Environmental Engineering Reference
In-Depth Information
Plant modifications were necessary in order to avoid the harmful effects of emergency
plant shutdown due to power failure.
8.1. Heat Collecting System
8.1.1. Cleaning the Solar Collector Field
The performance of the solar collector field is affected by the extent of dust deposition on
the glass tube which influences the transmittance of the glass tube to solar radiation. It is
therefore important to clean the collector field at regular intervals to maintain good
performance. The cleaning was carried out using a high-pressure water jet spray device. Since
fresh water is used for cleaning, it is important to economize on the use of fresh water for
collector cleaning without adversely affecting the performance of the collectors.
The amount of water required for each cleaning session depends on the extent of dust
deposition on the collectors; more water is required when more dust has accumulated on the
collectors. Since sandstorms are seasonal in character, the amount of dust deposited in a
particular period depends on the month of the year. Several tests were carried out to
determine the required amount of fresh water needed for each collector block. Figure 20
shows the measured water quantity used for each cleaning session for one block for different
months. As can be seen, there is wide variation in the quantity of cleaning water required
which may be attributed to variation in the personal skills of the different cleaners as well as
variation in the amount of dust deposition on the glass tubes. The average quantity of water
for each cleaning session is about 1000 liters.
Figure 20. Water quantity required for cleaning a single block for different months.
8.1.2. Corrosion of the Collector Air Vent Valves
A total of 76 air vent valves were installed on the arrays of solar collectors to vent the air
out during the water filling up process. Water started to leak from these valves after few
months of operation and several valves have to be replaced with spare ones. Because of a
limited supply of vent valves, few of the leaking valves have to be plugged as a makeshift
measure until new valves are procured, a procedure usually taking several months due to
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