Energy and exergy analysis of cold and power production from the geothermal reservoir of Torre Alfina

Highlights: • Organic Rankine cycle coupled with a LiBr/water absorption chiller is investigated. • Energy and exergy analysis were performed at system and component level. • The improved model is applied to an actual geothermal data. -- Abstract: Geothermal power plants can provide clean and renewable energy and can be proposed as integrated units for simultaneous production of cooling and power. This paper presents a cascade arrangement of an organic Rankine cycle (ORC) and a water/lithium bromide (LiBr) absorption chiller (ABS). Starting from a literature reference layout which is taken as benchmark, some improvements are proposed at system level. To assess the performance of the system, a thermodynamic model is developed in EES and the energy and exergy balance is calculated. The proposed system is re-evaluated with reference to resource conditions corresponding to a planned power plant in central Italy, Torre Alfina (TA). A sensitivity analysis is performed in order to investigate the operating range of the plant and the possibility of adapting its design to the requirements of the customers. Under optimized conditions, the TA Case (targeted on a 5 MW power output) showed an energy utilization factor (EUF) of 46.2% and an exergy efficiency of 27.7%, neglecting the brine reinjection loss. The highest exergy destructions occur in the ORC economizer (8.6%), in the ABS generator (6.3%) and absorber (5.5%). The good resource conditions in TA case drive the design optimization to production of power rather than cold.