There is a common misconception that solar pool heating increases the energy needed to operate a pump. That is NOT true!
It’s true that solar pool heating systems will increase the back pressure on your pump. On a single speed pump, that means your flow rate will be reduced. However, it also means that your energy consumption will be reduced. Without having a degree in fluid dynamics, you make be wondering how a pump can use less energy if the pressure is increased! The short answer is that the pump is doing LESS work – it’s moving less water.
This is a simplistic explanation of how a pumps energy requirements relate to the flow rate and system pressure, but suffice it to say that at a constant pump speed, less flow means less energy consumed.
Here is a little video I put together to show a real system in action.
Now, since you are reducing the flow rate with solar pool heating on, you would need to run your pump for a longer period of time to achieve the same turnover/filtration of your pool water. The net result would be no energy savings or loss for the same turnover each day.
Hi
I would like to ask in the winter months, I use the pool solar panels to heat the hot tub. Since the winter months have less sun and ambient temp is less
Is there a possibility that if the flow rate was slowed down the collectors may be quicker to heat?
I just recently purchased a variable speed pump and maybe use the slower pump motor cycle to collect more heat?
Thanks for your time.
Pete
Peter,
I wrote a post on this very subject a few months ago. It’s a common misconception. See:
http://www.solarsouthwestflorida.com/solar-pool-heater-optimum-flow-rate/
Unfortunately, your concept of decreasing the flow rate is exactly opposite of what we want to see happen. As water gets heated in a solar pool heated panel, the efficiency of the panel (the ability to transfer heat to the water) decreases. What results in the best efficiency is a large relative difference from the panel surface temperature and the water temperature. That means colder water in the panel makes it more efficient, and that is achieved with a higher flow rate (to an extent).
The manufacturer recommended flow rate for maximum annual yield is 4 gallons per minute per panel. Most manufacturers’ panels fall into a similar flow rate range.
Good question – and thanks for asking!