Haderslev is a 700yearold provincial town with 20,000 inhabitants situated in southern Jutland, 50 km north of the German border.
Up to 1959, the town's buildings were individually heated, and at this time many still used stoves as their heating source.
In 1959, the development of district heating (DH) began from the town's disused electricity works which had been purchased by Haderslev Municipal Council, but it was later taken over by Haderslev District Heating a consumerowned heating company.
Between 19591964, the DH system was fully developed to serve the town centre, and in the following years the network was extended to the town's lowrise suburban quarters. Up to 1966, all heat production took place at the town's old electricity works, in the town centre. Production was based solely on preheated, heavy fuel oil delivered by oil tanker lorries.
In 196566, Haderslev Municipal Council and the heating company collaborated in the construction of a refuse incineration plant combined with an oilfired peakload station for DH production.
To start with, in 1966, the refuse incineration plant was equipped with only one furnace, of capacity 3 tonnes of refuse per hour with a heat output of approx. 6 MJ/sec. In 1970, the plant was extended with an extra furnace at 4 tonnes per hour producing 8 MJ/sec. However, up to the present, the plant has used only one furnace at a time and has normally been out of operation during weekends and holidays.
Until it was phased out in 1992, this incineration plant provided 2535% of the network's total annual heat production. In the MayOctober period, this plant alone produced enough heat to cover the total network consumption, and this permitted the oilfired plant to be taken out of service during the same period. Waste incineration in this plant has thus solved a major environmental problem and at the same time provided consumers with inexpensive heating.
On introducing natural gas in Denmark in 1982, many heating facilities among these, Haderslev's responded to government directive to convert plants from oilfiring to natural gas. Haderslev's two existing heating stations were converted to natural gas in 1984 and 1985. These plants were, however, converted to socalled combination firing so that both natural gas and oil could be used. Over the years, Haderslev's DH system had expanded so that in 1985 there were 7 boiler plants with a total output of approx. 50 MJ/sec.
In the years following this, the boiler plants have been equipped with condensing flue gas coolers and oxygen control systems. These have further increased boiler output by approx. 4 MJ/sec, and decreased fuel consumption by 78%. Based on a return water temperature of 3840oC, a reduction of the flue gas temperature to 4550oC has also been accomplished. The produced condensate is collected and utilised for tempering.
After the incineration plant was shut down in 1992 the heat has been produced only with natural gas until the start of the combined heat and power (CHP) plant in 1993 (see below).
Since the mideighties, the DH company and Haderslev Municipal Council have worked on establishing a new wastefired heating station as a replacement for the existing plant, which does not meet current environmental requirements.
In 1989, the council and the heating company decided, in cooperation with The Power Station of Sonderjyllands Hojspaend ningsvaerk (SH) to construct a wastefired CHP plant. During 1990, it was agreed that the plant was to be built and owned by SH. This agreement requires local authorities in the area to provide waste and Haderslev town to take delivery of the produced power and heat.
This plant, sited approx. 7 km south of Haderslev, will burn 62,000 ton of waste and 1.8 mill m3 of natural gas annually in 2 furnaces, each with a capacity of 4.5 tonnes of waste. Plant output is 5.8 MW power and 14 MJ/sec heat.
The heat produced will be transported by a 7.2 km transmission pipeline into Haderslev District Heating's boiler and heat exchanger plant. The total annual heat supply will be in the range 330340 TJ. This plant is expected to be running commercially in June 1993.
As of 1992, the area's DH network has a heat demand of approx. 450 TJ. Demand is expected to rise to approx. 500 TJ over 35 years. Maximum peak load is expected to be approx. 40 MJ/sec. The existing boiler installations at 56 MJ/sec assure a sufficient safety margin in the event of a shutdown in the CHP plant. Heat production from the CHP plant is supplied to the consumer approx. 20% cheaper than identical production would be in a natural gasfired boiler.
As the production of CHP fulfils only 6570% of the total heat demand. Haderslev District Heating plans to build a natural gasbased CHP station for producing a further 100120 TJ annually. This plant will then be ready to produce heat by winter 199596.
Up to about 1970, pipe carrier lines were constructed mainly in concrete ducts and insulated with cellular concrete. However, since 1970, the expansion of networks has been carried out with preinsulated piping with PUR (Polyurethane) or PEH (High Density Polyethylene) shells. After 1980, most service pipes to singlefamily and semidetached houses have been laid as PEX (CrossLaced Polyethylene) and PB (Polybuten) plastics piping.
In 1984 Haderslev District Heating began a planned replacement of the existing piping in concrete ducts with the new preinsulated piping. The work is expected to take approx. 15 years and has been planned on a selffinancing basis. In 198485 the complete pipe network and consumer data were computer analysed as a basis for network optimisation. This data is now also in use in connection with pipeline renovation. In 1992 the length of the complete network was about 80 km.
As of 1992, approx. 70% of the duct pipelines have been replaced in accordance with an evaluation of the extent of damage and on the basis of annual thermographic surveys. We have thus managed to reduce water leakage from 4050 m3 down to less than 20 m3 per 24 hours. Heat loss in the network has been reduced by 2530% and it has been possible to lower the exstation temperature by 56oC while holding the temperature in the pipeline network's extremities constant. At the same time, with the aid of pumping control via differential pressure transmitters in the network, electricity consumption for pumping has been reduced by 2530%.
The majority of consumers are connected directly to the DH system which means that the heated mains water circulates inside the consumer's heat transference installations. The DH water is delivered at a feed temperature at 7080oC, depending on locality and time of the year. On delivery, water pressure lies between 1 and 4 bar, depending on locality. As of 1992, approx. 2,900 consumers are connected to the heat output of approx. 88 MJ/sec.
Haderslev District Heating has always stressed the importance of relevant information and service assistance to the consumers, thus ensuring that consumer installations are wellfunctioning and able to cool the DH water sufficiently (to approx. 40oC).
To ensure an accurate and fair billing to the consumers, all water volume meters are being replaced with ultrasonic energy meters.
During the last 58 years heat losses have been reduced so much in both the pipeline network and production plants that heating tariffs have fallen by approx. 10%, despite a 15% increase in oil and gas prices.
As of 1992, a districtheated house in Haderslev has an approximately 30% lower heating bill than a comparable house heated by oil.