Solar heating for salt water pool

We have come into a little money … Yooppee! … Not loads but, fingers crossed, enough to install some heating to the pool. It would be nice to extend the swimming season a little.

Can anyone personally recommend a company in the SW / pays basque who deals in solar heating?

Hi Vic, no I wasn't suggesting you preferred high turnover rates, just posing the question, as if something actually happened that made it worth the extra energy consumption I and many others would understand that but it's counter productive and while reasonable rather than low flow rates work better that also means it's affordable to run 24 hours so any dirt or leaves etc don't sink but get skimmed out (obviously in heavy rain etc dirt is already saturated so will sink anyway). but it reduces the manual cleaning and chemicals last longer.

I work with nature and not against it so using less power to do so. As I said earlier pool equipment wasn't designed to be efficient so people just slap on a bigger pump and as a lot of companies are American bigger is better and even the Aussies followed suit but things are changing and now the Aussies have a star rating for energy efficiency which I have already bettered but with the old ideas we are stuck with old rules. The problem with rules or codes in the US is once you have totally and irrevocably proven them wrong it takes an enormous amount to re write them. The CPO qualification recognised over a large part of the globe has portions which are totally misleading and wrong. Colleagues are trying to get this altered but as the CPO are seen as the defacto that would mean admitting they were wrong and that cannot be or could it? The chemistry has been known about since 1974, 40 years! and still pool guides/books are written and governments and governing bodies haven't altered their documents. No one really seems to care providing the pool industry keeps making money and highly stressed pumps need replacing more often than those just running along nicely.

John. Please don't confuse my request for T/O rates with an advocacy of high ones. I was trying to get a handle on the probable flow rates in order to better understand your theories. I'm now beginning to understand that you are saying that you reduce T/O rates & hence pump sizes to allow you to get reduced pump energy consumption. Sounds simple now so it must have been the 'consomme' cooking lesson that confused me :-) your statement that "The manufactures pump curves are pretty accurate even if they use 10x the power to pump that liquid than I do" still interests me so maybe you could explain that one if you have time. I'm no water treatment engineer & always employed others for that aspect so I must accept what you say in this respect. I always enjoyed the fluid dynamics bit & although the majority of the theory I learnt was seldom used it gave me a good working knowledge of 'fluids what flow & pumps what push 'em'. All very interesting especially your last sentence ;-)

I understand Vic, but here we are in a new century and most of the guidance came from the previous one and was that ever correct? Was a lot of it superstition designed to fuel more sales? Without a shadow of doubt I have met some pretty thick but well established member of the pool world. Unfortunately we have to wait for people to actually turn up their toes before we can get a seed change.

What actually happens in a pool with fast turnover that doesn't in a slow one? As the filtration systems are not able to capture the very fine particles and bacteria it just gets recirculated so what exactly is gained in fast turnover. Dirt even fine dirt we can't see gets colonised by bacteria. Chlorine has a fast kill time for common bacteria 1 min to 45 mins some take and age to kill and are almost resistant so how is that related to T/O? what we know is dirt is a hiding place for bacteria to shield themselves from chlorine by their sticky alginate secretions. Thus if we filter slower and finer we remove more dirt so less hiding places. Of course we need adequate backwash and that too is sadly lacking on a lot of domestic setups. In some commercial setups the source of infection is the filter. One report I read found a huge colony count in the filter and that had passed the health inspection less than 2 weeks earlier, the conclusion was the pool would be healthier if the filter was removed and the water just treated.

Sand is in millions of filters around the world but it has properties we don't want in a filter media. It sticks together nicely with a drop of water which is why we can make sand sculptures and a flow of water can easily cut channels through it which renders the filter useless. Our bodies can handle small amounts of bacteria but the filter is often the breeding ground so large amounts get broken off and then ingested so people get ill.

The manufactures pump curves are pretty accurate even if they use 10x the power to pump that liquid than I do. However as the head increase so does the electrical consumption and the marketing boys like to use the figures that favor them over competition. The problems are often the rest of the system, filters commonly rated at 15m3/hour but only 0.3m2 in surface area that is the main point of contention, forget T/O it should be a flow rate /m2 as it is in commercial pools but many of those are too fast as stated above the dirt is just shoved through and round it all goes in a big circle.

A Scandinavian company has been studying filters and notes in hi flow filtration the fine skin particles are actually broken up and re circulated and is a perfect food source for a host of unwanted bacteria. The pool industry believes and they are quite wrong, that a high flow rate + 1.5m/s will prevent biofilm growth, It has been proven at high flow rates the biofilm is thicker to resist being washed away so the chlorine can't break through the biofilm, that tends to make it a selective bacteria colony often of hard to kill types like cryptosporidium but lesser bacteria can also hide in the hosts alginate gel making the whole thing hard to treat. At slower flow the biofilms are thinner less gelatinous so chlorine can get through and attack the bacteria inside. Thus the industry has been promoting worse practice for years.

John. When I was running my predominately design & build business I had to be very careful in what I did. The only way to avoid getting my arse sued was to design to institute norms which of course included turnover rates, hence my interest. It may well be that lower T/O rates coupled with better water treatment solutions would work but I wasn't gonna chance it.

Regarding manufacturers figures being unrealistic etc. I have never had reason to doubt them as I always assumed a reputable companies R & D dept. would have far better facilities to test them than the flow metres we had in our instrument cupboard & would certainly not publish dodgy data on their gear. The few checks I did at my house didn't give me any cause for doubt though! Are you saying their flow rates & hence electric consumption are lower than they state & if so is this part of the reason you are measuring such low consumption. It's all very interesting & is re-kindling my interest in the stuff I used to do.

Sure Julian, I do agree and although it may not sound it from my posts I do like solar power in all forms and would have more of it, certainly in the next house as the main residence it comes very high on the priority list. Indeed if I lived in France full time underfloor heating from the evac tubes when not heating the pool would be the way I would go. There are soft start inverter heat pumps and although I haven't looked deeply at them I wonder if they are better suited to PV as they won't have the large start up current issues of the older on off units?

You rate LiFePo above lead acid for solar use? I wonder about the fire risk as they can produce so much power and can get very warm indeed.

Oops! sometimes one just can't see the wood for the trees :-)

To Vic: Oh yes I did give the pool dimensions… Check my reply to John on page 1 of the thread.

Reply by vic evans 19 hours ago

Very interesting John. Shows how out of touch I must be as I've just had a quick look online & the average pump I can find (Certikin for example) needs about 1- 1.5 hp to do the 22.5 M3/hr duty you mention @ about 8-10 M head. Your pump @ about 0.6hp must be a special or you have found a way to reduce the pump pressure & hence energy required to run it. You still haven't said what T/O rate you are looking for on your systems so any info. you are prepared to divulge would be interesting. Please don't think I'm here trying to trash your ideas. I'm genuinely interested in stuff related to my old profession which keeps the old grey matter ticking over & keeps me up to date with the latest technology .

Hi Vic, Sorry, turnover rates are basically something that has arrived from somewhere in the deep past but is relatively meaningless. On the pools with guests we have to be able to hit the 4 hour turnover as required by the DDASS regs hence 22.5 m3/hour but clarity in NTU's is far more relevant to what is actually really being filtered. As I said before it's about Civil servants and forms and tick boxes, all guff in the real sense. For non commercial pools I use 6 hour turn over which gives 4 turnovers in a 24 hour period.

Considering the turnover rates, even if people have 4 hour turnover they often like Elaine, run for only 7 or so hours so actually achieving very little by the way of filtration. There is the mythology of 50% of the temperature of the pool run time but that too has no basis in science. the water is then just left to stagnate, perfect for algae, mould and bacteria. The reason of course is cost but I have solved that one and 24 hour filtration brings out the best water, the least amount of work and that is the equation solved.

Although I would prefer you not to swear on the forum (Certikin) ;-( the figures stated on both filters and pumps is totally un realistic and never actually happens, 50% of the figure at best. Yes I have reduced wasted energy and friction to the minimums and also as I noted some time back, pool equipment was never designed to be efficient, most wasn't designed at all just copied from someone else. That means when you do as I have done and researched you find lots of additional issues, if someone just replaces a pump with a variable speed version they can turn a bad situation worse and end up with very poor turnover indeed.

As I said on the pool thread, the ability to pump and filter at so lower energy levels also means being able to take this to 3rd world countries where terrible drinking water accounts for more deaths than war. They can't setup a huge solar array to run inefficient pumps etc, a single small panel however is doable and the filter media can be specially prepared by nano etching the surface to remove contaminants like arsenic from raw water supplies.

Reply by Julian White 19 hours ago

You wouldn't need batteries, I would never consider that. And really, solar powered pumps don't need to be very complex, or expensive. A lot depends on the value attached to using renewable power, which Elaine expressed a desire to do.

Julian, you would require batteries to run the pump after the daylight level has reduced, and indeed overnight. Elaine didn't actually mention renewables, just wanting to be environmentally friendly and grid generated power can be greener than the manufacturing and shipping of solar and as in my case 30 cents of electricity a day means the payback point is some way off.

The other issue with solar heating, specifically evac tubes is what to do as a heat dump in summer when the pool is warm, and so is the hot water tank. That is what has prevented me from going that route. I considered reflective roller blinds to cover the tubes when not in use and these would also afford some protection from hailstones etc. A friend has a huge 3,000 litre heat storage tank and the system powers both underfloor and hot water so full use is maintained and with a family the hot water gets used but after the initial cost of install they save a substantial amount each year. Having the space and getting the permission to put up a solar array is also an issue. I love the tech but it just doesn't suit at the moment.

Elaine. The consensus is an air to water heat pump powered by your house electricity. You will need a serious ( for that read expensive) PV system to give you the current needed to run a heat pump let alone start one as the starting loads (amps) on these things can be high. If you want to extend the swimming season and/or heat your pool to a higher temperature it will cost. You will be able to reduce this cost with technology but it will still cost! If you intend staying in the house the best 'bang for your bucks' starts with insulation & draught proofing. Have a good look at what can be achieved & spend your dosh there to start. No point sitting in a freezing house or one you're pouring money into to heat whist looking forward to an extended swimming season ! :-)

Never thought you were! Quit while you're ahead, we're agreeing with you ;-)

Yes and no on the PV. The couple with Lorentz system are not on mains any longer, now self-sufficient because they see self-sustainability the only way to survive the next economic crash that the husband thinks will make the 1930s look like a children's playground. Although his livelihood is sport, he learned to go out to buy himself, mostly direct from German manufacturers and some things like a wood to gas converter stove from Poland. Installations are widely described on websites ad manufacturers usually have guides. Their pool heating was entirely installed by them with a bit of help from his father. His point is that PV prices are ridiculously high here and if he goes off to referee at a tournament in Germany, for instance, he uses the travel expenses to drive there and back and buy what he needs on the round trip. The point for Elaine is probably lost there unless they have somebody who can buy and install for them. With escalating grid power prices, EDF are expected to make a hike soon, the pay back is more like 12 or 13 years according to that couple's capital outlay against estimated grid power usage.

I have to agree with Tony. An air to water heat pump will probably be the simplest, cheapest & more understandable solution coupled with a good solar cover, assuming you have a suitable electric supply. I don't think you told us the pool size.

Thank you all for your replies and the stunning amount of research and information provided.

However … I feel no further forward. I am a retired IT teacher and have no knowledge of technical matters whatsoever.

For Vic’s information, my mum died not long after buying the house here and we already had the funds for the renovation of the house. We bought what we considered was a pool which gave us “the best bang for our bucks”. Now we have retired we are here full time and have decided that we would like to use the pool for a longer period and as we are living off our pensions we are probably more conscious of our outgoings. If we can heat the pool and cut down on our utility bills the would be great.

We have also undertaken a rolling programme of further house improvements, such as renovating doors and windows. We live in a village which is listed so cannot go wholesale for UPVC etc., and timber replacements are expensive. We are also gradually replacing older electrical equipment in the house to more Eco friendly products.

Now as to the business end of things, have I understood correctly that the consensus is a heat pump, powered by PV panels, which may or may not give us some payback on our electricity consumption?

Very interesting John. Shows how out of touch I must be as I've just had a quick look online & the average pump I can find (Certikin for example) needs about 1- 1.5 hp to do the 22.5 M3/hr duty you mention @ about 8-10 M head. Your pump @ about 0.6hp must be a special or you have found a way to reduce the pump pressure & hence energy required to run it. You still haven't said what T/O rate you are looking for on your systems so any info. you are prepared to divulge would be interesting. Please don't think I'm here trying to trash your ideas. I'm genuinely interested in stuff related to my old profession which keeps the old grey matter ticking over & keeps me up to date with the latest technology .

I don't want to leave out Elaine from her post as we are straying off her topic and we haven't heard from her in a while so she may be bored of us boys by now.

Vic, I wasn't being secretive I wasn't at home so couldn't give accurate information. I also need to correct myself from the 464 watts, it was actually 431 watts pumping 22.5m3/hour. we could have done better but it was a Magiline constructed pool and they had put 3 skimmers on one pipe which is too small and the equivalent of having one skimmer so 22.5 is the maximum we could drag through the pipework.

When not running flat out the owner runs at 124 watts which is a flow 14.1m3/hour.

that equates to 5.83 watts per m3 which is as far as I know the best in the world.

Getting hung up on solar is just adding yet another layer of complexity where it isn't really needed. On some of the youtube links they are proud of the 3 x 190 watt solar panels, why? so you have made an inefficient system run on even more expensive solar panels, daft but great for sales! With my pool running on 60/40 watts and costing about €0.30 per day the payback on the solar and deep cycle batteries etc would mean it's never going to get there. We have one pool running on solar in Spain because it was unfeasibly expensive to tunnel under the road to supply electricity so highly efficient flow systems run the pool powered by relatively small solar panels.

I am aware of the Australian star energy rating for pools which is now a regulation but when I first looked at it I already blew it away so my system would need the standard to go to 10 stars to compete with what I have already installed.

Exactly. Different strokes for different blokes! I use wood as my main source of heating 'cos I'm either mad or I like it ! I cut & stock my own wood & it's a hell of a lot of work to do it but I continue because of my perverse attitude I'm saving some money & a 'don't see why I should pay someone else to do it as long as I can' attitude. One of these days I'll give it up (or vice versa) & let a timer & thermostat switch on my heating.

I've willingly, & knowingly 'done' loads of dosh on things probably only I consider interesting so I'm certainly not knocking anybody's wish to play with technology or anything else come to that, but then I probably am better placed than most to sniff out the rubbish. It's just a pity that most people are taken in by the snake oil salesmen of this world & buy stuff thinking it'll save 'em money as against knowing it will. I've never been a 'bang for yer buck' type of bloke. If I want it I'll have it but that doesn't qualify me for the funny farm! It just makes me someone who's never cared much about money as long as I've had enough not to worry about it. :-)

I didn't mention waste Julian as nobody in their right mind would want that! I just can't quite get me head around all energy saving stuff that might save a few bob but costs a lot on a depreciating asset . These things don't last for ever & if one amortised the costs I wonder exactly how much they actually save. I had a pool in England & was sufficiently well breached to heat it with gas if I wanted. I never- the- less installed a solar system because a/ I could & b/ it was interesting. Did I save any money? dunno but it was fun doing it. Would I have a pool now ? not on your nelly! Far too much trouble for the use I would get out of it! Interesting answers though :-)

I don't heat my pool actively BUT I have a huge & not particularly pretty but useful rolling greenhouse-type cover on it which means it heats up passively in March and stays warm until Toussaint - & if it is windy you swim under the cover. Its initial purpose was stopping children/animals falling in & drowning but it also keeps it clear of leaves etc. In high summer I have to open it as much as poss as the pool quickly gets to over 30° in spite of being about 80m3.

Interesting question Vic - Probably because a pool is perceived as a frippery & an indulgence and people justify cars by saying they are essential for getting to work/going shopping etc.

I get a lot more fun & pleasure out of my pool (as does the rest of the family) than we do out of the car - but I know a lot of people for whom the type of car they drive/how shiny it is/ how powerful it is etc is really important as it seems some sort of extension of themselves because people see them out & about in it & they feel they are judged by it.

It all seems a bit fur-coat-&-no-knickers to me.