Geothermal energy for heating and cooling in agricultural greenhouses

Majid Rahnama, Navab Kazemi, Behroz Godarzi, Morteza Taki

Abstract


Geothermal source is a perspective technology able to use the ground as a thermal sink or heat source. It is one of the energy resources in Iran that can be used with long-term investment. This study provided a new idea to use of this energy for heating and cooling of buildings. Two wells were used for heating and cooling due to the constant temperature of the water in depth of 12 m underground (approximately is equal  to the annual temperature environment during the year). Water flowed in six speeds: 10, 11.5, 13, 16, 29 and 34 lit/min using a hydraulic pump (12 meters hydraulic height and 2 inch diameter) from first well, and after passing through radiator, discharge to other well. The outdoor temperature was 9oC, 40 °C and 15.5-16 °C for heating, cooling and well water respectively. An axial fan is used to passing the air in six speeds: 0.5, 1.1, 2.2, 3.3, 4.4 and 7.4 m/s through the radiator. The results showed that the use of water from this well can reduce the required power about 25% for heating and increase the air temperature from 9 to 25 °C. Also this system can reduce the required power between 38 to 60% for cooling and decrease the air temperature from 40 to 25 °C.


Keywords


Air speed, geothermal source, net energy ratio, water flow rate

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