It has been widely stated in recent years that the only zero-emissions method of providing the high-temperature heat required by heavy industry — in high-emission sectors such as steel, aluminium concrete and cement — is by burning green hydrogen derived from renewable energy.
Yet combusting hydrogen actually produces greenhouse gases — nitrous oxide that forms when the flame reacts with nitrogen in the air.
Electricity is used to power a resistance heater and a blower that heats about 1,000 tonnes of basalt rock [for the 30MW/130MWh pilot] to 750°C. When required, cold air is blown through the hot rocks, creating hot air that turns an electricity-generating steam turbine. Due to the effective insulation around the rocks, the heat can be stored for a week or longer.
Siemens Gamesa Renewable Energy (SGRE), which is known worldwide for its wind turbines, is now offering a truly zero-emissions alternative — high-temperature heat produced via renewable electricity.
The company’s Electric Thermal Energy Storage (ETES) technology was never intended to be used to produce heat for industry — it was created to store electricity in the form of heat, for later conversion back to electricity.
But in the 20 months since SGRE launched its hot-rock thermal energy storage pilot — in which electricity is used to heat basalt rocks to high temperatures (see panel, above) — the company has been inundated with queries from industrial players looking to replace the coal and gas they use.
“We were already the odd child in the Siemens Gamesa world, and suddenly we have to give bids to customers of multi-millions for heat,” says Hasan Oezdem, SGRE’s head of innovation hubs & large energy storage. “And [chief technology officer Antonio de la Torre] is, like, ‘are we doing heat now?’ And I’m, like, ‘yes, we’re doing heat now’.”
Oezdem, who leads the company’s ETES programme, tells Recharge that the basalt rocks in the system can be heated to between 200°C and 800°C. Any lower than 200°C and a water boiler can do the same job, and any higher than 800°C and more expensive, specialist steel equipment is required, which increases costs.
“Today, 90% of the industry processes [that require high-temperature heat] are actually in that bandwidth,” he says, including many of the processes used in the concrete, cement, aluminium, steel, paper and chemicals sectors.
“Not only can we replace [coal and gas use in heavy industry], we can replace it today. Hydrogen is the buzzword of the moment, but even Christian Bruch, CEO of Siemens Energy said — and Siemens Energy is investing heavily in hydrogen — at the earliest, it will be five to ten years until hydrogen will really make significant money.
“This supply of green heat to energy intensive industry is really where we shine. This is really easy for us to do because you’re just buying your heater and blower and you build an ETES and then you’re done.”
Other power-to-heat alternatives for heavy industry
According to a recent report from German think-tank Agora Energiewende and UK-based Afry Management Consulting, there are several existing power-to-heat technologies able to compete with green hydrogen in the industrial heat space.
The most well-known of these is the electric-arc furnace, which is widely used to melt scrap steel and can reach temperatures of 3,500C, but other options include resistance furnaces, infrared heaters, induction furnaces, plasma heating and microwave and radio heaters.
Electric systems appear to be more efficient than hydrogen systems because they require less energy conversion,” says the study, No-regret hydrogen: charting early steps for H2 infrastructure in Europe, published on 11 February.
“Available power-to-heat technologies can cover all temperature levels needed in industrial production.
“Given that the performance factor of electric heating is at the very least comparable to and at the very best – such as in the case of heat pumps – considerably better than burning hydrogen from electrolysis, power-to-heat technologies should be considered before thinking about producing heat from hydrogen.”