Machine-History.Com

March 2011
Although differing in technical maturity and commercial
status, the various solar refrigeration technologies discussed
in the previous sections are compared in terms of performance
and initial cost. The three last columns indicate
the specific cost of photovoltaic solar panels, the
specific cost of thermal solar collectors plus specific engine
costs and the specific chiller cost, respectively. Since the existing
chillers based on these technologies differ widely in cooling
capacity ranging from a few tens to several mega Watt, the
efficiencies and the unit cost values assumed are
those of the smallest machines available from the different refrigeration
technologies. It is also noted that solar collector efficiencies
listed in this article are only indicative and will
depend on ambient air temperature and solar radiation.
Solar electric systems are assumed to be equipped with
10%-efficient solar photovoltaic panels with a unit price at
€(euro)5/Wp (Solar Rechner). These solar panels convert a solar radiation
of 1000 W/m2 into 100W of electricity and the various
electric chillers transform this electric energy into cooling
power according to their specified COPs. As shown in the figure,
only magnetic chiller is comparable to vapour compression
chiller in terms of solar panel cost. No other electric
cooling technology is currently competitive with compression
refrigeration technology in terms of total cost.
In order to generate the same amount of electricity,
a thermo-mechanical system needs a high-temperature solar
thermal collector and a heat engine. In the efficiency of a solar collector is assumed 50% at 200 °C and that of a heat
engine is assumed 20% (56% second law efficiency). Among
non-tracking solar collectors, a Sydney type collector, which
is evacuated tubes with cylindrical absorbers and CPC concentrators
(ca. V600/m2, Collector Catalogue, 2004), may satisfy
this application. As shown in Fig. 8, the cost for a thermomechanical
system is far larger than that of an equivalent
solar electric system even without the engine cost. A solar
thermo-mechanical system is not likely to be cheaper than
a solar electric system in terms of operation cost either.
Among the solar thermal systems shown in Fig. 8, a
double-effect LiBr–water absorption chiller requires the highest
driving temperature at 150°C. A 50%-efficient evacuated
tube collector at this temperature would cost approximately
€550/m2 (Collector Catalogue, 2004) and a double-effect
LiBr–water chiller costs ca. €300/kWcooling (Peritsch, 2006).
All the rest of the thermally driven chillers are equipped
with a 50%-efficient flat collector at 90 °C, which costs ca.
€250/m2 (Collector Catalogue, 2004). The cost of a single-effect
LiBr–water absorption chiller is estimated at ca.(€)400/kWcooling
(Peritsch, 2006) and that of a single-stage adsorption chiller is
estimated at about (€)500/kWcooling (ECN, 2002).
Although an ejector chiller would cost less than the other
sorption chillers, its low COP would cost more for solar collectors.
A desiccant system would also cost more than the other
sorption systems due to the need of handling large quantities
of air and water. The double-effect LiBr–water absorption and
the single-stage adsorption systems are comparable in terms
of total cost at around (€)1200/kWcooling. The total cost of a single-
effect LiBr–water absorption system is estimated as the
lowest at (€)1000/kWcooling.

D.S. Kima, C.A. Infante Ferreirab
See article http://www.machine-history.com/Solar%20Powered%20Air%20Conditioning