Installation manual

80
3.4
3.4 Heat Source Absorber Systems (Indirect Use of Air or Solar Energy)
Brine temperature range -15...+ 50 °C
Operating range of the brine-to-water heat pump -5 to +25°C
Availability
Possible restrictions due to effects of the weather and
limited space.
Types of operation
 Bivalent
 Monovalent in combination with an additional ground heat
collector
Development costs
 Absorber system (energy roof, pipe bundle, solid absorber,
energy fence, energy tower, energy stack, etc.)
 Ethylene glycol or propylene glycol-based brine in a frost-
proof concentration
 Pipework and circulating pump
 Construction work
PAY SPECIAL ATTENTION TO:
 Building requirements
 Effects of the weather
Dimensioning absorber systems
Individual constructions vary considerably, so that the factory
specifications should normally be consulted when dimensioning
roof absorbers, energy towers and energy fences.
Experience has shown that the following data can be used as a
basis:
 The absorber surface should be designed according to the
specified off-peak (nighttime) output of the absorber.
 Even at temperatures over 0 °C, rain, dew or snow can
freeze on the surface of the absorber when the temperature
of the brine is very low. This could have a negative effect on
the flow rate.
 Monovalent operation is only possible in combination with
the utilization of ground source heat.
 With the use of solar energy, brine can reach temperatures
of 50 °C or more in the transition period. Such temperatures
greatly exceed the operating range of the heat pump.
ATTENTION!
If the heat source temperature can rise to over 25°C, then a temperature-
controlled mixer is required that, for temperatures over 25°C, adds the
cooling water to a partial volume flow of the cooling water return flow.
Brine concentration
Due to the low outdoor temperatures, frost protection down to –
25 °C is necessary for roof absorbers, energy fences, etc. The
brine concentration for this system is 40 %. When dimensioning
the brine circulating pump, it should be taken into consideration
that the higher the brine concentration, the higher the pressure
drops.
Filling the system:
The system should be filled as described in Chap. 3.1.3 on p. 72.
Design of the expansion vessel:
The brine temperatures vary between approx. –15 °C and
approx. +50 ° C for absorber-only operation. An expansion
vessel must be installed in the vicinity of the heat source system
to accommodate these large temperature fluctuations. The
admission pressure should be set to correspond to the height of
the system. The maximum overpressure is 2.5 bar.
Air pressure absorber
Brine concentration: ≈ 40%
Relative pressure drop ≈ 1,8