Energy conversion of heat from abandoned oil wells to mechanical refrigeration - Transient analysis and optimization

This study investigates the potential of using geothermal energy from abandoned oils in a novel three-loop system; geothermal, power and cooling loops to produce effect. The loop drives thermo-mechanical refrigeration (TMR) system consisting expander-compressor units (ECUs). advantages lie its simple, flexible, low-cost design as well ability be driven by low-temperature heat source (as low 60 °C). To evaluate performance system, comprehensive models are developed including transient model for oil (geothermal loop) spatial time domains thermodynamic optimization entire system. effects temperature variation geofluid over operation time, working fluids, high pressure temperatures sink investigated. Results show that at realistic conservative conditions, considerably decreases first four months (by an average 30 °C) tends constant after half year operation. However, still enough drive proposed TMR full period. Among 43 investigated refrigerants, R1234ze(E) has higher efficiency, lower Pumping Work Ratio (PWR), requires smaller size exchangers. Using genetic algorithm method with fluid both loops, maximum efficiency 6.3% COP 5.3 were obtained 29 bar (in minimal expander diameter 64, compressor 171 mm, 18 units.