How do utilities store electricity

Developing technology to store electrical energy so it can be available to meet demand whenever needed would represent a major breakthrough in electricity distribution. Helping to try and meet this goal, electricity storage devices can manage the amount of power required to supply customers at times when need is greatest, which is during peak load.

These devices can also help make renewable energy, whose power output cannot be controlled by grid operators, smooth and dispatchable. They can also balance microgrids to achieve a good match between generation and load. Storage devices can provide frequency regulation to maintain the balance between the network's load and power generated, and they can achieve a more reliable power supply for high tech industrial facilities.

Thus, energy storage and power electronics hold substantial promise for transforming the electric power industry. High voltage power electronics, such as switches, inverters, and controllers, allow electric power to be precisely and rapidly controlled to support long distance transmission. This capability will allow the system to respond effectively to disturbances and to operate more efficiently, thereby reducing the need for additional infrastructure.

A major challenge being addressed by DOE is to reduce the cost of energy storage technology and power electronics and to accelerate market acceptance. Of that total, 94 percent was in the form of pumped hydroelectric storage, and most of that pumped hydroelectric capacity was installed in the s. The six percent of other storage capacity is in the form of battery, thermal storage, compressed air, and flywheel, as shown in the following graph:.

Storing electricity can provide indirect environmental benefits. For example, electricity storage can be used to help integrate more renewable energy into the electricity grid. Electricity storage can also help generation facilities operate at optimal levels, and reduce use of less efficient generating units that would otherwise run only at peak times. Further, the added capacity provided by electricity storage can delay or avoid the need to build additional power plants or transmission and distribution infrastructure.

Potential negative impacts of electricity storage will depend on the type and efficiency of storage technology. For example, batteries use raw materials such as lithium and lead, and they can present environmental hazards if they are not disposed of or recycled properly.

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.

Operational control proved extremely complex. The 33 MW facility was completed by ZGlobal in November and will aid grid flexibility and increase reliability on the Imperial Irrigation District network by providing solar ramping, frequency regulation, power balancing and black start capability for an adjacent gas turbine.

It will supply evening peak demand, and partly replaces the Aliso Canyon gas storage km north which had to be abandoned early in due to a massive leak. It was used for peak-load gas generation. Beyond that, plans are tentative. The plant is responsible for frequency regulation and grid stability in the PJM market as well as arbitrage. The lithium-ion batteries were made by A Systems, and when commissioned in it was the largest lithium-ion BESS in the world.

The lithium-ion batteries and power electronics were supplied by BYD America, and consist of 11 containerized units totaling 20 MW. The company has more than MW of storage projects under development in North America. ON North America is installing two 9. The purpose is mainly for ancillary services. Lifetime of over 10, charge-discharge cycles is claimed. Powin Energy and Hecate Energy are building two projects totalling A large utility-scale electricity storage is a 4 MW sodium-sulfur NaS battery system to provide improved reliability and power quality for the city of Presidio in Texas.