2.1 Lämpöässä Vmi structure and operating principle
The Lämpöässä Vmi is especially suitable for use as the primary heating
system of new and renovated residential buildings and secondary resi-
dences, as well as for condominium-specic heating in terraced houses and
detached houses. In order to ensure trouble-free operation, all Lämpöässä
geothermal heat pumps have been test-run, set up and tested by the manu-
facturer. If a geothermal heat pump is being used in the part-power congu-
ration, for example, because high temperature is required in the radiator
system, the heating system must be dimensioned and adjusted so that the
return water temperature is always below +55 °C.
By part-power we hereby mean that the electric heating element (immer-
sion heater) is allowed to switch on if necessary. For the operating prin-
ciple and main components of Lämpöässä Vmi, see the picture below.
The picture has also been discussed in the following paragraphs.
2.1.1. Heat collection circuit
The geothermal heat system circulates water/ethanol mixture protected
against freezing in the heat collection circuit in order to collect thermal
energy accumulated in soil through solar radiation. The heat collection
piping used comprises a bore hole or plastic pipe (PEM 40/10) placed at
least 1-1.2 metres deep in soil or at least 3 metres deep in water. The
circulating mixture warms up by a few degrees and delivers this thermal
energy to the geothermal heat pump’s EVAPORATOR (1), i.e., the heat
exchanger. The temperature of the heat collection uid arriving from the
soil to the evaporator is approx. 0 ºC (conditions in Finland). This tem-
perature can be lower in winter and higher in summer. At the evaporator,
the energy of the heat collection uid is transferred to the low-pressure
refrigerant circulating inside the heat pump. The refrigerant is evaporated
using the thermal energy.
Ground
circuit in
Ground
circuit out
1. 2.
4.
6b
6a
7b
7a
3.
5.
1. Evaporator
2. Compressor
3. Superheater
4. Condenser
5. Expansion valve
6a. Upper storage tank
6b. Lower storage tank
7a. Upper storage tank
domestic water coil
7b. Lower storage tank
domestic water coil
2.1.2. Compressor unit
From the evaporator, refrigerant vapour is transferred to COMPRESSOR
(2) for ramping up the pressure. This is accompanied by steep tempera-
ture rise. In the course of the heat pump process, the refrigerant tem-
perature is the highest after the compressor, in excess of 100 ºC, and the
refrigerant is referred to as ’hot gas’.
The hot refrigerant is transferred from the compressor to heat exchangers
(condenser and superheater), through which it releases its thermal
energy into the heating water STORAGE TANK (6). The heat in the stor-
age tank is used for heating and hot domestic water production pur-
poses. When heat is extracted from the refrigerant vapour, a point is
reached where the vapour begins to revert into liquid – i.e., is condensed.
This point is close to temperature required for heating (in general,
approx. 35-55 ºC). Since the refrigerant gas leaves the compressor at
70-120 ºC, it cools rst and liquees later. The energy released in the
course of such cooling is referred to as superheating energy. The super-
heating energy can be efciently utilised in nal heating of domestic
water, by using a SUPERHEAT EXCHANGER (3).
After the superheater, the refrigerant is transferred to CONDENSER (4),
where it is transformed from vapour to liquid, releasing the heat to the
heating water storage tank and from there to the heating network. Hav-
ing conceded its thermal energy, the liquid refrigerant is transferred
through dehydration lter to EXPANSION VALVE (5), where the pressure
of the liquid refrigerant drops and a new cycle from the evaporator can
commence.
2.1.3. Hot water storage tank
Lämpöässä Vmi utilises carefully designed superheating technology
allowing advantageous generation of heating and domestic hot water.
The objective is to maximise the share of geothermal heat in overall
heating. A two-sectioned HEATING WATER STORAGE TANK (6)
equipped with partition enhances utilisation of superheating energy. The
coefcient of performance remains at a high level, since the energy-ef-
cient superheating mixture involves heat transfer between two tank sec-
tions using two different heat exchangers (condenser and superheater).
Water from the hot water storage tank is circulated in the heat distribu-
tion piping consisting of either one or two loops.
The top part of the storage tank, i.e. the TOP STORAGE TANK (6a), is
