Published on September 27th, 2012 | by Ellen R Delisio0
District heating in Denmark
It’s been called a “virtuous circle”— using energy from waste incineration, combined heat and power plants and renewable resources to produce heat. This virtuous circle is the key to district heating networks, which distribute heat broadly and have the advantage of being able to switch from one energy source to another.
One of the early leaders in this model was Denmark, which still leads Europe in district network heating – about two-thirds of the Danish population use district heating. Waste-to-energy, in the form of incinerating municipal solid waste, provides 16 or 17 percent of the heat for Denmark’s more than 400 district heating networks.
According to the Danish District Heating Association, “about 75 percent of Denmark’s district heating is produced in combined heat and power plants that generate both heat and electricity simultaneously. This allows more than 90 percent of the fuel energy to be utilized, in comparison with 40 percent utilization if electricity alone is produced.”
REACHING ENERGY GOALS
The system not only is economical and efficient, but is critical to helping Denmark meet its ambitious clean-energy goals. Since the heat is being generated in bulk, systems also can take advantage of renewable sources of energy, such as bio-mass and geothermal.
“District heating has been the most important single factor in Denmark’s struggle to reach the energy efficiency level we have today,” said Jens Overgaard, project director, district heating systems, for Ramboll, an engineering and consultant firm which has worked on district heating projects in more than 25 countries.
“The utilization of heat from the co-generation power stations, from waste-to-energy plants and from smaller combined heat and power plants has only been possible because district heating was expanded to the current level during the 1980s and 1990s.”
By using the energy and the fuels that others cannot or will not use, district heating delivers degrees of efficiency to the whole energy system, according to Birger Lauersen, manager of international affairs for the Danish District Heating Association. Heat comprises the major share, 37 percent, of the total demand for energy services in all Organisation for Economic Co-operation and Development (oecd) countries.
“Supplying that heat from new and more sustainable sources through district heating makes it much easier and cheaper to accomplish,” Lauersen said. “As we have such a high share of district heating, we only have to replace a few hundred heat-producing installations and not 1.6 million small, individual heat-producing installations. And we can collectively use
energy or fuels that are impossible, difficult or expensive to use individually.”
Denmark’s success with the model is due in part to implementing district heating several decades ago, before the widespread environmental concerns about fossil fuels. “We had 30 percent district heating even before anyone dreamed of an energy crisis, global warming or anything like that,” said Lauersen. In the 1960s, consumer cooperatives started district heating networks to take advantage of the price difference between heavy fuel oil and light heating oil, he added. Many of the country’s larger cities also had district heating to use surplus heat from power plants.
The push really began in the 1970s when the energy crisis took a toll on the country, which at the time imported 100 percent of its fuel for energy.
“Using what we had more efficiently by expanding the use of surplus heat from cogeneration and waste incineration was a logical choice,” explained Lauersen. “And since the energy crisis hit the economy so hard, no one questioned the need to develop a strong and interventionist energy policy.”
The shift to a networked form of heating also led to innovations that have made implementation even easier.
“The pre-insulated pipe was probably the game-changer,” Lauersen noted. “Rather than placing pipes in concrete ducts and then insulating them, a costly and time-consuming process, pipes already insulated and protected by an outer casing pipe could be laid, joined and then covered. It is easier, cheaper and faster.”
MORE SUPPORT NEEDED
While district heating’s growth is expected to continue in Denmark – by 2030 Danish officials hope to reach about 70 percent of the total market for building heating – more government support is needed for it to expand in other countries, according to Overgaard.
“Internationally, we have not yet seen any plans or projects for new district heating developments that can attract private investors, said Overgaard. “The growth in Denmark is supported at the government level by legislation, regulation and taxes. It would certainly be very difficult to see a further expansion without the energy taxes we have today.”
But just as district heating got Denmark through the economic crush of the energy crisis, it is expected to push it to its sustainability goals.
“We had our burning platform then (in the 1970s); now the climate challenge is our global collective burning platform,” said Lauersen. “District heating again is part of the solution.”
PHOTO DANISH DISTRICT HEATING ASSOCIATION