Solar hot water heater with seperated panels and a vertical tank system.?
Question by : Solar hot water heater with seperated panels and a vertical tank system.?
In a solar hot water system where the solar panels are placed on the roof but the collector is placed on the ground, how much energy is required to pump the heated water from the panels on the roof to the collector on the floor?
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3 Responses to Solar hot water heater with seperated panels and a vertical tank system.?
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In a convection loop, no energy will be required, as the cooler water in the tank will thermosiphon to the collector.
You would only have to pump it if the exit temp from the collector is lower than the temp of the bottom of the tank – and then you would not want to.
redbeardthegiant
April 20, 2013 at 8:45 am
Since the panels are on the roof, you cannot use convection because your warming the water at the highest point in the system. You will have to use a small water pump to circulate the water. The size of the pump will depend if this is a drain back system or not. Drain back systems use a larger pump to fill the piping during the day when the sun is warming the solar collectors. At night the outside pipes are allowed to drain into a storage tank to prevent freezing and heat loss.
If you use a sealed loop with antifreeze in it you can use a smaller circulate pump to move water in the loop. A flooded loop has a siphon effect where the water moving down from the top helps to draw water up to the top thus a smaller pump can be used to move the water. A drain back system needs a larger pump because it need to fill empty pipes and doesn’t have the benefit of an established siphon until the pipe loo becomes completely flooded. As such a flooded loop circulator pump can operate with as little as 1/40Hp (one fortieth of a Hp)
The use of temperature sensors and variable speed pumps will also save on operating costs by controlling when and how fast a pump operates.
Mark G
April 20, 2013 at 9:32 am
Depending on the distance the collectors are from the tank, and the size of the pipes, a Taco 006 is often used. It is a 1/40th HP pump and draws 60W. http://www.altestore.com/store/Solar-Water-Heaters/Solar-Hot-Water-Circulator-Pumps/Ac-Pumps/Taco-140-HP-Bronze-Pump-34-115-VAC-006-B4/p122/
An alternative is to use a DC powered pump, like the Laing D5, and have it run off a 10 – 30W PV panel. http://www.altestore.com/store/Solar-Water-Heaters/Solar-Hot-Water-Circulator-Pumps/Dc-Pumps/Laing-D5720B-PV-Circulating-Pump-sweated/p6065/
Amy
April 20, 2013 at 10:10 am