The Fe-Ti oxides from the andesitic volcanic rocks of the Bajawa Cinder Cone Complex display the invading of higher temperature and more mafic basaltic magma into the magma chamber. There were three batches of magma (0.73-0.49Ma, 0.43-0.23Ma and 0.20-0.14Ma) in the long life of the Bajawa Cinder Cone Complex. After the magma mixing occurred in the early crystallization of each magma batch, the well-mixed magma was placed in a normal fractionation crystallization state. The end products of magma mixing in the Bajawa Cinder Cone Complex before the eruption were in chemically equilibrium state at a temperature range of 797 to 997°C (average of 900°C). The magma batch 03 of the latest stage (0.14Ma) indicates a narrow temperature range of 865-928°C. It means that the magma of 0.14Ma eruption was well mixed and attained to equilibrium. The cooling rate in the last magma chamber of the Bajawa Cinder Cone Complex was approximately 2.7°C/1000 years (375°C/0.14Ma) from 0.14Ma to present with the assumption of magma temperatures of 900°C at 0.14Ma and 525°C at present.
The system is mainly composed of the underground heat exchangers using 75 building's piles, four 15HP heat pumps, a 140m3 heat storage tank, piping systems, air-conditioning and heating equipments. Each pile is drilled up to 50m deep by the earth drill technique and equipped with a double U-tube which carries the liquid for the geothermal system. The designed quantity of heat exchanged between the underground heat exchangers and these external formations is 114kW. The heat pumps are driven in the night when electricity cost is low, and the water in the storage tank is heated to 50°C in winter and is cooled to 5°C in summer, which are store in the heat storage tank. In the daytime, the former is used for heating the 970m2 floor of the gymnasium and the latter for cooling the control room and the special school room. The operating performance of the heat source equipments meets the evaluation standards : in the heating the inlet temperature of the underground heat exchanger tin> 0°C, the outlet temperature of the underground heat exchanger tout>atmospheric temperature tair, the system power q≥132kW, the storage temperature ts≥50°C and in the cooling tout>tair, q≥120kW, ts≤5°C. Heat pump heating and cooling coefficients of performance are respectively 3.04 and 4.5. The total quantity of heat given by the heating floor face of the gymnasium is 54kW by estimate from the floor temperature of 21.5°C and the room temperature of 15°C. Additionally the energy consumption of the geothermal system is 68 % that of the kerosene boiler and the carbon dioxide emission of the former is 56% that of the latter.
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