Kysynnän hallinta kaukolämpöjärjestelmissä

The main objective of the project was to show that lowering the cost of district heating (DH) is possible by using demand side management (DSM). The practical installation of DH DSM in a building is not expensive. Peak cut of 25-30 % is going to be achieved with exploiting the thermal mass of the building and by properly controlling the heating system. Indirect savings will also be evaluated. Hot tap water was not included in DSM. There were three case study buildings, two in Jyväskylä Finland and one in Mannheim Germany, where the DSM demonstrations were carried out. A calculation tool for test buildings has been developed for quick evaluation of proper DSM possibilities. The characteristic model of buildings is described using thermal capacity-resistance description. The research made in two Finnish case study buildings shows that the maximum heat load of a massive building (body of concrete) can be during 2-3 hours reduced as much as 20-25 % on the average because of the thermal capacity of radiator heating network. When the circulation water reaches the set DSM temperature level the heating load starts to increase up to the load level defined by any current DSM temperature setting. The loads of intake air heating are large but the thermal capacity of ventilation intake air heating is small compared to large room heating radiator systems. As the temperature change of ventilation can be felt immediately the DSM-control measures of ventilation must be very small and sensitive while the building is in a normal use. The only way to keep the heat demand of intake air heating low during the DH DSM operations is to slightly reduce the air flow temperatures by 1-2 °C. Peak cut of 20 % in Jyväskylä means about 160 buildings of the volume 20 000 m3. Based on simulations how to use energy production capacity in DSM, the total saving is evaluated 13 000 /a in the Jyväskylä case. Thus a DSM investment of 845 per consumer (5 %, 15 a) is aloud. If we assume to save an investment of 20 MW HOB (1,8 milj. EUR) because of DSM and we divide it to 20 years with 5 % interest, the additional saving will be 144 000 /a and in addition maintenance and other fixed costs. It means an investment of about 10 000 per consumer in the Jyväskylä case. In the German Tower Block case in Mannheim the daily heat demand peak could be reduced by 4.1 %. This increases the efficiency of heat production at the power plant on the average by 3 %. This increased efficiency has been reached during peak demand time, which means during 1-2 hours per day. By simply closing the valve larger reductions would be possible during very short time periods. This is no option because the subsequent peak when reopening the valve would actually increase the daily maximum. It is not feasible to shift peaks in this way to times of low demand in the district heating network because the relevant time span (around three hours) is far too long. The building is equipped with an air heating system and a computer based control system which tends to start the air conditioning system earlier when outdoor temperature is lower. It does so in order to insure the desired indoor temperature of 21.5 °C at 6:30 a. m. By doing so the computer system automatically flattens the daily heat demand when outdoor temperature is low. As a consequence it was not possible to achieve further peak reductions with DSM measures when the outdoor temperature is very low (<0 °C). The time constant of the air heated building is shorter than of buildings with radiator heating. Two kinds of tariff structure is recommended. A fixed agreement, where supplier has the right to cut daily peak load of the consumer by remote control in agreed limits up to 25 % of connected capacity and for a maximum 3 hour per day in one or two periods. The consumer can have some discount in fixed annual payments. The post heating period should be 1.5-2 hours longer than cut period and the thermal effect should be returned linearly to avoid the remarkable post heating peak in the buildings. In other case the consumer can decide how he cuts his peak load. Hourly peak load a day will be measured and based on the maximum annual or monthly peak load he must pay a fix thermal power capacity payment a year.