Caldera is a UK clean-energy company decarbonizing industrial heat with Warmstone, a thermal battery built from recycled aluminium and volcanic rock inside vacuum-insulated heat cells. Its electric Storage Boiler converts cheap off-peak renewable electricity into industrial steam and hot water up to roughly 200C, offering factories a zero-emissions alternative to gas boilers. Founded in 2017 in Fareham, England, Caldera closed a 10M pound Series A led by Germany's GEA Group in 2025 and landed its first commercial order from the NHS.
James Macnaghten is the co-founder and CEO of Caldera, a Hampshire-based climate-tech company turning cheap renewable electricity into stored industrial heat using blocks of volcanic rock and recycled aluminium. A Cambridge-trained mechanical engineer with 25+ years in business and 20+ patent families to his name, he spent a decade running grid-storage pioneer Isentropic before founding Caldera in 2017. He also owns Scudamore's Punting Co, Cambridge's largest tourist business. In 2025 Caldera closed a Series A backed by Germany's GEA Group and landed its first major order, a 10 MWh storage boiler for an NHS hospital.