With district heating toward a sustainable future System studies of district heating and cooling that interact with power, transport and industrial sectors

Sammanfattning: The aim of this thesis is to identify measures which should be taken in DH systems (DHSs) in order to contribute to the development of the DHSs and other energy systems (especially transport, industrial and power sectors) toward sustainability.Four business strategies were analysed: delivering excess heat from biofuel production industry to DHSs, conversion of industrial processes to DH, integration of biofuel production in DHSs and integration of DHdriven absorption cooling technology in DHSs. Delivering excess heat from biofuel production industry to DHSs was analysed with a focus on the biofuel production costs for four biofuel production technologies. Integration of biofuel production and integration of DH-driven absorption cooling technology in DHSs were analysed with a focus on Stockholm’s DHS, using an optimisation model framework called MODEST. When the conversion of industrial processes to DH was analysed, DHSs and industrial companies in Västra Götaland, Östergötland and Jönköping counties were used as case studies; a method for heat load analysis called MeHLA was used to analyse the effects on the local DHSs.The results showed that when considering biomass an unlimited resource, by applying the abovementioned business strategies DH has a potential to reduce global fossil fuel consumption and global GHG emissions associated with power, industrial and transport sectors.DH producers may contribute to the sustainable development of the  transport sector by buying excess heat from the biofuel production industry. This business strategy results in lower biofuel production costs, which promotes development of biofuel production technologies that are not yet commercial. Moreover, introduction of large-scale biofuel production into local DHSs enables development of local biofuel supply chains; this may facilitate the introduction of biofuel in the local transport sectors and subsequently decrease gasoline and fossil diesel use. Conversion of industrial processes from fossil fuels and electricity to DH is a business strategy which would make the industry less dependent on fossil fuels and fossil fuelbased electricity. DH may also contribute to the sustainable development of the industry by buying waste heat from industrial processes, since this strategy increases the total energy efficiency of the industrial processes and reduces production costs. Furthermore, DH has a possibility to reduce fossil fuel consumption and subsequently GHG emissions in the power sector by producing electricity in biomass- or waste-fuelled CHP plants.When the marginal electricity is associated with high GHG emissions (e.g. when it is produced in coal-fired condensing power (CCP)) plants, the reduction of the marginal electricity production (due to the conversion of industrial processes from electricity to DH and due to the conversion of compression cooling to DHdriven absorption cooling) results in higher environmental benefits. On the other hand, the introduction of biofuel production into DHSs becomes less attractive from an environmental viewpoint, because the investments in biofuel production instead of in CHP production lead to lower electricity production in the DHSs. The increased DH use in industry and introduction of the biofuel production and DH-driven absorption cooling production into the DHSs lead to increased biomass use in the DHSs. Because of this, if biomass is considered a limited resource, the environmental benefits of applying these business strategies are lower or non-existent.