Heywood Interconnector Failure Hammers SA Battery Owners On Tesla VPP – Solar Quotes

Tesla VPP battery cycling

Screen captures from a Tesla VPP customer’s monitoring app. Look at that battery go! Green is battery, grey is grid. Above the line is using battery/grid. Below the line is charging battery/exporting to the grid.

Tesla Powerwall owners taking part in South Australia’s Virtual Power Plant (VPP) project have a continuing exciting ride for a few more days yet.

With the Victoria-South Australia interconnector out of action following storm damage, their batteries will probably see ongoing heavy charge/discharge cycling as the VPP plays its role in keeping South Australia’s grid stable.

As South Australia’s InDaily reported, storms in late January damaged transmission towers near the Heywood interconnector, and on February 3 it was stated repairs could take up to two weeks. At the time of publishing, it’s estimated the fix will be complete on February 14.

A VPP participant contacted SolarQuotes early on in the event to tell us he noticed a big upswing in the number of charge/discharge cycles his battery was experiencing.

He told us his battery was being:

“cycled every day unnecessarily” (from his point of view),

and he is concerned this could be adding to his power bill, because it’s happening:

“even out of solar hours”

(hence his concern about costs).

He said Tesla had advised him that:

“anyone who is part the Tesla VPP plan will have their system used or abused in a similar manner”.

Our informant received the following explanation in an e-mail from Tesla:

“Your battery was charging and discharging in order to support the SA grid during what might have otherwise been an outage across the network. This is normal aggregation behavior and shouldn’t be considered unnecessary – it’s necessary as part of the virtual power plant operation.  Any grid charging the Powerwall experiences as part of the optimization in the VPP will be a credit line item on your power bill (meaning, this is not an additional expense or kW you will pay for).”

“The warranty guarantees 70% energy capacity at the end of 10 years. The activity you’re seeing is still covered by this warranty.”

SolarQuotes asked Tesla Australia to comment, but we haven’t yet had a response.

Our friend’s concern is reasonable, but we’d hope customers on the VPP won’t be hung out to dry.

As we commented in 2016 when the Powerwall 2 was released, the company’s “unlimited cycles” warranty (PDF) is not quite unlimited, but it’s pretty darn good. The warranty is only “unlimited” if the installation is only used to provide either daily usage or backup power for the customer.

Use in a VPP is obviously outside that spec, so the warranty is more limited (but still good), and we worked out that the “37,800 kWh delivered” warranty is 3,200 cycles – about eight years’ worth if cycled once a day.

What’s happening in South Australia at the moment could add up to be more than a “daily cycle”, so it’s fair for owners to be concerned. As our informant noted, this could well be the prevailing condition for users for the whole of the interconnector repair.

“Expect continual  aggressive battery power cycling  if you are a VPP participant for the next two weeks,” he wrote.

“Power generation, particularly solar generated power will have nowhere to  go, so the batteries will be sharing that power around.”

Tesla’s silence isn’t surprising – the company loves being completely in control of its media narrative1 – but it’s odd that with what looks like a good news story in the offing, it’s got nothing to say. At the cost of extra battery cycling (and the company promises customers will still get their warranted 70% capacity at the end of 10 years), the VPP is working as expected. It’s contributing to grid stability in the face of challenging conditions.

It would be interesting, for example, to chat to an engineer about what the challenge looks like from the VPP operations room – what are they learning about power flows between batteries? Is there anything to learn from what is, in practice, an experiment in accelerated aging? We’d love to hear from you, Tesla.

Footnotes

  1. And we’ve been on Tesla’s naughty list for years now ↩

Source: https://www.solarquotes.com.au/blog/tesla-vpp-experience/

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