scope:

Guideline VDI 4640 relates to the thermal use of the subsurface down to a depth of approx. 400 m. The following applications are dealt with in the guideline:

Ground-coupled heat pump systems

a) Heat pump systems for heating purposes

b) Heat pump systems for heating and cooling purposes

Note: In cooling mode, the cooling can be accomplished via the heat pump and/or directly from the subsurface, thus bypassing the heat pump

c) Chilling equipment for cooling purposes

The heat is transported via ground heat exchangers or directly by the groundwater

The types of ground heat exchanger used are: ground heat collectors, ground source heat exchangers and other special types of ground heat transfer system

The groundwater can be taken via wells from aquifers, but also from mines or from the drainage of tunnel works

UTES systems 

a) Storage systems for heating purposes Possible heat sources are: solar heating, waste heat, environmental heat.

b) Storage systems for cooling purposes (cold source: environmental cold)

c) Storage systems for heating and cooling purposes

• combined with heat pumps
• without heat pumps, using environmental cold/heat

The heat is transported via ground heat exchangers or directly by the groundwater (aquifer storage).

Direct uses 

No heat pump or cooling/chilling unit is used in these cases:

• Cooling with groundwater
• Heating with groundwater
• Heating/cooling air below the ground