Bidirectional low temperature networks in urban districts: A novel design methodology based on mathematical optimization

Abstract

Bidirectional low temperature networks (BLTN) are a sustainable and energy efficient concept to supply urban districts with heating and cooling. In this work, we present a linear program (LP) for designing BLTNs. Based on a superstructure, the optimal energy conversion units are selected and sized for each building connected to the network and an energy hub. The superstructure of HVAC systems in buildings comprises heat pumps, electric boilers, thermal storages, compression chillers, cooling towers and heat exchangers for direct cooling with the BLTN. Within a case study, the LP is applied to a district with 17 buildings on a research campus in Germany. The performance of the BLTN is compared to a heating and cooling supply by individual HVAC systems for each building. With a BLTN, the total annualized costs can be reduced by 42 % and the CO2 emissions by 56 %, compared to stand-alone HVAC systems.