Economic analysis of auxiliary heating systems planned for bigadiç geothermal district heating system

Well drilling in heating systems serving by generating geothermal energy can be an operating cost that needs to be repeated periodically, not only when the systems are installed, but also because the wells may lose their functionality over time. Drilling costs constitute a significant portion of the costs incurred during the lifetime of the systems. On the other hand, geothermal wells and circulation pumps operate continuously for basic activities such as extracting geothermal water and distributing the heat obtained from this water to the heated spaces. Therefore, geothermal district heating systems are also significant consumers of electricity. Anti-scaling chemicals added to the geothermal fluid can be another important expense that needs to be considered in terms of operating costs. Bigadiç Geothermal District Heating System (JBIS) is one of the five district heating systems in Balıkesir, providing heating services to 1.050 subscribers, mostly residential. From the first years of its operation until today, the system has provided heating support with hot water boilers operating with different fossil fuels, and today, additional thermal power is provided by coal fired boilers. In this study, unit heating energy costs are calculated for the current operating conditions of Bigadiç JBIS and for the cases where the system is supported with additional heating systems of different types and capacities. With the help of the 20-year levelized cost of heat (LCOH) analysis, the optimum capacities of the new natural gas boiler or new heat pump systems, which are considered to be included in the system as an alternative to the existing coal boiler or together with the existing coal boiler, were determined. Accordingly, it is seen that supplementing the existing geothermal energy with the coal boiler currently used in the system in such a way that 2.572 houses can be heated is the most economical alternative with the lowest unit heating cost. Supplementing the existing geothermal energy with a large capacity heat pump system, which can heat the equivalent of 2.572 houses, is the second most economical alternative in terms of unit heating cost. Providing heating services to more subscribers instead of the existing number of subscribers with new heating support systems has been found to reduce unit heating energy costs by 14%-50%.