Solar water heating model with sun tracking system for increasing biogas production

This study focuses on using solar energy to enhance biogas production. In this research one digester under the ground was used as study object, which is located at Runzhen middle school in Chunhua county, Shannxi province, and its volume is 100?m3. The raw material was human manure, which was fed to the system every day. The average temperature in January was -1.6oC, the lowest temperature was -15oC and the average of solar radiation in Runzhen area was 4.5 kwh/m2. Because in the winter the biogas yield without heating system will almost stop, the objective of this study is to investigate the feasibility of using solar energy for increasing biogas production. The system includes a 120 m2 greenhouse and 8 flat solar thermotube heaters with total surface area of 20 m2 to reach optimum temperature. Results show that in the winter the solar system can increase biogas yield by 12 m3 per day with cost 1.5 Yuan/m3, all the gas yield can be used in school kitchen by the designed pipe for cooking. In addition, the parabolic trough solar concentrator (PTC) with tracking system was developed for the heating system, which is expected for higher gas production per day without daily additional cost.