The sun is for everyone, but not everyone owns the roof they live under. A Queensland software company is looking to solve that problem. 

The solar rollout isn’t skipping a beat, with more than three million households across the country now sporting purple PV panels up top. It’s a different story for apartment-dwellers. Just because you own a unit doesn’t mean you own roofspace. As for renters, they never get far with investment property owners who see no reason to pay for a solar system if the bill savings go to someone else.

It’s not that solar is locked out from the rental market, it’s just that the various methods of having it approved for installation in shared properties means negotiating with many owners. When it’s one owner and many tenants, such as a shopping centre, things are more straightforward.

Queensland-based company Rex Energy has entered the shared-solar space with its X1 software, a sleek black box that decides every few seconds the optimal distribution of energy to tenants from a solar-and-storage system owned by the body corporate, an individual or Rex Energy itself. All energy users connected to an X1 system stay connected to the grid via a retailer, with energy from the shared solar and storage supplied at a fixed rate that is reset every five years. “Generally it’s about 20-30 per cent less than what they’re paying for grid energy,” says Rex Energy CEO Scott Graham, citing current rates around 24c/kWh for a commercial property in Victoria and 17c/kWh for a residential body corporate in Queensland.

Graham agrees it sounds a bit like a power purchase agreement. “It depends on the scenario,” he says. “If the building owner owns the system, we’re able to feed each tenant with the exact amount of energy they require. We’re monitoring their total demand and the amount of energy we’re feeding to them [from rooftop solar and stored solar energy] as well.” Another example Rex is working on with a couple of clients is where a body corporate chooses to only recoup the cost of maintenance, selling energy to tenants for less than 10c/kWh.

PV output stored for later

Rex’s work for owners of Homemaker Centre retail sites has seen rooftop systems producing double and in some cases up to 600 per cent of the required load, with surplus stored behind the meter to be drawn on during evening peak or made available to the grid if profits can be taken in the FCAS markets. “We can take that stored energy that would be used for that site for, say, 18 hours and blast it into the grid over 30 minutes or an hour, depending on what their needs are,” Graham says.

The Homemaker Centre projects range between 1.5MW and 2.5MW of rooftop solar, with storage capacity between 2MW and 5MW. All of that supply and storage is controlled in the cloud, with owners of multiple sites able to view an aggregate energy system. “You can drill down to each state, each region, each centre or even each tenancy,” he says.

These virtual power plants can be operated by third-party trading entities in response to grid events or to take advantage of opportunities for profit. Some sites will also have storage installed in front of the meter. “That front-of-meter battery sits and trades futures, FCAS or whatever is intelligent to trade in that region,” he says. Developers whose properties incorporate front-of-meter storage take a percentage of the trading profits.

Investors have backed Rex with $20-$50 million, Graham says, to find locations to build large-scale grid-forming and grid-following battery systems. The company is also hoping to cast out into the utility-scale storage sector, with plans for two sites totalling about 150MW of storage in northern NSW. “Pretty large installations,” he says. “We’re excited about that.”

For storage, Rex has chosen a graphene-based hybrid capacitor system and lithium-titanate-oxide technology. As for batteries that rely on lithium chemistry, Graham says maybe they should come with a free bag of marshmallows. “They’re bursting into flames constantly! I didn’t want that to happen in a residential setting. We decided we are not going to work with lithium chem batteries because there’s too much propensity for something bad to happen. So we are working with energy storage products that are benign.”

The company initially chose to work with an electrolyte battery but found them to be high-maintenance. “Their energy density isn’t that exciting.”

Light fades for the energy giants

Graham, an Ohio native, arrived in Australia from the US nine years ago. It was tough. “As an outsider, it’s very difficult to pierce the veil of corporate Australia,” he tells Ecogeneration. It took all his and his wife’s life savings, along with the proceeds from selling their furniture, to start a business. “We had one couch and I was working off an ironing board.”

Any moments of self-doubt were quickly dispelled. “I believed in what we were doing so much. Rex Energy is the energy company of the future. This is exactly how it’s going to be. The existing model of big power plants, big transmission and big distribution is going to only be there to act as a back up to what you cannot generate, store and consume on site in the future.”