Ground source heat pump designs

The use of heat from renewable sources is one of the most modern methods of energy conservation and environmental protection. Implementation of new acquisition technologies and processing of the energy allows for its efficient and rational use. Unconventional sources of heat should be considered in zoning. Renewable energy coming from the ground, surface water and groundwater can easily be used by the heat pump. Environmental possibilities should always be examined before the start of the construction.

The heat coming almost entirely from solar radiation and heat and mass exchange with the atmosphere is accumulated in about ten-meters surface layer of the ground. The heat both from solar radiation and conduction from the earth is accumulated in the deeper layers of less than 20 m. In addition, supplying groundwater enables direct use of the heat contained in the ground.

In practice there are two systems for of heat acquisition from the ground. We design systems in which heat is taken from the ground or the groundwater, depending on the prevailing geological conditions.

Designing of the ground heat exchangers is difficult and the results of theoretical calculation are largely uncertain. Cause of this is generally lack of information about the physical properties of the soils and the complex nature of the transient heat transfer processes. Therefore, the first task of the designer is to determine the temperature field in the area of the installed ground heat exchanger. Variable in time soil temperature field is the result of overlapping of two heat fluxes: solar and geothermal.

The heat exchange between the ground and the ground heat exchanger is very complex. The process of heat transfer depends on many factors such as:

• local climatic conditions
• physical properties of the soils: density, specific heat, thermal conductivity
• natural decomposition of soil temperature
• type and parameters of the ground heat exchanger
• Thermal soil test is performed directly in the field using a portable apparatus.

In addition to the hydrogeological condition, dimensioning of the installation requires knowledge of the following values:

• groundwater temperature
• level of the groundwater and thickness of the aquifer
• volume flow of the groundwater supplied to the evaporator
• chemical composition of the water

Installations for the heat acquisition are developed individually depending on prevailing local conditions.