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

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.

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.

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.”