Due to growing concerns about the environmental impacts of fossil fuels and the capacity and resilience of energy grids around the world, engineers and policymakers are increasingly turning their attention to energy storage solutions. Indeed, energy storage can help address the intermittency of solar and wind power; it can also, in many cases, respond rapidly to large fluctuations in demand, making the grid more responsive and reducing the need to build backup power plants. The effectiveness of an energy storage facility is determined by how quickly it can react to changes in demand, the rate of energy lost in the storage process, its overall energy storage capacity, and how quickly it can be recharged.
Energy storage is not new. Batteries have been used since the early s, and pumped-storage hydropower has been operating in the United States since the s. But the demand for a more dynamic and cleaner grid has led to a significant increase in the construction of new energy storage projects, and to the development of new or better energy storage solutions.
Fossil fuels are the most used form of energy, partly due to their transportability and the practicality of their stored form, which allows generators considerable control over the rate of energy supplied. In contrast, the energy generated by solar and wind is intermittent and reliant on the weather and season. As renewables have become increasingly prominent on the electrical grid, there has been a growing interest in systems that store clean energy
Energy storage can also contribute to meeting electricity demand during peak times, such as on hot summer days when air conditioners are blasting or at nightfall when households turn on their lights and electronics. Electricity becomes more expensive during peak times as power plants have to ramp up production in order to accommodate the increased energy usage. Energy storage allows greater grid flexibility as distributors can buy electricity during off-peak times when energy is cheap and sell it to the grid when it is in greater demand.
As extreme weather exacerbated by climate change continues to devastate U.S. infrastructure, government officials have become increasingly mindful of the importance of grid resilience. Energy storage helps provide resilience since it can serve as a backup energy supply when power plant generation is interrupted. In the case of Puerto Rico, where there is minimal energy storage and grid flexibility, it took approximately a year for electricity to be restored to all residents.
The International Energy Association (IEA) estimates that, in order to keep global warming below 2 degrees Celsius, the world needs 266 GW of storage by , up from 176.5 GW in . Under current trends, Bloomberg New Energy Finance predicts that the global energy storage market will hit that target, and grow quickly to a cumulative 942 GW by (representing $620 billion in investment over the next two decades).
In , the United States generated 4 billion megawatt-hours (MWh) of electricity, but only had 431 MWh of electricity storage available. Pumped-storage hydropower (PSH) is by far the most popular form of energy storage in the United States, where it accounts for 95 percent of utility-scale energy storage. According to the U.S. Department of Energy (DOE), pumped-storage hydropower has increased by 2 gigawatts (GW) in the past 10 years. In , the United States had 22 GW of PSH storage incorporated into the grid. Yet, despite the widespread use of PSH, in the past decade the focus of technological advancement has been on battery storage.
By December , there was approximately 708 MW of large-scale battery storage operational in the U.S. energy grid. Most of this storage is operated by organizations charged with balancing the power grid, such as Independent System Operators (ISOs) and Regional Transmission Organizations (RTOs). ISOs and RTOs are “independent, federally-regulated non-profit organizations” that control regional electricity pricing and distribution.
PJM, a regional transmission organization located in 13 eastern states (including Pennsylvania, West Virginia, Ohio and Illinois), has the largest amount of large-scale battery installations, with a storage capacity of 278 MW at the end of . The second biggest owner of large-scale battery capacity is California’s ISO (CAISO). By the end of , CAISO operated batteries with a total storage capacity of 130MW.
Most of the battery storage projects that ISOs/RTOs develop are for short-term energy storage and are not built to replace the traditional grid. Most of these facilities use lithium-ion batteries, which provide enough energy to shore up the local grid for approximately four hours or less. These facilities are used for grid reliability, to integrate renewables into the grid, and to provide relief to the energy grid during peak hours.
There is also a limited market for small-scale energy storage. While a minor portion of the small-scale storage capacity in the United States is for residential use, most of it is for use in the commercial sector—and most of these commercial projects are located in California.
In the past decade, the cost of energy storage, solar and wind energy have all dramatically decreased, making solutions that pair storage with renewable energy more competitive. In a bidding war for a project by Xcel Energy in Colorado, the median price for energy storage and wind was $21/MWh, and it was $36/MWh for solar and storage (versus $45/MWh for a similar solar and storage project in ). This compares to $18.10/MWh and $29.50/MWh, respectively, for wind and solar solutions without storage, but is still a long way from the $4.80/MWh median price for natural gas. Much of the price decrease is due to the falling costs of lithium-ion batteries; from to battery costs for electric vehicles (similar to the technology used for storage) fell 73 percent. A recent GTM Research report estimates that the price of energy storage systems will fall 8 percent annually through .
There are many different ways of storing energy, each with their strengths and weaknesses. The list below focuses on technologies that can currently provide large storage capacities (of at least 20 MW). It therefore excludes superconducting magnetic energy storage and supercapacitors (with power ratings of less than 1 MW).
Pumped-storage hydro (PSH) facilities are large-scale energy storage plants that use gravitational force to generate electricity. Water is pumped to a higher elevation for storage during low-cost energy periods and high renewable energy generation periods. When electricity is needed, water is released back to the lower pool, generating power through turbines. Recent innovations have allowed PSH facilities to have adjustable speeds, in order to be more responsive to the needs of the energy grid, and also to operate in closed-loop systems. A closed loop PSH operates without being connected to a continuously flowing water source, unlike traditional pumped-storage hydropower, making pumped-storage hydropower an option for more locations.
In comparison to other forms of energy storage, pumped-storage hydropower can be cheaper, especially for very large capacity storage (which other technologies struggle to match). According to the Electric Power Research Institute, the installed cost for pumped-storage hydropower varies between $1,700 and $5,100/kW, compared to $2,500/kW to 3,900/kW for lithium-ion batteries. Pumped-storage hydropower is more than 80 percent energy efficient through a full cycle, and PSH facilities can typically provide 10 hours of electricity, compared to about 6 hours for lithium-ion batteries. Despite these advantages, the challenge of PSH projects is that they are long-term investments: permitting and construction can take 3-5 years each. This can scare off investors who would prefer shorter-term investments, especially in a fast-changing market.
In Bath County, Virginia, the largest pumped-hydro storage facility in the world supplies power to about 750,000 homes. It was built in and has an output of approximately 3 GW.
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. Currently, there are only two operating CAES facilities: one in McIntosh, Alabama and one in Huntorf, Germany. The McIntosh plant, which was built in , has 110 MW of storage. A 317 MW CAES plant is under construction in Anderson County, Texas.
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. At the end of , the cost of a lithium-ion battery pack for electric vehicles fell to $209/kWh, assuming a cycle life of 10-15 years. Bloomberg New Energy Finance predicts that lithium-ion batteries will cost less than $100 kWh by .
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. New innovations, such as replacing graphite with silicon to increase the battery’s power capacity, are seeking to make lithium-ion batteries even more competitive for longer-term storage.
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. The battery storage facilities, built by Tesla, AES Energy Storage and Greensmith Energy, provide 70 MW of power, enough to power 20,000 houses for four hours.
Hornsdale Power Reserve in Southern Australia is the world’s largest lithium-ion battery and is used to stabilize the electrical grid with energy it receives from a nearby wind farm. This 100 MW battery was built by Tesla and provides electricity to more than 30,000 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.
A 200 MW (800 MWh) flow battery is currently being constructed in Dalian, China. This system will not only overtake the Hornsdale Power Reserve as the world’s biggest battery, but it will also be the only large-scale battery (>100 MW) that is made up of flow batteries instead of lithium ion batteries.
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. Fuel cell facilities can, therefore, produce hydrogen when electricity is cheap, and later use that hydrogen to generate electricity when it is needed (in most cases, the hydrogen is produced in one location, and used in another). Hydrogen can also be produced by reforming biogas, ethanol, or hydrocarbons, a cheaper method that emits carbon pollution. Though hydrogen fuel cells remain expensive (primarily because of their need for platinum, an expensive metal), they are being used as primary and backup power for many critical facilities (telecom relays, data centers, credit card processing…).
Flywheels are not suitable for long-term energy storage, but are very effective for load-leveling and load-shifting applications. Flywheels are known for their long-life cycle, high-energy density, low maintenance costs, and quick response speeds. Motors store energy into flywheels by accelerating their spins to very high rates (up to 50,000 rpm). The motor can later use that stored kinetic energy to generate electricity by going into reverse. Flywheels are commonly left in a vacuum so as to minimize air friction, which would slow the wheel. The Stephentown Spindle in Stephentown, New York, unveiled in with a capacity of 20 MW, was the first commercial use of flywheel technology to regulate the grid in the United States. Several other flywheel facilities have since come on line.
Energy storage is especially important for electric vehicles (EVs). As electric vehicles become more widespread, they will increase electricity demand at peak times, as professionals come home from work and plug in their cars for a nightly recharge. To prevent the need for new power plants to meet this extra demand, electricity will need to be stored during off-peak times. Storage is also important for households that generate their own renewable electricity: a car cannot be charged overnight by solar energy without a storage system.
Interestingly, electric vehicles can be used as back-up storage during periods of grid failure or spikes in demand. Although most EVs today are not designed to supply energy back into the grid, vehicle-to-grid (V2G) cars can store electricity in car batteries and then transfer that energy back into the grid later. EV batteries can still be used in grid storage even after they are taken off the road: utilities are using the batteries from retired EVs as second-hand energy storage. Such batteries can be used to store electricity for up to a decade for grid applications. An example of this can be found in Elverlingsen, Germany, where almost 2,000 batteries from Mercedes Benz EVs were collected to create a stationary grid-sized battery that can hold almost 9 MW of power.
In February , the Federal Energy Regulatory Commission (FERC) unanimously approved Order No. 841, which required Independent System Operators and Regional Transmission Organizations to remove barriers to entry for energy storage technologies, by having these groups reevaluate their tariffs. The FERC believes this will lead to greater market competition in the energy grid sector.
In May , the Department of Energy's Advanced Research Projects Agency (ARPA-E) committed up to $30 million in funding for long-term energy storage innovation. The funding went to the Duration Addition to electricitY Storage (DAYS) program, which focuses on developing new technologies that can make it possible for energy storage facilities in all U.S. regions to power an electrical grid for up to 100 hours.
Several U.S. states have taken a keen interest in energy storage, and their policies can serve as inspiration for others.
For the endnotes, please download the PDF version of this fact sheet.
Author: Alexandra Zablocki
A BESS collects energy from renewable energy sources, such as wind and or solar panels or from the electricity network and stores the energy using battery storage technology. The batteries discharge to release energy when necessary, such as during peak demands, power outages, or grid balancing. In addition to the batteries, BESS requires additional components that allow the system to be connected to an electrical network.
A bidirectional inverter or power conversion system (PCS) is the main device that converts power between the DC battery terminals and the AC line voltage and allows for power to flow both ways to charge and discharge the battery. The other primary element of a BESS is an energy management system (EMS) to coordinate the control and operation of all components in the system.
For a battery energy storage system to be intelligently designed, both power in megawatt (MW) or kilowatt (kW) and energy in megawatt-hour (MWh) or kilowatt-hour (kWh) ratings need to be specified.
The power-to-energy ratio is normally higher in situations where a large amount of energy is required to be discharged within a short time period such as within frequency regulation applications. For pricing purposes, however, the quoted measure is usually the energy rating.
A battery’s C rating is the rate at which a battery can be fully charged or discharged. For example, charging at a C-rate of 1C means that the battery is charged from 0 - 100% or discharged from 100 - 0% in one hour.
A C-rate higher than 1C means a faster charge or discharge, for example, a 2C rate is twice as fast (30 minutes to full charge or discharge). Likewise, a lower C-rate means a slower charge or discharge, as an example, a C-rate of 0.25 would mean a 4-hour charge or discharge.
The formula is:
T = Time
Cr = C-Rate
T = 1 / Cr (to view in hours), or T = 60 min / Cr (to view in minutes). For example:
Battery storage systems have several advantages when paired with renewable energy and non-renewable forms of generation. Solar and wind can be unpredictable, so battery storage systems are a key component in steadying energy flow by providing a steady supply whenever required, irrespective of weather conditions. Additionally, BESS can protect users from potential supply interruptions that could threaten the energy supply. Here are some of the benefits of battery storage systems:
Installing a battery energy storage system powered by renewable energy generation technologies helps reduce carbon emissions from fossil fuels and contributes to the net zero pathways in combatting the effects of global warming.
BESS allows consumers to store low-cost solar energy and discharge it when the cost of electricity is expensive. In doing so, it allows businesses to avoid higher tariff charges, reduce operational costs and save on their electricity bills.
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Battery storage systems guarantee a continuous energy supply, even at times when the network is unstable due to peaks in demand or extreme weather events.
The sun is not always “on.” A battery storage system works round the clock and therefore compensates for any fluctuations in solar energy supply by storing any excess energy and maximise renewable energy generation.
A full battery energy storage system can provide backup power in the event of an outage, guaranteeing business continuity.
Battery systems can co-locate solar photovoltaic, wind turbines, and gas generation technologies. In doing so, BESS co-location can maximise land use and improve efficiency, share infrastructure expenditure, balance generation intermittency, lower costs, and maximise the national grid and capacity.
The battery energy storage system can regulate the frequency in the network by ensuring it is within an appropriate range. Discrepancies between generated and required energy can cause short-term problems, such as outages or blackouts, but BESS can quickly react and secure sub-second frequency response, stabilising the network. Additionally, it guarantees voltage stability by keeping it within established boundaries.
In summary:
BESS solutions include these core components:
Battery System or Battery modules – containing individual low voltage battery cells arranged in racks within either a module or container enclosure. The battery cell converts chemical energy into electrical energy. The batteries are connected in series and parallel for the required capacity.
Storage enclosure - either as an outdoor module or containerised solution along with thermal management.
Battery Management System (BMS) – which ensures the battery cell's safe working operation, ensuring it operates within the correct charging and discharging parameters. In doing so, the BMS monitors the battery cell's current, voltage, and temperature and estimates its state of charge (SoC) and State-of-Health (SoH) to prevent safety risks and ensure reliable operation and performance.
Inverter or a Power Conversion System (PCS) – the battery cell produces direct current (DC), which the PCS converts into alternating current (AC) used for the power grid, commercial or industrial applications. Bidirectional inverters allow for the charging and discharging of the battery cell.
Energy Management System (EMS) – controls and monitors the energy flow of the BESS and systems. The EMS coordinates the BMS, inverters and other components of the battery energy system by collecting and analysing data used to manage and optimise the overall system performance.
Safety Systems – subject to system functionality and operating conditions, a BESS will include fire suppression, smoke detection, a temperature control system, and cooling, heating, and air conditioning systems. A dedicated monitoring and control system will ensure the safe operation of the BESS and the prevention of fire and hazardous incidents. The BESS will also be housed within a secure restricted access area and include CCTV monitoring.
Rated Power Capacity is the total discharge capability (usually in megawatts (MW)) or the maximum rate of discharge the BESS can achieve, starting from a fully charged state.
Rated Energy Storage Capacity is the total amount of stored energy in kilowatt-hours (KWh) or megawatt-hours (MWh). Capacity expressed in ampere-hours (100Ah@12V for example).
The amount of time storage can discharge at its power capacity before exhausting its battery energy storage capacity. For example, a battery with 1MW of power capacity and 6MWh of usable energy capacity will have a storage duration of six hours.
Depth of Discharge (DoD) expresses the total amount of capacity that has been used.
The amount of time or cycles a battery storage system can provide regular charging and discharge before failure or significant degradation. Cycle Life is the number of times a battery storage part can be charged and discharged before failure, often affected by Depth of Discharge (DoD), for example, one thousand cycles at a DoD of 80%.
Self-discharge occurs when the battery's stored charge (or energy) is reduced through internal chemical reactions or without being discharged from performing work for a customer or the grid. Self-discharge is usually expressed as a percentage of the charge lost over a certain period. It is an essential parameter in batteries intended for longer-duration applications.
Discharge Rate (C) describes the current that a battery can deliver for a period of time, as an example, C5 is the current a battery will provide over 5 hours to reach full discharge.
The state of charge is usually expressed as a percentage representing the battery's present charge level and ranges from wholly discharged to fully charged. The state of charge influences a battery's ability to provide energy or ancillary services to the network at any given time. The state of Charge expresses the amount of capacity remaining.
Round-trip efficiency is the ratio of energy charged to the battery to the energy discharged from the battery and is measured as a percentage. It can represent the battery system's total AC-AC or DC-DC efficiency, including losses from self-discharge and other electrical losses.
In addition to the above battery characteristics, BESS have other features that describe its performance.
The ramp rate is the rate at which the BESS may decrease or increase its power output - ramp down or up, respectively.
The response time is when BESS must move from the idle state and start working at full power.
Lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (NMC) are the two most common and popular Li-ion battery chemistries for battery energy applications. Li-ion batteries are small, lightweight and have a high capacity and energy density, requiring minimal maintenance and provide a long lifespan. Lithium-ion batteries can also be rapidly charged and have a low self-discharge rate.
The disadvantages of this battery technology include excessive cost, inflammability, intolerance to extreme temperatures, overcharge, and over-discharge.
Lead-Acid batteries are well-proven within the automotive industry and behind-the-meter grid and UPS applications. PbA batteries are widely available, low cost, widely recyclable, and can perform effectively at both hot and cold temperatures. However, due to advances in Li-ion battery technology, lead-acid batteries have a low energy density and are slow to charge.
A sodium-sulphur battery is a molten salt-based device. Na-S batteries have several advantages, including high energy and power density, a long lifespan, and reliable operation under extreme 300 to 350 degrees Celsius temperatures. However, this battery technology is primarily suited to large-scale stationary grid storage applications due to high operating temperatures and corrosion sensitivity. Sodium is also a dangerous component because it is highly flammable and potentially explosive.
Flow batteries store energy in liquid electrolyte solutions, unlike traditional rechargeable battery solid electrode material. The vanadium redox battery (VRB) is the most prevalent flow battery type and is suitable for longer durations of up to 8 hours or where an extended lifetime is required. Despite their low energy capacity and charge/discharge rate, flow batteries respond quickly and reduce fire risk due to the non-flammable electrolytes used.
A zinc-bromine battery is a rechargeable battery that uses the reaction between bromine and zinc metal to produce an electric current with an electrolyte composed of an aqueous solution of zinc bromide. The zinc-bromine battery was developed as an alternative to lithium-ion batteries for stationary power applications from grid-scale to domestic scale. The water-based electrolyte in Zinc-bromine batteries makes the battery system less prone to fire and overheating than lithium-ion batteries.
Battery energy storage can be beneficial for several reasons due to the flexibility of co-locating with other renewable energy sources or non-renewable sources. Battery energy storage also requires a relatively small footprint and is not constrained by geographical location. Let’s consider the below applications and the challenges battery energy storage can solve.
A battery energy storage system can balance loads between on-peak and off-peak periods. The electricity demand fluctuates depending on the day of the week, time of day, and seasonality. As such, when there is peak electrical demand, prices are at their most expensive. Alternatively, the power price is at the standard rate when demand is low during off-peak periods. Peak shaving allows users with battery energy storage systems the assets to store power during off-peak periods and discharge during peak times to reduce electricity costs.
Energy time shifting or arbitrage allows users with BESS solutions to store their purchased power during off-peak times to use on-site when the imported power price is high. Alternatively, users can trade their stored electricity via the flexibility markets (Energy Markets, Ancillary Services, and Capacity Market) for income generation.
Battery energy storage can supply fast response backup power in the event of a mains failure to ensure infrastructure is operational and downtime is minimal. Using these battery energy storage systems alongside power generation technologies such as gas-fired Combined Heat and Power (CHP), standby diesel generation, and UPS systems will provide increased resilience mitigating a potential loss of operational costs, whilst protecting your brand.
A BESS has a frequency response which allows it to provide active power output when there is a change in the electrical grid's frequency. A deviation from the nominal frequency indicates a mismatch between power supply and demand, which can destabilise the grid, causing outages or blackouts. To restore balance quickly, the BESS can adjust its active power output by reacting to deliver sub-second frequency response to stablise and balance supply and demand within the network. The growing share of renewable generation and decentralised power plants connected to the network, means battery storage will continue to play a critical role in our energy transition.
In Front-of-the-Meter (FtM) applications battery storage systems are typically referred to as utility or grid-scale battery storage and can be connected to transmission or distribution networks to reduce congestion management whilst also controlling voltage and providing reserve and ancillary services. A BESS can also support power generation assets.
BESS are typically Behind-the-Meter (BtM), and applications include avoiding electricity network charges, benefiting from tariff differences, delivering value-added balancing services, or enhancing on-site resilience and energy consumption when paired with on-site solar PV, thus saving money and optimising the sustainability benefits.
BESS can be paired with other renewable and non-renewable technologies to form a hybrid power solution. For example, these hybrid systems can enhance the performance of new and existing gas engine installations. Combining a battery storage system with gas generation and solar power will go a long way to making cheaper, cleaner and more reliable power more accessible.
BESS projects can be attractive by obtaining ‘stacked’ revenue streams. These include:
Participants may earn revenue for entering into commitments under a statutory contract called a ‘Capacity Agreement’ with the Government. These Capacity Agreements provide a backup electricity supply to meet peak demand during system stress. The agreements may have a duration of up to 15 years.
These agreements are with the consumers for a negotiated price. The contracts are known as Power Purchase Agreements or PPA. PPAs may have a duration of up to 15 years.
Dynamic Frequency Response provides an extremely valuable source of income. However, contracts with the National Grid typically have two years. Under the dynamic frequency response contracts, the operator responds to fluctuations in demand on the network by reducing or increasing its energy consumption. This is organised through the Dynamic Containment Service.
Users with BESS assets can optimise their energy usage to lower costs, improve sustainability or reduce costs. Electricity can be purchased and stored when prices are cheap and discharged during peak times to offset energy costs.
The main driver for battery storage in Ireland is the DS3 (Delivering a Secure Sustainable Electricity System) programme, which was brought in to enable Ireland to meet its renewable energy targets and to manage the increased amount of renewable generation connected to the grid.
The DS3 programme allows the system operator to procure ancillary services, including frequency response and reserve services; the sub-second response needed means that batteries are well placed to provide these services.
Aside from battery energy storage systems, other energy storage technologies include:
During periods of low electricity demand, surplus generation is used to pump water from a low-elevation reservoir up to a high-level elevation. When water is released from the high-level elevation, it flows down through a turbine to generate electricity to meet peak demand.
Electricity is used to compress ambient air, which is stored under pressure in underground caverns or containers. When electricity demand is high, the pressurised air is heated and released into an expansion turbine generator for power production.
It is a way by which mechanical energy may be stored in the form of potential or kinetic energy. Electric motors accelerate a flywheel at high speeds through which the energy is stored as kinetic rotational energy. When there is an electricity demand, the spinning force of the flywheel is connected to a generator to produce power.
Electricity may produce thermal energy, which can be stored until needed. For example, electricity can be used to make chilled water during low demand and later used for cooling during peak electricity consumption. The UK's gas system distributes about twice as much energy as electricity, and this energy is used for heating. Heating demands vary with season and time of day, and thermal energy storage can load shift and smooth demand on the plant. Move heat from the summer to the winter.
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