Illustration: Energy Revolution.
Thanks to its thousands of powerwalls deployed in private homes, Tesla has once again helped the Californian electricity grid through a major consumption peak. For each kilowatt-hour injected, the owners were generously compensated.
The “powerwall” is a domestic battery sold by Tesla to individuals, so that they can store their solar electricity production. Since spring 2021, the device is also compulsorily integrated into the photovoltaic roof offer (solar roof) marketed by the brand. Its 13.5 kWh of storage capacity and 10.5 kW of power are enough to cover a few days of consumption for a small house in complete autonomy.
Usually a powerwall is used to accumulate excess solar electricity production of its owner. It can thus self-consume all of the energy it generates, without ever injecting the surplus into the network. But in California, the Tesla battery has a curious additional feature: it can turn into powerful virtual power plant to help the public network when it is in difficulty.
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How does a virtual power plant work?
Clearly, a few days before the risk of voltage, the manager of the electricity network publishes a “Flex Alert”. This message “is generally emitted in the summer when high temperatures increase electricity consumptionmaking the electrical resource scarce” he explains on his website.
“This usually happens in the evening, when renewable energy is no longer available, but temperatures remain high and consumers go home and turn on air conditioners, lights and appliances” specifies California ISO.
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Once the alert has been issued, local electricity suppliers can then ask Tesla to implement its virtual power plant. Via a smartphone application, the brand informs owners of powerwalls that they can, if they wish, program the discharge of their battery in the network at a specific time slot, corresponding to the peak of consumption.
In return, participants are remunerated at $2 per kilowatt hour injected in the network. An extremely advantageous rate, electricity being sold between 0.28 and 0.49 $/kWh by the Californian operator PG&E.
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Not all powerwall owners play the game
After deploying this device for the first time in the summer of 2021, Tesla put it into service again on August 17. 2,616 owners agreed to participaterepresenting a theoretical power of 27.5 MW.
It is not considerable, but not negligible either. However, if the approximately 50,000 owners of powerwalls in California were to commit to the process, this power could climb to 525 MWthe equivalent of half a nuclear reactor.
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