Home energy storage devices store

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

locally, for later consumption. Electrochemical

energy storage Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery. Energy comes in ...

products, also known as "Battery Energy Storage System" (or "BESS" for short), at their heart are

rechargeable batteries A rechargeable battery, storage battery, or secondary cell (formally a type of energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or prima ...

, typically based on

lithium-ion A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also sees ...

or lead-acid controlled by computer with intelligent

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

to handle charging and discharging cycles. Companies are also developing smaller

flow battery A flow battery, or redox flow battery (after reduction–oxidation), is a type of electrochemical cell where chemical energy is provided by two chemical components dissolved in liquids that are pumped through the system on separate sides of a ...

technology for home use. As a local

technologies for home use, they are smaller relatives of battery-based

grid energy storage 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 inexp ...

and support the concept of

distributed generation Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical generation and storage performed by a variety of small, grid-connected or distribution system-connected devices referred to ...

. When paired with on-site generation, they can virtually eliminate blackouts in an

off-the-grid Off-the-grid or off-grid is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities. The term "off-the-grid" traditionally refers to not being connected to the electrical gr ...

lifestyle.

Operating modes

On-site generation

The stored energy commonly originates from on-site

solar photovoltaic A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and c ...

panels, generated during daylight hours, and the stored electricity consumed after sundown, when domestic energy demand peaks in homes unoccupied during the day.

Small wind turbine Small wind turbines, also known as micro wind turbines, are used for microgeneration of electricity, as opposed to large commercial wind turbines, such as those found in wind farms. Small wind turbines often have passive yaw systems as opposed ...

s are less common but still available for home use as a complement or alternative to solar panels.

Electric vehicles An electric vehicle (EV) is a vehicle that uses one or more electric motors for propulsion. It can be powered by a collector system, with electricity from extravehicular sources, or it can be powered autonomously by a battery (sometimes cha ...

used during weekdays, needing recharging overnight, are a good fit with home energy storage in homes with solar panels and low daylight-hour electrical consumption. Electric vehicle manufacturers BMW, BYD,

Nissan , trade name, trading as Nissan Motor Corporation and often shortened to Nissan, is a Japanese multinational corporation, multinational Automotive industry, automobile manufacturer headquartered in Nishi-ku, Yokohama, Japan. The company sells ...

and Tesla market own-brand home energy storage devices to their customers. By 2019, such devices had not followed the price reduction of automotive batteries. The units can also be programmed to exploit a

differential tariff Differential tariff is an example of demand side management where the price per unit of energy varies with the consumption. If a power utility uses differential tariff, it may change the rate per kWH of energy used during different times, such as r ...

, that provide lower priced energy during hours of low demand - seven hours from 12:30am in the case of Britain’s

Economy 7 Economy 7 is the name of a differential tariff provided by United Kingdom electricity suppliers that uses base load generation to provide cheap off-peak electricity during the night. Houses using the Economy 7 tariff require a special electricity ...

tariff - for consumption when prices are higher. Smart tariffs, stemming from the increasing prevalence of

smart meters A smart meter is an Electronics, electronic device that records information such as consumption of electric energy, voltage levels, current, and power factor. Smart meters Telemetering, communicate the information to the consumer for greater c ...

, will increasingly be paired with home energy storage devices to exploit low off-peak prices, and avoid higher-priced energy at times of peak demand.

Advantages

Overcoming grid losses

Transmission of electrical power from

power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many p ...

s to population centres is inherently inefficient, due to transmission losses in electrical grids, particularly within power-hungry dense

conurbation A conurbation is a region comprising a number of metropolises, cities, large towns, and other urban areas which through population growth and physical expansion, have merged to form one continuous urban or industrially developed area. In most ca ...

s where power stations are harder to site. By allowing a greater proportion of on-site generated electricity to be consumed on-site, rather than exported to the energy grid, home energy storage devices can reduce the inefficiencies of grid transport.

Energy grid support

Home energy storage devices, when connected to a server via the

internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

, can theoretically be ordered to provide very short-term services to the energy grid:- * Reduced peak hour demand stress - provision of short-term

demand response Demand response is a change in the power consumption of an electric utility customer to better match the demand for power with the supply. Until the 21st century decrease in the cost of pumped storage and batteries electric energy could not be ...

during periods of peak demand reducing the need to inefficiently stand up short generation assets like

diesel generators A diesel generator (DG) (also known as a diesel Genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine generator. A diesel compression-ig ...

. * Frequency correction - the provision of ultra short-term corrections, to keep

mains frequency The utility frequency, (power) line frequency (American English) or mains frequency (British English) is the nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to th ...

within the tolerances required by regulators (e.g., 50 Hz or 60 Hz +/- n%).

Reduced reliance on fossil fuels

Due to the above efficiencies, and their ability to boost the amount of solar energy consumed on-site, the devices reduce the amount of power generated using

fossil fuels A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ...

, namely

natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

and

diesel Diesel may refer to: * Diesel engine, an internal combustion engine where ignition is caused by compression * Diesel fuel, a liquid fuel used in diesel engines * Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...

Disadvantages

Environmental impact of batteries

Lithium-ion batteries, a popular choice due to their relatively high

charge cycle A charge cycle is the process of charging a rechargeable battery and discharging it as required into a load. The term is typically used to specify a battery's expected life, as the number of charge cycles affects life more than the mere passage of ...

and lack of

memory effect Memory effect, also known as battery effect, lazy battery effect, or battery memory, is an effect observed in nickel-cadmium rechargeable batteries that causes them to hold less charge. It describes the situation in which nickel-cadmium batter ...

, are difficult to

recycle Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...

. Lead-acid batteries are relatively easier to recycle and, due to the high resale value of the

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

, 99% of those sold in the US get recycled. They have much shorter useful lives than a lithium-ion battery of a similar capacity, due to having a lower

, narrowing the environmental-impact gap. In addition, lead is a

toxic heavy metal A toxic heavy metal is any relatively dense metal or metalloid that is noted for its potential toxicity, especially in environmental contexts. The term has particular application to cadmium, mercury and lead, all of which appear in the World He ...

and the

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

in the

electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

has a high environmental impact.

Second life for electric vehicle batteries

To offset the environmental impact of batteries, some manufacturers extend the useful life of used batteries taken from electric vehicles at the point where the cells won't sufficiently hold charge. Though considered end of life for electric vehicles, the batteries will function satisfactorily in home energy storage devices. Manufacturers supporting this include Nissan, BMW and Powervault.

Salt water batteries

Home Energy Storage devices can be paired with salt water batteries, which have a lower environmental impact due to their lack of

and ease of

recyclability Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...

. Saltwater batteries are no longer being produced on a commercial level after the bankruptcy of

Aquion Energy Aquion Energy was a Bethlehem, Pennsylvania and Washington, D.C.-based company that manufactured sodium ion batteries ( salt water batteries) and electricity storage systems. The company claimed to provide a low-cost way to store large amounts o ...

in March 2017.

Alternatives or complement

Cratzenbach, Modell Pumpspeicherkraftwerk

Using a

pumped-storage Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...

system of

cistern A cistern (Middle English ', from Latin ', from ', "box", from Greek ', "basket") is a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater. Cisterns are distinguished from wells by t ...

s for energy storage and small generators,

pico hydro Pico hydro is a term used for hydroelectric power generation of under 5 kW. These generators have proven to be useful in small, remote communities that require only a small amount of electricity for example, to power one or two fluorescent ...

generation may also be effective for "closed loop" home energy generation systems. A

storage heater A storage heater or heat bank (Australia) is an electrical heater which thermal energy storage, stores thermal energy during the evening, or at night when electricity is available at lower cost, and releases the heat during the day as required. ...

or heat bank (Australia) is an electrical

heater Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HV ...

which stores thermal energy during the evening, or at night when electricity is available at lower cost, and releases the heat during the day as required. Accumulators, like a

Hot water storage tank A hot water storage tank (also called a hot water tank, thermal storage tank, hot water thermal storage unit, heat storage tank and hot water cylinder) is a water tank used for storing hot water for space heating or domestic use. Water is a con ...

, are another type of storage heater but specifically store hot water for later use.

References

{{Electricity delivery Energy storage