With compressed air storage, air is pumped into an underground hole, most likely a salt cavern, during off-peak hours when electricity is cheaper.
When energy is needed, the air from the underground cave is released back up into the facility, where it is heated and the resulting expansion turns an electricity generator. This heating process usually uses natural gas, which releases carbon; however, CAES triples the energy output of facilities using natural gas alone.
CAES can achieve up to 70 percent energy efficiency when the heat from the air pressure is retained, otherwise efficiency is between 42 and 55 percent. The McIntosh plant, which was built in , has MW of storage. Thermal energy storage facilities use temperature to store energy. When energy needs to be stored, rocks, salts, water, or other materials are heated and kept in insulated environments. When energy needs to be generated, the thermal energy is released by pumping cold water onto the hot rocks, salts, or hot water in order to produce steam, which spins turbines.
Thermal energy storage can also be used to heat and cool buildings instead of generating electricity. For example, thermal storage can be used to make ice overnight to cool a building during the day. Thermal efficiency can range from 50 percent to 90 percent depending on the type of thermal energy used.
First commercially produced by Sony in the early s, lithium-ion batteries were originally used primarily for small-scale consumer items such as cellphones. Recently, they have been used for larger-scale battery storage and electric vehicles. Lithium-ion batteries are by far the most popular battery storage option today and control more than 90 percent of the global grid battery storage market.
Compared to other battery options, lithium-ion batteries have high energy density and are lightweight. Additionally, lithium-ion batteries are now frequently used in developing countries for rural electrification. In rural communities, lithium-ion batteries are paired with solar panels to allow households and businesses to use limited amounts of electricity to charge cell phones, run appliances, and light buildings. Previously, such communities had to rely on dirty and expensive diesel generators, or did not have access to electricity.
When the Aliso Canyon natural gas facility leaked in , California rushed to use lithium-ion technology to offset the loss of energy from the facility during peak hours. This MW battery was built by Tesla and provides electricity to more than 30, households. General Electric has designed 1 MW lithium-ion battery containers that will be available for purchase in They will be easily transportable and will allow renewable energy facilities to have smaller, more flexible energy storage options.
Lead-acid batteries were among the first battery technologies used in energy storage. However, they are not popular for grid storage because of their low-energy density and short cycle and calendar life. They were commonly used for electric cars, but have recently been largely replaced with longer-lasting lithium-ion batteries. Flow batteries are an alternative to lithium-ion batteries.
While less popular than lithium-ion batteries—flow batteries make up less than 5 percent of the battery market—flow batteries have been used in multiple energy storage projects that require longer energy storage durations.
Flow batteries have relatively low energy densities and have long life cycles, which makes them well-suited for supplying continuous power. The Avista Utilities plant in Washington state, for instance, uses flow battery storage. Solid state batteries have multiple advantages over lithium-ion batteries in large-scale grid storage.
Solid-state batteries contain solid electrolytes which have higher energy densities and are much less prone to fires than liquid electrolytes, such as those found in lithium-ion batteries. Their smaller volumes and higher safety make solid-state batteries well suited for large-scale grid applications. However, solid state battery technology is currently more expensive than lithium-ion battery technology because it is less developed.
Fast-growing lithium-ion production has led to economies of scale, which solid-state batteries will find hard to match in the coming years. Hydrogen fuel cells, which generate electricity by combining hydrogen and oxygen, have appealing characteristics: they are reliable and quiet with no moving parts , have a small footprint and high energy density, and release no emissions when running on pure hydrogen, their only byproduct is water.
The process can also be reversed, making it useful for energy storage: electrolysis of water produces oxygen and hydrogen. It comprises Batteries store and release energy electrochemically. The requirements for battery storage are high energy density, high power, long life charge-discharge cycles , high round-trip efficiency, safety, and competitive cost.
Other variables are discharge duration and charge rate. Various compromises are made among these criteria, underlining the limitations of battery energy storage systems BESS compared with dispatchable generation sources.
The question of energy return on energy invested EROI also arises, which acutely relates to how long a battery is in service and how its round-trip efficiency holds up over that period. Various megawatt-scale projects have proved that batteries are well-suited to smoothing the variability of power from wind and solar systems over minutes and even hours, for short-duration integration of these renewables into a grid.
They also showed that batteries can respond more quickly and accurately than conventional resources such as spinning reserves and peaking plants. As a result, large battery arrays are becoming the stabilization technology of choice for short-duration renewables integration.
This is a function of power, not primarily energy storage. The demand for it is much lower than for energy storage — the California ISO estimated its peak frequency regulation demand for at MW from all sources. Some battery installations replace spinning reserve for short-duration back-up, so operate as virtual synchronous machines using grid forming inverters. Smart grids Much discussion of battery storage is in connection with smart grids.
A smart grid is a power grid which optimizes power supply by using information on both supply and demand. It does this with networked control functions of devices with communication capabilities such as smart meters. Lithium-ion batteries are the most popular technology for distributed energy storage systems Navigant Research. They have a cycle and year lifespan, depending on use. There is obvious compatibility between solar PV and batteries, due to them being DC.
In Germany, where solar PV has an average KfW requires that sufficient PV electricity be used for onsite consumption and storage so that no more than half of the output reaches the transmission network. In this way, it is claimed that 1. In , MWh of installed storage capability was reported for Germany.
Over one-third of the 1. In Germany, installed utility-scale battery storage increased from about MW in to about MW in About 70 MW of the capacity is contracted to the state government to provide grid stability and system security, including frequency control ancillary services FCAS through Tesla's Autobidder platform in timeframes of six seconds to five minutes. The other 30 MW of capacity has three hours of storage, and is used as load shifting by Neoen for the adjacent wind farm.
There are several types of lithium-ion battery, some with high energy density and fast charging to suit motor vehicles EVs , others such as lithium iron phosphate LiFePO 4 , abbreviated as LFP , are heavier, less energy-dense and with longer cycle life.
Concepts for long-duration storage include repurposing used EV batteries — second-life batteries. Sodium-sulfur NaS batteries have been used for 25 years and are well established, though expensive. Service life is about cycles. It is part of a set-up with a 7. Redox flow cell batteries RFBs developed in the s have two liquid electrolytes separated by a membrane to give positive and negative half-cells, each with an electrode, usually carbon.
The voltage differential is between 0. They are charged and discharged by a reversible reduction-oxidation reaction across the membrane. During the charging process, ions are oxidised at the positive electrode electron release and reduced at the negative electrode electron uptake. This means that the electrons move from the active material electrolyte of the positive electrode to the active material of the negative electrode. When discharging, the process reverses and energy is released.
The active materials are redox pairs, i. Vanadium redox flow batteries VRFB or V-flow use the multiple oxidation states of vanadium to store and release charge. They suit large stationary applications, with long life approx. V-flow batteries become more cost-effective the longer the storage duration — often about four hours — and the larger the power and energy needs.
The crossover economic scale is said to be about kWh capacity, beyond which they are more economic than lithium-ion. Also they operate at ambient temperature, so are less prone to fires than lithium-ion. With RFBs energy and power can be scaled separately. The power determines the cell size or the number of cells, and the energy is determined by the amount of the energy storage medium.
Modules are up to kW and may be assembled up to MW. This allows redox flow batteries to be better adapted to particular requirements than other technologies.
However, if they are to be used for frequency regulation, they are better located close to the urban or industrial load centres. Since the frequency control revenue stream is much better than arbitrage, utilities will normally prefer downtown rather than remote locations for assets they own.
As the use of lithium-ion batteries has increased, and the future projections have increased even more, attention has turned to the sources of materials. Most supply comes from Australia and South America. See also companion information paper on Lithium. Electrode materials of lithium-ion batteries are also in demand, notably cobalt, nickel, manganese and graphite. Graphite is mostly produced in China — 1. Resources are mainly in DRC and Australia.
Lithium-ion batteries may be categorized by the chemistry of their cathodes. The different combination of minerals gives rise to significantly different battery characteristics:. A capacitor stores energy by means of a static charge as opposed to an electrochemical reaction.
Supercapacitors are very large and are used for energy storage undergoing frequent charge and discharge cycles at high current and short duration. They have evolved, and cross into battery technology by using special electrodes and electrolyte. They operate at 2. Discharge is under 60 seconds, and the voltage drops off progressively.
To compensate for the lack of synchronous inertia in generating plant when there is high dependence on wind and solar sources, synchronous condensers syncons , also known as rotating stabilisers, may be added to the system.
They are used for frequency and voltage control where grid stability needs to be enhanced due to a high proportion of variable renewable input. They provide reliable synchronous inertia and can help stabilize frequency deviations by generating and absorbing reactive power. These are not energy storage in the normal sense, and are described in the information page on Renewable Energy and Electricity.
Total installed non-hydro storage capacity in Europe reached 2. This includes household systems, which comprise more than one-third of additions. To qualify for commercial operation, the batteries need to respond to automated calls within 30 seconds and be capable of feed-in for a minimum of 30 minutes. It has operated since It also participates in the weekly tendering for primary control reserve. The battery is to supply primary reserve to the grid and enhance grid stability in a region with many wind turbines and grid congestion problems.
Both appear to have frequency response as part of their role. It will have a nominal output of 2 MW and able to store 1 MWh of electricity, to be offered to the TSO for frequency regulation and output smoothing.
It is similar to the system operating in the Aube region of France, linking two wind farms, total 18 MW. Saft has deployed over 80 MW of batteries since In this, 11 projects ranged from 10 to 87 MW, most with enhanced frequency response contracts. The system consists of over 53, lithium-ion batteries arranged in separate nodes with control system which responds to grid changes in under a second.
It is the largest advanced energy storage system in the United Kingdom and Ireland, and the only such system at transmission scale according to AES.
This Kirkwall power station uses Mitsubishi batteries in two Tesla claims that the powerpacks can be configured to provide power and energy capacity to the grid as a standalone asset, offering frequency regulation, voltage control, and spinning reserve services. From it is to store excess production, reduce balancing costs, and allow the project to regulate its own power supply and capture peak prices through arbitrage.
Used for energy arbitrage charging when price was low and discharging when price high , the 6 MWe set-up barely covered operating expenses.
The optimum use of the BESS was confirmed as frequency regulation, with batteries maintained half-charged and ready to charge or discharge as required to compensate for mismatches between generation and load. The thicker gray line in the figure shows a smoother system response after damping of the fluctuations shown by the undulating yellow line with frequency regulation.
Figure 1. Notes: DOE—U. Peaking generation is power generation normally operated only during the hours of highest daily, weekly, or seasonal loads. Intermediate load generation is normally operated on a daily cycle to serve on-peak loads during the day but not off-peak loads during nights and weekends. Baseload generation serves the minimum level of electric power demand of a utility, region, or utility customer delivered or required over a given period of time at a steady rate.
Renewables generation in this instance represents variable electric generation primarily from intermittent wind or solar photovoltaic sources whose peak generation does not necessarily coincide with electricity system periods of peak demand.
Energy storage is one way to decrease the need for power generation on the grid at peak demand periods. But storage is not the only means of meeting these goals. Other means of potentially reducing the generation of electricity from large, central station power plants include:.
The capacity for storing large amounts of energy on the electric grid is presently limited. In one study, curtailing excess energy was reportedly seen as a possibly cost-effective alternative to deploying expensive energy storage options at higher levels of solar photovoltaic PV penetration.
An arbitrage opportunity also exists under some circumstances to take advantage of power storage in regulatory regimes that attach value to such opportunities. Under such a scenario, electricity can be purchased from the grid and stored during times of lower demand. An energy storage system can be charged at this time so that the stored energy can be used or sold at another time when the price or costs are higher.
Alternatively, energy storage can provide the opportunity to store excess energy production that may otherwise be curtailed from renewable sources such as wind or solar PV. However, the number opportunities for the storage system to perform efficiently in an arbitrage role can be limited by the technology.
Energy storage can take many forms, and can involve the storage of electricity directly or as potential or kinetic energy that can be used to generate electricity when it is needed.
Electricity can also be stored in the chemical systems of batteries, both in bulk scale and in modular forms as summarized below. Storage systems generally replenish their energy using electricity generated at low-demand off-peak times. Hydropower pumped storage HPS , compressed air energy storage CAES , and cryogenic energy storage are examples of technologies that store potential or kinetic energy.
These examples of the mostly large, monolithic systems used for energy storage today do not store electricity directly, but provide a means of producing electricity by use of a stored medium e.
The gradual release of the stored medium physically turns the shaft of a turbine connected to an electric generator, converting potential energy from the stored medium to electricity. Other opportunities for energy storage from the production of hydrogen gas are being explored, but are not a focus of this report. Batteries are chemical systems that produce electricity when the component parts and chemicals combine to create a flow of electrons, thus creating an electrical current.
The potential to produce an electrical charge can be stored directly in large chemical systems e. The smaller cells of modular battery systems do not store large amounts of electricity individually, but can be aggregated in battery systems to provide larger amounts of power.
The major potential energy and battery storage technologies for energy storage discussed in this report are summarized below:. Hydropower pumped storage : Water stored in an upper reservoir is released to a lower reservoir through a turbine to generate electricity. Water is pumped in reverse at times of low demand to store energy. HPS is the most widely-used technology for storing energy on the electric grid.
Compressed air energy storage : Compressed air is heated and expanded in a turbine to generate electricity. Compressing air causes it to cool, and it is stored in a tank or cavern using off-peak electricity to store energy.
Liquid air cryogenic energy storage : Ambient air cooled to a liquid state is re-gasified and injected into a turbine when used to generate electricity. Ambient air is cooled and compressed to a liquid state to restore the system, and is stored in insulated tanks. Flywheels : A cylinder rotating around a core in a vacuum at high speeds stores kinetic energy.
Slowing the cylinder releases energy to turn a generator to produce electricity, and speeding up the cylinder stores energy. Flow Batteries : Liquid electrolytes 14 with positive and negative charges are stored in large, separate tanks. Electric charge is drawn from the electrolytes by electrodes as they are pumped through a central tank where the liquids are separated by a membrane based on charge, and the spent liquids returned to separate tanks.
Lead-acid batteries : One of the oldest and most used methods of energy storage uses connected compartments cells made of a lead alloy and lead, immersed in a water-sulfuric acid electrolyte, which combine to generate an electric charge. Lithium ion Li Ion batteries : Movement of lithium ions from the positive electrode cathode to the negative electrode anode through an electrolyte commonly a lithium salt solution creates an electric charge.
Li Ion batteries have a cathode made of lithium-cobalt oxide, and an anode made of carbon. When batteries are recharged, the lithium ions move in reverse. Commonly, the movement of charged particles from cathode to anode through an electrolyte generates an electric current.
These technologies are described in more detail in Appendix A of this report. Energy storage can help maintain the balance between supply and demand on an electricity system, and assist with system reliability by providing back-up power for several hours at a time during electricity outages.
Since the storage of potential energy in larger, monolithic systems e. Battery storage technologies can also supply energy to the grid, and can also provide many of the ancillary services 15 necessary to ensure the grid's stability. These services are described in more detail in Appendix B of this report. Currently, however, the best value of grid energy storage for energy storage project developers is likely to come from supplying energy to the grid, and additionally providing the ancillary services best-suited to the storage technology, when available as the storage resource cannot do both simultaneously.
Once stored energy is sent to the grid, how quickly the energy storage technology can recharge may influence when and how often recharging of the system is accomplished. When recharging, the energy storage system is a load on the grid, and is not a generation resource. The timing of the charging and recharging cycle during a day can affect the value proposition of storage, since it is unlikely that recharging would be scheduled at times of peak demand. The ability of an energy storage system to provide several services to the grid may also bear on the economics of a system.
Figure 2 presents a current view of the opportunities for energy storage technologies to provide capacity and energy for the grid and various ancillary services. It provides a general summary and comparison of energy storage technologies for applications over various timescales for electric grid services.
Figure 2. Larger, more monolithic bulk power energy storage projects such as HPS or CAES can supply electric power in a discharge time over tens of hours. Battery systems and flywheel energy storage are sometimes used for uninterruptible power supply UPS in backup power applications. UPS applications solely for energy storage typically have enough energy to operate for up to several minutes.
UPS systems may also incorporate generation e. Energy storage can also provide a power quality service by storing power and quickly discharging energy to smooth out variations in voltage supply or frequency, or service interruptions from a fraction of a second to several minutes, which could negatively affect a customer's manufacturing process or operations.
By using energy stored in off-peak hours, customers of utilities can potentially shift their energy use from one time period to another. Alternatively, utilities or energy storage providers can store energy in periods of low demand to serve loads in times of higher demand. Supercapacitors may be used in energy storage applications undergoing frequent charge and discharge cycles at high current and a very short duration.
However, the components for SMES limit its uses, as the cost of high-temperature superconducting wires would make grid-scale SMES systems prohibitively expensive. SMES has long been pursued as a large-scale technology because it offers instantaneous energy discharge and a theoretically infinite number of recharge cycles. Matching an energy storage technology to the opportunity is key, and considerations will include:.
All rechargeable batteries have a similar physical structure that allows for the flow of electricity from an outside source to recharge the chemical system once depleted. As shown in Figure 4 , the cathode is the positive terminal, and the anode is the negative terminal.
The anode of a device is the side where current flows in, while the cathode is where current flows out. Figure 3. Lithium Iron Phosphate Battery Cell. A conductive electrolyte allows the flow of electrons between the anode and the cathode. When a battery is discharged, electrons are released from the negative end and captured by the positive end. Cells can be built by stacking parallel plates i. They have the same chemistry with the main difference residing in their construction and ability to dissipate internally generated heat.
Wound cells, and small cylindrical cells in particular, are cheaper to manufacture than the larger prismatic ones for a given capacity.
They also have a higher volumetric energy density, but their round cross-section prevents from packing them together without gaps and this advantage does not extend to the assembled battery.
The gaps between the cells can present an advantage for cooling when thermal management is necessary due to very high currents Mechanically, cylindrical cells are very robust and very resilient to mechanical damage from shocks and vibrations, which is good in electric vehicles. The evaluation of the performance and suitability of modular batteries for an application is typically based on several key characteristics, including:.
For example, specific energy can determine the battery weight required to achieve range of a vehicle given its energy consumption. For example, specific power can determine the battery weight required to achieve a given performance target for an engine. The three characteristics listed above are functions of the battery chemistry and its packaging, with the controlling characteristic being dependent on the particular application.
For photovoltaic systems, the key technical considerations are that the battery experience a long lifetime under nearly full discharge conditions. Common rechargeable battery applications do not experience both deep cycling and being left at low states of charge for extended periods of time. For example, in batteries for starting cars or other engines, the battery experiences a large, short current drain, but is at full charge for most of its life. Similarly, batteries in uninterruptible power supplies are kept at full charge for most of their life.
For batteries in consumer electronics, the weight or size is often the most important consideration. According to the U. Energy Information Administration EIA , energy storage projects can be used in a variety of electricity production applications. Electricity storage can be deployed throughout an electric power system—functioning as generation, transmission, distribution, or end-use assets—an advantage when it comes to providing local solutions to a variety of issues.
Sometimes placing the right storage technology at a key location can alleviate a supply shortage situation, relieve congestion, defer transmission additions or substation upgrades, or postpone the need for new capacity. Utility scale battery storage consists of projects of one MW or greater in capacity.
EIA expects U. Grid-connected battery storage projects commonly require a power management system to protect the battery and prevent uses that would damage or destroy the system. Of these systems for battery storage, balance of plant BOP costs are the most significant. BOP includes basic infrastructure such as a building foundation and security fencing , and on-site electrical systems comprised of any equipment required to interconnect a battery storage system to the electric utility transmission or distribution grid.
A project capacity of 60 MW was used for the estimates. Most power outages occur in electric distribution systems where wind or other weather cause vegetation e. Power outages can also result from equipment failure, vehicle accidents knocking down distribution poles, and even animal incursions into equipment.
Outages caused by these factors typically last in the range from minutes to a few hours. Most of the longer-lived power outages i. More extreme events i. In the wake of recent major weather events 45 in the United States e. A recent study examined the statistical relationship between annual changes reported by U. We find statistically significant correlations between the average number of power interruptions experienced annually by a customer and a number of explanatory variables including wind speed, precipitation, lightning strikes, and the number of customers per line mile….
In addition, we find a statistically significant trend in the duration of power interruptions over time—especially when major events are included. This finding suggests that increased severity of major events over time has been the principal contributor to the observed trend. Energy storage could conceivably help reduce the impact of power outages in these instances.
However, storage would have to be energized and available, which underscores the source of the electricity used to charge the batteries or other storage media. Wind power is variable, and often the winds are strongest at night, while solar photovoltaic storage only charges in the daytime.
The discharge characteristics would also determine the usefulness of battery storage, as power form these sources may only last for several hours.
The type of event causing a power outage would also be key, as a severe weather event could stress or potentially take down power lines over a wide, possibly multistate region. Power can only reach electricity customers if the electrical wires particularly the distribution lines are still serviceable and connected.
The plug-in hybrid and battery electric share of the U. Some utilities have been considering whether EVs will be a longer-term avenue for increasing electricity demand, providing opportunities for vehicle-to-grid V2G energy storage and related services. Under V2G, EV batteries could eventually be used as storage of off-peak energy for the grid, and help provide demand response when the vehicles are not in use.
A report from the Smart Power Electric Alliance observed that "utilities do not want to just serve this new load—they want to take advantage of EVs as a distributed energy resource DER with the ability to modulate charge i.
However, while the V2G concept has been discussed for well over a decade in the United States, some have expressed doubts about its adoption. The idea is attractive because of the growing amount of lithium-ion battery capacity tied up in electric vehicles, and the fact that this capacity is not being used for around 95 percent of the time. Ten new Nissan Leafs can store as much energy as a thousand homes typically consume in an hour However, despite numerous pilot studies over the last decade, V2G has yet to become a commercial reality.
Among the major concerns expressed about V2G is the effect on the vehicle's batteries. V2G allows a utility to draw on energy storage from stationary vehicles, which could increase the stress on the batteries, one of the most expensive parts of the vehicle.
As at least one observer has noted, it is unclear who would cover the cost of this usage or battery replacements under a V2G regime, or how vehicle owners might be otherwise compensated for taking part in V2G programs. Electrification of the transportation sector can conceivably reduce GHG emissions—depending on the electricity generation source, among other factors 54 —seen as a contributor to potential climate change.
According to projections by the U. Energy Information Administration, new sales of battery electric vehicles may increase by a factor of seven by the year , over model year , under a reference case scenario.
Batteries charged from renewable electricity sources may reduce climate change concerns, and aid renewable energy growth goals. However, fuel cell vehicles 57 could present a competitive or alternative pathway to a potential transportation future dominated by battery-powered EVs.
The LBL case study discussed California's growing system-wide balancing problems forecast out to , as more renewables especially solar PV are deployed. This has been epitomized as the "California Duck Curve" issue. This regime is referred to as V1G, representing the "one-way" charging of EVs.
According to the LBL researchers, the technology for a one-way charging regime largely exists i. In addition, implementing a regime to also allow a V2G two-way flow of power from EVs could potentially allow the benefits of EV batteries to become even more pronounced. Finding ways to increase the recycling and reuse of Li Ion battery components would seem to be an option, given the potential cost and difficulty of obtaining the lithium and cobalt used in battery manufacture.
Reuse can provide the most value in markets where there is demand for batteries for stationary energy-storage applications that require less-frequent battery cycling for example, to cycles per year.
Based on cycling requirements, three applications are most suitable for second-life EV batteries: providing reserve energy capacity to maintain a utility's power reliability at lower cost by displacing more expensive and less efficient assets for instance, old combined-cycle gas turbines , deferring transmission and distribution investments, and taking advantage of power-arbitrage opportunities by storing renewable power for use during periods of scarcity, thus providing greater grid flexibility and firming to the grid.
In , second-life batteries may be 30 to 70 percent less expensive than new ones in these applications, tying up significantly less capital per cycle. Under the Federal Power Act 68 FPA , the Federal Energy Regulatory Commission FERC has authority over the sale and transmission of wholesale power, 69 the reliability of the bulk power system, utility mergers and acquisitions, and certain utility corporate transactions. The Energy Policy Act of P. The next step was to ensure that these transactions could take place as efficiently as possible, and momentum for allowing access to the transmission grid for all users was realized with the issuance of FERC Order No.
The order required electricity transmission owners to allow open, non-discriminatory access to their transmission systems, thus promoting wholesale competition.
This may provide an opportunity for renewable generators, in particular, to sell power when the renewable capacity is unavailable. In Order No. However, FERC also acknowledged that existing market rules for traditional resources can create barriers to entry for emerging technologies. Order No. Electric storage resources may be a buyer and a seller of electricity from the markets, since they must charge and discharge their resources.
FERC requires that the sale of electric energy from the wholesale electricity market to an electric storage resource that the resource then resells back to those markets must be at the wholesale locational marginal price i. FERC recognized that various energy storage resources had the potential to provide ancillary services e.
FERC also recognized that "electric storage resources tend to be capable of faster start-up times and higher ramp rates than traditional … generators and are therefore able to provide ramping, spinning, and regulating reserve services without already being online and running.
Several compliance responses are discussed in the following summaries. One filing submitted details of PJM's proposed energy storage resource participation model i. However, PJM noted that although ESRs are currently eligible to provide services in each of these markets, the ESR participation model explicitly addresses each available product to ensure that ESRs are eligible to provide all services which they are technically capable of providing. PJM said that its review of its markets and operations indicated that "certain changes are needed to fully support the ESR participation model required by Order No.
This feature provides significant flexibility and allows Market Participants of ESRs to best manage a resource's changing and discharging cycles. If an ESR is physically disconnected from the grid and capable of providing energy within ten minutes, then the resource's reserve MWs shall be treated as Non-Synchronized Reserve. Cost-Based Offers : PJM proposes to continue to apply the same offer development rules applied to all generation resources.
PJM was developing a methodology to determine wholesale vs. PJM says that this may be complicated since ESRs that are behind the customer meter or that otherwise directly serve retail load may not, in some cases, resell that energy to PJM per its proposed rules.
Nevertheless, NYISO proposed to establish a participation model with energy storage resources as a subset of generators under its tariffs. Electric storage facilities unable to satisfy a qualification as generators would be able to elect to participate in existing participation models that accommodate their physical and operational characteristics.
For example, some storage resources may be able to participate as "energy limited resources," e. Alternatively, other energy storage resources may be able to participate as "limited energy storage resources," i.
These included whether metering would be required for storage resources, and how storage resources should be treated under models of dispatch for energy i. As one example of the information requested, FERC asked each grid operator to provide details of various aspects of energy storage market participation models, including size requirements, state of charge management, and how storage resources can participate as both buyers and sellers in wholesale market.
In June , the Senate Energy and Natural Resources Committee held a hearing to examine opportunities for the expanded deployment of grid-scale energy storage in the United States. Among the key statements from witnesses were observations on the developing nature of battery storage systems. Among the observations from Dr. George Crabtree, the director of the Joint Center for Energy Storage Research and Argonne National Laboratory was a statement on the readiness of battery technologies for long-term grid support:.
In addition, we must be able to purpose-design batteries for a diversity of applications in the grid spanning generation, transmission, and distribution. An example is long duration storage, needed to fill in for renewable generation when the wind does not blow or the sun is blocked by clouds for as many as seven days in a row.
These long, cloudy, or calm periods are common in weather patterns in the Northeast and Midwest. The present generation of lithium-ion batteries can optimally discharge for about four hours, much too short to span many weather-related generation gaps.
New battery materials, concepts, and technology are needed to meet the challenges of long-duration-discharge energy storage. Among other observations, the witness from Xcel Energy, Mr. Ben Fowke noted that Xcel Energy's long-term carbon strategy depends on the deployment of advanced clean technologies. He said that grid-scale storage helps with renewable integration, allowing higher renewable energy levels than would otherwise be possible. Storage can also provide other system benefits, including more reliable grid operations, voltage support and frequency control.
At the same time, he pointed out that storage today still has limitations. Two significant challenges for storage were described in his testimony:. First, storage cannot today solve the problem of the wide seasonal variation in renewable energy generation, which is the chief factor preventing the creation of fully renewable electricity system. Second, while storage can initially help integrate renewables by moving energy from the time it is produced to when it is needed, the value of each additional increment of storage capacity declines as more is added to the system.
Finally, although storage can bring multiple services to the grid—power quality and grid support, for example—the value of all of these services are not all additive or "stackable". As a general rule, these services are not all available at the same time. While lithium ion batteries are the dominant technology in the battery storage industry today, a federal research agenda should target those technologies that have the greatest potential to address long-term system needs and reach commercialization.
Those technologies include pumped storage, flow batteries, compressed air energy storage, and other forms of mechanical, thermal and ice storage. The federal research agenda should also encourage the development of hydrogen and other power-to-gas technologies that have the potential to link renewables and other sources of clean electricity to the rest of the economy and dramatically increase the amount of energy storage capacity in the nation. Andrew Ott, discussed the readiness of ESRs for grid applications.
He also discussed the potential for competition between demand response resources, ESRs, and other generation resources. One issue that has garnered attention is how energy storage resources can participate in PJM's capacity market and therefore displace a coal, nuclear or natural gas unit to be available on call to provide energy when needed in system emergencies.
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