Uploaded August 2026 | Updated September 2026, 3 weeks ago
Around the world, factories making food, drink, pharmaceuticals and other everyday products rely on steam, often produced by fossil-fuel boilers. James Macnaghten, founder and CEO of Caldera, is betting that thermal batteries can provide a cheaper and more flexible alternative that stores electricity as heat, and delivers steam on demand.
This week on Cleaning Up, Bryony Worthington visits Caldera's factory to see how it makes its heat batteries: combining recycled aluminium and iron ore pellets to create a long-lasting, efficient heat store. The technology is designed for industrial processes up to 200°C, which James sees as a major opportunity for electrification.
They discuss how thermal storage can help factories manage peaks in demand, use electricity when it is cheap or abundant, and reduce pressure on congested grids. They also explore Caldera's plans to scale, its journey from domestic heating to industry, and why James believes a more pragmatic approach to electrification is needed.
Topics discussed in this episode:
• The hidden opportunity in industrial heat
• How Caldera's heat batteries work
• Why steam still matters
• Heat pumps and thermal storage
• Managing industrial demand spikes
• Turning surplus power into heat
• Scaling a UK climate-tech company
• The case for pragmatic electrification
Leadership Circle
Cleaning Up is proud to be supported by its Leadership Circle. The members are Actis, Alcazar Energy, Arup, Copenhagen Infrastructure Partners, Cygnum Capital, Davidson Kempner, EcoPragma Capital, EDP, Eurelectric, the Gilardini Foundation, KKR, Mitsubishi Heavy Industries, National Grid, Octopus Energy, Quadrature Climate Foundation, Schneider Electric, SDCL and Wärtsilä. For more information about the Leadership Circle, visit cleaningup.live
Links
• James Macnaghten’s bio: linkedin.com/in/james-macnaghten
• Caldera: caldera.co.uk
• Professor Ning Li on Cleaning Up: youtube.com/watch?v=xCUASv01bVY
• Subscribe to our newsletter: cleaninguppod.substack.com
• JVs - Joint Ventures
• IP - Intellectual Property
Chapters
00:00: Intro
01:53: About Caldera Batteries
03:42: Heat Storage
09:47: Caldera Factory Tour
14:40: Funding Caldera
17:44: Scaling Up
25:37: Thermal Storage
29:02: Energy Price Shocks
30:27: Flexible Demand
35:22: UK Success Story
37:32: Outro
Around the world, factories making food, drink, pharmaceuticals and other everyday products rely on steam, often produced by fossil-fuel boilers. James Macnaghten, founder and CEO of Caldera, is betting that thermal batteries can provide a cheaper and more flexible alternative that stores electricity as heat, and delivers steam on demand.
This week on Cleaning Up, Bryony Worthington visits Caldera's factory to see how it makes its heat batteries: combining recycled aluminium and iron ore pellets to create a long-lasting, efficient heat store. The technology is designed for industrial processes up to 200°C, which James sees as a major opportunity for electrification.
They discuss how thermal storage can help factories manage peaks in demand, use electricity when it is cheap or abundant, and reduce pressure on congested grids. They also explore Caldera's plans to scale, its journey from domestic heating to industry, and why James believes a more pragmatic approach to electrification is needed.
Topics discussed in this episode:
• The hidden opportunity in industrial heat
• How Caldera's heat batteries work
• Why steam still matters
• Heat pumps and thermal storage
• Managing industrial demand spikes
• Turning surplus power into heat
• Scaling a UK climate-tech company
• The case for pragmatic electrification
Leadership Circle
Cleaning Up is proud to be supported by its Leadership Circle. The members are Actis, Alcazar Energy, Arup, Copenhagen Infrastructure Partners, Cygnum Capital, Davidson Kempner, EcoPragma Capital, EDP, Eurelectric, the Gilardini Foundation, KKR, Mitsubishi Heavy Industries, National Grid, Octopus Energy, Quadrature Climate Foundation, Schneider Electric, SDCL and Wärtsilä. For more information about the Leadership Circle, visit cleaningup.live
Links
• James Macnaghten’s bio: linkedin.com/in/james-macnaghten
• Caldera: caldera.co.uk
• Professor Ning Li on Cleaning Up: youtube.com/watch?v=xCUASv01bVY
• Subscribe to our newsletter: cleaninguppod.substack.com
• JVs - Joint Ventures
• IP - Intellectual Property
Chapters
00:00: Intro
01:53: About Caldera Batteries
03:42: Heat Storage
09:47: Caldera Factory Tour
14:40: Funding Caldera
17:44: Scaling Up
25:37: Thermal Storage
29:02: Energy Price Shocks
30:27: Flexible Demand
35:22: UK Success Story
37:32: Outro
