Home energy storage refers toresidentialenergy storage devices that storeelectrical energy locally for later consumption. Usually,electricity is stored inlithium-ionrechargeable batteries, controlled by intelligentsoftware to handle charging and discharging cycles. Companies are also developing smallerflow battery technology for home use. As a local energy storage technologies for home use, they are smaller relatives of battery-basedgrid energy storage and support the concept ofdistributed generation. When paired with on-site generation, they can virtually eliminate blackouts in anoff-the-grid lifestyle.
The stored energy commonly originates from on-sitesolarphotovoltaic system such asrooftopsolar panels, which generatedirect current electricity during daylight hours. The solar electricity can bebackfed to thegrid (often rewarded with afeed-in tariff) via asolar inverter, or it can be stored in a home energy storage system as astand-alone power system for later consumption after sundown. This allows the household to take advantage of the peak solar generation during the day hours (when homes are typically unoccupied with low electricity usage due to the occupants being away atwork or atschool) and use it later to offset after-hour consumption from the grid, thus avoid thehigher power costs during the domesticpeak demand hours (usually from mid-afternoon to mid-evening). The home energy storage can also serve as abackup battery in the events ofpower outage to keep essentiallighting,heating,computing andhome medical equipment running without disruption.
Small wind turbines are less common but still available for home use as a complement or alternative to solar panels.
There has been a trend of automotive companies cooperating with other leaders in the energy industry in order to develop home energy storage solutions. This is likely due to a lot of the research and development that goes into powerful batteries having the potential to benefit both automotive and residential industries. Manufacturers suchBMW[1] in their partnership with Solarwatt[2] andNissan[3] in conjunction withEaton[4] are strong examples of this trend. Additionally,BYD andTesla market own-brand home energy storage devices to their customers.
Despite initial high costs bringing a lot of scrutiny,[5] the home energy storage market is seeing an increase in revenue following a trend in lowering prices[6]
The units can also be programmed to exploit adifferential tariff, that provide lower priced energy during hours of low demand - seven hours from 12:30am in the case of Britain'sEconomy 7 tariff - for consumption when prices are higher.
Smart tariffs, stemming from the increasing prevalence ofsmart meters, 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.
Transmission of electrical power frompower stations topopulation centres is inherently inefficient, due totransmission losses in electrical grids, particularly within power-hungry denseconurbations where power stations are harder to site.[7] 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.
Home energy storage devices, when connected to a server via theinternet, can theoretically be ordered to provide very short-term services to the energy grid:
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 usingfossil fuels, namelynatural gas,coal,oil anddiesel.
Lithium-ion batteries, a popular choice due to their relatively highcharge cycle and lack ofmemory effect, are difficult torecycle.
Lead-acid batteries are relatively easier to recycle and, due to the high resale value of thelead, 99% of those sold in the US get recycled.[8] They have much shorter useful lives than a lithium-ion battery of a similar capacity, due to having a lowercharge cycle, narrowing the environmental-impact gap. In addition, lead is atoxic heavy metal and thesulfuric acid in theelectrolyte has a high environmental impact.
To offset the environmental impact of batteries, some manufacturers extend the useful life of used batteries taken fromelectric vehicles at the point where the cells will not sufficiently hold charge. Though considered end of life for electric vehicles, the batteries will function satisfactorily in home energy storage devices.[9] Manufacturers supporting this include Nissan,[10] BMW[11] and Powervault.[12]
Home Energy Storage devices can be paired withsalt water batteries, which have a lower environmental impact due to their lack oftoxic heavy metal and ease ofrecyclability.
Saltwater batteries are no longer being produced on a commercial level after thebankruptcy ofAquion Energy in March 2017.
With an increasing amount of consumers choosing to implement solar panels that feed energy solely to their home and home batteries, grid defection has continued to grow. As the number of people of grid increases, the cost of the grid will be spread across fewer consumers making, "the incentive to go off-grid only grow".[13] This is seen as an increasingly large disadvantage to home energy storage, as it could lead to the abandoning of a large infrastructure network created to maintain grids, price inflation for those on grid, and a hindrance to the energy transition.[14]
Storing energy in batteries is far from the only option. Multiple forms of storing energy exist such as flywheels, hydroelectric, and thermal energy.[15]
Using apumped-storage system ofcisterns for energy storage and small generators,pico hydro generation may also be effective for "closed loop" home energy generation systems.[16][17]
Astorage heater or heat bank (Australia) is an electricalheater whichstores 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 ahot water storage tank, are another type of storage heater but specifically store hot water for later use.
Some systems may be portable[18] or partially portable[19] for easier transportation to another location, or use during transportation or travel.
