Drammen heats a Norwegian city of 65,000 with heat pumps running on 8°C fjord water

Drammen, the county capital 40 miles west of Oslo, keeps warm in the Nordic cold with heat drawn mostly from its own fjord — water that averages 8°C all year, cold enough that open-water swimmers call it freezing. By 2009 the city had grown until its existing district heating system could not cope. Researching how to expand capacity, the heating company led by Jon Ivor Bakk found the fjord's temperature ideal for heat pumps, and instead of buying in gas to burn, ran a tender.

The winner, Glasgow's Star Renewable Energy, was best known for refrigeration at Tesco and Asda stores and had no experience of water-sourced heat pumps — 'we were the new kids on the block', director Dave Pearson said. Its winning move was refrigerant choice: ammonia, which contains no carbon, where competitors proposed hydrofluorocarbons. Four pumps run the fjord-water-to-90°C cycle described above, and by the beginning of 2011 the system supplied 85% of the hot water for the whole city's heating — the biggest installation of its type in the world.

The economics did the convincing: the pumps deliver about 3kW of heat per 1kW of electricity, and with Norway's cheap power a unit of heat costs 1p against 3p for biomass, 5p for gas and almost 8p for oil — Bakk says the company would be losing money on biomass. The plant has already paid for itself, saving around €2m a year and, per the report, carbon equal to taking more than 300,000 cars off the road for a year. The 90°C output is the quiet breakthrough: old buildings piped for gas boilers can switch without new radiators, which is what had made heat-pump retrofits unrealistic.

Bakk's team has won awards for the project, and professor Paul Younger of Glasgow University said any remaining doubts about the technology are settled: 'Drammen nails it beyond any reasonable doubt.'

Water holds a steady temperature, so one fjord loop at district scale avoids both the €15,000-plus drilling of ground-source home pumps and the winter wobbles of air-source units.

Rivals bid HFC refrigerants, a potent greenhouse gas the EU is banning; Star's ammonia has no carbon and tolerates the heat of high compression.

90°C output versus the usual 50–60°C means gas-heated buildings keep their existing radiators — removing the largest hidden cost of decarbonizing heating.

At 3kW of heat per 1kW of electricity and 1p-per-unit Norwegian power, the plant undersells every fossil alternative, so the retrofit pays for itself.

The barrier to electrifying heat is output temperature, not the pump: deliver the 90°C old radiators expect and gas-heated buildings can switch without rebuilds.

By the start of 2011 the pumps covered 85% of Drammen's heating hot water and exceeded expectations; the system has since paid for itself with annual savings around €2m. Star Renewable Energy moved on to Glasgow housing associations, talks with a dozen UK councils including Newcastle, Manchester and Durham, projects in Zurich and the South of France, and a bid in Belgrade; it calculates the Thames alone could host 1.25GW of capacity, enough for 500,000 homes. 'There are no easy ways to decarbonise heating, but I'm mystified as to why there are not more,' said Doug Parr of Greenpeace UK.