User:Holymoor/Draftthermogeology

Thermogeology has been defined as the study of the occurrence, movement and exploitation of low enthalpy heat in the relatively shallow geosphere. This low enthalpy heat may also be referred to as "ground source heat".

In this context, “relatively shallow” typically means depths of not more than 200-300 m and "low enthalpy" means ground temperatures in the range 0°C to around 40°C. For comparison, typical natural ground temperatures vary from around 2°C (groundwaters in the north of Norway) to around 35° (shallow groundwaters in saharan or sub-saharan Africa).

The earth or its groundwater can be used for both heating and cooling of buildings. This can be achieved, for example, by simply circulating cool groundwater around heat exchange elements in a building during summer (so-called passive cooling), or by circulating relatively ground-coupled fluid around a heat exchange element under a paved area to achieve snow-melting / pavement deicing in winter. Alternatively, a ground source heat pump (geothermal heat pump) can be used to extract heat from (or actively reject heat to) the ground or groundwater to provide higher-temperature space-heating (or lower-temperature space-cooling).

Thermogeology or Geothermal Energy?
The terms "geothermal energy" and "geothermics" have traditionally been applied to more conventional, higher temperature geothermal resources. However, the recent European Union Directive on Renewable Energy 2009/28/EC states that ‘geothermal energy’ means energy stored in the form of heat beneath the surface of solid earth. Thus, ground source heat is, strictly speaking, also defined as a form of geothermal heat.

Terminology and Parallels with Hydrogeology
The term "thermogeology" is applied to invite an analogy with the science of hydrogeology - the study of the occurrence, movement and exploitation of groundwater in the relatively shallow geosphere. The physical laws governing the conduction of heat in solids, and the flow of groundwater through permeable strata are directly analogous:

The US hydrogeologist, Charles Vernon Theis, explicitly acknowledged his debt to the heat conduction mathematics of Horatio Scott Carslaw when formulation his Theis equation for radial flow of groundwater towards a well.