CASE 2: The network that survived - Avedøre Holme District Heating Company
Avedøre Holme District Heating Company is located in an old seabed area next to Avedøre CHP plant in Copenhagen. The company supplies mainly industrial consumers. Some of them use low-pressure steam to processes and therefore the system operation temperature has been 165 O C ever since the network was constructed back in 1967. The network was constructed as a concrete duct system cast on site and insulated with cellular concrete and drained. However, the draining systemwas poorly constructed and the pipes started to corrode as ground water was penetrating into the ducts. It was decided to renovate the whole network by efficient outside deep draining and by protecting the top and the sides of the duct with waterproof asphalt filt. As a result, the network survived. In 1990, we presented this success story in News from DBDH (former name of Hot Cool). Now we can confirm that the almost 50-year-old network is still in good shape. There is only a small leak to be repaired from time to time. The water losses are so low that we can detect any new leak. Besides, we use the same maintenance strategy and leak detection methods as Fjernvarme Fyn. The lesson learned is that poorly constructed concrete duct systems may have a lifetime of less than 10 years, however efficient draining and ventilation can prolong the lifetime to more than 50 years.
Fig 3. This is definitely not drain water
As a result of the rehabilitation and systematic leak detection, we have reduced our water losses from 700 m3/year/km in 1990 to 80 m3 in 2012 as shown on the graph. Now the losses are so low that we can detect a major leak at once by observing the need for make-up water.
water consumption m3/k
Fig 4. Make water consumption during 20 years.
FJERNVARME FYN - 97 % owned by the municipality of Odense and 3 % owned by the municipality of Nordfyn
AVEDØRE HOLME DHC - 100% owned by the consumers - 134 building level heat meters and heat exchangers
- 60,100 building level heat meters - Heat production 7,808 TJ in 2013
- Heat production 297 TJ in 2013 - Share of heat from CHP ~ 97 % - Heat losses 20 %
- Heated floor area 15 mill. m2 - Share of heat from CHP ~ 95 % - Share of waste and biomass ~48 % - Supply temperature 70-90 O C - Heat losses ~ 18 % - Water volume 70,000 m3 in the network - Water losses 9,643 m3 in 2013 (80 m3/km/year x 1,996 km = 160,000 m3/year) - 1,996 km network including branch lines, from DN15 to DN1000 - 0 heat exchangers - Heat storage tank 75,000 m3 - Maximal production demand 790 MW and 13,834 m3/h in 2013 - Coal fuelled CHP 407 MWelec and 570 MWheat = ~ 650,000 ton coal - Straw fuelled CHP 35 MWelec and 110 MWheat = ~ 180,000 ton straw/year - Waste fuelled CHP 24 MWelec and 64 MWheat = ~ 200,000 ton waste/year - 23 peak and spare boiler plants, 743 MW (42 oil boilers and 14 gas boilers)
- Supply temperature 160 dgr .C constant - Water volume 690 m3 in the network - Water losses in 2013 3,507 m3 /year
- Water losses in 2014 3 m3 /day(after detecting one leak) - 21 km network including branch lines, fromDN25 to DN300 - 19 km old renovated concrete ducts, - 2 km preinsulated pipes in new branchlines (LOGSTOR HT3) - Maximal production demand, 34 MW in 2013 - 1 peak and spare boiler plant, 55 MW
For further information please contact:
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