Home energy storage

A render of a type of home battery.

Home energy storage devices store electricity locally, for later consumption. At their heart are batteries, typically lithium-ion or lead-acid, and intelligent software. An energy storage technology, they are downstream relatives of battery-based grid energy storage and support the concept of distributed generation. When paired with on-site generation, they can virtually eliminate blackouts in an off-the-grid lifestyle.

Operating modes

On-site generation

The stored energy commonly originates from on-site solar photovoltaic panels, generated during daylight hours, and the stored electricity consumed after sundown, when domestic energy demand peaks in homes unoccupied during the day.

Electric vehicles (EVs) 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. EV manufacturers Tesla, Mercedes-Benz,[1] BMW,[2] Nissan[3] and BYD[4] market own-brand home energy storage devices to their customers, with Tesla's Powerwall enjoying significant media exposure.

Differential tariffs and smart meters

The units can also be programmed to exploit a differential tariff, that provide lower priced energy during hours of low demand - seven hours from 12:30am in the case of Britain’s Economy 7 tariff - for consumption when prices are higher.

Smart tariffs, stemming from the increasing prevalence of smart 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.

Advantages

Overcoming grid losses

Transmission of electrical power from power stations to population centres is inherently inefficient, due to transmission losses in electrical grids, particularly within power-hungry dense conurbations 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, 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 during periods of peak demand reducing the need to inefficiently standing up of short generation assets like diesel generators.
  • Frequency correction - the provision of ultra short-term corrections, to keep mains frequency within the tolerances required by regulators (e.g. 50Hz or 60Hz +/- 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, namely natural gas, coal, oil and diesel.

Disadvantages

Environmental impact of batteries

Lithium-ion batteries, a popular choice due to their relatively high charge cycle and lack of memory effect, are difficult to recycle.

Lead-acid batteries are relatively easier to recycle and, due to the high resale value of the lead, 99% of those sold in the US get recycled.[5] They have much shorter useful lives than a lithium-ion battery of a similar capacity, due to having a lower charge cycle, narrowing the environmental-impact gap. In addition, lead is a toxic heavy metal and the sulphuric acid in the electrolyte has a high environmental impact.

Second life for EV 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.[6] Manufacturers supporting this include Nissan,[7] BMW[8] and Powervault.[9]

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 toxic heavy metal and ease of recyclability.

Alternatives

Pico Hydro

Using a pumped-storage system of cisterns for energy storage and small generators, pico hydro generation may also be effective for "closed loop" home energy generation systems. [10][11]

See also

References

  1. ↑ Spector, Julian. "Mercedes-Benz Launches a US Energy Storage Company". Greentech Media. Wood Mackenzie.
  2. ↑ Moloughney, Tom. "BMW Announces Home Energy Storage System Utilizing i3 Battery Packs". cleantechnica. Sustainable Enterprises Media. Retrieved 7 March 2017.
  3. ↑ Muoio, Danielle. "Nissan could rival Tesla with its new at-home battery". Business Insider. Axel Springer. Retrieved 13 March 2017.
  4. ↑ "BYD unveils its B-BOX energy storage system in the uk". Solar Power Portal. Henley Media. Retrieved 7 March 2017.
  5. ↑ "Recycling Rate Study". Battery Council International (BCI). Retrieved 7 March 2017.
  6. ↑ Gaines, Linda. "The future of automotive lithium-ion battery recycling: Charting a sustainable course". Sustainable Materials and Technologies. 1–2 (December 2014): Pages 2–7. Retrieved 13 March 2017.
  7. ↑ Gibbs, Nick. "Nissan gives Leaf batteries a 'second life' as home energy storage units". Automotive News Europe. Crain Communications, Inc. Retrieved 13 March 2017.
  8. ↑ Pyper, Julia. "BMW Is Turning Used i3 Batteries Into Home Energy Storage Units". Greentech Media. Wood Mackenzie. Retrieved 13 March 2017.
  9. ↑ "Second Life Batteries for Domestic Electricity Storage - International Feasibility Study". Gateway to Research. Research Councils UK. Retrieved 13 March 2017.
  10. ↑ "Is energy storage via pumped hydro systems is possible on a very small scale?". Science Daily. 2016-10-24. Retrieved 6 September 2018.
  11. ↑ Root, Ben (December 2011-January 2012). "Microhydro Myths & Misconceptions". 146. Home Power. Retrieved 6 September 2018. Check date values in: |date= (help)
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