A top-notch residential solar and storage project shows the potential of renewables when the decision is based on ideological reasons, not economic ones.

Even the experts agree that adding battery storage to a residential solar PV system doesn’t make immediate economic sense – until prices come down a wee way. But if the motivation to upgrade your home to renewable energy isn’t so much about saving money than it is about crystallising the possibilities of self-sufficiency, then why wait?

That’s the philosophy behind a project in Balwyn, east Melbourne, recently completed by solar design, install and consultancy company Greenwood Solutions.

No two solar-and-storage installs are the same, of course, but Greenwood director Eddie Greco told EcoGeneration the Balwyn project was more about fulfilling ideological objectives than economical ones. “It was [also] about adding value to the property, using quality equipment that was going to go the distance,” Greco says.

With that brief, Greenwood recommended a few options. The winner was a 15kW array with 27kWh of storage, using 48 LG Neon PV Array panels, at 315 watts each, a bank of SimpliPhi lithium batteries, Selectronic SP Pro inverter/charger and Schneider solar charge controller.

Suit the size

The house is a big one, with a tennis court and swimming pool, and the occupants were consuming about 50-60kWh a day. Greco says a 15kW solar PV system in Victoria can produce about 50kWh a day year round, “give or take”. Night time consumption in the Balwyn home was estimated to be about 25kWh, so the 27kWh battery bank was felt to be adequate, with a discharge to 90%.

“On average, throughout the year, we’re trying to make the house as sustainable as possible,” Greco says.

Since the installation was completed a couple of months ago the customers haven’t needed to use electricity from the grid, he says. “Keep in mind it’s only been installed for two months, and we are talking about summer months where’s there’s lots of generation.”

The system is designed with AC and DC couplings and 5kW of the 15kW PV array is connected to a grid-tied inverter, so any excess energy can be exported for 6c/kWh.

“We’re trying to maximise and utilise every bit of available energy,” Greco says. “We don’t want to not produce energy because I think that’s just a waste.”

The 26.9kW lithium battery bank will be set to 90% depth of discharge providing 24.2kWh of available energy storage when required. Based on averages, this system will create power independence for the property, based on an 50kW/h daily load.

Up on the roof

Panels face east, north and west, in an effort to maximise self-consumption in the morning and afternoon. “With batteries you get a lot of yield at noon, but a lot of energy isn’t consumed at those hours. It’s mainly consumed in the hours 8am until 9am, when the kids are getting ready for school, then when people are coming home around 3.30-4pm until about 9pm at night,” he says. “We’ve got some of it AC-coupled, so we directly feed the load from the roof, when it’s most efficient.”

The system also supplies multiple pool pumps and a few air-conditioning units. Greco is working on efficiency measures to get the consumption down from 50kWh to about 40kWh. “By doing that we should have a completely sustainable house.”

Challenges included making allowances to aesthetics in the architect-designed house, which was completely renovated two years ago. “They did not want to see one conduit or cable,” Greco says. “The difficulties of the installation were as high as they could get from an electrical standpoint.”

The home-owners were determined to create a complete renewable system that would help them be as sustainable as possible throughout the entire year. Are they happy with the result?

“We’ve secured independence from the grid as well as a back-up power source,” the Balwyn property-owner says. “I’m sure we’ll see a significant drop in our ongoing power costs, but it was big picture we had in mind when developing this project. We’ve invested in this system for the long term. Not just for the long-term benefit to the environment, but also for the value of our property over the long term.”

System components

  • 1 x 15.1 kW LG PV Array (48 x 315W panels)
  • 8 x Simpliphi Lithium batteries (528Ah Ah @ 48 VDC)
  • 1 x 5kW ABB single phase inverter
  • 1 x 7.5kW Selectronic SP Pro inverter charger
  • 2 x 60 Ah Schneider maximum power point trackers