Direct solar pv pump vs solar controller and pump

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C

Caco

0
Dec 27, 2015
445
Hawera, Taranaki, New Zealand
Hi all
I have a homemade solar sytem I use to heat the pool
It currently works off of an old intex pump to circulate the water, on its own plumbing loop and I currently turn it on in the morning and turn it off at night

I have approx 100sq ft of panels, about 6 ft away from the pool level with the pool floor. Eventually I would like to move them to about 15 ft from the pool and approx 8ft high

The problem is I think a lot of the time I might actually be cooling my pool when clouds come over or it rains in the afternoon. Or I leave it off for the day because it is raining and then at 10am we get sunshine for the rest of the day and I miss out on 8+hrs of sunshine :(

So I looked into hooking up a solar controller and was horrified at the price, the cheapest I could find was just over $500

I was thinking why not replace the pump with one that was directly driven by the solar panels, like those little fountain pumps you can get. I thought this may be a cheaper option

Is this possible and if so what pump specs would I need?
 
Solar cooling your pool or missing out on heating is a valid concern. I definitely had days where those things happened before I got a solar controller. And my heat gain noticeably improved after. The Hayward GL-235 and the Pentair Solartouch are the two cheapest ones. A solar powered pump isn't a bad idea but I don't know a thing about them.
 
I am missing something. What problem would a solar powered pump resolve?

The little pumps that move solar water are not big power hogs - typically only a few amps at the most.

To run a pump directly off solar requires a controller to smooth the voltage from solar PV panels. The cost of a DC pump (which is what you would require), plus the solar PV panels, plus the requisite MPPT controller would more than likely exceed 1,000$...

Maybe I am misunderstanding your purpose here.


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I think the theory is that when the sun is shining (solar heat is available) it will pump water to solar and when it is cloudy (solar heat not available) it won't pump water to solar.
 
Yeah pooldv you got it. Basically I end up using the solar panel as the controller. Sun shines on panel, pump starts, no sun on panel, pump stops

One of the systems I was looking at had max 2.5m lift, 1500l/hr (8ft, 400gal/hr) and only costs $150, with obviously no ongoing running costs. This one here in fact http://www.trademe.co.nz/home-livin...naments/water-features/auction-1195866926.htm


Not sure if that would be enough flow for my system
 
The problem I guess I am trying to solve is a cost problem. I have no issue with spending 150-200 but 500+ is too much

As for the prices pooldv quotes, yep I can get the similar price off of amazon too. I saw a Hayward GLC-2P-A Solar Pool Heating Control System with 3-Way Valve, Actuator and 2 PC Sensors, at $262 US that would ship here. Currency conversion brings it to $371, shipping $42 (6 week est), import fees est $120 so total cost $538. Controllers from retail stores locally are approx $950.....
 
Caco said:
One of the systems I was looking at had max 2.5m lift, 1500l/hr (8ft, 400gal/hr) and only costs $150, with obviously no ongoing running costs.
Click to expand...
Usually, those specs are where you get either maximum lift with no flow rate or maximum flow rate with no lift but you don't get both at the same time. So you probably won't get 400gal/hr at 8' lift. But even if you did get 400 g/hr, 6 GPM is really slow and would only be sufficient for panels that were less than 60 square ft (0.1 GPM/sqft).
 

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That is not how solar pv pumps work. You need a different type of controller for pv vs solar hot water.

A solar pv pump runs on voltages that range from about 40 to 100 V. They are DC pumps, but require a controller in order to run - you cannot just take a solar PV panel and connect it directly to a DC pump. Again, I think I am missing something.




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Hi tlevy
There are systems on the market, where you can do just that
PV direct from array and only operate when teh sun is shining. There is no need for batteries, charge controllers or inverters. They are often used for irrigation, livestock tanks, off grid water supply etc.

However the pumps used for irrigation would produce too much pressure for my solar panels and the ones used for fountains/waterfalls are cheap but too low in flow for me. So that idea is not going to work.

Here is one of the oversized systems I referred to above. There are many others available
http://www.solardyne.com/solsoldirwat.html


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This has come up before and you're not alone. It's really challenging to run it manually and get the most from your system.

For AU$299, this might be worth checking out - PoolMasterpro2 - Automatic Pool Heating Controller by Dontek - EcoOnline

I have this and while it's very simple, it does the job for me.
When roof sensor gets more than 8C above pipe temp, it samples by running the solar circuit for 3 mins
If pipe temp is still 8C less than the roof sensor, it continues running
If roof temp shows less than 8C hotter it stops (like clouds obscuring the sun)
Repeats as conditions change
Once pool temp setpoint is reached, it goes into a 4-hour wait before re-sampling
Also has winter mode (3 minute flush once per day)
Also has tropical mode (heats same as above, but cools the pool when possible/necessary)

I did my solar on a separate circuit with an AU$260 pump, so that pump just plugs into the controller. A booster pump and check valves would also work.

Good luck with your project :)
 
Caco said:
Hi tlevy
There are systems on the market, where you can do just that
PV direct from array and only operate when teh sun is shining. There is no need for batteries, charge controllers or inverters. They are often used for irrigation, livestock tanks, off grid water supply etc.

However the pumps used for irrigation would produce too much pressure for my solar panels and the ones used for fountains/waterfalls are cheap but too low in flow for me. So that idea is not going to work.

Here is one of the oversized systems I referred to above. There are many others available
http://www.solardyne.com/solsoldirwat.html


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Click to expand...

That is exactly my point - I agree. I have a solar PV direct pump - but you still need a controller (MPPT), and additional solar (PV) panels. The cost of such a system, in excess of the solar hot water system (manifold, collectors and controller), would be in excess of 1K.

My solar PV direct pump and controller cost me 1,500$, excluding the 1.5 kW of PV needed, plus associated racking and balance of plant electrical wiring etc.

I guess I am confused at what the overall objective is here....


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When you say "solar panels" you are talking about the hot water collectors? That requires a controller for heat differential, not a PV (photovoltaic) controller. The PV option is expensive, and will not resolve your issue. For example, there are many days when there is enough energy from the sun to run my PV-powered pump, but not enough sun irradiance to yield large temperature gains in a solar hot water collector....


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