Swiss researchers store summer’s heat for winter

Steam rises off homes in Bern being heated in winter. Swiss researchers have found a new heat transfer method that could change home heating options Keystone

Researchers at Switzerland’s Empa research institute are working on a possible way to stockpile summer’s heat for the cold days of winter thanks to a chemical process. 

By dissolving solid, highly concentrated sodium hydroxide in water, they were able to utilise a solution called caustic soda – also known as lye – which stores heat over a long period of time. When the caustic soda is heated, the water evaporates and heat is stored until the solution comes into contact with water again. 

A heat storage system based on that chemical reaction is behind testing taking place at the Swiss Federal Laboratory for Materials Testing and Research, known as Empa. The heat storage test system, which can store enough energy to heat an entire house, has been in place since autumn 2016 and is working reliably, according to the latest information from the institute. 

When the first prototype was not able to store enough heat, researcher Benjamin Fumey conceived a heat exchanger in the form of a spiral, which allows the caustic soda to flow along it and release heat created by the addition of water. The caustic soda recharges its heat when more heated water, generated from solar panels, enters the system. 

The process could allow heat from summer’s sun to be stored until winter, and could also allow it to be transported in the form of solid caustic soda. 

Empa researchers are now seeking industrial partners to develop the system for home heating.