A Study On Low Temperature Solar Thermal Comprehensive Utilization System Based On The Organic Rankine Cycle

At present the solar thermal collection technology with the low and medium temperature is relatively mature. In the meanwhile, the organic Rankine cycle (ORC) technology is one of the most favorable and promising techniques in low-temperature applications. Compared with high-temperature solar power generation on using high-concentration collectors for heat collection and steam Rankine cycle for power conversion, the system combined with ORC and the low and medium temperature solar collectors shows a great potential for development. There are several advantages to establish the distributed energy sources system based on the solar ORC technology. The domestic hot water or room heating can be easily got for the condensing process of the ORC system. Also the thermal driven chiller can work well with the low and medium temperature solar collectors. The technology of heat storage in the range of low and medium temperature is much easier to realize compared with high-temperature heat storage. In this thesis, a solar ORC worked under the low and medium temperature was presented. The system were researched and analyzed both experimentally and theoretically under the different work conditions.Firstly, the mathematical model of the low and medium temperature Solar ORC system working under different operation mode was established. The effects of key factors on the system performance were analyzed to obtain the rules. The impact of beam solar radiation, the average temperature of collector and the environmental conditions on the solar collecting performance and on the whole system performance were analyzed. Also the impact of the evaporation pressure, condensation pressure, degrees of superheat, degrees of subcooling and the expander performance on the ORC system performance under the different operation modes were analyzed. Based on the thermal flow analysis, the regenerative ORC and the CHP system is presented. Both of them can effectively improve the cycle performance and improve the utilization rate of solar energy, especially for the actual system with overheating.Secondly, two combined cooling heating and power solar system with different structure were presented based on organic Rankine cycle and LiBr absorption refrigeration technology. The system performance and the suitable application scope of them were pointed out based on the theoretical analysis.Then, the low and medium temperature solar ORC experimental system was set up. Also the combined cooling heating and power experimental system driven by solar energy was set up. Different operation modes, solar collector test mode, basic ORC mode and regenerative ORC mode were experimental researched respectively on the days with the typical weather. For the solar collector performance test, the impact of the main parameters on the collector performance under the constant heat conduction oil flow rate and variable heat conduction oil flow rate were experimentally studied. Also the experimental system performance of the ORC system and the regenerative ORC system were studied under the different working conditions. The comparative studies were carried out to get the impact of the key factors of the system on the system performance and to verify the theoretical analysis.In the last, the generator load was found that it has a direct effect on the power output characteristics of the experimental system. And with the basic ORC mode and the regenerative ORC mode, the experiments were designed and carried out to under different working fluid flow rate. For the established experimental system, the power output reached the maximum value while the generator load was about 800W.