Utilisation of Ambient Air and Shallow Geothermal Energy - Renewable Energy: Technology, Economics and Environment - page 424

exchanger and heat pump systems connected to the groundwater are defined
(Table 9.7). These heat pump systems generate space heat and domestic hot water,
with a priority for the generation of domestic hot water. The working medium
used in all systems is R407C. The heat pump is always installed in the basement
of the building to be supplied. The achievable SPFs are determined by the heat
pump technology and the characteristics of the heat source plus the share of do-
mestic hot water generation as part of the entire demand for heat. Due to the
higher temperature level, the domestic hot water generation is characterised by
lower COPs than space heating. When measuring the SPF auxiliary energy con-
sumption for e.g. control purposes the brine or the groundwater pump has to be
considered as well.

Table 9.7 Reference-configurations of the analysed heat pump systems
System SFH-I a SFH-II b SFH-III c MFH d

Space heating demand in GJ/a 22

10.7
5

45
10.7
8

108
10.7
18

432
64.1
60

Domestic hot water demand in GJ/a

Nominal heating requirement in kW

Heat source
Ambient air (without preheating of air ) (AWO)
Ambient air (with preheating of air) (AW)
Ground-coupled horizontal collector with brine
circuit (GB)
Ground-coupled horizontal collector with direct
evaporation (GD)
Ground-coupled probe with brine circuit (GP)
Groundwater (GW)

X
X
X
X

X
X
X
X
X
X

X
X
X
X

X
X
a Single family house (SFH-I) with low-energy design; b single family house (SFH-II) accord-
ing to current heat insulation standards, c single family house (SFH-III) as an old building with
an average heat insulation, d multi family house (MFH); for the definition of SFH-I, SFH-II,
SFH-III and MFH see Table 1.1 and Chapter 1.3 respectively.

The SPFs assumed in the following are higher for those single family houses
that are not so well insulated. The relative share of domestic hot water generation
compared to heating decreases in that case. Domestic hot water generation re-
quires a higher temperature level than heating, which leads to a lower COP of the
heat pump.
− Ambient air with/without preheating (AW/AWO). For systems without pre-
heating, the air is transported to and from the heat pump via insulated
galvanised sheet steel ducts. Opposed to that, in the system AW, the ambient
air is preheated with a so-called air well. This is a concrete duct of approxi-
mately 60 m length and a diameter of 25 cm. It is sunk into the ground at a
depth of 1.5 m. The SPFs of the analysed reference systems are assumed to be
2.17 (SFH-I) and 2.37 (SFH-II) for systems without air preheating (AWO) and
2.40 (SFH-I) and 2.65 (SFH-II) for systems with preheating (AW).
− Ground-coupled heat pumps with brine circuit (GB). HDPE tubes are sunk
1.2 m deep as collectors. The heat carrier - like in all analysed media with a