Novel district heating and cooling energy network using CO2 as a heat and mass transfer fluid

Compact district energy networks in a temperature range of 10 to 16°C have a great potential for energy savings by providing a heat source for decentralized heating heat pumps, a cold source for air-conditioning and a heat sink for refrigeration or cogeneration units. The energy balance of the network is done by a central plant equipped with a heating heat pump for Winter operation and a heat dissipater for Summer operation. They typically facilitate the synergy between users and allow the concept of a city without chimneys or cooling towers in the various buildings. One such concept is based on using the latent heat of the transfer fluid (CO2),with one saturated CO2 vapor pipe and one saturated CO2 liquid pipe, in which the flow is bidirectional in the function of the predominance of the heating or cooling demands. While the concept has already been published this paper discusses some of the potential dynamic phenomena as well as further extension to allow those networks to collect CO2 from hybrid decentralized SOFC-GT cogeneration systems for either further disposal, use or contribution to power to gas concepts. Additional extensions to using reversible supercritical CO2 heat pump or ORC is also mentioned. A reminder of the technico-economic results obtained on the actual demands of an existing district is also done including the evaluation of the uncertainty margins.