Environmental Engineering Reference
In-Depth Information
Table 15.3.1
Summary of cooling and energy performances of principal solar-thermal air-conditioning
systems.
Year-round
Energy saving vs.
total E
p
per
corresponding
Type of solar
Year-round
Year-round
AC area
ACVCC/
Type of system
collectors
averaged SF
averaged COP
(kWh/m
2
) WCVCC
Solar absorption
refrigeration (RA)
Flat-plate
collectors
0.497
0.769
371
4.4%/2.2%
Evacuated tubes
0.818
0.763
252
35.1%/33.6%
Solar adsorption
refrigeration (RA)
Flat-plate
collectors
0.313
0.435
657
−
69.0%/
−
72.9%
Evacuated tubes
0.577
0.437
478
−
23.0%/
−
25.9%
Solar desiccant
cooling (OA)
Flat-plate
collectors
0.336
1.066
762
−
11.0%/
−
14.8%
Evacuated tubes
0.552
1.059
653
4.9%/1.5%
ACVCC (RA)
NA
NA
2.859
389
NA
WCVCC (RA)
NA
NA
3.195
380
NA
ACVCC (OA)
NA
NA
2.802
687
NA
WCVCC (OA)
NA
NA
3.177
664
NA
Remarks:
1. RA refers to the return air scheme, in which a conventional air handling unit is applied with return air and
outdoor air mixed together to form the supply air for the building zone.
2. OA refers to the outdoor air scheme, in which the air handling unit takes the full outdoor air to form the supply
air for the building zone.
3. NA means not applicable.
and this merit can guarantee good indoor air quality and ventilation effectiveness.
Therefore the application potential of solar desiccant cooling remains valid.
15.3.2 SHAC with load sharing
The SHAC system (i.e. the principal SHAC) with load sharing has been introduced in
Section 15.2.3.1. In the study by Fong et al. (2010b) the absorption chiller is designed
to handle the zone cooling load of the office building, while desiccant cooling tackles
the ventilation load. Solar-thermal gain is used to drive both the related refrigeration
cycle and desiccant unit. The performance results also cover the year-round averaged
zone temperature (T
z
) and zone relative humidity (RH
z
), the coefficient of performance
of chiller (COP
ch
) and the coefficient of performance of desiccant cooling (COP
dc
), as
summarized in Table 15.3.2. As described in Section 15.3.1, evacuated tubes are more
effective than flat-plate collectors in hot and humid climates, so only the former type
is involved here.
Compared to the year-round primary energy consumption of conventional
ACVCCs and WCVCCs shown in Table 15.3.1, the SHAC-Ab system with load shar-
ing clearly gives substantial savings of 36.8% and 35.3% respectively. Although the
primary energy consumption of the SHAC-Ab system is only 2.4% lower than that of
solar absorption refrigeration shown in Table 15.3.1, the SHAC-Ab system has tight
control of the design zone temperature and relative humidity. While the SHAC-Ad
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