In this paper, the effects of different operating conditions of the Gonen geothermal district heating system (GDHS) on its annual energy and exergy performance are investigated. The system parameters such as temperature, pressure and flow rate are monitored by using fixed and portable measuring instruments over a one-year period. Thus the main differences in the annual system operation are detected. The measurements show that the Gonen GDHS has six different operating cases depending on the outside temperature throughout the year. The energy and exergy analysis of the system is carried out for each case using the actual system parameters at the corresponding reference temperatures, which are 3.86, 7.1, 8:88, 11.83, 15.26 and 20.4 degrees C. The highest and lowest energy (57.32%, 35.64%) and exergy (55.76%, 41.42%) efficiencies of the overall system are calculated at the reference temperatures of 15.26 C and 3.86 degrees C, respectively. Besides, taking the six case-based energy and exergy analyses into account, the annual average energy and exergy efficiencies are determined to be 45.24% and 47.33%, respectively. (C) 2014 Elsevier Ltd. All rights reserved.
