Improving the ocean thermal energy conversion by solar pond

The low thermal efficiency of ocean thermal energy conversion (OTEC), resulting from narrow temperature difference in ocean thermal energy, can be improved by introducing a solar pond to preheating warm seawater entering the OTEC system. Therefore, a solar pond-assisted OTEC system is proposed and its thermodynamic model is developed in this paper. By this model, the role of extraction temperature and pumping depth of cold seawater on power generation potential of the system are analyzed. Furthermore, a comparative analysis is conducted among solar pond-assisted OTEC systems using Rankine cycle, Kalina cycle, and thermoelectric module from thermodynamic, economic, and environmental aspects. The results indicate that the overall thermal efficiency is only 3.97 % for solar pond-assisted OTEC system using Carnot cycle at an extraction temperature of 86 degrees C. The solar pond-assisted OTEC system using the Kalina and Rankine cycles produce almost the identical annual power generation, which significantly outperforms the system employing thermoelectric module. The exergy efficiency of the thermoelectric module improves with higher extraction temperatures, while Rankine and Kalina cycles demonstrate optimal extraction temperatures of 80 degrees C and 75 degrees C. Moreover, the systems using Rankine cycle, Kalina cycle, and thermoelectric module exhibit minimum levelized CO2 emission of electricity at 0.961 kg/kWh, 0.98 kg/kWh, and 10.7 kg/kWh, respectively.