Grid energy storage
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Grid energy storage (also called large-scale energy storage) is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexpensive (especially from variable renewable energy sources such as wind power and solar power) or when demand is low, and later returned to the grid when demand is high, and electricity prices tend to be higher.
As of 2023[update], the largest form of grid energy storage is pumped-storage hydroelectricity, with utility-scale batteries and behind-the-meter batteries coming second and third.[1] Developments in battery storage have enabled commercially viable projects to store energy during peak production and release during peak demand, and for use when production unexpectedly falls giving time for slower responding resources to be brought online.
Green hydrogen, which is generated from electrolysis of water via electricity generated by renewables or relatively lower carbon emission sources, is a more economical means of long-term renewable energy storage in terms of capital expenditures than pumped-storage hydroelectricity or batteries.[2][3]
Two alternatives to grid storage are the use of peaking power plants to fill in supply gaps and demand response to shift load to other times.
Benefits
[edit]Energy storage can provide multiple benefits to the grid: it can move electricity from periods of low prices to high prices, it can help make the grid more stable (for instance help regulate the frequency of the grid), and help reduce investment into transmission infrastructure.[4] Any electrical power grid must match electricity production to consumption, both of which vary significantly over time. Any combination of energy storage and demand response has these advantages:
- fuel-based power plants (i.e. coal, oil, gas, nuclear) can be more efficiently and easily operated at constant production levels
- electricity generated by intermittent sources can be stored and used later, whereas it would otherwise have to be transmitted for sale elsewhere, or shut down
- peak generating or transmission capacity can be reduced by the total potential of all storage plus deferrable loads (see demand side management), saving the expense of this capacity
- more stable pricing – the cost of the storage or demand management is included in pricing so there is less variation in power rates charged to customers, or alternatively (if rates are kept stable by law) less loss to the utility from expensive on-peak wholesale power rates when peak demand must be met by imported wholesale power
- emergency preparedness – vital needs can be met reliably even with no transmission or generation going on while non-essential needs are deferred
Energy derived from solar, tidal and wind sources inherently varies on time scales ranging from minutes to weeks or longer – the amount of electricity produced varies with time of day, moon phase, season, and random factors such as the weather. Thus, renewables in the absence of storage present special challenges to electric utilities. While hooking up many separate wind sources can reduce the overall variability, solar is reliably not available at night, and tidal power shifts with the moon, so slack tides occur four times a day.
How much this affects any given utility varies significantly. In a summer peak utility, more solar can generally be absorbed and matched to demand. In winter peak utilities, to a lesser degree, wind correlates to heating demand and can be used to meet that demand. Depending on these factors, beyond about 20–40% of total generation, grid-connected intermittent sources such as solar power and wind power tend to require investment in grid interconnections, grid energy storage or demand-side management.
In an electrical grid without energy storage, generation that relies on energy stored within fuels (coal, biomass, natural gas, nuclear) must be scaled up and down to match the rise and fall of electrical production from intermittent sources (see load following power plant). While hydroelectric and natural gas plants can be quickly scaled up or down to follow the demand, wind, coal and nuclear plants take considerable time to respond to load. Utilities with less natural gas or hydroelectric generation are thus more reliant on demand management, grid interconnections or costly pumped storage.
Demand side management and grid storage
[edit]The demand side can also store electricity from the grid, for example charging a battery electric vehicle stores energy for a vehicle and storage heaters, district heating storage or ice storage provide thermal storage for buildings.[5] At present this storage serves only to shift consumption to the off-peak time of day, no electricity is returned to the grid.
The need for grid storage to provide peak power is reduced by demand side time of use pricing, one of the benefits of smart meters. At the household level, consumers may choose less expensive off-peak times to wash and dry clothes, use dishwashers, take showers and cook. As well, commercial and industrial users will take advantage of cost savings by deferring some processes to off-peak times.
Regional impacts from the unpredictable operation of wind power has created a new need for interactive demand response, where the utility communicates with the demand. Historically this was only done in cooperation with large industrial consumers, but now may be expanded to entire grids.[6] For instance, a few large-scale projects in Europe link variations in wind power to change industrial food freezer loads, causing small variations in temperature. If communicated on a grid-wide scale, small changes to heating/cooling temperatures would instantly change consumption across the grid.
A report released in December 2013 by the United States Department of Energy further describes the potential benefits of energy storage and demand side technologies to the electric grid: "Modernizing the electric system will help the nation meet the challenge of handling projected energy needs—including addressing climate change by integrating more energy from renewable sources and enhancing efficiency from non-renewable energy processes. Advances to the electric grid must maintain a robust and resilient electricity delivery system, and energy storage can play a significant role in meeting these challenges by improving the operating capabilities of the grid, lowering cost and ensuring high reliability, as well as deferring and reducing infrastructure investments. Finally, energy storage can be instrumental for emergency preparedness because of its ability to provide backup power as well as grid stabilization services".[7]
Energy storage for grid applications
[edit]Energy storage assets are a valuable asset for the electrical grid.[8] They can provide benefits and services such as load management, power quality and uninterruptible power supply to increase the efficiency and supply security. This becomes more and more important in regard to the energy transition and the need for a more efficient and sustainable energy system.
Numerous energy storage technologies (pumped-storage hydroelectricity, electric battery, flow battery, flywheel energy storage, supercapacitor etc.) are suitable for grid-scale applications, however their characteristics differ. For example, a pumped-hydro station is well suited for bulk load management applications due to their large capacities and power capabilities. However, suitable locations are limited and their usefulness fades when dealing with localized power quality issues. On the other hand, flywheels and capacitors are most effective in maintaining power quality but lack storage capacities to be used in larger applications. These constraints are a natural limitation to the storage's applicability.
Several studies have developed interest and investigated the suitability or selection of the optimal energy storage for certain applications. Literature surveys comprise the available information of the state-of-the-art and compare the storage's uses based on current existing projects.[9][10] Other studies take a step further in evaluating energy storage with each other and rank their fitness based on multiple-criteria decision analysis.[11][12] Another paper proposed an evaluation scheme through the investigation and modelling of storage as equivalent circuits.[13][14] An indexing approach has also been suggested in a few studies, but is still in the novel stages.[15] In order to gain increased economic potential of grid connected energy storage systems, it is of interest to consider a portfolio with several services for one or more applications for an energy storage system. By doing so, several revenue streams can be achieved by a single storage and thereby also increasing the degree of utilization.[16] To mention two examples, a combination of frequency response and reserve services is examined in,[17] meanwhile load peak shaving together with power smoothing is considered in.[18]
Forms
[edit]Air
[edit]Compressed air
[edit]Compressed air energy storage (CAES) stores electricity by compressing air. The compressed air is typically stored in large underground caverns. The expanding air can be used to drive turbines, converting the energy back into electricity. As air cools when expanding, some heat needs to be added in this stage to prevent freezing. This can be provided by heat stored from a low-carbon source, or in the case of advanced CAES, from reusing the heat that is released when air is compressed. As of 2023[update], there are three advanced CAES project in operation in China.[19] Typical efficiencies of advanced CAES are between 60% and 80%.[20]
Liquid air
[edit]Another electricity storage method is to compress and cool air, turning it into liquid air, which can be stored, and expanded when needed, turning a turbine, generating electricity. This is called liquid air energy storage (LAES).[21] The air would be cooled to temperatures of −196 °C (−320.8 °F) to become liquid. Like with compressed air, heat is needed for the expansion step. In the case of LAES, low-grade industrial heat can be used for this.[22] Energy efficiency for LEAS lies between 50% and 70%. As of 2023[update], LAES is moving from pre-commercial to commercial.[23]
Batteries
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Lithium-ion batteries
[edit]Lithium-ion batteries are the most commonly used batteries for grid applications, as of 2024[update], following the application of batteries in electric vehicles (EVs). In comparison with EVs, grid batteries require less energy density, meaning that more emphasis can be put on costs, the ability to charge and discharge often and lifespan. This has led to a shift towards lithium iron phosphate batteries, which is cheaper and has a longer lifespan than traditional lithium-ion batteries.[27] Lithium-ion batteries is highly suited to short-duration storage (<8h), but unlikely to become the cheapest form of electricity storage for longer-duration storage.[27]
Costs of batteries are declining rapidly; from 2010 to 2023 costs fell by 90%.[28] As of 2024[update], utility-scale systems account for two thirds of added capacity, and home applications (behind-the-meter) for one third.[29]
Flow batteries
[edit]In redox flow batteries, energy is stored in liquids, which are placed in two separate tanks. When charging or discharging, the liquids are pumped into a cell with the electrodes. The amount of energy stored (as set by the size of the tanks) can be adjusted separately from the power output (as set by the speed of the pumps).[30] Flow batteries have the advantages of low capital cost for charge-discharge duration over 4 h, and of long durability (many years). Flow batteries are inferior to lithium-ion batteries in terms of energy efficiency, averaging efficiencies between 60 and 75%. Vanadium redox batteries is most commercially advanced type of flow battery, with roughly 40 companies making them as of 2022[update].[31]
Other battery types
[edit]Sodium-ion batteries are possible alternative to lithium-ion batteries, as they rely on cheaper materials and less on critical materials. It has a lower energy density, and possibly a shorter lifespan. If produced at the same scale as lithium-ion batteries, they may become 20% to 30% cheaper.[30]
Molten salt batteries are composed of two molten metal alloys separated by an electrolyte. They are simple to manufacture but require a temperature of several hundred degree Celsius to keep the alloys in a liquid state. This technology includes ZEBRA, sodium-sulfur batteries and liquid metal.[32] Sodium sulphur batteries are being used for grid storage in Japan and in the United States.[33]
Technology | Less than 4h | 4h to 8h | Days | Weeks | Seasons |
---|---|---|---|---|---|
Li-ion | Yes | Yes | No | No | No |
Sodium-ion | Yes | Yes | No | No | No |
Vanadium flow | Maybe | Yes | Yes | No | No |
Iron-air | No | No | Maybe | Yes | No |
Electric vehicles
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The electric vehicle fleet has a large overall battery capacity, which can potentially be used for grid energy storage. This could be in the form of vehicle-to-grid (V2G), where cars store energy when they are not in use, or by repurposing batteries from cars at the end of the vehicle's life. Car batteries typically range between 33 and 100 kWh;[35] for comparison, a typical upper-middle-class household in Spain might use some 18 kWh in a day.[36] As of 2024[update], there have been more than 100 V2G pilot projects globally.[37] The effect of V2G charging on battery life can be positive or negative. Increased cycling of batteries can lead to faster degradation, but due to better management of the state of charge and gentler charging and discharing, V2G might instead increase the lifetime of batteries.[37][38] Second-hand batteries may be useable for stationary grid storage for roughly 6 years, when their capacity drops from roughly 80% to 60% of the initial capacity. LFP batteries are particularly suitable to second-use application, as they degrade less than other lithium-ion batteries and recycling is less attractive as their materials are not as valuable.[37]
Flywheel
[edit]![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/2f/G2_front2.jpg/220px-G2_front2.jpg)
Mechanical inertia is the basis of this storage method. When the electric power flows into the device, an electric motor accelerates a heavy rotating disc. The motor acts as a generator when the flow of power is reversed, 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. Greater flywheel speeds allow greater storage capacity but require strong materials such as steel or composite materials to resist the centrifugal forces. The ranges of power and energy storage technology that make this method economic, however, tends 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 such as the 20MW system in Ireland.[39][40]
Flywheel storage is also currently used in the form of the Diesel rotary uninterruptible power supply to provide uninterruptible power supply systems (such as those in large datacenters) for ride-through power necessary during transfer[41] – 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.
This potential solution has been implemented by EDA[42][better source needed] in the Azores on the islands of Graciosa and Flores. This system uses an 18 megawatt-second flywheel to improve power quality and thus allow increased renewable energy usage. As the description suggests, these systems are again designed to smooth out transient fluctuations in supply, and could never be used to cope with an outage exceeding a couple of days.
Powercorp in Australia have been developing applications using wind turbines, flywheels and low load diesel (LLD) technology to maximize the wind input to small grids. A system installed in Coral Bay, Western Australia, uses wind turbines coupled with a flywheel based control system and LLDs. The flywheel technology enables the wind turbines to supply up to 95 percent of Coral Bay's energy supply at times, with a total annual wind penetration of 45 percent.[43]
Hydrogen
[edit]Hydrogen can be used as a long-term storage medium.[44] Green hydrogen is produced from the electrolysis of water, and converted back into electricity in an internal combustion engine, or a fuel cell, with a round-trip efficiency of roughly 41%.[45] It is expected to be a more economical means of long-term renewable energy storage than pumped-storage hydroelectricity or batteries.[2][3]
The low efficiency of hydrogen storage imposes economic constraints.[46][47] The price ratio between purchase and sale of electricity must be at least proportional to the efficiency in order for the system to be economic. Whether hydrogen can use natural gas infrastructure depends on the network construction materials, standards in joints, and storage pressure.[48]
Underground hydrogen storage
[edit]Underground hydrogen storage is the practice of hydrogen storage in caverns, salt domes and depleted oil and gas fields.[49][50] Large quantities of gaseous hydrogen have been stored in caverns by Imperial Chemical Industries (ICI) for many years without any difficulties.[51] The European project Hyunder[52] indicated in 2013 that for the storage of wind and solar energy an additional 85 caverns are required as it cannot be covered by PHES and CAES systems.[53]
Power to gas
[edit]Power to gas is a technology which converts electrical power to a gas fuel. There are 2 methods, the first is to use the electricity for water splitting and inject the resulting hydrogen into the natural gas grid. The second less efficient method is used to convert carbon dioxide and water to methane, (see natural gas) using electrolysis and the Sabatier reaction. The excess power or off peak power generated by wind generators or solar arrays is then used for load balancing in the energy grid. Using the existing natural gas system for hydrogen, fuel cell maker Hydrogenics and natural gas distributor Enbridge have teamed up to develop such a power to gas system in Canada.[47]
Pipeline storage of hydrogen where a natural gas network is used for the storage of hydrogen. Before switching to natural gas, the German gas networks were operated using towngas, which for the most part consisted of hydrogen. The storage capacity of the German natural gas network is more than 200,000 GW·h which is enough for several months of energy requirement. By comparison, the capacity of all German pumped-storage power plants amounts to only about 40 GW·h. The transport of energy through a gas network is done with much less loss (<0.1%) than in a power network (8%)[clarification needed].
Ammonia
[edit]The power-to-ammonia concept offers a carbon-free energy storage route with a diversified application palette. At times when there is surplus low-carbon power, it can be used to create ammonia fuel. Ammonia may be produced by splitting water into hydrogen and oxygen with electricity, then high temperature and pressure are used to combine nitrogen from the air with the hydrogen, creating ammonia. As a liquid it is similar to propane, unlike hydrogen alone, which is difficult to store as a gas under pressure or to cryogenically liquefy and store at −253 °C.
Just like natural gas, the stored ammonia can be used as a thermal fuel for transportation and electricity generation or used in a fuel cell.[54] A standard 60,000 m³ tank of liquid ammonia contains about 211 GWh of energy, equivalent to the annual production of roughly 30 wind turbines. Ammonia can be burned cleanly: water and nitrogen are released, but no CO2 and little or no nitrogen oxides. Ammonia has multiple uses besides being an energy carrier, it is the basis for the production of many chemicals, the most common use is for fertilizer.[55] Given this flexibility of usage, and given that the infrastructure for the safe transport, distribution and usage of ammonia is already in place, it makes ammonia a good candidate to be a large-scale, non-carbon, energy carrier of the future.
Hydroelectricity
[edit]Pumped water
[edit]In 2008, world pumped-storage generating capacity was 104 GW,[56] while other sources claim 127 GW, which comprises the vast majority of all types of grid electric storage – all other types combined are some hundreds of MW.[57]
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. Pumped storage recovers about 70% to 85% of the energy consumed, and is currently the most cost effective form of mass power storage.[58] The chief problem with pumped storage is that it usually requires two nearby reservoirs at considerably different heights, and often requires considerable capital expenditure.[59]
Pumped water systems have high dispatchability, meaning they can come on-line very quickly, typically within 15 seconds,[60] which makes these systems very efficient at soaking up variability in electrical demand from consumers. There is over 90 GW of pumped storage in operation around the world, which is about 3% of instantaneous global generation capacity. Pumped water storage systems, such as the Dinorwig storage system in Britain, hold five or six hours of generating capacity,[60] and are used to smooth out demand variations.
Another example is the 1836 MW Tianhuangping Pumped-Storage Hydro Plant in China, which has a reservoir capacity of eight million cubic meters (2.1 billion U.S. gallons or the volume of water over Niagara Falls in 25 minutes) with a vertical distance of 600 m (1970 feet). The reservoir can provide about 13 GW·h of stored gravitational potential energy (convertible to electricity at about 80% efficiency), or about 2% of China's daily electricity consumption.[61]
A new concept in pumped-storage is utilizing wind energy or solar power to pump water. Wind turbines or solar cells that direct drive water pumps for an energy storing wind or solar dam can make this a more efficient process but are limited. Such systems can only increase kinetic water volume during windy and daylight periods. A study published in 2013 showed rooftop solar, coupled to existing pumped-storage, could replace the reactors lost at Fukushima with an equivalent capacity factor.[62]
Hydroelectric dams
[edit]![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/FeiCueiReservoir.jpg/220px-FeiCueiReservoir.jpg)
Hydroelectric dams with large reservoirs can also be operated to provide peak generation at times of peak demand. Water is stored in the reservoir during periods of low demand and released through the plant when demand is higher. The net effect is the same as pumped storage, but without the pumping loss. Depending on the reservoir capacity the plant can provide daily, weekly, or seasonal load following.
Many existing hydroelectric dams are fairly old (for example, the Hoover Dam was built in the 1930s), and their original design predated the newer intermittent power sources such as wind and solar by decades. A hydroelectric dam originally built to provide baseload power will have its generators sized according to the average flow of water into the reservoir. Uprating such a dam with additional generators increases its peak power output capacity, thereby increasing its capacity to operate as a virtual grid energy storage unit.[63][64] The United States Bureau of Reclamation reports an investment cost of $69 per kilowatt capacity to uprate an existing dam,[63] compared to more than $400 per kilowatt for oil-fired peaking generators. While an uprated hydroelectric dam does not directly store excess energy from other generating units, it behaves equivalently by accumulating its own fuel – incoming river water – during periods of high output from other generating units. Functioning as a virtual grid storage unit in this way, the uprated dam is one of the most efficient forms of energy storage, because it has no pumping losses to fill its reservoir, only increased losses to evaporation and leakage.
A dam which impounds a large reservoir can store and release a correspondingly large amount of energy, by controlling river outflow and raising or lowering its reservoir level a few meters. Limitations do apply to dam operation, their releases are commonly subject to government regulated water rights to limit downstream effect on rivers. For example, there are grid situations where baseload thermal plants, nuclear or wind turbines are already producing excess power at night, dams are still required to release enough water to maintain adequate river levels, whether electricity is generated or not. Conversely there's a limit to peak capacity, which if excessive could cause a river to flood for a few hours each day.[65]
Thermal
[edit]In Denmark the direct storage of electricity is perceived as too expensive for very large scale usage, albeit significant usage is made of existing Norwegian Hydro. Instead, the use of existing hot water storage tanks connected to district heating schemes, heated by either electrode boilers or heat pumps, is seen as a preferable approach. The stored heat is then transmitted to dwellings using district heating pipes.
Molten salt is used to store heat collected by a solar power tower so that it can be used to generate electricity in bad weather or at night.[66]
Building heating and cooling systems can be controlled to store thermal energy in either the building's mass or dedicated thermal storage tanks. This thermal storage can provide load-shifting or even more complex ancillary services by increasing power consumption (charging the storage) during off-peak times and lowering power consumption (discharging the storage) during higher-priced peak times.[67] For example, off-peak electricity can be used to make ice from water, and the ice can be stored. The stored ice can be used to cool the air in a large building which would have normally used electric AC, thereby shifting the electric load to off-peak hours. On other systems stored ice is used to cool the intake air of a gas turbine generator, thus increasing the on-peak generation capacity and the on-peak efficiency.
A pumped-heat electricity storage system uses a highly reversible heat engine/heat pump to pump heat between two storage vessels, heating one and cooling the other. The UK-based engineering company Isentropic that is developing the system claims a potential electricity-in to electricity-out round-trip efficiency of 72–80%.[68]
A Carnot battery is a type of energy storage systems that stores electricity in heat storage and converts the stored heat back to electricity via thermodynamics cycles. This concept has been investigated and developed by many research projects recently.[69] One of the advantage of this type of system is that the cost at large-scale and long-duration of thermal storage could be much lower than other storage technologies.
Gravity
[edit]Alternatives include storing energy by moving large solid masses upward against gravity. This can be achieved inside old mine shafts[70] or in specially constructed towers where heavy weights are winched up to store energy and allowed a controlled descent to release it.[71][72] In rail energy storage, rail cars carrying large weights are moved up or down a section of inclined rail track, storing or releasing energy as a result;[73] In disused oil-well potential energy storage, weights are raised or lowered in a deep, decommissioned oil well.
Economics
[edit]The levelized cost of storing electricity depends highly on storage type and purpose; as subsecond-scale frequency regulation, minute/hour-scale peaker plants, or day/week-scale season storage.[74][75][76]
Using battery storage is said to have a levelized cost of $120[77] to $170[78] per MWh. This compares with open cycle gas turbines which, as of 2020, have a cost of around $151–198 per MWh.[79]
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 a volume of water capable of producing 1,200 MW·h after all losses are factored in (evaporation and seeping in the reservoir, efficiency losses, etc.). If the marginal cost of electricity during off-peak times is $15 per MW·h, and the reservoir operates at 75% efficiency (i.e., 1,500 MW·h are consumed and 1,200 MW·h of energy are retrieved), then the total cost of filling the reservoir is $22,500. If all of the stored energy is sold the following day during peak hours for an average $40 per MW·h, then the reservoir will see revenues of $48,000 for the day, for a gross profit of $25,500.
However, the marginal cost of electricity varies because of the varying operational and fuel costs of different classes of generators.[80] 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".
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.[81] 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.
It may be more economical to find an alternative market for unused electricity, rather than try and store it. High Voltage Direct Current allows for transmission of electricity, losing only 3% per 1000 km.
Load leveling
[edit]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 morning peak as offices open and air conditioners get switched on)
- Hourly (one method for estimating television viewing figures in the United Kingdom is to measure the power spikes during advertisement breaks or after programmes when viewers go to switch a kettle on[82])
- 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 110–120 V or 220–240 V. 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 generation can be brought online. Typically, these would be hydroelectric or gas turbines, which can be started in a matter of minutes.
The problem with standby gas turbines is higher costs; expensive generating equipment is unused much of the time. Spinning reserve also comes at a cost; plants running below maximum output are usually less efficient. Grid energy storage is used to shift generation from times of peak load to off-peak hours. Power plants are able to run at their peak efficiency during nights and weekends.
Supply-demand leveling strategies may be intended to reduce the cost of supplying peak power or to compensate for the intermittent generation of wind and solar power.
Reliability
[edit]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.
See also
[edit]- Battery electric vehicles
- Battery-to-grid
- Cost of electricity by source
- Distributed generation
- Energy demand management
- Energy storage as a service (ESaaS)
- Gravity battery
- Hydrogen economy
- List of energy storage projects
- Power-to-X
- Rechargeable battery
- U.S. Department of Energy International Energy Storage Database, a list of grid energy storage projects
- Virtual power plant
References
[edit]- ^ Cozzi, Petropoulos & Wanner 2024, p. 68.
- ^ a b Schrotenboer, Albert H.; Veenstra, Arjen A.T.; uit het Broek, Michiel A.J.; Ursavas, Evrim (October 2022). "A Green Hydrogen Energy System: Optimal control strategies for integrated hydrogen storage and power generation with wind energy" (PDF). Renewable and Sustainable Energy Reviews. 168: 112744. arXiv:2108.00530. Bibcode:2022RSERv.16812744S. doi:10.1016/j.rser.2022.112744. S2CID 250941369.
- ^ a b Lipták, Béla (24 January 2022). "Hydrogen is key to sustainable green energy". Control. Retrieved 12 February 2023.
- ^ Armstrong & Chiang 2022, pp. 6–7.
- ^ "Grid Energy Storage" (PDF). U.S. Department of Energy. December 2013. p. 28. Archived (PDF) from the original on 28 February 2017. Retrieved 13 February 2017.
- ^ Doug Hurley; Paul Peterson; Melissa Whited (May 2013). "Demand Response as a Power System Resource" (PDF). RAP Energy Solutions, Synapse Energy Economics. p. 13. Archived (PDF) from the original on 30 April 2017. Retrieved 13 February 2017.
- ^ "Energy Department Releases Grid Energy Storage Report". 12 December 2013. Archived from the original on 13 May 2017.
- ^ Lai, Chun Sing; Locatelli, Giorgio; Pimm, Andrew; Wu, Xiaomei; Lai, Loi Lei (September 2020). "A review on long-term electrical power system modeling with energy storage". Journal of Cleaner Production. 280: 124298. doi:10.1016/j.jclepro.2020.124298. hdl:11311/1204822.
- ^ Palizban, Omid; Kauhaniemi, Kimmo (May 2016). "Energy storage systems in modern grids—Matrix of technologies and applications". Journal of Energy Storage. 6: 248–259. Bibcode:2016JEnSt...6..248P. doi:10.1016/j.est.2016.02.001.
- ^ Luo, Xing; Wang, Jihong; Dooner, Mark; Clarke, Jonathan (1 January 2015). "Overview of current development in electrical energy storage technologies and the application potential in power system operation". Applied Energy. 137: 511–536. Bibcode:2015ApEn..137..511L. doi:10.1016/j.apenergy.2014.09.081.
- ^ Daim, Tugrul U.; Li, Xin; Kim, Jisun; Simms, Scott (June 2012). "Evaluation of energy storage technologies for integration with renewable electricity: Quantifying expert opinions". Environmental Innovation and Societal Transitions. 3: 29–49. Bibcode:2012EIST....3...29D. doi:10.1016/j.eist.2012.04.003.
- ^ Pham, Cong-Toan; Månsson, Daniel (November 2015). "Suitability analysis of Fuzzy Logic as an evaluation method for the selection of energy storage technologies in Smart Grid applications". 2015 International Symposium on Smart Electric Distribution Systems and Technologies (EDST). Vol. 2015 International Symposium on Smart Electric Distribution Systems and Technologies (EDST). pp. 452–457. doi:10.1109/SEDST.2015.7315251. ISBN 978-1-4799-7736-9. S2CID 42921444.
- ^ Pham, Cong-Toan; Månsson, Daniel (October 2017). "On the physical system modelling of energy storages as equivalent circuits with parameter description for variable load demand (Part I)". Journal of Energy Storage. 13: 73–84. Bibcode:2017JEnSt..13...73P. doi:10.1016/j.est.2017.05.015.
- ^ Pham, Cong-Toan; Månsson, Daniel (August 2018). "Optimal energy storage sizing using equivalent circuit modelling for prosumer applications (Part II)". Journal of Energy Storage. 18: 1–15. Bibcode:2018JEnSt..18....1P. doi:10.1016/j.est.2018.04.015. S2CID 64857425.
- ^ Raza, Syed Shabbar; Janajreh, Isam; Ghenai, Chaouki (December 2014). "Sustainability index approach as a selection criteria for energy storage system of an intermittent renewable energy source". Applied Energy. 136: 909–920. Bibcode:2018JEnSt..18....1P. doi:10.1016/j.est.2018.04.015. S2CID 64857425.
- ^ Moreno, Rodrigo; Moreira, Roberto; Strbac, Goran (January 2015). "A MILP model for optimising multi-service portfolios of distributed energy storage" (PDF). Applied Energy. 137: 554–566. Bibcode:2015ApEn..137..554M. doi:10.1016/j.apenergy.2014.08.080. hdl:10044/1/39706.
- ^ Lee, Rachel; Homan, Samuel; Mac Dowell, Niall; Brown, Solomon (15 February 2019). "A closed-loop analysis of grid scale battery systems providing frequency response and reserve services in a variable inertia grid" (PDF). Applied Energy. 236: 961–972. Bibcode:2019ApEn..236..961L. doi:10.1016/j.apenergy.2018.12.044. S2CID 116444177.
- ^ Reihani, Ehsan; Motalleb, Mahdi; Ghorbani, Reza; Saad Saoud, Lyes (February 2016). "Load peak shaving and power smoothing of a distribution grid with high renewable energy penetration". Renewable Energy. 86: 1372–1379. Bibcode:2016REne...86.1372R. doi:10.1016/j.renene.2015.09.050.
- ^ Smith 2023, p. 19.
- ^ Zhang, Xinjing; Gao, Ziyu; Zhou, Bingqian; Guo, Huan; Xu, Yujie; Ding, Yulong; Chen, Haisheng (2024). "Advanced Compressed Air Energy Storage Systems: Fundamentals and Applications". Engineering. 34: 246–269. doi:10.1016/j.eng.2023.12.008. ISSN 2095-8099.
- ^ Smith 2023, p. 20.
- ^ IPCC AR6 WG3 Ch6 2022, p. 655.
- ^ Liang, Ting; Zhang, Tongtong; Lin, Xipeng; Alessio, Tafone; Legrand, Mathieu; He, Xiufen; Kildahl, Harriet; Lu, Chang; Chen, Haisheng; Romagnoli, Alessandro; Wang, Li; He, Qing; Li, Yongliang; Yang, Lizhong; Ding, Yulong (2023). "Liquid air energy storage technology: a comprehensive review of research, development and deployment". Progress in Energy. 5 (1): 012002. doi:10.1088/2516-1083/aca26a. ISSN 2516-1083.
- ^ Hawkins, Nehemiah (1917). Hawkins Electrical Guide ...: Questions, Answers & Illustrations; a Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to Acquire a Working Knowledge of Electricity and Its Applications; a Practical Treatise. T. Audel & Company. pp. 989–.
- ^ Ziegler, Micah S.; Trancik, Jessika E. (2021). "Re-examining rates of lithium-ion battery technology improvement and cost decline". Energy & Environmental Science. 14 (4): 1635–1651. arXiv:2007.13920. doi:10.1039/D0EE02681F. ISSN 1754-5692. S2CID 220830992.
- ^ "The price of batteries has declined by 97% in the last three decades". Our World in Data. Retrieved 26 April 2022.
- ^ a b Cozzi, Petropoulos & Wanner 2024, p. 45.
- ^ Cozzi, Petropoulos & Wanner 2024, p. 18.
- ^ Cozzi, Petropoulos & Wanner 2024, p. 20.
- ^ a b Cozzi, Petropoulos & Wanner 2024, p. 46.
- ^ Tolmachev, Yuriy V. (1 March 2023). "Review—Flow Batteries from 1879 to 2022 and Beyond". Journal of the Electrochemical Society. 170 (3): 030505. Bibcode:2023JElS..170c0505T. doi:10.1149/1945-7111/acb8de. ISSN 0013-4651.
- ^ David L. Chandler, MIT News Office (19 November 2009). "Liquid battery big enough for the electric grid?". MIT News. Archived from the original on 13 February 2010.
- ^ "Appalachian Power Dedicates Mega Battery; New Technology Provides Extra Power, Reliability" (Press release). Appalachian Power. 20 July 2006. Archived from the original on 22 October 2006.
- ^ Cozzi, Petropoulos & Wanner 2024, p. 47.
- ^ Xu, Chengjian; Behrens, Paul; Gasper, Paul; Smith, Kandler; Hu, Mingming; Tukker, Arnold; Steubing, Bernhard (17 January 2023). "Electric vehicle batteries alone could satisfy short-term grid storage demand by as early as 2030". Nature Communications. 14 (1). doi:10.1038/s41467-022-35393-0. ISSN 2041-1723.
- ^ García-Vázquez, Carlos Andrés; Espinoza-Ortega, Hernán; Llorens-Iborra, Francisco; Fernández-Ramírez, Luis M. (1 November 2022). "Feasibility analysis of a hybrid renewable energy system with vehicle-to-home operations for a house in off-grid and grid-connected applications". Sustainable Cities and Society. 86: 104124. doi:10.1016/j.scs.2022.104124. ISSN 2210-6707.
- ^ a b c Aguilar Lopez, Fernando; Lauinger, Dirk; Vuille, François; Müller, Daniel B. (16 May 2024). "On the potential of vehicle-to-grid and second-life batteries to provide energy and material security". Nature Communications. 15 (1). doi:10.1038/s41467-024-48554-0. ISSN 2041-1723.
- ^ Bhoir, Shubham; Caliandro, Priscilla; Brivio, Claudio (1 December 2021). "Impact of V2G service provision on battery life". Journal of Energy Storage. 44: 103178. doi:10.1016/j.est.2021.103178. ISSN 2352-152X.
- ^ "Energy Storage Plant in Europe announced in Midlands". Department of Business, Enterprise and Innovation. 26 March 2015. Archived from the original on 28 November 2016. Retrieved 28 January 2020.
- ^ "New energy storage plant could 'revolutionise' renewable sector". The Guardian. Archived from the original on 4 December 2016.
- ^ David Hamilton (8 January 2010). "Terremark Installs Space-Saving Flywheel UPS in New Data Center". Web Host Industry Review. Archived from the original on 28 April 2010. Retrieved 16 November 2010.
- ^ "EDA – Electricidade dos Açores". Archived from the original on 28 November 2007.
- ^ "Coral Bay PowerStore Flywheel Project". DOE Global Energy Storage Database. Archived from the original on 26 August 2017. Retrieved 26 August 2017.,
- ^ Smith 2023, p. 5.
- ^ Smith 2023, p. 14.
- ^ Eberle, Ulrich; Mueller, Bernd; von Helmolt, Rittmar (15 July 2012). "Fuel cell electric vehicles and hydrogen infrastructure: status 2012". Royal Society of Chemistry. Archived from the original on 9 February 2014. Retrieved 8 January 2013.
- ^ a b Anscombe, Nadya (4 June 2012). "Energy storage: Could hydrogen be the answer?". Solar Novus Today. Archived from the original on 19 August 2013. Retrieved 3 November 2012.
- ^ "Conversion of the UK gas system to transport hydrogen". Archived from the original on 16 May 2016.
- ^ Eberle, Ulrich; von Helmolt, Rittmar (14 May 2010). "Sustainable transportation based on electric vehicle concepts: a brief overview". Royal Society of Chemistry. Archived from the original on 21 October 2013. Retrieved 8 June 2010.
- ^ Olaf Kruck; Fritz Crotogino (14 August 2013). "Benchmarking of selected storage options" (PDF). HyUnder.
- ^ Reinhold Wurster; Werner Zittel. "Hydrogen Energy". HyWeb – The LBST Information Portal on Hydrogen and Fuel Cells. Archived from the original on 2 January 2004.
- ^ "Why storing large scale intermittent renewable energies with hydrogen?". HyUnder. Archived from the original on 11 November 2013.
- ^ "Storing renewable energy: Is hydrogen a viable solution?" (PDF).[permanent dead link]
- ^ Lan, Rong; Tao, Shanwen (5 May 2018). "Ammonia as a Suitable Fuel for Fuel Cells". Frontiers in Energy Research. 2. doi:10.3389/fenrg.2014.00035.
- ^ Service, Robert F. (12 July 2018). "Ammonia—a renewable fuel made from sun, air, and water—could power the globe without carbon". Science | AAAS. Retrieved 15 April 2021.
- ^ "International Energy Statistics". Archived from the original on 3 October 2011.
- ^ Rastler; et al. (2010). "Electric Energy Storage Technology Options: A White Paper Primer on Applications, Costs, and Benefits". EPRI. Archived from the original ((Free download)) on 17 August 2011. Retrieved 30 September 2011.
- ^ "Pumped Hydro (PH)". Electricity Storage Association. Archived from the original on 15 March 2013. Retrieved 26 March 2013.
- ^ "Pumped Hydroelectric Energy Storage". Imperial College London. Archived from the original on 29 October 2007.
- ^ a b "First Hydro Dinorwig Power Station". Archived from the original on 12 May 2016.
- ^ "CIA – The World Factbook – China". Archived from the original on 13 August 2008.
- ^ Stoll, B L; Smith, T A; Deinert, M R (1 March 2013). "Potential for rooftop photovoltaics in Tokyo to replace nuclear capacity". Environmental Research Letters. 8 (1): 014042. Bibcode:2013ERL.....8a4042S. doi:10.1088/1748-9326/8/1/014042. ISSN 1748-9326. S2CID 56317922.
- ^ a b "Hydroelectric Power" (PDF). United States Bureau of Reclamation. Archived from the original (PDF) on 21 October 2008. Retrieved 13 October 2008.
- ^ "SCPPA Hoover Project Page". Southern California Public Power Authority. Archived from the original on 27 September 2008. Retrieved 13 October 2008.
- ^ "Rethinking our Water Ways - 5.3 Water Use Plans". www.rethinkingwater.ca. Archived from the original on 5 October 2017. Retrieved 5 May 2018.
- ^ Advantages of Using Molten Salt Archived 5 June 2011 at the Wayback Machine Tom Mancini, Sandia National Laboratories, Albuquerque, NM Accessed December 2007
- ^ Lee, Zachary E.; Sun, Qingxuan; Ma, Zhao; Wang, Jiangfeng; MacDonald, Jason S.; Zhang, K. Max (February 2020). "Providing Grid Services With Heat Pumps: A Review". Journal of Engineering for Sustainable Buildings and Cities. 1 (1). doi:10.1115/1.4045819. S2CID 213898377.
- ^ "Isentropic's PHES Technology". Archived from the original on 10 October 2014.
- ^ Dumont, Olivier; Frate, Guido Francesco; Pillai, Aditya; Lecompte, Steven; De paepe, Michel; Lemort, Vincent (2020). "Carnot battery technology: A state-of-the-art review". Journal of Energy Storage. 32: 101756. Bibcode:2020JEnSt..3201756D. doi:10.1016/j.est.2020.101756. hdl:2268/251473. ISSN 2352-152X. S2CID 225019981.
- ^ "How UK's disused mine shafts could be used to store renewable energy". The Guardian. 21 October 2019.
- ^ Gourley, Perry (31 August 2020). "Edinburgh firm behind incredible gravity energy storage project hails milestone". www.edinburghnews.scotsman.com. Retrieved 1 September 2020.
- ^ Akshat Rathi (18 August 2018). "Stacking concrete blocks is a surprisingly efficient way to store energy". Quartz.
- ^ Massey, Nathanael and ClimateWire. Energy Storage Hits the Rails Out West: In California and Nevada, projects store electricity in the form of heavy rail cars pulled up a hill Archived 30 April 2014 at the Wayback Machine, ScientificAmerican.com website, 25 March 2014. Retrieved 28 March 2014.
- ^ "Some energy storage already cost competitive, new valuation study shows". Utility Dive. 24 November 2015. Archived from the original on 18 October 2016. Retrieved 15 October 2016.
- ^ "Lazard's Levelized Cost of Storage Analysis" (PDF). Archived (PDF) from the original on 2 February 2017. Retrieved 2 February 2017.
- ^ Lai, Chun Sing; McCulloch, Malcolm D. (March 2017). "Levelized cost of electricity for solar photovoltaic and electrical energy storage". Applied Energy. 190: 191–203. Bibcode:2017ApEn..190..191L. doi:10.1016/j.apenergy.2016.12.153. S2CID 113623853.
- ^ Chip Register (13 January 2015). "The Battery Revolution: A Technology Disruption, Economics and Grid Level Application Discussion with Eos Energy Storage". Forbes. Archived from the original on 11 November 2016.
- ^ "Eos Energy Storage – Technology and Products". eosenergystorage.com. Archived from the original on 6 February 2014.
- ^ "Levelized Cost of Energy and of Storage". Archived from the original on 20 February 2021. Retrieved 5 January 2021.
- ^ Lai, Chun Sing; Jia, Youwei; Xu, Zhao; Lai, Loi Lei; Li, Xuecong; Cao, Jun; McCulloch, Malcolm D. (December 2017). "Levelized cost of electricity for photovoltaic/biogas power plant hybrid system with electrical energy storage degradation costs". Energy Conversion and Management. 153: 34–47. Bibcode:2017ECM...153...34L. doi:10.1016/j.enconman.2017.09.076.
- ^ Energy Information Administration / Annual Energy Review 2006 Archived 25 June 2008 at the Wayback Machine, Table 8.2a
- ^ "BBC News – Christmas Television – The great TV ratings war". BBC. Archived from the original on 12 January 2009.
Cited sources
[edit]- Armstrong, Robert; Chiang, Yet-Ming (2022). The Future of Energy Storage: An Interdisciplinary MIT Study (PDF). Massachusetts Institute of Technology. ISBN 978-0-578-29263-2.
- Cozzi, Laura; Petropoulos, Apostolos; Wanner, Brent (April 2024). Batteries and Secure Energy Transitions (PDF). International Energy Agency.
- Clarke, L.; Wei, Y.-M.; De La Vega Navarro, A.; Garg, A.; et al. "Chapter 6: Energy Systems" (PDF). IPCC AR6 WG3 2022 . doi:10.1017/9781009157926.008.
- Smith, Chris Llewellyn (2023). Large-scale electricity storage (PDF). Royal Society. ISBN 978-1-78252-666-7.