Energy assessment of waste water heat exchanger and solar energy panel connected to district heating

Abstract

This project has the aim of calculating the efficiency of the tap water system, in explicit the heating of tap water, in Furugården, Valbo. Furugården is a new retirement home, building Furugården finished in 2013. The building is equipped with a waste water heat exchanger, solar collectors and in addition to that district heating. The temperature of hot water has to be above 55°C to minimize the change of legionella to develop in the system. The process of heating a building and tap water is a high energy using process. An aspect what also has to be taken in account is the environment. The waste water and solar collectors can be seen as sustainable efficient systems. These systems should lower the output of pollutions and lower the costs of heating tap water. The waste water system increases the temperature of fresh cold water from an average temperature of 12°Celcius to 20°Celcius. This results in a increasing of 8°Celcius. From this result we can conclude that the system will save energy and costs. It would be an improvement install sensors of temperatures inside the incoming and outgoing pipes of the waste water system in order to know the efficiency of that Regarding the efficiency of solar collector heat exchanger, the results obtained has been successfully as theoretically expected. It is around 95% of the heat transfer from the solar collector is absorbs for the water flow on the second circuit of such system. The efficiency of the water tanks are not always working. This is because of a too high temperature in the collector system. When the temperature is too high, the pumps are not working and the system stops. This problem can be solved when the system has the right adjustments.