Solar-desiccant air-conditioning systems - Solar Energy Sciences and Engineering Applications - page 532

manometer

pyranometer

orifice
plate
solar air
heater

evap. cooler

auxiliary
heater

ambient
air

20 °

sol. integ.

amb. air

venturi
meter

desiccant
wheel

thermocouple

heat
exchanger

d.b. thermometer
w.b. thermometer

Figure 16.5.5 Solar-desiccant air-conditioning system ( Joudi and Madhi, 1987).

compared to the conventional system. One of the problems encountered is the diffi-
culty of controlling air humidity and temperature due to the heat exchange and coolant
flow to the evaporator. Camargo et al. (2005) looked at the application of solid des-
iccant air-conditioning systems in Latin America and in tropical and equatorial cities.
This system comprises a desiccant wheel and evaporative cooler and was shown to
be applicable as an alternative to the vapour compression system since it can provide
human thermal comfort conditions.
Dupont et al. (1994) showed that a silica compact-bed desiccant air-conditioning
system powered by solar energy in the tropical climate of Guadeloupe can produce
cooling power. However, the system is not efficient due to losses. Hamed (2003) inves-
tigated the packed porous bed with burned clay as desiccant carrier, and desiccant
impregnated with liquid calcium chloride. He showed that the mass transfer rate had
a significant effect on the concentration gradient in the bed. Jain et al. (1995) inves-
tigated the solid desiccant air-conditioning system in 16 Indian cities, showing that a
cycle with a wet surface heat exchanger gives a higher COP than other cycles. The
Dunkle cycle has been found to be better in all climatic conditions. Heat exchanger
effectiveness of above 0.8 is desirable for better performance of the cycles not using a
wet surface heat exchanger. The effect on COP of the evaporative cooler is insignificant
but it can control the room sensible load factor. Joudi and Madhi (1987) investigated
the applicability of the solar desiccant air-conditioning system in Basrah, Iraq (Figure
16.5.5). For the local weather conditions, they showed that a regeneration temperature
of 70 ◦ C can be provided using solar energy in clear skies. Kabeel (2007) investigated
the application of the calcium chloride desiccant wheel constructed from iron wire and
a cloth layer. The system uses sole solar energy for the regeneration of the desiccant.
Tested in the climate of Egypt, the system had a high performance after the solar noon,
with the wheel's effectiveness dependent on solar radiation and air flow rate.
The tri-generation plant installed in Politecnico di Torino (Italy) was developed to
support the air-conditioning system shown in Figure 16.5.6 (Badami and Portoraro,
2009). The layout of the system, presented in Figure 16.5.7, shows the internal combus-
tion co-generator, open-cycle absorbent air-conditioning system, cooling tower, two