Pareto principle-based advanced exergetic evaluation of geothermal district heating system: Simav case study

Abstract

Geothermal energy has been used in district heating systems for many years. In these old-fashion systems, the heat of geothermal fluid is transferred to secondary fluid (water) by pipes, pumps, and heat exchanger systems. Although these systems have an easy engineering structure, the efficient use of the geothermal source is deficient depending on the thoughtless installations. In this regard, the operating parameters such as temperature and operations provided against the losses such as insulation are much more important; however, the limits of these treatments are not definite. In this regard, advanced exergy analysis is a useful tool since it takes the systems' real, unavoidable, and ideal cases into consideration through conventional exergy analysis. So, the advanced exergy method enables the determination of the improvement potential of the systems. In the advanced exergy method, the unavoidable conditions are decisive factors that should be determined, taking the economic, technological, and available thermodynamic factors into account. Pareto principle can be an alternative solution to determine the unavoidable conditions. Pareto principle indicates that 80% of the impact is sourced from the 20% potential cause. Therefore, according to Pareto principle, it is available to increase benefits by 80% through a change of 20% in the technical parameters. In this study, the advanced exergy method was conducted for the whole Simav geothermal district heating system. The unavoidable conditions were determined based on Pareto principle. According to the analysis, the highest avoidable exergy destruction ratio was determined as 8.14% for the production (well) field, where the total was 19.96%. In conclusion, an improvement potential of 10.33% was determined for the overall system.