Ffestiniog pumped storage power station upper reservoir

Grid energy storage lets energy producers send excess electricity over the electricity transmission grid to temporary electricity storage sites that become energy producers when electricity demand is greater. For example: Image File history File links Stwlan. ... Image File history File links Stwlan. ... Llan Ffestiniog, also known as Ffestiniog or Llan is a small town in Gwynedd, traditional county of Merionethshire, north Wales, lying south of Blaenau Ffestiniog. ... Itaipu Dam is a hydroelectric generating station Electricity generation is the first process in the delivery of electricity to consumers. ... Power line redirects here. ... Energy storage is the storing of some form of energy that can be drawn upon at a later time to perform some useful operation. ...

• A large expensive nuclear or coal plant can optimally run at full power 24/7, including overnight when businesses and households need about half their daily electricity maximum.

• The cheap nightly electricity on the grid is used by a pumped-storage hydroelectric power plant to push water hundreds of feet uphill from a lower storage lake to an upper storage lake, effectively storing the electricity as higher elevation water.

• When electricity demand begins peaking in the afternoon and whenever rapid supply adjustments are needed, the pumped water storage power plant becomes an electricity producer by sending water downhill from the upper to lower lakes through a turbine that generates electricity.

• Photovoltaic and wind turbine users can avoid the necessity of having battery storage by connecting to the grid, which effectively becomes a giant battery. Very Large Scale photovoltaic operation will in turn necessitate storage for night time use.

• "Grid energy storage" is closely related to distributed generation. For distributed generation to function correctly, specialized technical and economic arrangements (such as net metering and vehicle-to-grid power systems) may be needed, and often require regulatory support.

Connecting everyone to the same electricity grid increases economic efficiency and lowers costs for everyone by promoting specialization: A nuclear power station. ... Mohave Generating Station, a 1,580 MW coal power plant near Laughlin, Nevada A fossil fuel power plant is an energy conversion center that burns fossil fuels to produce electricity, designed on a large scale for continuous operation. ... Pumped storage hydroelectricity is a method of storing and producing electricity to supply high peak demands by moving water between reservoirs at different elevations. ... Pumped storage hydroelectricity is a method of storing and producing electricity to supply high peak demands by moving water between reservoirs at different elevations. ... A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ... Worldwide installed capacity and prediction 1997-2010, Source: WWEA Wind power is the conversion of wind energy into more useful forms, usually electricity, using wind turbines. ... A Pair of AA Energizer Alkaline Cells Symbols representing a single Cell (top) and Battery (bottom), used in circuit diagrams. ... Distributed generation is a new trend in the generation of heat and electrical power. ... Net metering is a state level electricity policy for consumers who own qualifying facilities, which are generally smaller, renewable energy sources such as a wind or solar power. ... Vehicle to Grid (V2G) technology is a bi-directional grid interface for gridable vehicles such as Battery Electric Vehicles and Plug-in Hybrid Electric Vehicles. ...

1. Nearly everyone connected to the grid consumes power, i.e. homeowners, businesses, etc.
2. A tiny percentage of users produce net power for the grid.
3. Another tiny percentage of users temporarily draw power from the grid to store energy, then use the stored energy to produce electricity at other times. They profit from time-of-day pricing, i.e. buy power when demand and prices are low, then sell power when demand and prices are higher.

Portability

This is the area of greatest success for current energy storage technologies. Single-use and rechargeable batteries are ubiquitous, and provide power for devices with demands as varied as digital watches and cars. Advances in battery technology have generally been slow, however, with much of the advance in battery life that consumers see being attributable to efficient power management rather than increased storage capacity. This has become an issue as pressure grows for alternatives to the internal combustion engine in cars and other means of transport. These uses require far more energy density (the amount of energy stored in a given volume or weight) than current battery technology can deliver. Liquid hydrocarbon fuel (such as gasoline,ethanol/petrol and diesel) have much higher energy densities. This article does not cite any references or sources. ... Energy density is the amount of energy stored in a given system or region of space per unit volume or per unit mass, depending on the context. ... Oil refineries are key to obtaining hydrocarbons; crude oil is processed through several stages to form desirable hydrocarbons, used in fuel and other commercial products. ... Gasoline or petrol is a petroleum-derived liquid mixture consisting mostly of hydrocarbons and enhanced with benzene or iso-octane to increase octane ratings, used as fuel in internal combustion engines. ... Gasoline, as it is known in North America, or petrol, in many Commonwealth countries (sometimes also called motor spirit) is a petroleum-derived liquid mixture consisting primarily of hydrocarbons, used as fuel in internal combustion engines. ... Diesel or diesel fuel is a specific fractional distillate of fuel oil (mostly petroleum) that is used as fuel in a diesel engine invented by German engineer Rudolf Diesel. ...

Reliability

Virtually all devices that operate on electricity are adversely affected by the sudden removal of their power supply. Solutions such as UPS (uninterruptible power supplies) or backup generators are available, but these are expensive. Efficient methods of power storage would allow for devices to have a built-in backup for power cuts, and also reduce the impact of a failure in a generating station. Examples of this are currently available using fuel cells and flywheels. An uninterruptible power supply (UPS), uninterruptible power source or sometimes called a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ...

Economics of electricity storage

Generally speaking, energy storage is economical when the marginal cost of electricity varies more than the costs of storing and retrieving the energy plus the price of energy lost in the process. For instance, assume a pumped-storage reservoir can pump to its upper reservoir water equivalent to 1,200 MWh during the night, for $15 per MWh, at a total cost of $18,000. The next day, all of the stored energy can be sold at the peak hours for $40 per MWh, but from the 1,200 MWh pumped 50 were lost due to evaporation and seeping in the reservoir. 1,150 MWh are sold for $46,000, for a final profit of $28,000. In economics and finance, marginal cost is the change in total cost that arises when the quantity produced changes by one unit. ... Pumped storage hydroelectricity is a method of storing and producing electricity to supply high peak demands by moving water between reservoirs at different elevations. ... The megawatt-hour (symbol: MWh) is a unit for measuring energy. ...

However, the marginal cost of electricity varies because of the varying operational and fuel costs of different classes of generators. At one extreme, base load power plants such as coal-fired power plants and nuclear power plants are low marginal cost generators, as they have high capital and maintenance costs but low fuel costs. At the other extreme, peaking power plants such as gas turbine natural gas plants burn expensive fuel but are cheaper to build, operate and maintain. To minimize the total operational cost of generating power, base load generators are dispatched most of the time, while peak power generators are dispatched only when necessary, generally when energy demand peaks. This is called "economic dispatch". A base load power plant is one that provides a steady flow of power regardless of total power demand by the grid. ... A fossil fuel power plant is an energy conversion center that combusts fossil fuels to produce electricity, designed on a large scale for continuous operation. ... A nuclear power station. ... Peaking power plants (also known as Peaker Plants) are power plants that generally run only when there is a high demand, known as peak demand, for electricity. ... This machine has a single-stage centrifugal compressor and turbine, a recuperator, and foil bearings. ... Natural gas is a gaseous fossil fuel consisting primarily of methane but including significant quantities of ethane, butane, propane, carbon dioxide, nitrogen, helium and hydrogen sulfide. ...

Demand for electricity from the world's various grids varies over the course of the day and from season to season. For the most part, variation in electric demand is met by varying the amount of electrical energy supplied from primary sources. Increasingly, however, operators are storing lower-cost energy produced at night, then releasing it to the grid during the peak periods of the day when it is more valuable. In areas where hydroelectric dams exist, release can be delayed until demand is greater; this form of storage is common and can make use of existing reservoirs. This is not storing "surplus" energy produced elsewhere, but the net effect is the same - although without the efficiency losses. Renewable supplies with variable production, like wind and solar power, tend to increase the net variation in electric load, increasing the opportunity for grid energy storage. Lightning strikes during a night-time thunderstorm. ... Worldwide installed capacity and prediction 1997-2010, Source: WWEA Wind power is the conversion of wind energy into more useful forms, usually electricity, using wind turbines. ... Solar power describes a number of methods of harnessing energy from the light of the sun. ...

Load Levelling

The demand for electricity from consumers and industry is constantly changing, broadly within the following categories:

• Seasonal (during dark winters more electric lighting and heating is required, while in other climates hot weather boosts the requirement for air conditioning)
• Weekly (most industry closes at the weekend, lowering demand)
• Daily (such as the peak as everyone arrives home and switches the television on)
• Hourly (one method for estimating television viewing figures in the United Kingdom is to measure the power spike when advertisements are shown and everyone goes to switch the kettle on)
• Transient (fluctuations due to individual's actions, differences in power transmission efficiency and other small factors that need to be accounted for)

There are currently three main methods for dealing with changing demand:

• Electrical devices generally having a working voltage range that they require, commonly 110-120V or 220-240V. Minor variations in load are automatically smoothed by slight variations in the voltage available across the system.
• Power plants can be run below their normal output, with the facility to increase the amount they generate almost instantaneously. This is termed 'Spinning Reserve'.
• Additional power plants can be brought online to provide a larger generating capacity. Typically, these would be combustion gas turbines, which can be started in a matter of minutes.

The problem with relying on these last two methods in particular is that they are expensive, because they leave expensive generating equipment unused much of the time, and because plants running below maximum output usually produce at less than their best efficiency. Grid energy storage is used to shift load from peak to off-peak hours. Power plants are able to run closer to their peak efficiency for much of the year. International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ...

Energy demand management

Main article: Energy demand management Energy demand management is also known as demand side management (DSM). ...

The easiest way to deal with varying electrical loads is to decrease the difference between varying generation and demand. This is referred to as demand side management (DSM). For decades, utilities have sold off-peak power to large consumers at lower rates, to encourage these users to shift their loads to off-peak hours, in the same way that telephone companies do with individual customers. Usually, these time-dependent prices are negotiated ahead of time. In an attempt to save more money, some utilities are experimenting with selling electricity at minute-by-minute spot prices, which allow those users with monitoring equipment to detect demand peaks as they happen, and shift demand to save both the user and the utility money. Demand side management can be manual or automatic and is not limited to large industrial customers. In residential and small business applications, for example, appliance control modules can reduce energy usage of water heaters, air conditioning units, and other devices during these periods by turning them off for some portion of the peak demand time or by reducing the power that they draw. Energy demand management includes more than reducing overall energy use or shifting loads to off-peak hours. A particularly effective method of energy demand management is the installation of more energy efficient equipment. For example, many utilities give rebates for the purchase of insulation, weatherstripping, and appliances and light bulbs that are energy efficient. Companies with factories and large buildings can also install such products, but they can also buy energy efficient industrial equipment, like boilers, or use more efficient processes to produce products. Companies may get incentives like rebates or low interest loans from utilities or the government for the installation of energy efficient industrial equipment. The spot price of a commodity or a security or a currency is the price that is quoted for settlement (payment and delivery) of the transaction immediately. ... A trio of propane water heaters. ... Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ... Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. ... Thermal insulation on the Huygens probe The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. ... Weatherstripping is the process of sealing openings such as doors, windows, and trunks from the elements. ... The light bulb is one of the most significant inventions in the history of the human race, illuminating the darkness of the evening and bringing light indoors at all times in order focus on the task at hand. ... A boiler is a closed vessel in which water or other fluid is heated under pressure. ...

Pumped water storage

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

In many places, pumped storage hydroelectricity is used to even out the daily generating load, by pumping water to a high storage reservoir during off-peak hours and weekends, using the excess base-load capacity from coal or nuclear sources. During peak hours, this water can be used for hydroelectric generation, often as a high value rapid-response reserve to cover transient peaks in demand. There is over 90 GW of pumped storage in operation, which is about 3% of global generation capacity. Pumped storage recovers about 75% of the energy consumed, and is currently the most cost effective form of mass power storage. The chief problem with pumped storage is that it usually requires two nearby reservoirs at considerably different heights, for which there are few suitable locations, and often requires considerable capital expenditure. Traditional hydroelectric dam configurations are far more common than pumped storage; in this configuration, release is delayed until needed. The net effect is the same as pumped storage, but without the round-trip efficiency loss. Additionally a new concept in pumped-storage is utilizing wind energy to pump water. Wind turbines that direct drive water pumps for an 'energy storing wind dam' can make this a more efficient process. Hydroelectric dam diagram The waters of Llyn Stwlan, the upper reservoir of the Ffestiniog Pumped-Storage Scheme in north Wales, can just be glimpsed on the right. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Horizontal-axis wind turbine, the Enercon model E-66 wind energy converter, in Germany. ...

Compressed air storage

Main article: Compressed air energy storage Compressed Air Energy Storage (CAES) refers to the compression of air during periods of low energy demand, for use in meeting periods of higher demand. ...

Another grid energy storage method is to use off-peak electricity to compress air, which is usually stored in an old mine or some other kind of geological feature. When electricity demand is high, the compressed air is heated with a small amount of natural gas and then goes through expanders to generate electricity. Compressed air is used to refer to: Pneumatics, the use of pressurized gases to do work, as used in the Air car Breathing gas, often used in scuba diving, also to inflate buoyancy devices Compressed air can also be used for cooling using a vortex tube. ... Chuquicamata, the largest open pit copper mine in the world, Chile. ... Natural gas is a gaseous fossil fuel consisting primarily of methane but including significant quantities of ethane, butane, propane, carbon dioxide, nitrogen, helium and hydrogen sulfide. ...

Thermal energy storage

Main article: Thermal energy storage Thermal energy storage can refer to a number of technologies that store energy in a thermal reservoir for later reuse. ...

Off-peak electricity can be used to make ice from water, and the ice can be stored until the next day, when it is used to cool either the air in a large building, thereby shifting that demand off-peak, or the intake air of a gas turbine generator, thereby increasing the on-peak generation capacity. Snowflakes by Wilson Bentley, 1902 Ice is the name given to any one of the 14 known solid phases of water. ... This machine has a single-stage centrifugal compressor and turbine, a recuperator, and foil bearings. ... “Dynamo” redirects here. ...

Battery storage

Main article: Battery (electricity) A Pair of AA Energizer Alkaline Cells Symbols representing a single Cell (top) and Battery (bottom), used in circuit diagrams. ...

Battery storage was used in the very early days of electric power networks, but is no longer common. Many "off-the-grid" domestic systems rely on battery storage, as well as most telephone systems, but means of storing large amounts of electricity as such in giant batteries or by other electrical means have not yet been put to general use. Batteries are generally expensive, have maintenance problems, and have limited lifespans. One possible technology for large-scale storage are large-scale flow batteries. Sodium-sulfur batteries could also be inexpensive to implement on a large scale and have been used for grid storage in Japan and in the United States[1]. Vanadium redox batteries and other types of flow batteries are also beginning to be used for energy storage including the averaging of generation from wind turbines. Battery storage has relatively high efficiency, as high as 90% or better. This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... A Flow Battery is a form of secondary battery in which the electrolytes are not confined to within the power cell its self. ... A NaS battery is a type of battery constructed from sodium (Na) and sulfur (S). ... The vanadium redox ( and redox flow ) battery was first patented by the University of New South Wales in Australia in 1986. ...

When battery electric vehicles come in to wide use with modern high cycle batteries [2] [3], such mobile energy sinks could be utilized for their energy storage capabilities. Vehicle-to-grid technology could be employed, turning each vehicle with its 20 to 50 kWh battery pack into a distributed load-balancing device or emergency power source. This represents 2 to 5 days per vehicle of average household requirements of 10 kWh per day, assuming annual consumption of 3650 kWh. This quantity of energy is equivalent to between 40 and 300 miles of range in such vehicles consuming 0.5 to 0.16 kWh per mile. These figures can be achieved even in home-made electric vehicle conversions. The Toyota RAV4 EV was powered by twenty-four 12 volt batteries, with an operational cost equivalent of over 165 miles per gallon at 2005 US gasoline prices. ... Vehicle to Grid (V2G) technology is a bi-directional grid interface for gridable vehicles such as Battery Electric Vehicles and Plug-in Hybrid Electric Vehicles. ... A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. ... An electric vehicle conversion is the modification of a conventional internal combustion engine (ICE) driven vehicle to battery electric propulsion, creating a battery electric vehicle. ...

Flywheel storage

Main article: Flywheel energy storage NASA G2 flywheel Flywheel Energy Storage (FES) works by accelerating a rotor to a very high speed and maintaining the energy in the system as inertial energy. ...

Mechanical inertia is the basis of this storage method. A heavy rotating disc is accelerated by an electric motor, which acts as a generator on reversal, slowing down the disc and producing electricity. Electricity is stored as the kinetic energy of the disc. Friction must be kept to a minimum to prolong the storage time. This is often achieved by placing the flywheel in a vacuum and using magnetic bearings, tending to make the method expensive. Larger flywheel speeds allow greater storage capacity but require strong materials such as steel or composite materials to resist the centrifugal forces (or rather, to provide centripetal forces). The use of carbon nanotubes as a flywheel material is being researched. The ranges of power and energy storage technically and economically achievable, however, tend to make flywheels unsuitable for general power system application; they are probably best suited to load-leveling applications on railway power systems and for improving power quality in renewable energy systems. One application that currently uses flywheel storage is applications that require very high bursts of power for very short durations such as tokamak and laser experiments where a motor generator is spun up to operating speed and may actually come to a stop in one revolution. Flywheel storage is also currently used to provide Uninterruptible Power Supply systems (such as those in large datacenters) the ride-through power necessary during transfer. (That is, the relatively brief amount of time between a loss of power to the mains and the warm-up of an alternate source, such as a diesel generator.) Rotating magnetic field as a sum of magnetic vectors from 3 phase coils An electric motor converts electrical energy into mechanical energy. ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... friction is the force that opposes the relative motion or tendency toward such motion of two surfaces in contact. ... A magnetic bearing is a bearing which supports a load using magnetic levitation. ... The steel cable of a colliery winding tower. ... A cloth of woven carbon fiber filaments, a common element in composite materials Composite materials (or composites for short) are engineered materials made from two or more constituent materials with significantly different physical or chemical properties and which remain separate and distinct within the finished structure. ... The expression centrifugal force is used to express that if an object is being swung around on a string the object seems to be pulling on the string. ... The centripetal force is the external force required to make a body follow a circular path at constant speed. ... 3D model of three types of single-walled carbon nanotubes. ... Power quality is a term used to discuss events on electric power grids that can damage or disrupt sensitive electronic devices. ... World renewable energy in 2005 (except 2004 data for items marked* or **). Enlarge image to read exclusions. ... A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot. ... Experiment with a laser (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: Light Amplification by Stimulated Emission of Radiation. ... An uninterruptible power supply (UPS), uninterruptible power source or sometimes called a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available. ... A data center is a facility used for housing a large amount of electronic equipment, typically computers and communications equipment. ... A diesel generator is the combination of a diesel engine with an electrical generator (often called an alternator) to generate electric energy. ...

Superconducting magnetic energy storage

Main article: Superconducting magnetic energy storage Superconducting magnetic energy storage (SMES) uses superconductivity - the ability of certain materials to conduct electricity without resistance - to store electrical energy. ...

Superconducting magnetic energy storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature. A typical SMES system includes three parts: superconducting coil, power conditioning system and cryogenically cooled refrigerator. Once the superconducting coil is charged, the current will not decay and the magnetic energy can be stored indefinitely. The stored energy can be released back to the network by discharging the coil. The power conditioning system uses an inverter/rectifier to transform alternating current (AC) power to direct current or convert DC back to AC power. The inverter/rectifier accounts for about 2-3% energy loss in each direction. SMES loses the least amount of electricity in the energy storage process compared to other methods of storing energy. SMES systems are highly efficient; the round-trip efficiency is greater than 95%. The high cost of superconductors is the primary limitation for commercial use of this energy storage method. Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges, such as those in electric currents and bar magnets. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. ... Cryogenics is a branch of physics (or engineering) that studies the production of very low temperatures (below –150 °C, –238 °F or 123 K) and the behavior of materials at those temperatures. ... A coil is a series of loops. ... An inverter is an electronic circuit for converting direct current (DC) to alternating current (AC). ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ... City lights viewed in a motion blurred exposure. ... Lightning strikes during a night-time thunderstorm. ...

Due to the energy requirements of refrigeration, and the limits in the total energy able to be stored, SMES is currently used for short duration energy storage. Therefore, SMES is most commonly devoted to improving power quality. If SMES were to be used for utilities it would be a diurnal storage device, charged from base load power at night and meeting peak loads during the day. Refrigeration is the process of removing heat from an enclosed space, or from a substance, and rejecting it elsewhere for the primary purpose of lowering the temperature of the enclosed space or substance and then maintaining that lower temperature. ... Power quality is a term used to discuss events on electric power grids that can damage or disrupt sensitive electronic devices. ... A public utility is a company that maintains the infrastructure for a public service. ... Look up day in Wiktionary, the free dictionary. ... A base load power plant is one that provides a steady flow of power regardless of total power demand by the grid. ... Peaking power plants (also known as Peaker Plants) are power plants that generally run only when there is a high demand, known as peak demand, for electricity. ...

Hydrogen

Main article: Hydrogen economy A hydrogen economy is a hypothetical economy in which energy is stored and transported as hydrogen (H2). ...

Hydrogen is not a primary energy source, but a portable energy storage method, because it must first be manufactured by other energy sources in order to be used. However, as a storage medium, it may be a significant factor in using renewable energies. See hydrogen storage. [4] Hydrogen may be used in conventional internal combustion engines, or in fuel cells which convert chemical energy directly to electricity without flames, similar to the way the human body burns fuel. Making hydrogen requires either reforming natural gas with steam, or, for a possibly renewable and more ecologic source, the electrolysis of water into hydrogen and oxygen. The former process has carbon dioxide as a by-product. With electrolysis, the greenhouse burden depends on the source of the power. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Hydrogen storage is the main technological problem of a viable hydrogen economy. ... This article does not cite any references or sources. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ... Hoffman voltameter used to electrolyze water. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... In order to meet Wikipedias quality standards, this article requires cleanup. ...

With intermittent renewables such as solar and wind, the output may be fed directly into an electricity grid. At penetrations below 20% of the grid demand, this does not severely change the economics; but beyond about 20% of the total demand, external storage will become important. If these sources are used for electricity to make hydrogen, then they can be utilized fully whenever they are available, opportunistically. Broadly speaking, it does not matter when they cut in or out, the hydrogen is simply stored and used as required.

Nuclear advocates note that using nuclear power to manufacture hydrogen would help solve plant inefficiencies. Here the plant would be run continuously at full capacity, with perhaps all the output being supplied to the grid in peak periods, and any not needed to meet demand being used to make hydrogen at other times. This would mean far better efficiency for the nuclear power plants. High temperature (950-1,000°C) gas cooled nuclear reactors have the potential to split hydrogen from water by thermochemical means using nuclear heat (i.e. without using electrolysis).

About 50 kWh (180 MJ) is required to produce a kilogram of hydrogen by electrolysis, so the cost of the electricity clearly is crucial. At $0.03/kWh, common off-peak high-voltage line rate in the U.S., this means hydrogen costs $1.50 a kilogram for the electricity, equivalent to $1.50 a US gallon for gasoline if used in a fuel cell vehicle. Other costs would include the electrolyzer plant, compressors, liquefaction, storage and transportation, which will be significant. The round trip efficiency for hydrogen storage is typically 50 to 60% for generation and 50 to 60% for storage or 25 to 36%, much lower than pumped storage or batteries. Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from... Gasoline or petrol is a petroleum-derived liquid mixture consisting mostly of hydrocarbons and enhanced with benzene or iso-octane to increase octane ratings, used as fuel in internal combustion engines. ... A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. ... Liquefaction may refer to: Soil liquefaction, the process by which sediments are converted into suspension, as in earthquake liquefaction, quicksand, quick clay, and turbidity currents. ...

See also

Energy Portal

• Battery-to-grid
• Distributed generation
• Energy storage
• Virtual power plant
• Wind farm

Image File history File links Portal. ... Vehicle to Grid (V2G) technology is a bi-directional grid interface for gridable Electric vehicles such as Battery Electric Vehicles (BEV) and Plug-in Hybrid Electric Vehicles (PHEV). ... Distributed generation is a new trend in the generation of heat and electrical power. ... Energy storage is the storing of some form of energy that can be drawn upon at a later time to perform some useful operation. ... A virtual power plant is a cluster of distributed generation installations (such as microCHP, wind-turbines, hydrogen stations, back-up gensets etc. ... A wind farm is a collection of wind turbines in the same location. ...

External links

• Electricity storage technologies
• Graphical comparisons of different energy storage systems:
  • System power ratings
  • Energy density
  • Cost per unit
  • Efficiency
  • Capital cost per cycle
  • A large grid-connected nickel-cadmium battery