Energy and exergy analysis of geothermal district heating systems: an application

In this study we present an energy and exergy assessment and modeling of geothermal district heating systems for their system analysis, performance evaluation and optimization. A comprehensive case study is conducted in Balcova geothermal district heating system (BGDHS) in Izmir, Turkey and actual thermal data are collected and employed for analysis. Using actual system data, an assessment of the district heating system performance, energy and exergy efficiencies, and exergy destructions in the system is conducted in this regard. The exergy destructions in the overall BGDHS are quantified and illustrated using exergy flow diagram. Furthermore, both energy and exergy flow diagrams are exhibited for comparison purposes. It is observed through analysis that the exergy destructions in the system particularly take place as the exergy of the fluid lost in the pumps, the heat exchanger losses, the exergy of the thermal water (geothermal fluid) reinjected and the natural direct discharge (hot water distribution losses) of the system, accounting for 1.64%, 8.57%, 14.84% and 28.96%, respectively, of the total exergy input to the BGDHS. For system performance analysis and improvement, both energy and exergy efficiencies of the overall BGDHS are investigated and are determined to be 41.9% and 46%, respectively.