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Cascade
Tank Arrangement
| Storage |
For the
large open loop installations two or more tanks may be connected
to the collector arrays as shown. |
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How
the system works
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Depending on
temperature level of tanks, pump 1, 2, or 3 will run. If
water temperature in the tank 1 is lower than a setting point Ts1
(T1 <= Ts1), only pump 1 is running. Whenever the tank 1
setting point (T1>Ts1) reached, pump 1 stops and pump 2 starts.
Once tank 1 and tank 2 have reached their set points, pump 3
starts and so on.
The advantages of the connection are:
1) The preheat tanks can be easily isolated for the purpose
of maintenance. This is very important for commercial hot water
supply systems.
2) Temperature levels for preheat tanks can be easily
controlled. The developed thermal stratification from tank to tank
can reduce heat losses and subsequently, improve the performance
of the entire solar energy system.
It should be noticed that for commercial hot water service
systems standby pumps are normally required, which means more than
three water pumps may be needed for the solar system with three
storage tanks. |
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Recirculation
Loop
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Recirculation
loop approach is suitable for existing commercial hot water
service systems, for instance, in hotels, sport clubs, hospitals,
and schools, etc. A solar collector subsystem can be integrated
into the hot water return loop. The schematic diagram of the
layout is presented below. |
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Hot water
return from the load in the ring main loop is diverted by a
three-way motorized valve, depending on the temperature
difference Tc (collector temperature) and T (water temperature
return from the load), Tc - T. When the temperature difference
is higher than a preset point, water from the load will be
passed through the collector loop and then flows into the
storage tank. Otherwise, the motorized valve will divert water
from the load directly into the storage tank.
During potential freezing conditions, for instance,when the
temperature drops below 2 ºC , the system controller can
energize the collector pump to cycle water through the collector
loop. |
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| Simplified
Recirculation Loop |
The only
different thing in the system is that water in the bottom part
of the storage tank is circulated to the collector by the
collector pump, when the temperature difference Tc (collector
temperature) and T (water temperature in the bottom part of the
tank) is higher than a presetting point. |
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