District-scale lake water free cooling in Zurich, Switzerland: System performance simulation and techno-economic feasibility

Abstract

Lake water district cooling systems have been shown to reduce greenhouse gas emissions in several cases, including projects in heating-dominated climates. Due to the highly cooling-intensive functions in the Hochschulquartier area in Zurich, Switzerland, a district-scale free cooling network based on lake water has been proposed, but its feasibility has yet to be demonstrated. This paper presents the methodology for thermal network simulation developed for the City Energy Analyst (CEA), an open-source software for energy demand simulation and system operation modeling and optimization. This methodology was then applied to simulate the free cooling system’s operation for four scenarios of urban development for the area featuring different functional mixes. The results were then compared to decentralized vapor compression chillers in order to analyze the network’s feasibility from an economic and environmental perspective. The simulation results showed that the district cooling network would reduce the electricity demand for cooling in the area by about 60% compared to the use of standard vapor compression chillers. This improvement in performance was however achieved at the expense of much higher annualized costs due to the large investment associated with building the network. Thus, the proposed free cooling network might require further economic incentives for its construction.