is my 800w pool pump overkill for solar project

[J.P.M.]

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.

As a real loose 1st approx., pool heat energy loss, as manifested by pool water temp. decrease, is about, very roughly, evenly split between conduction losses and evaporative losses. If the cover has standing, accumulated liquid on top of it, the effectiveness of such a cover will be reduced somewhat due to the evaporation of the that collected rainwater that takes place just like that of an uncovered pool, with less evaporative loss as the insulating value of the cover (thickness/bubble size) increases.

[Mike90250]

For a water coil in a burner, don't use copper, it will erode both inside and out, and fail in a spectacular manner.
Get a stainless steel coil and be sure the water flow never fails

[J.P.M.]

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)

Unless you know as much as a seasoned boiler designer, this is a bad idea for more reasons than I've got time to explain. Don't do it. sooner or later someone will get hurt and/or property damage will result. Consider this a serious warning.

[foo1bar]

Unless you know as much as a seasoned boiler designer, this is a bad idea for more reasons than I've got time to explain. Don't do it. sooner or later someone will get hurt and/or property damage will result. Consider this a serious warning.

Go ahead - explain.

It isn't going to be a pressure vessel - it's directly connected to a giant body of water that's open to the air.
So the most pressure would be a few inches of water (However high it is above water level plus a little for the length of line to the pool.

There are risks - like doing something stupid like putting valves on it which could be closed off and lead to a steam explosion.
But it isn't as risky as doing a boiler. (And even those have been built by farmers for hydronic heating)

There are risks - like putting valves on it and no pressure release valve.
But JPM is IMO making it sound much worse than it is.

However I wouldn't do it - it's going to be very inefficient, probably more costly overall than a gas-fired furnace (over the lifetime), and much messier. (smoke, ash, soggy mess when it burns through the waterline, etc.)

[J.P.M.]

Go ahead - explain.

It isn't going to be a pressure vessel - it's directly connected to a giant body of water that's open to the air.
So the most pressure would be a few inches of water (However high it is above water level plus a little for the length of line to the pool.

There are risks - like doing something stupid like putting valves on it which could be closed off and lead to a steam explosion.
But it isn't as risky as doing a boiler. (And even those have been built by farmers for hydronic heating)

There are risks - like putting valves on it and no pressure release valve.
But JPM is IMO making it sound much worse than it is.

However I wouldn't do it - it's going to be very inefficient, probably more costly overall than a gas-fired furnace (over the lifetime), and much messier. (smoke, ash, soggy mess when it burns through the waterline, etc.)

I'll explain why that's my opinion. After an engineering career, a sizeable portion of which was spent designing boilers and other pressurized heat transfer equipment, seeing the effects of boiler explosions and trying to figure W.T.F. happened, and seeing what DIY ignorance can do to put family and friends at risk, I shake my head. What people don't know can, indeed, hurt them.

Not my house, family, safety. I'm probably making it sound safer than it will actually be.

How this forum keeps its tit out of the ringer is NOMB, and I'm not the world's pressure vessel police, and even though retired, with my malpractice insurance lapsed, I'd still be concerned about what a litigious society might allow some lawyer to do if I got serious about professional advise beyond offering a stern warning that the OP's possible/likely ignorance could create a real safety issue. The OP has been warned.

You want an explanation, spend 4-6 years in a real university and get a BSME/MSME. Then, learn/live with the ASME Boiler & Pressure Vessel Codes for a bunch of years, or hire some P.E. to explain it to you.

As usual, take what you want, scrap the rest.

[inetdog]

Your system may be a open system connected at atmospheric pressure to a large body of water. Fine, but be very sure that your design does not include valves (including check valves) that could accidentally be closed to create a closed portion of the system. Same for pipes that might get clogged shut.

[barnsley]

Ok points noted thanks. I'm not going to bother with the wood burner now. (Not that I'd ever put my family at risk anyway )

If I did build one it would never be in unattended except for when dying down over night. There would be no closed valves no chance of pressure building up and no children in the garden when live (my kids don't live with me full time so I'd just heat it up day before they came).

[barnsley]

Plan E
Think I'll get a trampoline for the garden instead

[Mike90250]

Plan E
Think I'll get a trampoline for the garden instead

And lawn darts