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Taking the heat out of the sea

Discussing ways to expand the Lerwick district heating scheme are (from left): Star Renewable Energy director David Pearson, SHEAP manager Neville Martin and SHEAP board member Andrew Blackadder - Photo: Hans J Marter/ShetNews

HEAT from the sea could soon be used to help expand Lerwick’s innovative district heating scheme to meet growing demand from new customers.

Shetland Heat Energy and Power (SHEAP) is in discussions with a Glasgow-based heat pump manufacturer to extend the network that already supplies about half of Lerwick’s households and businesses’ heat demand.

Star Renewable Energy said heat pumps using sea water were proven technology with many environmental benefits.

SHEAP manager Neville Martin added that they could help the district heating scheme meet the urgent need for new capacity, which at peakloads exceeds the 6.3 megawatt output of the energy recovery plant run by Shetland Islands Council.

The plan is to extract sea water and cool it down from around eight to four degrees, harnessing enough energy to add a further 2MW in capacity.

Star Renewables director David Pearson said: ” We are an industrial refrigerating company, an expert in cooling things down by taking out the heat.

“Normally, like in fridges in people’s house, that heat is thrown away. What we are doing is capturing that heat and using it.

“It is a heat multiplier as we get three units of heat for every unit of electricity we consume, and that means that we can make heat cheaper and cleaner.”

The company’s uses ammonia as a natural refrigerant, a gas with no impact on global warming.

Martin said he was enthusiastic about the proposal, as it was the “most promising” option to further expand the district heating scheme while reducing its dependency on oil.

The company hopes to decide on the sea water project soon and if it proceeds complete it before the end of next year to take advantage of a generous government subsidy scheme.

“District heating is the most effective way of reducing carbon emissions and I think governments are slowly realising that,” Martin said.

“The Renewable Heat Incentive (RHI), offering payments of 3.5 pence per unit, have turned things around and have made these projects more attractive.”

He added: ” There is a large demand for more connections, so we will be able to allow more people on to the network. That’s the main advantage. We have a large waiting list for a connection.

“It definitely is more green as it reduces our dependency on oil, and therefore also improves our viability.”

The company is currently talking to interested parties such as Lerwick Port Authority and Scottish & Southern Energy.

Heat pumps that abstract heat from the sea have been a tried and tested technology since at least the 1980s.

The Swedish capital of Stockholm currently operates the world’s largest sea water-based heat pump with a capacity of 180MWs.

Star Renewable Energy installed a 14 megawatt system for the Norwegian town of Drammen in 2011.

The Lerwick district heating scheme is the largest of its kind in Scotland.

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