Performance analysis of different orc power plant configurations using solar and geothermal heat sources

ABSTRACT

Energy optimization is performed on hybrid solar-geothermal power plant working according to Organic Rankine Cycle and installed in southern Tunisia. The performances of four different configurations of the power plant are studied. Mass and energy balances are established for the different compounds. The effects of the main operating parameters such as the geothermal water temperature, ambient temperature and direct normal irradiation on the power plant performances are analyzed. A code is established using Engineering Equation Solver software (EES) to perform the required calculations. Obtained results show that the hybrid solar-geothermal power plant with a heat recovery system is the most suitable configuration design giving a better overall energy efficiency of 15.77 and13.11% and a maximum net power of 1089 and 1882 kW in winter and summer, respectively. However, in the summer season, using a heat recovery system can valuable only when the water temperature is higher than 66°C. For air-cooled condenser, the suitable condensing pressure is 1 bar in winter and 1.9 bars in summer.

KEYWORDS:

• Energy Optimization
• geothermal
• hybrid
• n-pentane
• orc cycle
• power Plant
• solar
• thermal analysis

Highlights

• Thermal and energy optimization is conducted on different configurations of solar and hybrid solar-geothermal power plants using n-pentane as working fluid and operating according to an Organic Rankine Cycle.

• The power plants are designed for the local environmental conditions of Kibili zone in southern Tunisia (33°42ʹN, 8°57ʹE)

• Mass and energy balances are established for the different compounds of the power plants.

• The effects of the operating parameters such as geothermal water temperature, ambient temperature, and direct normal irradiation on the power plant performances are analyzed.

• The hybrid solar-geothermal power plant with heat recovery is selected as the most suitable configuration giving better efficiency and maximum net power.