Solar pioneer to use Tesla to test energy home of future vision

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Solar pioneer David Mills intends to use his Tesla Model S to integrate with solar and storage in his home. He expects to be “energy neutral” and generate enough solar to power his home and two EVs.

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David Mills, one of Australia’s greatest solar pioneers, is among the first recipients of a Tesla Model S vehicle in Australia, and says he will combine the electric vehicle with solar and storage to get a taste of the future of energy systems.

Mills, a world leader in solar thermal technology whose company Ausra was sold to French nuclear giant Areva for an estimated $200 million, would have been at the official launch of Tesla on Tuesday, but for a pre-planned holiday. The other eight first adopters got their cars on Tuesday. Mills will get his Model S next week.

“Having worked in the solar field all my life, I want to live in the future even though I am retired,” Mills told RenewEconomy in an interview. “Having an electric vehicle helps that.”

Mills intends to combine the Tesla EV with a large solar array at his northern Sydney home – and at his Blue Mountains weekender – but he is not one of those who plans to disconnect from the grid.

That’s because he thinks that the grid is the cheapest battery – at least of last resort, as long as it is priced right.

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Photo: Sam Parkinson

At his Sydney home, Mills is doubling the size of his rooftop array to 7kW and will introduce battery storage as well. He expects that he will generate enough solar electricity to power his home and two EVs. For nine months of the year he will produce more than he needs, and export back into the grid, but for around three months he will have to draw down from the grid.

“I am not interested in the daily balance (between production and consumption), what I am interested in is the annual balance. That is what matters to the Earth,” he says.

“The grid will be essential in allowing us to do that. We have a dream of not trying to disconnect from the grid – but living in an urban situation where we match usage with production from the home.

“Basically what we want to demonstrate is that we can living environmentally both in the domestic and the transportation sectors.”

Mills is working with a bunch of companies and consultants to see what combination of technology works best. Storage will likely come from a 10kWh battery array, to mop up excess power produced in summer and not used to charge the EVs.

Another option is to use the excess electricity to heat water. “If storage is full, you can put electricity through hot water system, or load some to the car. It just means that you don’t waste it. You are using that to your best advantage.”

Mills’ house does not have a car port, or a garage. His house has reverse cycle for heating or cooling, but with ceiling fans and thermal mass the cooling capability is not used except on the very hottest days, and on those days he has plenty of solar. But does require heating in winter. He says the solar array helps keep the sun off the roof in summer.

“If the grid has a proper business model, then it will be cheaper than a lot of storage. If you have to disconnect then the amount of storage needed is at least double or triple, and you need more PV.”

Mills says he agrees with the principal of peer-to-peer metering, which allows someone to sell electricity to a neighbour, or a network of buildings. That would require charges for the electricity and the distance travelled.

“That is what grid should be for. Instead of calling solar a scam,  the grid should encourage peer to peer for renewables. It would be perfectly sustainable, and allow the grid to serve society for a very long time.”

As for the second EV, Mills hasn’t decided yet. It will be a small city EV rather than the large performance-based Tesla. “None of the other models in Australia yet fits the bill.”

Mills says his own house is complicated by the fact that his roof is not facing north and is surrounded by trees. But he still says it can be done.

“I fully believe we can match the annual load from the roof. And it will be hardly visible from the street. That means that the appearance of the neighbourhood is unchanged, yet we are now going to be powering both the home and the transport sectors. If we can do it, then a whole lot of people can do this in Australia.”

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7 Comments
  1. Rob 5 years ago

    That’s the holy grail for your average punter of course. Be able to supply all your own electricity for your household needs and be able to charge 1 or 2 EVs, all from the energy generated by your own solar system. What would make this achievable sooner would be if the grid could be used as your storage system. When you have excess production from your system you “deposit” your spare kWhs in the grid storage “energy bank” ( literally for a rainy day! ). And when you are short of kWhs, say during the above mentioned 3 months, you withdraw and use your saved kWhs. Wether this would work would depend, as David mentions, on how much the “energy bank” would charge you for storage or “depositing” your excess kWhs. I live in a 2 person household that has gas hot water and gas cooking but everything else uses electricity including our 2 air conditioners. We have had a 1.5 kW solar system for 4 years and it has produced 1850 kWhs of spare electricity in that time. If we could have “banked” it, we would be feeling pretty secure as far as future energy needs might go such as for charging an EV or two. I’m assuming that saving and withdrawing energy would be cheaper for the prosumer than being paid for excess kWhs and then having to then buy extra kWhs should you need them. I’m also assuming that the generators and/or transmittors would be able to organise the storage of large amounts of consumer’s energy. The problem with home storage is you will never probably be able to store all your excess, unless your demand and supply is very finely tuned. Even then there would be a limit to how much of your excess you could store. Grid connected storage could also save the big generators and transmittors from losing clients whom would otherwise have gone off-grid. It might also justify the immense amount of money that has been spent on the poles and wires which are increasingly looking like becoming irrelevant in the future. I guess the main questions are would it be possible for utilities to “store” very large amounts of prosumer energy or is simply selling excess and buying more when you need it a cheaper equivalent. At the moment, selling excess and buying energy when you run short, is not really working for the prosumer and won’t stop mass grid defection in the future.

    • Stop the TPP 5 years ago

      China says 30% of their govt cars will be electric by 2016. I imagine this will mean an influx of cheap EVs around the world.

    • John Silvester 5 years ago

      We use to have what you are referring to, Net Metering, though it was based on the billing cycle and not on annual use.

  2. Chris Fraser 5 years ago

    David…You and me brother…even if you can’t swap out the Tesla battery at home, you could, for a minor round trip loss, charge a stationary battery first. Then save yourself $5000/yr on petrol.

  3. coomadoug 5 years ago

    This is vaguely the future. However living throughout the world will be high density. There will not be the roof space for solar in most homes. So the electric car will be the poles and wires for the home. The solar will be large scale and the city infrastructure on the grid will provide the charging for cars. The homes in various blocks of flats will be interconnected and car computers will co ordinate the unit complex energy sharing and exchange.

  4. schererd 5 years ago

    The battery bank can be charged at night at off-peak rates and you can use the power to run your house during on-peak hours and bank full solar credits and a payout at the end of the year which helps pay for your whole system. That’s my next step.

  5. jstack6 5 years ago

    We do the same with our 100% Electric Home, LEAF and ELF. We use no other fuels not even a fireplace. We are in Super Sunny Arizona and our 4 kW system makes 10% extra on an annual basis. I help our Utility during Peak Hours and only use excess they have Off Peak.
    We have Solar PV 4 kW, Solar how water, Solar tube lights, 4 Solar ovens, and even a Solar clothes dryer (line). We only use LED lights and super efficient heat pump.

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