Is thermal heat energy hotting up?

As energy price rises in the wake of the war in Ukraine and the push to net zero drive continued investment in renewables, is thermal energy about to have its moment in the sun?

Technologies such as heat pumps and thermal storage are not yet widely used in Australia, but have demonstrated their potential overseas.

Let's look at some of that potential, how industry and manufacturing is starting to use thermal energy here, and what the future may bring.

What can thermal energy deliver?

Jarrod Leak, CEO of the Australian Alliance for Energy Productivity (A2EP), says technologies that recover, store and use waste heat or cold represent one of the most exciting developments in the renewables space.

“When you couple it with thermal storage, you can start matching that energy demand with an abundant energy supply and potentially capture negative wholesale prices, as we see in the South Australia electricity grid every day. You are actually getting paid to use your heat pump," he says.

“You often end up with other side benefits, [such as] being able to use the cold produced from heat pumps to reduce the heat load on a refrigeration plant that may be running at the same time. In summer you might use it to cool staff working in a warehouse.”

How much does the transition cost?

On a like-for-like basis, heat pumps are 7-10 times more expensive in capital costs than gas-fired central boilers and steam reticulation systems, Jarrod says. However, if they are matched with thermal storage and cheap solar power, the levelised cost of heating (capital plus operating costs) is typically half that of using fossil fuels.

While most of the attention has been on advances in lithium ion batteries, thermal batteries have great potential too. Rather than storing energy in a chemical form, like a lithium ion battery, they store it as heat.

The thermal qualities of concrete are well known, and a new project funded by ARENA is investigating the potential of graphite blocks embedded with aluminium alloy.

Phase-change materials such as molten salts can also be used to store energy at higher temperatures. These are solid at room temperature and change to a liquid when heat is applied. Where a manufacturing process requires temperatures below 80-90°C, energy can be economically stored simply as hot water.

“On a simple case you’re looking at very low costs for energy storage, less than half of what a lithium ion battery would cost, and none of the issues of recycling that battery at the end of its life. A thermal battery will effectively go for ever,” Jarrod says.

Thermal storage enables manufacturers to match energy demand with a cheap energy supply from a heat pump. Having thermal storage in place can potentially mean the required capacity of a heat pump can be reduced by up to 30%, with matching savings. A smaller heat pump may also mean manufacturers avoid the need for expensive electrical upgrades.

How the technology is being used in Australia

Hardwick Meatworks at Kyneton in Victoria is part way through introducing new technology to reduce gas usage by 75%. Renewable electricity from its own solar arrays will power heat pumps, and waste heat from chillers will be used to produce hot water for cleaning, sterilisation and packaging.

Gippsland dairy processor Burra Foods recently installed a tubular heat exchange unit to warm frozen dairy concentrates from -5 to 18C for processing. Waste heat is particularly useful in low temperature (<90°C) processes in beverage or confectionery manufacturing.

“Any industry that needs heating at low temperatures is going to find it very beneficial. In confectionery and chocolate manufacture, they just need to heat the chocolate to 40-50°C,” Jarrod says.

The new technologies are also a game changer for aquatic centres, typically huge guzzlers of energy.

Last month, Brimbank Council in Melbourne’s west opened Australia’s first totally renewable energy aquatic centre at St Albans. A 500kw rooftop solar system is coupled with a heat pump to heat and cool air temperature and water. An 88,000-litre hot water storage unit provides a thermal battery backup.

Jarrod says other aquatic centres in Victoria, including Northcote, Cardinia and Geelong, have also made the switch.

“They’re all doing it in different ways, and probably in a year or two we’ll get more indication of the best way.”

What does the future hold?

There's certainly a lot of potential for thermal energy. Jarrod credits ARENA for the boost it's giving the sector by sharing knowledge along with the grants it awards. While hardware costs will likely not move much, installation and knowledge costs should trend down over the next few years.

“You’ll have a lot of people sitting back waiting for the first movers to get those learnings," Jarrod says.

"Once they see the projects are getting results, I think you’ll see quite a flood of change in two or three years, with industry more confident to proceed."