锘军img width="352" height="267" style="margin-right: 5px; float: left;" src="http://hyy.com.cn/images/icon/TemperatureInsideEarth.jpg"/>Geothermal Energy is low 鈥搕emperature heat (compared to energy from soil, sandstone and underground water in thermostat layer) reserved under the surface layer formed under the combined effect of solar energy and heat energy from the earth鈥檚 core. There is no big change to the temperature of the thermostat layer in different seasons or regions: slightly lower in winter and slightly higher during the summer. It is always under 25鈩? which is the result of the combination of solar energy and the heat energy of the earth鈥檚 core. As indicated by geological surveys, due to the great influence of heat energy of the earth鈥檚 core, there is temperature gradient under the thermostat layer. Temperature will increase by 3-4鈩僽nderground for every 100 meters in depth underground.  However, solar energy has great influence and top 100 meters below the earth's surface can be exploited to harvest the geothermal energy stored within. Chart 1 is schematic view of shallow geothermal energy.  

           Balance of shallow geothermal energy is indicated by chart1.  Shallow geothermal energy is regenerative energy which mainly uses the indirect solar energy. 30% of solar energy is reflected by cloud layer and the earth鈥檚 surface.15% is absorbed by the cloud and the rest absorbed by land and sea. In this way, the thermostat layer is formed in the 100 meters under the surface layer. However, the absorbed solar energy is released to the atmosphere and space in different forms.

           Indicated by chart 2, every year radiation from sun amounts to the heat released by 95000 billion tons of raw coal, which is 6500 times of the energy consumption of the world in 2004. The radiation is the major supply source of the shallow geothermal energy in underground 400 meters.            

           Chart3 indicates that shallow geothermal energy is mainly reserved in the thermostat layer ( in 400 meters underground ) under which heat energy of the earth鈥檚 core starts to make great influences. This is not included in the geothermal energy.

           Shallow  geothermal energy features in  rich  reservation, swift regeneration, wide distribution, constant temperature in the  whole year and inexhaustible. It is a huge treasury of green energy.