IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask C1 Report, 31 October 2010
condenser temperature is low enough as the COP value increases. This correlation is used
for the controlling concept of a SJEC and leads to the fact that the COP value of a SJEC
depends predominantly on the condenser temperature. Furthermore, the COP value
depends on the evaporator temperature as well. Figure 35 shows the influence of the
condenser and evaporator temperatures on the COP value of a SJEC.
COP [-]
2,5
2
1,5
1
0,5
0
Evaporator temp. 7°C
Evaporator temp. 13°C
Evaporator temp. 17°C
0 10 20 30 40
Condenser temp. [°C]
Figure 35: COP value as function of the condenser and evaporator temperature.
The COP value of the SJEC increases as the condenser temperature decreases or as the
evaporator temperature increases. The condenser temperature is related to the cooling water
temperature. The evaporator temperature is related to the chilled water temperature and may
be raised when the cold load is lower. This means that at lower ambient temperatures or at
part load the COP value of the SJEC increases. In view of a typical cold load curve for a
comfort cooling system, which is characterised by long operation periods at low ambient
temperatures and at part load of the system, a good mean COP value of SJEC can be
expected.
7.3 Research and development
There are many companies producing steam jet ejector chillers for industrial use. This
technology is currently used for large continuous flows of chilled water in industrial
applications. As it is a well established product, there is no necessity in listing down the
companies that manfucture these products in this report.
Until now, it is not known whether any solar driven steam jet chiller has come into the market
as yet. However, there have been some test rigs and prototypes developed and tested. In
1966 Kakabaev and Davletov described in [182] a first test rig with a cold capacity of 1 kW th
with a total efficiency between 0.11 and 0.22. The motive heat is provided by a parabolic
mirror sized 12 m². Freon is used as the working fluid and refrigerant. Huang, Petrenko and
Chang describe in [183,184] a solar SJEC combined with flat plate collectors and R-141b as
refrigerant. The temperature of the motive heat is 95 °C and the system reaches a total
efficiency of 0.22 at a solar irradiation of 700 W/m². In [185] Wolpert and Riffat present a 7
kW test plant for air-conditioning of a hospital in Mexico. Water is used as the working fluid
and refrigerant. In [186], a small test rig is described and its operational behaviour
investigated. The SJEC has a cold capacity of 1 kW th and is solar thermally driven by a
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