is my 800w pool pump overkill for solar project

[barnsley]

I have 300ft of half inch PVC pipe (i used PVC pipe because in UK its the cheapest option: about $100 for 300ft and about the same for 100ft of rubber hose).

I am putting it on my shed roof 8ft high with a 800watt pump (53 Litres/min or 11 gal/min and 40m or 120ft of head).
I'm Tee-ing off half of it back to the pool (after its all gone through a commercial solar power heater from Athena (only holds 8 litres or 2 gallons of water in a spiral dome) - as that likes at least 2,000 Litres/hr or 7.5 gal/min). So my solar contraption of 300ft hose pipes will get a flow rate of around 5.5 gal/min.

My pipes from the pool start at 32mm or 1 and 1/4 inch which reduces down to 1inch inlet for the pool pump. At the top of my shed I will use a T junction and half inch will go to through the solar pipes and half inch back to the pool.
I'm concerned that my pump might be too fast and too powerful for what i need?
And also not sure of any benefits of re-joining the two half inch pipes back to a 25mm or 32mm (inch or 1.25 inch) pipe before going back to the pool.

I've heard that 1-2 gallons per minute is a good flow rate to minimise friction loss?
But also heard that a higher flow rate is better due to less radiant heat loss?

[foo1bar]

So my solar contraption of 300ft hose pipes will get a flow rate of around 5.5 gal/min.

Unless you've actually measured, I wouldn't rely on things splitting the way you *think* they will.
It's very difficult to correctly determine how much flow goes each direction on a split - lots of variables that can affect things.

I think a higher flow rate is good - less temperature delta increase per gallon of water, BUT more water means more overall heat gain for the pool.
(within reason of course - at a certain point, you're putting more energy into pumping than you're getting in solar gain.

[barnsley]

Your right, so many variables and here's what I measured today.
Pool temperature morning 22°c.
air temperature about 20°C.
Pool temperature in afternoon 24.
Solar cover on througout.
50% sun all day.

280ft solar system (pvc hose in frame covered with polycarbonate). 8.2L per min or 180 gallons per hr. - gave about 1.2°c rise in temp and at that rate I'd only be able to turn over half of my 1700 gallon pool in 8 hrs.
The other side of the T which goes through a small and poor commercial Athena solar heater outputted the following:
31L /min
or 415 gallons/hr
about 0.25°c rise in the output

[barnsley]

Have to say I'm a bit disappointed with my results after so much effort. Ive also got a rain cover on for night and have wrapped the pool in black bin bags.
if I can keep temperature fairly constant throughout the night maybe I could increase the temperature another notch. But can't help but think that most of the pool temp rise today was down to the pool cover.
I also tested it without the cover on and didnt notice much difference in results - about 1°c rise at the output

[Mike90250]

Line the inside (water) with black plastic to absorb more energy. Insulate the outside to retain the heat, and use a "bubble pack" style pool cover to insulate

[Logan5]

this solar contraption, you made this yourself? or purchased? how many of them, cause given the volume it holds, your going to need a lot of them to make any difference in the temp of your pool water. You should not buy anything more until you have a better basic understanding of the science involved. Thermodynamics, fluid dynamics, insulation and so on.

[J.P.M.]

this solar contraption, you made this yourself? or purchased? how many of them, cause given the volume it holds, your going to need a lot of them to make any difference in the temp of your pool water. You should not buy anything more until you have a better basic understanding of the science involved. Thermodynamics, fluid dynamics, insulation and so on.

+1 .

[foo1bar]

use a "bubble pack" style pool cover to insulate

I haven't done the calculations - however what I have read is that it's not really "insulate" as much as "reduce evaporation significantly" (and avoid the heat losses due to that evaporation.)

I have a large pool cover - but it's so much work to take on/off that I haven't used it in a while - so I'm thinking about getting some of those rings.

[barnsley]

I made some of ur myself and bought another solar heater. Mine increases temp by 1°c + ir 3°f and the one I purchased is four times less effective.
I'm kinda learning on the job because everything I've done works in theory from the research I've done.

[barnsley]

Line the inside (water) with black plastic to absorb more energy. Insulate the outside to retain the heat, and use a "bubble pack" style pool cover to insulate

thanks.
how do you get the plastic to stick to the inside?

[foo1bar]

the one I purchased is four times less effective.

No!

It does 415 gallons/hr with .25 degree rise
vs. your 180 gallons/hr with 1.2 degree rise.

415 * .25 is about HALF (not quarter) of 180 * 1.2.

Your goal is to increase temp of entire pool - so you need to look at entire amount of heat gained so you should multiply by number of gallons/hr.
Another way to look at it - if you sent the same 100 gallons through the commercial one 4 times in an hour, you'd have about a 1 degree rise.
If you recirculate 100 gallons through yours, you'd get about a 2 degree rise.

[barnsley]

Yes you're right. I stand corrected mine is not 4 times better. An oversight on my behalf.

First time I searched for black hose pvc looked like the cheapest I could find. Now I've discovered some polyethylene which is even cheaper! I'm curious to know what % difference I'd get with this material instead.

[Mike90250]

don't need to stick the plastic to anything inside, could even use black trash bags, weight them with a rock, The black absorbs more heat than the common pale blue liner

[Logan5]

I wonder if you could order a darker liner, either black or dark blue, either when replacement is necessary or when buying a new above ground pool.. I know with in ground pools they make a dark sapphire color masonry finish, that many use in colder environments.

[barnsley]

thanks, but I don't think a darker liner is an option. It's a shame they don't sell black (maybe it would be a problem in hot countries to do this?).
I'm coming to the conclusion that there might not be enough sun in the UK (3-4hrs per day average). When I get full sun I can warm up the pool by 4°C (or 7°F), but lose 3°c (5.5°F) overnight.
That's with a solar cover and a rain cover on top of that.

[barnsley]

Plan B -
I've also put 300 ft of polyethlyene hose on the other side of the T instead of going to the pool - and this also outputs 1°c higher along with the the PVC hose. Although I've not covered up this hose yet from the wind. So Plan B is to wrap this up with some leftover solar pool cover (400 micron).

Plan C -
To put the polyethylene hose into the shed (south facing window - so it gets warm in here) and cover the back of the 300ft hose all around with black sheets to keep the warm air in.

Plan D -
A wood burning stove! - Ok, it might cost a bit for fuel, but I'll try and use salvaged wood where possible.
I'll use a 45 gallon oil drum (cost about £10 or $13),
20m (60ft) - copper coiled pipe: £60 ($80),
T - off 1inch pipe from pump into 2 half inch copper pipes into the wood burning incinerator and then back to the pool.
(or maybe 3 x 8mm copper pipes would be better, but just means more T's and connections etc)