Danish Design in District Heating

Jann Sjursen
Minister of Energy

Danish Energy Policy

The Danish energy sector has developed significantly during the last 20 years. In 1973 the consumption of energy per inhabitant was very high and the country was completely de pendent on imported oil. Today Denmark has an extremely varied energy supply system mostly based on domestic resources and efficient utilisation of energy. The overall energy efficiency in Denmark has improved by about 20% during this period, and the best results have been achieved in the area of space heating where energy consumption per m2 has fallen by some 45%.

These results have been obtained in a joint effort by local and central authorities, supply companies, and private enterprises. Some of the biggest, and most efficient, combined heat and power (CUP) systems in the world have been built up around large Danish towns. Natural gas from the Danish fields in the North Sea is being utilised in a supply system that covers most of the country. More thinly populated areas are supplied by small- scale district heating (DH) plants that are currently undergoing a large-scale process of development. To an increasing extent, these plants are utilising straw, wood chips, biogas, and other domestic sources of energy.

Efforts to increase energy efficiency have been intensified by Denmark adopting a plan of action (ENERGY 2000) aimed at reducing primary energy consumption by 15% by the year 2000. Also the Danish Government has set a goal of reducing CO emissions by at least 20% by 2005.

Energy Research and Development

Since the middle of the 1970s efforts to define energy policy have been backed up by considerable research activities. The Ministry of Energy has provided support worth DKK 2 billion from the Energy Research Programmes to research centres, supply companies, and private enterprises, each of which has also contributed significant sums of money to this goal-oriented research activity. A number of sectors in the Energy Research Programmes have contributed to developments In district heating technology as a whole. In the period 1987-1992 DH alone has been allocated funds at approximately DKK. 25 mill. This sum covers, however, only a small part of the total Danish effort being applied to research and product development within this field. Power plants and DH companies have been able to increase their energy efficiency and limit losses in the pipelines as a result of research projects. e.g. on loading control. low-temperature operation and assembling DH pipes. Environmental improvements have been gained by utilising the new waste cleansing technology and waste products from electricity production. In the present publication, a number of experts describe Danish DH systems and developments in this field. Particular emphasis has been given to the results gained from targeted research and technological develop- ment.

The Technology of District Heating

The trend in total Danish energy consumption is markedly different from that in other countries. DH can take a large part of the credit for the improvements in energy efficiency in Denmark. From 1972 the overall contribution by DH to space and water heating in Denmark has grown from 30 to 50% while, at the same time, the primary energy to produce DH has fallen slightly. A major reduction has taken place in fuel consumption per energy unit supplied by DH due to the ability of the systems to utilise surplus heat/CUP as well as improvements in technology.

Danish DH manufacturers produce over half of the world's total of preinsulated DH pipes. Overall energy efficiency is increased via CHP production. optimised operation, and steering of the systems involved. Also. there is a growing interest in other countries for information about Danish experience in DH. The main characteristics of this are:

The major CHP networks in Greater Copenhagen, in the Arhus, Aalborg, Odense, Esbjerg, and TVIS (Vejle. Kolding, and Fredericia) areas were expanded extensively throughout the 1980s, in parallel with the development of (he Danish natural gas net work. Today, a key issue is the development of small DH systems based on decentral cogeneration. Systems have become cost-efficient in villages of only 100-150 inhabitants.

Efficiency and Flexibility

DH as such Is both an efficient and flexible form of heat supply. Fuel utilisation is at an optimum, and It Is technically and economically possible to switch over from one fuel to another if supply conditions, fuel prices, or environmental requirements make this appropriate.

Via the Danish Energy Research Programme new technologies have been developed for the combustion process and heat transmission and distribution, including metering and regulation at consumption points. Straw firing has now become more reliable and efficient. Biogas plants convert environmentally burdening organic animal wastes and crop residues to clean biogas energy.

Danish manufacturers of DH pipes have provided preinsulated piping for the extensive replacement of the steel pipelines in concrete ducts, which were used in the earlier years. The net result of this is a reduction in heat loss, maintenance costs, and initial construction costs. In very recent years, an intensified effort has made possible the development of preinsulated pipes which are produced virtually without the use of ozone-depleting gases.

District Heating in the 90s

In 1986 the power companies agreed to establish decentral CUP facilities to reach a total rated power of 450 MW. In 1990. the government published its energy action plan ENERGY 2000. An important element in this is an agreement of March 1990 on further developing decontrol CHP and DH- based systems on biomass. The agreement states that the major coal and natural gas- Bred DH plants are the first to be converted in this case to natural gas-based coproduction. Following this, the smaller coal, oil. and gas-fired plants will be converted to coproduction. Finally, the remaining non- gas-supplied DH stations will be converted to coproduction based on biofuels. The con version will be completed by 1998. Further more. approx. 1300 heating substations will be connected to DH or natural gas networks.

In 1992, further initiatives were taken to advance the importance of environmental considerations in connection with the Danish energy supply system. A carbon dioxide emission tax, levied in relation to the emission of this gas has sharpened interest in more environmentally compatible fuels and energy efficiency. In the coming years economic support will be given for expanding the DH grid, building new DH plants using biofuels, and connecting more residences to coproduction facilities. A special subsidy to CUP production based on natural gas and renewable energy sources makes conversion to coproduction an attractive option.

Domestic Heating in Denmark

In Denmark the public is involved strongly in energy supply issues. Most of the approximately 330 Danish DH companies are consumer-owned and the remainder are local authority supply companies. These forms of ownership have ensured a local involvement which will be mobilised in the coming efforts toward realising the goals set by ENERGY 2000. In the immediate years, many local initiatives win be taken concerning the establishment of new DH systems burning straw. woodchips. or biogas. Local consumer groups as well as farmers are involved in these activities.

The Heat Supply Act of 1979 has formed the framework for a comprehensive effort aimed at exploiting surplus heat from power production and utilising waste incineration, natural gas, and renewable energies in DH systems. In June 1990 a new Heat Supply Act formed the basis for the technical development in the 90s mentioned above.

Many initiatives have also been taken to Increase the rate of connection to DH net works. As mentioned earlier, today the cover age of DH in Denmark is about 50%. In 2005. it is expected to reach the 60% mark thanks to the installation of new facilities, ex tension of existing networks, and connections to even more consumers. One of the initiatives taken is a support scheme for installing coproduction-based central heating in older buildings.

Concluding Remarks

The rational use of energy is an important energy saving issue. In many countries DH and CHP technologies have the potential to increase energy efficiencies substantially, thereby improving the global environment including the reduction of CO: emissions.

Today. Danish consultants, manufacturers. supply companies, and energy authorities convey their know-how to many countries on such items as construction of DH networks. evaluating possibilities for conversion to CHP, organisation of the energy sector, heat planning, legislation, prices, and tariffs. In particular this know-how can be utilised in connection with system refurbishment in Central and Eastern Europe where major DH systems built up over many years are now in need of rehabilitation.

Some of the resources Denmark has allocated to aid Central and Eastern Europe are to be used in the fields of energy and environmental protection. In this context it is welcomed that the technical advisers to the World Bank have given the environmentally compatible Danish production technology for DH piping their stamp of approval.

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