Image by Ken Boyd from Pixabay

Around 2400 South Australian households will treat their electric hot water systems like one big coordinated battery to soak up excess solar generation in the middle of the day in a new trial.

Water heater manufacturer Rheem Australia has secured $9.9 million from the SA government and $1.98 million funding from ARENA for the new “active hot water control trial”, which will try out different incentives to encourage households with and without rooftop solar to heat their hot water while the sun is shining. The pilot will also include households from a range of socioeconomic backgrounds.

A fast growing renewable energy industry in South Australia has led to excess solar generation in the middle of the day – a supply-demand relationship known as the “duck curve” – causing grid stability issues. In response, the state government last year implementing a suite of new rules to allow the market regulator to better match supply with demand.

The challenge still remains to find inexpensive ways to shift loads to make the most of cheap and plentiful midday solar, and support a stable grid.

In homes without solar, hot water systems are typically charged in the middle of the night when energy has traditionally been cheaper. Homes with solar also aren’t making the most of the midday solar glut, and are typically charged in the early morning or evening when demand is high as people are at home using energy.

That’s why Rheem Australia’s renewables brand, Solahart, will establish a virtual power plant (VPP) to aggregate the load of all 2400 hot water systems in the pilot program, allowing the company to trial different demand response strategies, participate in electricity price arbitrage and provide network services to the grid.

Photo by Artem Labunsky on Unsplash

To do this, the company will install its “solar smart, grid interactive” Solahart PowerStore electric water heaters and home energy management systems into participating houses.

“By aggregating and optimising the energy use of hot water systems and other household appliances, VPPs could play a major role in managing system stability and reducing power bills for customers in South Australia and nationally,” ARENA CEO Darren Miller said.

“This trial will help to create a pathway to scale up the use of hot water systems in demand management, while rewarding customers for taking part in the trial through cheaper energy bills,” he said.

With around 200,000 electric hot water systems across South Australia, there are significant opportunities for using electric hot water system for low cost load shifting.

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  1. We’ve been doing this ever since we had solar. We took our hot water off the night tariff and put it on the day tariff, we got our sparky to put a timer on the switch and allocated the hot water system a certain amount of time during the day. We have never run out of hot water.

  2. once upon a time I read that solar hot water systems – with a tank on the roof like Solahart – were more efficient than solar PVR generating electricity

    but they were unpopular as too heavy for roofs, etc.

    my other thought about midday maximum solar is showering at night as most East Asians do – get into bed clean is nice, and makes going to bed dirty pretty disgusting when you think about it in retrospect