Sänkt returtemperatur i Göteborg Energis fjärrvärmenät : Miljömässiga och ekonomiska konsekvenser undersöks vid en sänktreturtemperatur genom reinvestering i fjärrvärmecentraler

Sammanfattning: District heating is a spread technology where buildings and industries are supplied with heatand hot tap water. This technology is used in 285 out of Sweden’s 290 municipalities. GöteborgEnergi has a theoretical possibility to lower their return temperature from 38 ◦C to 30 ◦C. This change corresponds to economic savings at 54 millions [kr/year] in production costs, anddecreased carbon dioxide emissions at 3 390 [ton CO2e/ year]. Ineffective heat exchangers indistrict heating centrals is one of the reasons why the return temperature is high in the districtheating grid, though the goal is to have the lowest return temperature as possible.To identify which district heating centrals that are ineffective has the Överkonsumstionsmetodenbeen applied. Through reinvestments of new heat exchangers in district heating centrals with ahigh return temperature, the company could lower the return temperature. Reinvesting in 247profitable apartment building centrals would lower the nets average return temperature with 0,44◦C, a saving in production costs of 2,84 [Mkr/year] and decreased carbon dioxide emissions of189 [ton CO2e/year]. However, calculations show that it is only profitable at 22% to reinvest innew heat exchangers at apartment buildings. The reinvestments tend to be profitable when thereturn temperature and heat use is high. A table has also been developed to determine when it isprofitable to do this reinvestment, dependent on return temperate, delivered heat and installedefficiency for the specific district heat central.