Life cycle assessment and comparison of an evaporative cooling system and a conventional vapour-compression cooling system for an office building in Denmark

Rising temperatures from climate change are increasing the demand for global cooling in buildings, which is also true for northern countries like Denmark. Currently, mechanical cooling is mainly provided by vapour-compression systems operating with refrigerants that present sustainability issues. Evaporative cooling technology could be a promising alternative to the latter. A combined direct/indirect evaporative cooling and ventilation system has been developed, implemented and tested in a pilot project for an office building in Denmark. The heat source for the indirect evaporative process is the local district heating network. This presents a key advantage by diverting the cooling load from the electrical grid onto the thermal network. Indeed, the latter is a low-grade energy source, especially during the cooling periods when solar collectors and industrial heat surplus can cover most of the heat demand, and the thermal network is only used for domestic/sanitary hot water production in buildings. To quantify the environmental benefits of this evaporative cooling system, a comparative life cycle assessment is performed with a conventional vapour-compression cooling system implemented in the same building case. The results show that the evaporative cooling system has a global warming potential score [kgCO2eq] 24% to 40% better than the conventional system, with an improvement of 60%-71% and 5%-12% for embodied impacts (raw materials, manufacturing, transportation, maintenance and end-of-life disposal) and operational impacts (electricity, heat and water use, respectively. These results are a good motivation for fostering the development and optimisation of evaporative cooling systems in countries with cold climates.