Determination and evaluation of the operation characteristics for two configurations of combined heat and power systems depending on the heating plant parameters in low-temperature geothermal applications

This paper analyzes impact of the required heating plant parameters on the Organic Rankine Cycle (ORC) power plant and the total plant behavior for two connections of CHP systems; they are the parallel plant and CHP integration according to Glewe-plant, Germany. And also, degree of utilizing the geothermal heat source will be discussed, and all CHP systems presented in the literature will be compared under the same conditions. R134a as working fluid in power plant will be employed. Exergy efficiency, net output power of ORC, irreversibility especially with exhausted geothermal water and the total heat exchange areas will be evaluated. From the calculations, it could be concluded that when operating the power plant in the both aforementioned CHP connections, its performances will be destructed at high heating plant parameters. So the compromised values of the low return temperatures and the heat exchange areas will enhance the power production and the performance of the total CHP systems at unchanged heat demand and supply temperature. The supply temperature does not have any effects on the power generation in case of the parallel connection, while the high values of this temperature affect negatively the other integration. The analysis also proved that the increasing heat demand will reduce the ORC productivity, but it will enhance the heat source utilization. The comparison between the CHP plants showed that the parallel connection is more economical and the series connection is energetically more efficient, while the integration according to Glewe-plant does not provide significant optimization. Finally, it could be noticed that the maximal optimized mechanical power in all present CHP configurations is so restricted, where it does not surpass 50% of the maximal power produced by stand-alone ORC plant.