A comparative thermodynamic and exergoeconomic scrutiny of four geothermal systems with various configurations of TEG and HDH unit implementations

Among the most prominent renewable energy sources worldwide, geothermal heat is plentiful in almost every location containing subterranean geofluid, primarily water. Additionally, given the excessive consumption of water in various manners globally, serious focus has been driven towards means of compensation for freshwater resources. The present study proposes four systems powered by geothermal sources, thereby introduced as geothermal systems. System D, comprised of a double-flash geothermal system, a humidification dehumidifi-cation desalination system, and two thermoelectric generators, demonstrated the most promising results among all systems after being analyzed thermodynamically and exergoeconomically, all of which performed using EES software. The evaluated parameters are sum unit cost of products, net generated power output, energetic and exergetic efficiencies, which yielded 4.532$/GJ, 106.8 kW, 45.83 %, and 51.53 %, respectively. In order to generate overplus power and further exploit waste heat, thermoelectric generators were implemented in the systems as substitutions for the condensers. The findings suggested an extra sum of 10.112 kW generated power and exergetic improvement by 1.15 % taking event in system D due to the application of two thermoelectric generators. Moreover, optimization scenarios were run to maximize energetic and exergetic performances and minimize the sum unit cost of products. Three weight coefficients were assumed for each of the target parameters within the single-objective optimization scenarios, namely the thermal efficiency mode, exergy efficiency mode, and economic mode. Moreover, a multi-objective optimization mode was carried out. The optimal results are addressed further along the paper. The present study aims at proposing an optimal system respondent to two of contemporary society's fundamental requisites, power and freshwater, and in order to do so, an evolutional sequence has been undertaken to satisfy the stated requirements.

Automated summary

This study proposes four geothermal-powered systems and finds that System D shows the most promising results. By using two thermoelectric generators, additional power generation can be achieved and energy efficiency can be improved. Furthermore, optimization scenarios are carried out to enhance energy and exergy efficiencies and reduce the overall unit cost of products.