Direct Use of Geothermal Energy

Abstract

Abstract Direct utilization of geothermal energy refers to its use for a thermal purpose, rather than to its conversion to some other form of energy such as electrical energy. In theory, then, geothermal energy can be directly used for any process or application that relies on heat, but in practice, actual applications are limited to the geothermal resource temperature and the useful quantity of heat that can be extracted. The most popular direct uses of geothermal energy (excluding geothermal heat pump applications) include spas and swimming pools, space heating (including district applications), greenhouse heating, aquaculture, industrial uses, snow melting, and agricultural drying. On a worldwide basis, on the order 80 countries directly use geothermal energy for a thermal purpose, with spas and recreation being the most popular at approximately 50% of the total worldwide use, followed by space heating on the order of 30% of the total worldwide use. Direct‐use geothermal projects are intensely driven by economics, and there are a number of factors that dictate their viability. These factors include the resource access and regulatory hurdles, level of effort needed for exploration, depth to the resource, distance between resource location and application site, well yield, allowable geothermal fluid temperature drop, resource temperature, thermal load and load factor, geothermal fluid chemical composition, and ease of geothermal fluid disposal.