scope:

Guideline VDI 4640 applies to the thermal use of the underground up to approximately 400 meters depth. The following application cases are dealt with in the guideline:

Ground source heat pump systems (are dealt with in this Part 2)

a) Heat pump systems for heating

b) Heat pump systems for heating and cooling

Note: In cooling operation, the cooling can be achieved via the heat pump and/or directly from the underground by circumventing the heat pump.

c) Refrigeration machines for cooling

Ground heat exchangers or the groundwater directly (see Part 4) are used as heat transfer media.

• Ground heat collectors, borehole heat exchangers and other special ground heat exchanger models are in use as ground heat exchangers.
• The groundwater can originate from aquifers via wells, but also from pits or the tunnel drainage.

Underground thermal energy storage (see Part 3)

a) Storage systems for heating Solar energy, waste heat, environmental heat are all used as heat sources.

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

c) Storage systems for heating and cooling

- in connection with heat pumps

- without heat pumps, using environmental cold/ heat.

Ground heat exchangers or direct use of the groundwater as a heat transfer fluid (aquifer storage) are used.

Direct uses (see Part 4)

A heat pump or a refrigeration unit are not used here:

• Cooling using groundwater
• Heating using groundwater
• Air heating/cooling in the underground