Study On Evaluation Method Of Site Suitability Of Shallow Geothermal Energy Development In Dongli District,Tianjin

Shallow geothermal energy is one of the new green and clean energy with great potential.The pioneering work of its efficient exploitation and utilization is to carry out the evaluation of the suitability of development site according to the geological conditions,engineering geological conditions,hydrogeological conditions,occurrence conditions,etc.In this paper,through field investigation,field in-situ test,sample collection and indoor sample analysis,real-time dynamic data monitoring and literature data collation,the hydrogeological conditions and geothermal geological conditions of the study area are fully analyzed.For the first time,a hierarchical analysis-comprehensive scoring method is used to establish an evaluation system for the suitability of shallow geothermal energy development sites in the study area.The main research results of this piper are as follows:?1?In the 120m area,the average initial temperature of the shallow stratum is about 14.5¹4.6?,the average heat conduction coefficient of the stratum is about1.66².10 W/?m.k?,the heat absorption per meter is about 54.72W/m,the heat release per meter is about 38.43W/m,the depth of the thermostatic stratum is 20.5²7.5m,the temperature is within the range of 14.5¹4.6?,and the average geothermal gradient is between 2.5⁵.5?/100m;?2?A system for evaluating the suitability of water source heat pump in the study area was established from four aspects of hydrogeological conditions,dynamic characteristics,hydrochemical characteristics and social conditions,including 10indexes of 4 index layers,and a system for evaluating the suitability of ground source heat pump in the study area was established from four aspects of heat storage,thermal conductivity,safety and sociality,including 8 indexes of 4 index layers;?3?In this paper,the analytic hierarchy process-comprehensive scoring method combined with GIS is used to evaluate and analyze the suitability of shallow geothermal energy in the study area.The area of better suitability of the buried tube ground source heat pump is about 42.7km²;the area of good suitability is about147.3km²;the general suitability area is distributed in most of the research area,with an area of about 248.4km²;The worse suitability area is only 0.6km²;the area of the groundwater heat pump with good suitability is only 6.8km²;most of the area is the general suitability area,with an area of about 432.2km²;the area with poor suitability is about 38.08km²;?4?The thermal equilibrium theory was used to calculate the shallow geothermal energy capacity of the study area,and the heat storage method and groundwater volume conversion algorithm were used to calculate the heat exchange power.The results show that the shallow geothermal energy capacity in the study area is 190.43×10¹²kJ/?,of which the shallow geotechnical geothermal capacity is104.72×10¹² kJ/?,and the shallow water geothermal capacity is 86.71×10¹² kJ/?.