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Supplying process heat using concentrated solar thermal energy with molten salt storage

Alicia Wongel, Jacqueline A. Dowling, Gerhard Weinrebe, Steven J. Davis, and Ken Caldeira · Environmental Research: Energy 3, 025004 · 2026

Key finding. At a gas fuel cost of $50/MWh — a level observed during a seasonal peak in Californian industrial gas prices in February 2025 — concentrated solar thermal with molten salt storage can deliver cost savings while supplying more than 50 per cent of industrial heat demand in most regions below 45° latitude with appropriate land availability.

Four world maps in two columns. The left column shades the share of industrial heat demand met by concentrated solar thermal, from 0 to 100 per cent, at a gas fuel cost of 50 dollars per megawatt-hour (top) and 500 dollars (bottom); at 50 dollars the tropics and subtropics are yellow, above 75 per cent, while high latitudes are dark blue near zero, and at 500 dollars almost everything below the Arctic is yellow. The right column shades the gas fuel cost, from 10 to 500 dollars per megawatt-hour, at which solar thermal supplies any share at all (top) and more than half (bottom).
Latitude sets the answer. At a gas cost of 50 dollars per megawatt-hour, concentrated solar thermal with molten salt storage already supplies most industrial heat demand across the tropics and subtropics and almost none at high latitudes; the right column reads the same result the other way, as the gas price each place would need to reach. Figure 4 from Wongel et al. (2026), Environmental Research: Energy 3, 025004. Reproduced under CC BY 4.0. Extracted from the published PDF and resized for web display.

What question did this research address?

Industrial process heat accounts for roughly a quarter of global energy use and a fifth of CO2 emissions, and carbon-free options are scarce in the medium-to-high temperature range between about 200 °C and 550 °C.

Concentrated solar thermal can reach those temperatures where the solar resource is strong. This paper asked where, and under what gas prices, it would actually be the cheaper option for supplying steady industrial heat.

What did we find?

The study uses a stylized model to quantify the share of concentrated solar thermal in least-cost systems globally, requiring that the system deliver steady, reliable heat rather than intermittent supply.

Molten salt thermal storage is what makes reliability possible. Industrial heat demand is continuous while sunlight is not, so the storage is what converts a variable resource into a usable one.

Latitude and land availability set the geography of the result. Below about 45° latitude, where the solar resource is strong enough, more than half of industrial heat demand can be met at a saving when gas costs $50/MWh.

The competitiveness threshold is a gas price rather than a technology breakthrough, so the result moves with fuel markets — the reference price cited is one that has actually occurred, not a hypothetical.

Why does it matter?

Industrial heat is one of the parts of the energy system repeatedly identified as hard to decarbonize, and much of the difficulty is concentrated in the temperature range this technology addresses.

Framing the answer as a gas price rather than a subsidy requirement changes the character of the finding. It says the technology is already competitive under conditions that occur, which is a different claim from saying it would be competitive if costs fell.

Citation

Alicia Wongel, Jacqueline A. Dowling, Gerhard Weinrebe, Steven J. Davis, and Ken Caldeira (2026). Supplying process heat using concentrated solar thermal energy with molten salt storage. Environmental Research: Energy 3, 025004.

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