Towards energy-autonomous cities using CO2 networks and Power to Gas storage

Under Energy Strategy 2050, the federal government of Switzerland plans to greatly reduce per capita energy consumption, decrease the share of fossil fuels, and replace the nuclear electricity generation by gains in efficiency and use of renewable energy sources. This work investigates the feasibility of defined goals through both the improvement of the efficiency of current energy systems and the increase in renewable energy sources. For efficiency improvement, a new district energy network is proposed. District heating and cooling networks - usually use centralized, energy efficient conversion technologies based on water networks, which is not suitable for multi-temperature supply and heat recovery. This work investigates a network using CO2 as a refrigerant for heat transfer. The system utilizes the latent heat of vaporization as the main source of storage and transfer of heat, and allows for recovery of waste heat from cooling in heating, due to the two-pipe system. This study also investigates the potential of this CO2 network when coupled with renewable energy sources to satisfy the heating, cooling, and electricity requirements of urban areas in Switzerland.