Half of all the energy we use globally goes on heating and cooling. We need heating for all sorts of things; from keeping our homes warm to industry which needs super high temperatures. At the moment, the heat we use is mostly powered by polluting fossil fuels, a huge driver of climate change. But can renewables deliver the high temperatures and a constant supply which are so vital? In this episode we visit the world's first commercial-scale sand battery in Finland and find out how it’s using renewables to heat 100 homes and a public swimming pool. Presenters Luke Jones and Graihagh Jackson are joined by: Erika Benke, Journalist, Finland Professor Amin Al-Habaibeh, Professor of Intelligent Engineering Systems, Nottingham Trent University Professor Dan Gladwin, Department of Electronic and Electrical Engineering, University of Sheffield Email us: theclimatequestion@bbc.com Producer: Lily Freeston Researcher: Natasha Fernandes Production Coordinators: Siobhan Reed and Helena Warwick-Cross Series Producer: Alex Lewis Editor: Bridget Harney Sound Engineers: Tom Brignell and Graham Puddifoot