Potential CO2 Reduction by Increased Integration of Absorption Cooling in a Swedish District Energy System

Comfort cooling demand is increasing also in temperate countries. There, the cooling demand is characterised by strong seasonal as well as daily demand variations. The utilisation of heat-driven absorption chillers instead of conventional electricity-driven compression chillers is decreasing the power used for cooling but this option is mainly of interest where there is low-cost heat available. Thus, within district-heating (DH) systems with large excess heat supplies this might be a particularly attractive solution. In other DH systems this may instead provide the basis for expanded combined heat and power operation. In Sweden, this is a potentially interesting option since cooling demand is rapidly increasing, albeit from low levels, and DH systems cover most of the areas with potential cooling demand. The aim of the study is to analyse the potential CO2 reduction due to increased substitution of compression chillers by DH-driven absorption chillers. The study is a case study using the district heating and cooling (DHC) system of Göteborg, characterised by a high share of industrial and municipal solid waste incineration excess heat. The DHC production is simulated with a detailed time slice division using the least-cost DH supply model MARTES. The heat needed in the absorption chillers is assumed to be supplied by marginally produced DH. The results show that an increased share of absorption cooling capacity can lead to cost-effective CO2 emissions reduction. The simulation results show that the heat used in the absorption chillers mainly is low-cost industrial excess heat. As long as this is available, or if e.g. new biomass-based CHP is installed within the DHC system, an increased cooling demand can be met by generation associated with low net CO2 emissions due to the avoided and replaced marginal power generation