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Lessons from Denmark: how district heating could improve energy security



After the oil crisis of the 1970s, Denmark developed district heating schemes which heat homes more cheaply and efficiently. Photograph: Alamy


Powered by article titled “Lessons from Denmark: how district heating could improve energy security” was written by Frederika Whitehead, for on Wednesday 20th August 2014 10.25 UTC

When the oil crisis hit in the winter of 1973 the price per barrel quadrupled, and countries that were heavily dependent on oil were in dire straits. Denmark was one such nation: more than 90% of its energy came from imported oil. Danish citizens shivered in their homes while factories were forced into temporary shutdowns, alternate street lights were switched off and driving was banned on a Sunday.

After that long and painful winter Denmark vowed to ween itself off oil imports, determined to improve its energy security. Ever since it has invested heavily in renewables, energy efficiency and “district heating”.

District heating is exactly as it sounds: colossal boilers provide heat for entire districts through a network of heating pipes. While in the UK households buy gas, which is piped into individual boilers to provide heating, Danish neighbourhoods do away with individual boilers and instead have their hot water piped directly into their houses from one larger, and much more efficient, shared boiler.

What is particularly clever about district heat networks is that they also capture and redistribute heat that would otherwise be wasted. The surplus heat produced by electricity generating stations, factories, server farms and public transport networks is funnelled into the network, eliminating waste, lowering carbon emissions, lowering fuel consumption and saving everybody money.

Fast forward 40 years from the original oil crisis and district heating networks provide heat to a whopping 63% of Danish households. Denmark has become a net exporter of oil and expects to remain so until at least 2018.

Here in the UK, a 2013 report by the engineers Buro Happold found that there is enough heat wasted in London alone to meet 70% of the city’s heating needs. If all the heat that is wasted were captured and put into district heating it would make a dramatic difference to our fuel bills, fuel poverty, carbon emissions and fuel security.

Having harnessed all the waste heat, the remaining requirement can be met by combined heat and power stations (CHPs). These are 20-60% more efficient than standard power plants because, as well as supplying electricity, they also provide heat. Standard power stations are only 30-50% efficient because the heat produced when creating electricity is wasted. In a CHP station the heat released during electricity generation is captured and used to heat homes and offices, making CHP power stations between 70-90% efficient.

Denmark has built an enormous network of pipes under its towns and cities, collecting waste heat from factories, incinerators, transport systems, and combining it with heat generated from solar thermal energy plants, wind turbines, and conventional gas and coal power stations, to produce a low cost and highly efficient heat supply.

Britain was far less affected by the oil crises of 1973 and 1979; we had recently discovered North Sea oil and gas. So while Denmark has spent the past 40 years developing a system that captures and harnesses waste heat and puts it into a grid with heat from CHP, Britain has spent the past four decades developing its gas grid. Now the North Sea reserves are dwindling and we are increasingly reliant of imported gas: in 2012 UK gas imports reached their highest since 1976 at 43%.

So the British government is trying to increase the number of households connected to district heating networks. The Department for Environment and Climate Change (Decc) would like to see the number of connected properties increased from a paltry 2% (just under 200,000 nationwide) to 20% by 2030 and 40% by 2050. To facilitate this, Decc has made £7m available to councils to carry out feasibility studies for district heating systems.

More than 50 UK local authorities have taken the government up on its offer. Between them they have been awarded £4m and there is £3m remaining in the pot.

The Greater London Authority has set a target that 25% of its energy supply will come from decentralised sources by 2025. The first step towards this was creating a map of London’s heat resources. The map shows where London’s power plants are, where its energy from waste plants is, its CHP sites and the proposed sites for heating networks.


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