A methodology for selecting a sustainable development strategy for connecting low heat density consumers to a district heating system by cascading of heat carriers

Abstract The paper presents a methodology for supporting the decision making on how to sustainably develop an existing district heating system when consumers located in a remote, low-heat consumption density area are connected to the system. Several scenarios are proposed where a multi-generative system is assessed by implementation of industrial heat pumps (HP), solar photovoltaic (PV) system, and low-temperature regime into an existing district heating system in various combinations. The methodology is based on multi-criteria analysis allowing for energy, economic, exergy, and environmental (4E) assessment. The research is based on a case study of an autonomous district heating system in a medium-sized urban settlement with an average heat generation of 8.3 GWh/year. The primary heat consumers are apartments and industrial buildings. In the system, the power-to-heat concept is realized, and solar PVs serve as a price-balancing instrument of power. The results show that in such a system, the most sustainable scenario for connecting the consumers located in the low-heat consumption density area is to transition from the use of natural gas to biomass as a fuel in addition to installing booster HP coupled with solar PV panels and implementation of energy efficiency measures. That allows reducing primary energy factor, increasing the avoided CO2 emissions, and decreasing the levelized cost of heat.