The US electric car manufacturer Tesla Energy has launched a range of Li-ion storage batteries for homes, utilities and businesses. They are intended to enable owners to store sustainable and renewable energy to manage power demand, provide backup power and increase grid resilience.
Known as the Tesla Powerwall it is a rechargeable lithium-ion battery designed to store energy at a residential level for load shifting, backup power and self-consumption of solar power generation. It consists of Tesla's battery pack, liquid thermal control system and software that receives dispatch commands from a solar inverter. The unit mounts on a wall and is integrated with the local grid to draw on excess power (ie power that is cheaper at times of low demand) and give customers the flexibility to draw energy from their own reserve. Its bene?ts to the customer are said to include load shifting - charging during low rate periods and discharging during more expensive rate periods - increasing the self-consumption of solar power generation by storing surplus solar energy not used at the time it is generated - and back-up power, to use in the event of an outage.
The Powerwall is available rated at 10kWh, for backup applications, or 7kWh for daily use. Both can be connected to solar generation or to the grid and both can provide backup power. Both are rated at 2 kW continuous power, 3 kW peak power with a round trip efficiency >92%. Operating temperature range is -20C (-4F) to 43C (110F).
Tesla's USA selling price to installers is $3500 for 10kWh and $3000 for 7kWh, excluding the inverter and installation cost. Deliveries are due to begin in late summer in the USA and in the UK before the end of the year.
Tesla has not yet states which kind of Li-ion call is being supplied (LiCoO2, lithium iron phosphate, lithium manganese oxide lithium sulphur etc) although one report at least suggests is being made by Panasonic. Lifetime (ie the number of discharge cycles) is implied by a warranty of 10 years and a suggestion of daily cycling, but not specified. A recent study (Andreas Gutsch, Karlsruhe Institute of Technology) suggests that Li-ion storage battery lifetime could vary by a factor of five, from 1000 cycles to 5000 cycles. The study estimated that batteries with lifespans of 3000 cycles were needed for profitable operation.
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