Energetic, exergetic, economic and environmental assessments of the bigadic geothermal district heating system as a potential green solution

In this study, we assess the Bigadic Geothermal District Heating System ( GDHS), which has the world's third longest and Turkey's longest geothermal pipeline, for its energetic, exergetic, economic and environmental factors. The thermal energy capacity of the Bigadic geothermal field is rated as 31.83 MW for a discharge temperature of 45 C. As of the end of 2006, there were two wells actively running ( 429 m and 307 m in depth). The well head temperature is 98 C with a yield of over 100 kg/ s. The actual thermal data taken from the Technical Department of the GDHS are utilized in the analysis to determine the exergy destructions in each component of the system, and the overall energy and exergy efficiencies of the system with a reference temperature of 11 C for December. The energy and exergy flow diagrams are clearly drawn to illustrate how much destructions/ losses take place in addition to the inputs and outputs. The average energy and exergy efficiencies are found to be 40% and 49%, respectively. Exergy content provided by the geothermal fluid is found to be about 11% of its corresponding energy content. Also, we introduce some new parameters - energetic renewability ratio, exergetic renewability ratio, energetic reinjection ratio, and exergetic reinjection ratio - for the geothermal systems, apply them to the Bigadic GDHS, and end up with the following results: 0.46, 0.21, 0.40, and 0.50, respectively. Some economic factors of the GDHS are outlined and discussed. For Bigadic GDHS both quantity and quality values of the other fossil fuels are studied for comparison purposes. The quality factor for geothermal exergy price of the system is investigated for a year, and the average value used in calculations is 0.137. We finally investigate how much reduction in consumption of traditional fossil fuels and greenhouse gas emissions is possible through the use of the Bigadic GDHS.