The Sonntlan Mexicali Solar Cooline Proiect
The Solar Cooling project Pilatowsky et al. (1992) consisted of six one-family houses, five attached to each
other and one separated all that incorporated passive elements for reducing the cooling load and a machine
tower containing components of the active solar system. The collectors were installed on the roofs of the
houses. The reduced cooling load of 7 kW (against a typical value of 18 kW for a normal house in
Mexicali) was provided by a 90 kW ARKLA-WFB 300 solaire lithium bromide / water absorption chiller.
The chilled water was first delivered to a cold water storage tank and then distributed to air handling units
installed on the upper level of each house. Table I shows the technical data for the system. During 1983 the
houses were not yet occupied and system operation was for test purposes only. A modification of subsystem
components based on the operational experience of 1983 and 1984 was completed by the end of 1985. The
modifications included decentralisation of air handler control, replacement of control computer capable of
withstanding the severe environmental conditions in the machine tower, bypassing of the heat exchanger
between collector area and hot water storage tanks, elimination of parts of hot water and chilled water
tubing. These modifications increased the overall collector field efficiency from 26 to 29%. The yearly
solar fraction increased from 59% in 1985 to 75% in 1986, as shown in Figure 13. The efficiency of the
chiller varied from 53 to 73%. For reasonable operating hot water inlet conditions of 75-95 ‘C, cooling
water temperatures of 29 to 32’C and chilled water temperatures of 8 to IO’C the steady state efficiency
showed almost constant figures of about 69% and daily efficiencies of 64%. From 1984 to 1986 the major
part of the houses were inhabited continuously and cooling service was provided to the houses. Inside
conditions were regularly kept within a comfortable range of approximately 26-280C and 50% relative
humidity even during the extreme hot season with outside highs of 42- 48oC.