A growing number of Australian households are looking to cut out gas, but challenges remain, from paying more upfront for appliances to matching electricity usage with renewable generation.

California climate tech startup, Harvest thermal, is delivering clean heating and cooling and hot water for households via one a single heat pump system that intelligently draws clean energy when the sun is at its brightest.

By running both systems from a single electric heat pump, and aligning usage to when renewables are most readily available, the company not only reduces emissions on traditional gas systems by around 90 per cent, but by 60 per cent compared to other heat pump methods.

Jane Melia

The company was one of six to be chosen for EnergyLab’s startup accelerator program this year, with company chief executive and co-founder Jane Melia telling The Fifth Estate the transition from gas to all-electric households was only just starting to heat up.

“By 2050 when we need to be carbon neutral, we won’t be able to do that if we keep gas in our homes,” Ms Melia said. 

However, she emphasises the way we transition from gas to electricity is important, and should take into consideration the major challenges facing grid operators.

“[In many parts of the world now] grid operators are getting a lot of solar on the grid in the middle of the day,” Ms Melia explained.

“But if we all start using electric utilities in the morning and the evenings, which is when we need our heating, we’re not using that solar electricity — we’re using the dirtiest, most expensive electricity on the grid.”

“And that’s making it much harder for the grid operators to deliver on their mandate of clean, affordable, reliable electricity, because we’re just not buying it, we’re purchasing at the wrong times of day.”

Using hot water storage as a thermal battery

Harvest Thermal’s system works by heating and storing hot water during the day, which can be used for home heating and other needs when demand is highest, at night and in the mornings. The storage tank then acts like a battery.

“The trick really is how you actually manage a ‘dumb’ hot water tank as a thermal battery. And that’s where a lot of work and know-how of our team has come into play,” Ms Melia says. 

Water is stored based on need, with the “brains” behind the system, the Harvest Pod, determining not only when to run the heat pump to access the cheapest, greenest electricity available, but how much hot water to create based on usage habits.

“Because of our ability to store water and then know to a high level of accuracy what’s inside the tank and only load it up the amount you need and when you need. That’s really our innovation and that’s what’s allowing us to use one single tank to deliver heating and hot water.”

Ms Melia adds that by decoupling the delivery of home heating from when the energy is generated, the team is able to resize the heat pump so it meets the energy load of the coldest day of the year, rather than the coldest hour, as with a typical system. 

“So the hot water storage, acting as a thermal battery, is a real buffer. You can load it up ahead of the coldest time of day, which is going to be mornings in winter. That load is going to be three times, maybe four times the average,” Ms Melia said.

“If you can load up the tank ahead of time with that heat pump which we do, you can deliver plenty of heat to the home without that heat pump having to be oversized.”

According to Ms Melia there are a number of businesses using hot water storage as a thermal battery, but most had failed to crack the challenge of also directing that for household heating on a scale larger than a small apartment, which is one of the things setting her business apart. 

The product is in a pilot stage, with systems already installed in six homes in California and due to be deployed in 30 more starting next year.

WIth nine full time employees plus consultants, Ms Melia said it was all hands on deck to meet the goal of 100 systems installed by the end of the financial year. 

She added things were moving quickly in California to get more and more properties off gas, and she had been watching similarly rapid developments occurring Down Under, most visibly in the ACT and Victoria. 

“It’s gonna be an exciting year. Getting that first 100 [systems installed] would mean we have proved the market exists, proved the performance of the system, proved our training capabilities for builders, and you proved our ability as a company to execute,” Ms Melia said.

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  1. What about indirect evaporative? We’ve been using it for years now in schools, as pre-coolers for reverse cycle systems for large offices, and even in our own office. It doesn’t heat but it’s incredibly effective for cooling even on our west coast with our increasingly humid summers. It’s also now available for domestic applications.