Grangetown Nursery School is being heated by warm groundwater pumped from underneath the building.
The groundwater – a few metres beneath – is at a temperature of around 14 degrees Centigrade because it is kept warm by heat lost from buildings, sewers and other underground piping.
The school on Avondale Road has been fitted with a pump and heat exchanger to remove this heat from underground in a green energy project involving Cardiff Council, Cardiff Harbour Authority, British Geological Survey and WDS Green Energy.
The groundwater is pumped from a borehole and passed through the heat exchanger. With only 20C removed by the heat pump system, the spent water then goes backto the aquifer through a second borehole in a loop.
Nursery school Jan Comrie said the system had kept the school “cosy”.
“We were delighted to take part in this project as it builds on the work we’ve already done as a school.
“We’re the only nursery school in Wales to have received a Platinum Award from Eco-Schools Wales. Our attitude is that if organisations don’t try new eco-technologies we’ll never know if they work or not. ”
The experiment could one day see the idea rolled out and used elsewhere in the city.