| When system property data has been recorded, simulation tools
can be validated and substantiated design guidelines compiled.
Feedback from building users will provide a direct indication
of how the products are accepted, which, in turn, will point
out valuable optimization potential to manufacturers and planners.
Evaluating the metrological data with respect to saving energy
will enable energy suppliers to incorporate PCM systems into
their energy consultations. Energy suppliers will also be in
a position to evaluate the effects of wide-scale use of PCM
systems on power plant and grid capacities by carrying out an
energy-economical analysis on the basis of the load shift measured.
Rear-ventilated cooling ceilings with PCM
PCM foil bags with salt hydrates are already being implemented
in passive cooling ceiling systems (metal cassette ceilings).
Such systems are easy to install (see photo below) and yield
a passive cooling capacity of 25 bis 40 W/m2.
Inserting PCM foil bags into a metal cassette ceiling.
Due to the lower thermal conductivity of, for example, gypsum
boards, the cooling capacity of such a system is clearly reduced
when the suspended construction is not made of metal. An active
rear ventilation is therefore necessary. The regeneration of
the system at night is achieved with the cool outside air.
Calculated temperature curve of an office with rear-ventilated
ceiling construction with PCM (red). The temperatures without
PCM (blue dots) are also shown as a comparison. The peak temperatures
have been reduced by about 2K thanks to the PCM.
Such rear-ventilated cooling ceilings with PCM have been
installed in two offices at EnBW in Karlsruhe as well as in
a seminar room at the University of Würzburg. Cooling
is achieved via recirculated air by day and the PCM is regenerated
at night through the absorption of the cool outside air.
PCM boards being inserted into the suspended ceiling (left)
and the requisite rear-ventilation system (right).
Water-flow cooling ceilings with PCM
Suspended water-flow cooling ceilings achieve high cooling
capacities (about 100 W/m2) in short reaction times,
but often require high peak loads to provide the cooler temperatures.
By integrating PCM, a purely passive basic cooling capacity
of about 40 W/m2 can be provided during the day
when the cooling load is at its highest. The PCM is then regenerated
at night with cold water. In this way, the peak loads during
the day can be avoided and the cooling load balanced out.
This presents clear advantages over producing cooling capacity
via geothermal systems (probes), since geothermal probes have
to be designed for the peak loads. By combining PCM systems
with conventional technology, the advantage of short reaction
times is maintained and only the peak loads that exceed the
basic load have to be compensated.
Water-flow cooling ceilings with PCM have been integrated
into a lecture theatre at Stuttgart University of Applied
Sciences as well as two offices at Kassel City Hall. Cooling
is achieved in the rooms passively by day, and cold water
flows through the cooling ceilings at night to regenerate
Cooling ceiling with PCM in a lecture
theatre at Stuttgart University of Applied Sciences.
The cooling ceiling elements have been installed in
such a way that they can be pulled down and easily accessed.
Solar protection with PCM
Inside solar protection systems are implemented over large areas
(no wind loads, cost-efficient), but have a higher energy yield
(g-value) in comparison to outside systems. In addition, irradiation
heats up inside systems to such an extent that people near to
the windows feel uncomfortable due to the heat radiating from
the blinds. This problem can be remedied using inside solar
protection with PCM. The advantages are lower blind temperatures
and reduced heat input into the room. Enough PCM is used to
completely buffer a south facade on a sunny summer's day. The
PCM is regenerated over night by the cool outside air.
Calculated frequency of functional room temperature in a
large-scale glazed office with coated glazing and solar protection
with (blue) and without (red) PCM. The PCM clearly reduces
the hours with high room temperatures.
Solar protection systems using PCM have been installed in
four offices (two in Kassel City Hall and two in the EnBW
building in Karlsruhe). The solar protection system consists
of vertical blinds; there is an approx. 1 cm thick layer of
PCM in each of the slats. Operation is purely passive - the
PCM blinds are used in the same way as conventional blinds,
yet absorb excess solar radiation. The PCM is regenerated
at night by cool air (from outside ventilation flaps or tilted-open
PCM solar protection in an office in Karlsruhe