Environmental Engineering Reference
In-Depth Information
was planned due to unexpected power failures and pump troubles. The average
concentration of the chemical in the collector water during the first year of operation was
approximately 2,8000 ppm. Table 13 shows the results of analysis of the heat collecting
water of four samples taken during the first year of operation. It can be seen that there was
virtually no change in the total Fe content indicating an adequate anticorrosive effect for
Fe. On the other hand, the Cu content tended to increase gradually as the concentration of
the anticorrosive chemical drops. The thickness of the copper tubes corroded in the solar
collector field was estimated at 0.001 mm/year[5].
Table 13. Chemical analysis of heat collecting water
Sampling data
31 Jan. 85
27 Mar. 85
30Jul. 85
21 Oct. 85
pH
8.6
8.5
7.9
8.2
209
210
373
242
Conductivity (μS/cm)
Temperature (
o
C)
-
20
28
18
M Alkalinity (ppm as CaCO
3
)
526
486
468
452
Total hardness (ppm as C(ppm)aCO
3
)
22
8
20
4
Chloride (ppm as Cl
-
)
37
21
44
33
Silica (ppm as SiO
2
)
1.3
2.0
1.9
2.8
Total iron (ppm as Fe)
1.6
1.82
1.1
1.4
Copper (ppm as Cu
++
)
0.55
0.62
1.8
2.83
Total Nitrogen (ppm as N)
217
177
156
161
High-Clean CL-100
5,167
4,214
3,714
3,843
8.1.6. Measures against Power Failure
The original plant design was such that in the case of a power failure during the day, the
heat collecting pump stops and the water in the collectors, subject to solar radiation,
evaporates resulting in dangerous water hammer in the header pipes. In order to protect
against such power failure, the solar field piping system was modified by installing three
motorized valves (normally closed) on three 25 mmφ lines, one motorized valve (normally
open) on the 125 mmφ on the outlet piping of the heat collecting pump and a check valve on
the 125 mmφ on the return header pipe from the collector field to the accumulator. The
modifications are shown in figure 21. In the modified system, following a power failure, the
three 25 mmφ motorized values will be open thus draining all the water in the collector field
and the 125 mmφ motorized valve in the pump outlet will close thus preventing the collector
water from flowing by gravity from the heat accumulator to the collector field. The modified
system proved effective in protecting against the hazard of evaporation in the collector field.
The collector field so not automatically restart following the restoration of power and the
valves has to be rest manually by the operator.
Search WWH ::
Custom Search