​​The carbon elephant in the room
​​What do sterilizing food, drying paper pulp and distilling solvents have in common?
They all rely on heat in the 100–250 °C range typically delivered as saturated steam at pressures between 3 and 20 bar.
Across industries, heat is essential for transforming raw materials into finished products, whether through heating, drying, distilling, sterilizing or cleaning. In France, industrial heat accounts for around 70% of industrial energy use[1] and approximately 15% of the country’s final energy consumption[2]. These figures closely mirror the global average, which stands at 80% and 19%, respectively[3].
But not all heat is created equal. Different technologies deliver heat at different temperature levels. Combustion, especially using fossil fuels, can cover the entire temperature spectrum, making it flexible and widely adopted. In contrast, heat pumps are generally restricted to low-temperature output. Other renewable sources like biomass and solar thermal face limitations tied to land use, feedstock availability or sunlight.​​​​​​
Figure 1 - Overview of final energy use in French industry
The result? Industrial heat, particularly in the medium-to-high temperature range, remains one of the hardest sectors to decarbonize — and one of the most fossil-fuel-dependent. Despite growing awareness, the share of renewable heat in global industrial processes has edged up only slightly, from 11% in 2017 to 12% in 2024[4].
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Yet this challenge carries immense climate weight. Industrial process heat is responsible for roughly 16% of global energy-related greenhouse gas emissions[3], nearly equivalent to the combined annual emissions of the United States and India. That makes it one of the most under-addressed fronts in decarbonization.​​
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​​Why not just use electricity?
​​​Using a premium energy source like electricity to produce something as basic as heat has long been considered wasteful. When electricity is primarily generated from fossil fuels, converting it back into heat is both a thermodynamic and economic absurdity. If the goal is simply to produce heat, direct combustion of fossil fuels has historically been more efficient and cost-effective.
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But that logic is being upended. From April to mid-May, France had to curtail 0.7 TWh[5] of solar energy, meaning that a 12% of available solar electricity was intentionally not fed into the grid because, during peak sun hours, supply exceeded demand, causing power prices to drop below zero. Yet even with this curtailment, the system still experienced negative prices during 16% of the hours, with consumers being paid to consume electricity. In a low-carbon energy system dominated by intermittent renewables, this is becoming the new definition of waste.
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Figure 2 – Duck curve trends and what it means for power vs. gas prices
Figure 3 – How our thermal energy storage battery works
Addressing it requires one essential capability: flexibility. The ability to consume electricity during fluctuating moments of high renewable generation is becoming a real superpower. It not only provides access to low-carbon energy that is largely immune to geopolitical or commodity shocks but also opens the door to very low-cost power. That is because the energy is consumed when supply outstrips demand, and this responsiveness provides a valuable balancing service to the grid. This is how, at certain times of day, electricity becomes cheaper than gas — a shift that occurred 56% of the time this April, compared to 6% in 2019.
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This trend is only accelerating as the “duck curve” deepens in renewables-driven markets. The term refers to the phenomenon where, as more solar capacity comes online, power prices drop sharply during daylight hours and then surge after sunset, creating a pronounced "belly" during sun hours[6].
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​​Modernizing an old method: storing heat in bricks​​​
Flexibility is fundamentally about balancing supply and demand, and storage has always been the holy grail of power systems, which are inherently non-storable and thus difficult to balance.
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While electrochemical batteries and pumped hydro storage are the most well-known solution for storing electricity to release it later, storing energy in the form of heat to release heat is one of the oldest and most practical ways of managing energy. In everyday life, cast iron radiators and water heaters rely on a simple principle: store heat when it is available, release it when it is needed.
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Industry has followed this logic for millennia. As far back as the Bronze Age, refractory clay was used to retain the heat of kilns. Today’s refractory bricks – or firebricks – continue that legacy, insulating kilns[7], furnaces, and other high-temperature enclosures. In some applications, they serve primarily as insulators, in others, they store the very heat they help contain[8]. They are, for instance, a critical thermal energy storage material in regenerators used in steel and glassmaking – a proven solution with decades of industrial pedigree, made from abundant, low-cost ceramic materials that are easy to source.
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That is what Epyr is all about: turning renewable electricity into high-temperature heat, storing it in firebricks, and delivering a low-cost, on-demand, fully decarbonized heat. By combining bold innovation with grounded solutions, we are not just navigating the energy transition: we are turning it into a lever for lasting industrial transformation.
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​​References
[1] Industrial final energy consumption, excluding non-energy uses such as feedstocks
[2] Source: Bilan énergétique de la France, SDES
[3] Source: IEA, McKinsey & Company “Net-zero electrical heat: A turning point in feasibility”
[4] Source : IEA, Renewable Energy Progress Tracker
[5] Calculation based on forecasted day-ahead and actual solar production in France during hours of negative electricity prices
[6] The Duck Curve first appeared in California, based on data from CAISO. As solar generation grows, midday demand on the grid drops sharply — but when the sun sets, demand for other sources surges, creating a steep ramp-up in the evening that resembles a duck’s tail on the graph
[7] Source: Historical overview of refractory technology in the steel industry, K. Sugita, Nippon Steel Technical Report, 2008
[8] Source : Effects of firebricks for industrial process heat on the cost of matching all-sector energy demand with 100% wind–water–solar supply in 149 countries, MZ Jacobson, PNAS Nexus, 2024
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About Epyr
Epyr develops innovative thermal energy storage solutions to help industries transition away from fossil fuels. By making clean industrial high-temperature heat cost-effective and scalable, Epyr aims to accelerate the energy transition and reduce global emissions.​​​