global greenfield pumped hydro atlas lists more than 800,000 potential sites around the world with combined storage of 86 million GWh (equivalent to
Goldisthal Pumped Storage Station - Misplaced Pages Continue
2646-461: The fluid head (upstream pressure) is low. In the case of steam turbines, such as would be used for marine applications or for land-based electricity generation, a Parsons-type reaction turbine would require approximately double the number of blade rows as a de Laval-type impulse turbine, for the same degree of thermal energy conversion. Whilst this makes the Parsons turbine much longer and heavier,
2709-435: The grid. The quantity of power created when water is let in, grows proportionally to the height of the column of water above the sphere. In other words: the deeper the sphere is located, the more densely it can store energy. As such, the energy storage capacity of the submerged reservoir is not governed by the gravitational energy in the traditional sense, but by the vertical pressure variation . RheEnergise aim to improve
2772-421: The impulse of the wind, by deflecting it at an angle. Turbines with multiple stages may use either reaction or impulse blading at high pressure. Steam turbines were traditionally more impulse but continue to move towards reaction designs similar to those used in gas turbines. At low pressure the operating fluid medium expands in volume for small reductions in pressure. Under these conditions, blading becomes strictly
2835-415: The lakes of conventional hydroelectric plants of similar power capacity, and generating periods are often less than half a day. The round-trip efficiency of PSH varies between 70% and 80%. Although the losses of the pumping process make 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
2898-714: The largest PHES in the world at 5 GW. China has the largest capacity of pumped-storage hydroelectricity in the world. In January 2019, the State Grid Corporation of China announced plans to invest US$ 5.7 billion in five pumped hydro storage plants with a total 6 GW capacity, to be located in Hebei, Jilin, Zhejiang, Shandong provinces, and in Xinjiang Autonomous Region. China is seeking to build 40 GW of pumped hydro capacity installed by 2020. There are 9 power stations capable of pumping with
2961-539: The mid 19th century. Vector analysis related the fluid flow with turbine shape and rotation. Graphical calculation methods were used at first. Formulae for the basic dimensions of turbine parts are well documented and a highly efficient machine can be reliably designed for any fluid flow condition . Some of the calculations are empirical or 'rule of thumb' formulae, and others are based on classical mechanics . As with most engineering calculations, simplifying assumptions were made. Velocity triangles can be used to calculate
3024-489: The number of underground pumped storage opportunities may increase if abandoned coal mines prove suitable. In Bendigo , Victoria, Australia, the Bendigo Sustainability Group has proposed the use of the old gold mines under Bendigo for Pumped Hydro Energy Storage. Bendigo has the greatest concentration of deep shaft hard rock mines anywhere in the world with over 5,000 shafts sunk under Bendigo in
3087-628: The operation point in pumping usually differs from the operation point in PAT mode. In closed-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 that is 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; conventional hydroelectric plants that have significant storage capacity may be able to play
3150-408: The overall efficiency of a reaction turbine is slightly higher than the equivalent impulse turbine for the same thermal energy conversion. In practice, modern turbine designs use both reaction and impulse concepts to varying degrees whenever possible. Wind turbines use an airfoil to generate a reaction lift from the moving fluid and impart it to the rotor. Wind turbines also gain some energy from
3213-483: The potential of adding 4.8GW to the national grid if a second interconnector beneath Bass Strait was constructed. The Snowy 2.0 project will link two existing dams in the New South Wales' Snowy Mountains to provide 2,000 MW of capacity and 350,000 MWh of storage. In September 2022, a pumped hydroelectric storage (PHES) scheme was announced at Pioneer-Burdekin in central Queensland that has the potential to be
SECTION 50
#17327661600043276-438: The power and flow rate. The specific speed is derived to be independent of turbine size. Given the fluid flow conditions and the desired shaft output speed, the specific speed can be calculated and an appropriate turbine design selected. The specific speed, along with some fundamental formulas can be used to reliably scale an existing design of known performance to a new size with corresponding performance. Off-design performance
3339-554: 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, gas and oil, but have been designed for flexibility rather than maximal efficiency. Hence pumped storage systems are crucial when coordinating large groups of heterogeneous generators . Capital costs for pumped-storage plants are relatively high, although this
3402-1022: The proposed Summit project in Norton, Ohio , the proposed Maysville project in Kentucky (underground limestone mine), and the Mount Hope project in New Jersey , which was to have used a former iron mine as the lower reservoir. The proposed energy storage at the Callio site in Pyhäjärvi ( Finland ) would utilize the deepest base metal mine in Europe, with 1,450 metres (4,760 ft) elevation difference. Several new underground pumped storage projects have been proposed. Cost-per-kilowatt estimates for these projects can be lower than for surface projects if they use existing underground mine space. There are limited opportunities involving suitable underground space, but
3465-410: The ratio of power to mass, or power to volume) because they run at very high speeds. The Space Shuttle main engines used turbopumps (machines consisting of a pump driven by a turbine engine) to feed the propellants (liquid oxygen and liquid hydrogen) into the engine's combustion chamber. The liquid hydrogen turbopump is slightly larger than an automobile engine (weighing approximately 700 lb) with
3528-403: The same unit, typically varying the degree of reaction and impulse from the blade root to its periphery. Hero of Alexandria demonstrated the turbine principle in an aeolipile in the first century AD and Vitruvius mentioned them around 70 BC. Early turbine examples are windmills and waterwheels . The word "turbine" was coined in 1822 by the French mining engineer Claude Burdin from
3591-619: The sea area replacing seawater by constructing coastal reservoirs . The stored river water is pumped to uplands by constructing a series of embankment canals and pumped storage hydroelectric stations for the purpose of energy storage, irrigation, industrial, municipal, rejuvenation of over exploited rivers, etc. These multipurpose coastal reservoir projects offer massive pumped-storage hydroelectric potential to utilize variable and intermittent solar and wind power that are carbon-neutral, clean, and renewable energy sources. The use of underground reservoirs has been investigated. Recent examples include
3654-430: The second half of the 19th Century. The deepest shaft extends 1,406 metres vertically underground. A recent pre-feasibility study has shown the concept to be viable with a generation capacity of 30 MW and a run time of 6 hours using a water head of over 750 metres. US-based start-up Quidnet Energy is exploring using abandoned oil and gas wells for pumped storage. If successful they hope to scale up, utilizing some of
3717-424: The total installed capacity of small pumped-storage hydropower plants in 2011 could be increased by 3 to 9 times by providing adequate policy instruments . Using a pumped-storage system of cisterns and small generators, pico hydro may also be effective for "closed loop" home energy generation systems. In March 2017, the research project StEnSea (Storing Energy at Sea) announced their successful completion of
3780-410: The upper lake collects significant rainfall, or is fed by a river, then the plant may be a net energy producer in the manner of a traditional hydroelectric plant. Pumped storage is by far the largest-capacity form of grid energy storage available, and, as of 2020 , accounts for around 95% of all active storage installations worldwide, with a total installed throughput capacity of over 181 GW and
3843-434: The working fluid and, for water turbines, maintains the suction imparted by the draft tube . Francis turbines and most steam turbines use this concept. For compressible working fluids, multiple turbine stages are usually used to harness the expanding gas efficiently. Newton's third law describes the transfer of energy for reaction turbines. Reaction turbines are better suited to higher flow velocities or applications where
SECTION 60
#17327661600043906-524: Was considered for Lanai, Hawaii, and seawater-based projects have been proposed in Ireland. A pair of proposed projects in the Atacama Desert in northern Chile would use 600 MW of photovoltaic solar (Skies of Tarapacá) together with 300 MW of pumped storage (Mirror of Tarapacá) lifting seawater 600 metres (2,000 ft) up a coastal cliff. Freshwater from the river floods is stored in
3969-714: Was contested with broad resistance from environmental protection groups, in particular from the Green League. The project was first discussed in 1965 and in 1975 geological investigations were carried out. Planning was halted in 1980–1981 due to funding issues but was then resumed in 1988. Construction eventually began in 1997 and the first generators were commissioned in 2003. It was officially opened on 30 September 2003. In 2004, all four generators were commissioned. The construction costs amounted to 600 million euros. Pumped-storage Pumped-storage hydroelectricity ( PSH ), or pumped hydroelectric energy storage ( PHES ),
#3996