Heat batteries: The oft overlooked low-carbon heat solution and Caldera’s Warmstone offering

The need to decarbonise heat in the UK is increasingly a focus as the country shifts its attention away from pure energy to other highly polluting sectors.

Currently the vast majority of home heating is powered by fossil fuels, but this needs to change in order to reach net zero. Heat pumps and hydrogen as well as heat batteries are regarded as key technologies.

British start-up Caldera recently launched its large-scale household heat battery, which provides an alternative green heating source that is particularly suitable for off-grid and oil-powered homes.

“There are 1.2 million households in the UK using oil or liquefied petroleum gas,” Caldera founder and CEO James Macnaghten recently told Current ±. “In Europe there are 14 million. At the moment, the British government has not yet decided how households connected to the gas network should be decarbonised. If the UK is fully electric for heating or hydrogen, we believe we can compete in the current on-gas market as well. Our solution then applies to around 25% of UK homes (completely detached with space for an external unit). ”

The switch offers a number of advantages, as oil is both more expensive and generates 40% more CO2 per kilowatt hour than the heat pump.

Caldera’s solution is based on patented Warmstone technology, an idea that came to Macnaghten in the middle of the night. “The next day I went to the factory and Guy [Winstanley, Caldera’s COO] and I was trying to make a block of Warmstone in a lunch box, ”he explained. “Three lunch boxes later it turned out to be working. We started to manufacture larger and larger blocks and can now manufacture them up to a weight of 1.3 tons. ”

Warmstone is designed in such a way that it can be heated to 500 ° C overnight with cheap, green low power, a time-of-use tariff, a smart meter and intelligent software to optimize the charging process. Reaching this temperature is particularly important as it corresponds to a conventional boiler and can therefore provide a similar level of heat for a property with the original pipes without the need for additional insulation and energy efficiency measures.

“I’ve had some really nice, interesting conversations with people where they’re going: ‘My radiator pipes are small in diameter and they’re under the floor in concrete. I would basically have to hit the ground up with a jackhammer [to fit a new system] and I can’t buy the same tiles because they’re no longer in production, ”Macnaghten continued. “For me it really helps them because we can achieve equivalent temperatures, but also because there is equivalent performance and temperatures, you can actually combine them.”

The units are expected to be 90% efficient for a house that requires 16,000 kWh of energy, with the team having worked throughout development to minimize the system’s heat loss. It is therefore equipped with high-quality vacuum insulation, which makes it possible to store energy for days or even weeks.

“If the current device is not in use, it takes 19 days to cool from 500 ° C to 200 ° C,” said Macnaghten. “For comparison: conventional night storage heaters can lose up to 40% of their energy in just 12 hours.”

Although there are some thermal batteries on the market, MacNaghten believes that the combination of the efficiency of the modules, the cost of £ 12,000 including VAT to install, the charging power of 20 kW and the storage capacity of 100 kWh make it a leading solution for solution greater properties.

The price of a heat battery vs. a heat pump

The cost comparison with other technologies is crucial for the technology, with the effort involved in decarbonising heat being one of the greatest challenges. This represents other low-carbon technologies like hydrogen and heat pumps, with the Environmental Review Committee warning last year that decarbonization of heat could fail due to the high price of electricity, which makes heat pumps uneconomical compared to existing gas boilers.

Another cost factor for heat pumps is that they often require additional insulation or energy efficiency measures as they produce less heat.

“We estimate that if you have to retrofit a house before installing a heat pump, the heat pump will cost 50% more annually to keep your house warm for 15 years,” says MacNaghten. “For new buildings or more modern houses with built-in underfloor heating, we expect a heat pump to be the better option.”

Caldera contracted Gemserv to conduct an independent study of the cost of its Warmstone technology compared to other low-carbon heating technologies. Using the example of a large living area of ​​a 153 m² house that has an annual heat requirement of 25,236 kWh and is currently operated with oil.

For such a property, Gemserv determined that attic insulation, massive wall insulation, double glazing and a PVC door would have to be installed in order to make a heat pump profitable, which requires 16,068 kWh per year.

In comparison, installing a heat pump with attic insulation would cost £ 10,000 and £ 10,600, respectively, to meet a demand of 25,236 kWh and 24,208 kWh, respectively. While the heat pump is cheaper to run after the modification – it costs £ 889 in fuel bill per year while the battery costs £ 1,493 – this dramatic difference in upfront cost brings the annualized cost of a Caldera heater battery to £ 2,297 without retrofitting and a heat pump without retrofitting to £ 3,512, while with the retrofit they would be £ 3,569.

The economics of such a property could improve if carbon taxes on oil are increased, a situation MacNaghten believes is likely given the ongoing pursuit of net zero by 2050. This would therefore reduce the annual cost of an oil boiler without retrofitting from an estimated £ 2,129 per year to £ 2,583 per year, according to Gemserv, making the cost of thermal batteries competitive from 2030 and beyond.

Next steps for caldera

Caldera will install 12 Warmstone thermal batteries over the next year to test the technology after the launch was announced in May. However, the company had 150 pre-orders in just two weeks, MacNaghten said.

“It was always the same conversation, that is, they are in our target market, they are on oil, they are in an old property, they want to do something to reduce their carbon footprint. And because of the type of property they live in, they didn’t want to build a heat pump. ”

While the UK is the best place to start adopting the technology, with the adoption of smart meters and the proliferation of renewable energy leading to an increasing number of negative wholesale prices for energy, MacNaghten suggested that the company be in the next five Years to expand into Europe wants years in which the energy systems across the continent continue to change.

Caldera did crowdfunding on Crowdcube and achieved 100% of its goal on the day of launch. The funding round is currently open to the public, but is expected to end on June 10, 2021.

Comments are closed.