| In the past decades, the social and economic boom has exacerbated the contradiction between humans, resources, and environment, particularly between humans and energy, which has brought to the forefront the exploration and utilization of renewable and pollution-free energy for tackling with energy crisis across the world. The geological environment is the upper part of the lithosphere and groundwater circle, which has a major impact on human activities.For thousands of years, the shallow geological environment has been the main source of human required energy. As a sort of low-temperature thermal energy stored in the soil rocks and groundwater within several hundred meter-depth of the shallow earth surface, the shallow geothermal energy can help deal with such problems as cooling&heating of buildings and hydrothermal supplies, and can bear a strategic role in improving energy structure, promoting energy-conservation&emission-reduction, and securing a sustainable development.From the hydro-geological perspective, this paper systematically analyzes the influence of hydro-geological factors on the shallow geothermal energy development&utilization, and puts forward the suitability evaluation index for the shallow geothermal energy development&utilization by drawing on other environmental constraint conditions, which is of great help to the national suitability regionalization of the shallow geothermal energy development&utilization. Based on the available temperature difference of the shallow geothermal energy development&utilization in different regions, this paper also develops the regional shallow geothermal energy assessment method, calculates the shallow geothermal energy amount in major cities in China, and carries out environmental influence simulation and prediction based on the typical demonstration projects of shallow geothermal energy development&utilization. The main results of this paper consist of the following parts:1. Groundwater source heat pump system is mainly affected by hydrogeological factors, site construction factors, socio-economic factors, weather factors and environmental factors. To carry out regional groundwater source heat pump suitability assessment, emphasis should be focus on the aquifer water abundance, ground water temperature, salinity, annual precipitation, average annual temperature of the cone of depression distribution, geological environmental problems, as well as topography and other site construction conditions and other related indicators, and the the analytic hierarchy method can be used for evaluation. 2. The regions which are suitable for heat pump application are mainly distributed in parts of Northeast China and North-China Plain, as well as parts of Yunnan, Guizhou, Sichuan, Hubei, and Hunan, the majority areas of which belong to plains, basins and areas with sound water storage. The regions that are not suitable for heat pump application mainly include parts of Qinghai, Tibet Autonomous Region, and Xinjiang, most parts of Inner Mongolia Autonomous Region, northern parts of Heilongjiang, and particularly the desert area, areas with extreme water scarcity, and parts of extremely cold areas.3. The application of soil source heat pump mainly subjects to the system's heat exchange efficiency and technological&economic conditions. The more close to the piedmont an area is, the better suitability it will have; instead, the more close to the coast an area is, the worse suitability it will possess. The soil source heat pump system is better applied in areas with more saturated sand layers, higher groundwater levels, stronger groundwater movability, and higher precipitation infiltration coefficient.4. Different from conventional geothermal resources, shallow geothermal energy resource assessment is the evaluation of the regulation and storage capacity of the underground heat. Shallow geothermal energy resource potential isrelated to the regional thermal capacity, underground thermal regulation and storage capacity and technology.The shallow geothermal energy amount of287cities of China is estimated to reach7.71×1013kWh/a, which is equivalent to the energy amount released by9.486billion tons of standard coal. The utilizable amount of shallow geothermal energy is about2.89×1012kWh, which is equivalent to the energy amount of356,000,000tons of standard coal, and the total installed air-conditioner area can reach156,189.97-120,949.99km25. In the areas with hot summer and cold winter, the heat pump exploration and back-irrigation in the typical demonstration projects of groundwater source heat pump development&utilization have little impacts on the environment for most parts of the regions. There is no heat burst between water-extraction wells and back-irrigation wells. Based on the current operation mode and status, the heat pump system will not be affected within the next ten years.6. In terms of the soil source heat pump development&utilization in the areas with hot summer and cold winter, the overall variation of underground temperature field tends to reach a balance. The heat pump operation keeps a balance between the heat release and heat absorption, and the geothermal temperature variation takes on a periodic process of temperature incline in the cooling stage and temperature decline in the heating stage. The geothermal temperature variation stays within the range of local temperature changes, thus avoiding environmental issues. |
