In Denmark most district heating plants are combined heat and power plants that distribute the heat made from the surplus heat generated by the production of electricity. An example is the Sønderborg Kraftvarmeværk (CHP) in Southern Denmark, which burns waste to generate heat and electricity.
The Danish District heating system is the result of visionary thinking and long term planning. During the oil crises in the 70s the foundation of today's district heating system was built based on a strong demand to save energy.
Heat planning has been the central driver for the successful implementation of district heating. Gradual replacement of natural gas and oil supply to district heating along with other initiatives such as incentives for insulation of buildings and a switch to renewable power production has put Denmark in the front seat of energy savings.
A large part of the CO2 savings and reduced energy consumption in Denmark are owed to co-production of heat and power. A traditional power plant only converts approximately 40% of the total energy input to electricity while 60% is wasted to the surroundings as heat. In a combined heat and power plant, 50% of energy input will be converted to heat and distributed to consumers in a district heating network. Thus, energy waste is reduced from 60% to 10%!
While fossil fuels have been the dominant fuel in both CHP's and pure heat plants in the 70s and 80s, there is a strong tendency towards the use of renewable energy sources. While wind energy has been the predominant renewable method for producing electricity, geothermal heating, biomass and solar energy are employed in the production of heat or in the combined production of the two.
In 1984 the first geothermic heating installation was built in Thisted as a pilot project for research - since then the plant has been expanded and today we also have a geothermic installation in Copenhagen and more are planned in other parts of Denmark.
In Denmark we have CHP plants in many cities that burn straw or wood to generate heat and electricity. Often they are supplemented by co-firing of gas or coal, but in some cases biomass is the sole energy source.
Waste is the primary type of biomass used in Denmark, and in many cities waste is used for heat and electricity generation. Furthermore, incinerating the waste reduces the demand for landfills vastly.
Around the country, solar thermal systems have been installed as supplements to existing district heating utilities. The world's largest solar heating system, which covers almost 20,000 m2 is situated in Marstal on the island Ærø. The solar collectors make sure that 600 households are solely heated by solar energy all year. It includes seasonal storage of solar heat in a soil deposit.
The district heating sector and the CHPs in Denmark have managed to maintain stable energy consumption for years – and even a decreasing consumption during times of economic growth. This has made an impression on both politicians, district heating plants and district heating sectors across the world. And with this in mind it is safe to say that Denmark is a world leader in district heating. Danish district heating technology is an important export, a fact that also benefits the Danish economy!