Borehole heatexchanger wellfields

Vertical borehole heatexchanger (BHE) wellfields can be used virtually regardless of the geology and groundwater conditions. Allthough thermal properties vary with strata and have their influence on borehole spacing and wellfield geometry, factors such as building energy requirements and heating and cooling cycles are of equal importance when designing heatexchanger systems.

Groenholland exclusively do BHE wellfields and through experience found them to provide efficient and maintenance free longterm service. Well designed, using the right materials and the right implementation, wellfields should have a life span of at least 50 years.

The vertical heatexchanger, the connecting horizontal pipework and the system headers, form the complete groundsource heatexchanger assembly. Circulating through the pipework is the energy transfer medium, usually a water based antifreeze such as monopropylene glycol.

The hydraulic design of the complete BHE wellfield and the viscosity of the circulating medium at the anticipated operating temperatures and specified flow rates determine pump requirements. Pipework diameters, heatexchanger  and valve selection, pump types and pumping strategies should be reviewed in detail as pumping energy is a lifetime factor in a BHE wellfield and to a large extent determines the overall efficiency of the heatpump installation




Open or closed loop

Using groundsource energy can be done through an open (well type) loop or with a closed loop (PE loop type BHE.

Open wells extract and re-inject groundwater and use the pumped water for heating or cooling. To avoid thermal short circuiting, extraction and injection wells need horizontal or vertical separation.

Both quantity and quality of the groundwater are key issues.

BHE systems do not pump groundwater, but exchange energy only. The wellfield, that can even be installed under a building, provides both heating and cooling, is very compact and has a limited thermal extent in de ground.