A sea-water heat pump will cut carbon footprint of Orkney Islands' building

Sea-source heat pump cuts cost and carbon for council

Council offices on the Orkney Islands have been fitted with technology that uses heat from the surrounding sea to provide a low-emission sustainable source of heating.

The Warehouse Buildings in Stromness, run by the Orkney Islands Council, have been fitted with a heat pump that absorbs warmth from the city harbour through 12 stainless steel platforms submerged beneath the pier.

Pipes transport the sea water into a control room, where its temperature is raised to 55°C before being distributed to radiators and underfloor heating.

“Across the country very few buildings currently use sea-source heating systems,” said James Stockan, the chair of the Orkney Islands Council’s Development and Infrastructure Committee.

“As the Warehouse Buildings stand close to the sea, it made sense to opt for this innovative approach to keeping them warm.”

The Warehouse Buildings house customer services, a library facility and meeting rooms.

The system was developed by UK-based heat-pump manufacturer Kensa Heat Pumps.

The cost of the electricity used to run the 40kW heat pump was £1,550 over a 12-month monitoring period since the building opened in 2015. It would have been £2,420 for an oil-based system. 

The carbon emissions linked to keeping the Warehouse Buildings warm are calculated to be six tonnes of CO2 per year, compared to more than 15 tonnes if an oil boiler had been fitted.

This figure of six tonnes is based on the UK average for electricity generated for the National Grid.


In reality, the Orkney Islands produce more renewable electricity throughout the year than they consume, with the surplus exported to mainland Scotland, so the overall carbon footprint of the heating system could be considered a zero.

“As we’re using heat from the sea and electricity primarily from renewables, these buildings are an excellent example of how the Council is making significant steps towards creating buildings that are virtually carbon-neutral in terms of their energy consumption,” said Stockan.

Heat pumps of the type used at the buildings can utilise a number of heat sources. In traditional ground source heating systems the heat pumps are linked to pipes buried in coils in trenches or in boreholes deep underground.

Water is an excellent heat source due to its exceptional thermal conductivity and flow, which ensures constant energy replacement. Ponds, lakes, streams and rivers can be used as sources of heat – as well as the sea.

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