Impacts of global warming and building renovation on the heating energy demand and district heating capacity: Case of the city of Riga

Changes in weather conditions due to global warming affect the energy demand of buildings, resulting also in changes in the installed heat capacity in district heating (DH) systems. The study provides a methodology to support decision-making for decarbonization scenarios of cities by developing a sustainable 4th generation district heating (4GDH) system combined with renovation of existing building stock and development of newly built areas in the long-term perspective (till 2050). Several scenarios are proposed where a multi-generative DH system is assessed by implementation of industrial heat pumps, solar systems, and low-temperature regime into an existing DH system that currently is based on biomass and natural gas combustion technologies. Changes in the heating load of a DH system due to improvement of building energy efficiency are studied in combination with three weather scenarios – low RCP2.6 (Representative Concentration Pathway); medium – RCP6.6, and high – RCP8.5. The developed scenarios consider the integration of heat energy produced by prosumers in local energy communities. Heat demand model combined with techno-economic model estimates the potential of climate change impacts on the DH system of the Riga city. The research considers the influence of the energy carriers’ price (fuel, electricity, etc.) on economic parameters, feasibility and environmental performance of the DH system and investigates the balance point between investment at the source and heat consumers’ side. A sustainability assessment was performed for the interconnected climate change, heat demand of buildings, and energy production based on the 4GDH technologies. The interaction of global warming, buildings heating energy demand and installed capacity of the DH system, that make up urban environmental nexus, was identified by levelized investment approach. The research results show that building renovation process has significantly higher impact on heat demand compared to influence of temperature changes due to global warming.