Lågtempererade uppvärmningssystem och dess potential i nybyggda och energieffektiva kontorshus : En studie i att använda returtemperatur från befintlig bebyggelse till uppvärmning

This master thesis examine how a low temperature radiator systemcan be implemented in a new built office and what effects this will have on the return temperature. One point in the system was logged and data was collected. A model was then developed in VIP-Energy to determine the heating demand for an office building which were compared to the supply. A cost analysis was also performed on different types of low temperature radiator systems. These were compared to a conventional radiator system with a supply temperature of 55°C and a return temperature of 45°C. A cost analysis was also done on whether to build energy efficient or not. The study shows a strong correlation between the heat demand and the time of day. The demand is low during office hours and high during nights and weekends with a peak demand of 70 kW. The low demand is due to the high amount of process energy an office uses. The point in the system can supply the heat demand during almost every hour of the year. For the few hours where there is a mismatch between supplied heat and demand, a shunt solution can supply the return water with primary heat. If the heat demand is scaled up with ten or twenty identical houses the point will be unable to supply enough power to cover the heat demand for more hours a year. The most cost-effective radiator system is Purmo Belize with a supply temperature of 40°C and a return temperature of 30°C. Purmo Belize has built in fans that can improve the heat supply to the room with up to 80 %. Compared to a conventional radiator the payback time is 9 years, with a return on investment of 12,8 percent and a net present value of 151 762 kr. A 40/30°C-system will lower the return temperature in the measured point with 0,4°C. For the whole system this means a reduced temperature of 0,00003°C if the total flow is 50 m3/s and the average return temperature is 50°C. From a strictly economic point of view, an extra energy efficient house will be beneficial if the extra cost is up to 5 000 000 kr or around 700 kr/m2 with a depreciation time of 25 years