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Solar Energy
Solar refrigerator with ice bank
4
RESEARCH AND DEVELOPMENT
The refrigerator body, capable of storing
10 kg ice in annular space around the
evaporator compartment was fabricated
and tested under no-load condition.
However, the ice compartment was
found to have accommodated 26 l water
when filled to capacity. The temperature
of the water dropped from initial 31.1°C
to final –5.2°C in 64 h of compressor
operation. The ambient temperature
during the period varied from 23.2 to 38.7
°C. Besides, another refrigerator of 80 l
capacity was modified to use one of its
two storage compartments as ice chamber
by providing evaporation coil, which was
kept submerged in 10 l water filled in the
chamber. The water was converted into
ice in 40 h of the compressor operation.
Thereafter, the compressor operation
was switched off and temperature upto
5°C was maintained in the refrigerator
for three successive days.
It was found that a special electronic
controller, which works in a voltage
range of 10 to 45 V DC and is equipped
with soft start function to significantly
reduce the starting current, is available.
The controller will be able to operate the
Danfoss BD compressor (fitted with our
refrigerator) without requiring storage
battery(s). The controller was procured
and fitted with the modified refrigerator.
The refrigerator was tested with direct
PV panels of 150 Wp capacity without
storage battery(s). During 9:00 a.m. to
5:00 p.m., the compressor run time was
found varying between 2 to 3 hours only.
The temperature of the water dropped
to 0°C, but there was no ice formation.
The matter was taken up with M/s
Danfoss, Germany and they provided
a new controller unit. The refrigerator
fitted with the new controller unit was
tested with direct PV panels of 180
Wp capacity. Besides, the refrigerator
was equipped with an aluminium tray
containing the evaporator coil, which
was submerged in 4 l water filled in the
tray. Temperatures of the water and the
storage space and ambient temperatures
were measured at every 15 min interval.
The compressor operation started around
9:30 a.m. and continued uninterrupted upto
4:15 p.m. Around 3.25 kg of ice was found
formed in the tray by 4:15 p.m. Overnight
(upto 9:00 a.m. next morning), around 2.20
kg of ice melted and temperature inside the
storage compartment varied between 5 °C
to 8 °C. The next day by 4:15 p.m., all the
4 kg of water in the Al tray was converted
into ice. Further testing of the refrigerator
without battery is under progress.
Solar PV panel
180 Wp
Electronic controller
10 and 45 V DC
Circuit diagram to connect the PV module
to Electronic controller