/ Heating a pool - any ideas?
My daughter's primary school has a heated outdoor pool. It's a great facility for the school. It's used for swimming lessons, and it's open in the evenings and weekends for the children and parents to use. The children love it.
However, the pool boiler broke on Friday last week and the new boiler will apparently cost around £7,000. It will take ages to raise the money and get the work done, so parents have assumed that the pool will be out of action for the whole summer.
Ever the optimist, I'm thinking about how best to get the pool back in use. For reference - the pool is approx 16m*6m and an average of 1m deep. Call it 100m3. I'm guessing the ambient temperature is around 18oC. The target water temp is 25oC, although cooler may be acceptable. The pool is in a sheltered location and has a decent insulated cover.
I'm figuring out how to heat the water for the period until the school gets a new boiler, which could be the whole summer. Call it 3 months. In terms of energy, to heat from 18oC to 25oC will require around 820kWh (http://processheatingservices.com/water-heating-time-calculator/). And then it'll need some energy to maintain the temperature over the summer.
The best I have come up with so far is to buy two or three basic 3kW pool heaters, run them 24h for a couple of days, and then drop down to overnight use of one to maintain temperature. Does anyone else have a better idea? I can't think of a practical way to heat vats of pool water, although I could probably persuade someone to donate a few m3 of seasoned logs. However I don't have an appropriate solid fuel boiler.
All ideas welcome!
820/9 (3 x 3kW) isn't going to get very far, especially with the losses for sch a wide area as a swimming pool.
We've recently fitted three smaller boilers, in a production plant, to cover one large boiler, to cope with breakdowns and to give some redundancy.
Not much I can suggest, other than that.
Do you know anyone nearby with a combi boiler and a long hose? (and no water meter)
You can hire boilers rather than buying things for temporary use.
My school pool was solar heated... a pump drew water out of the pool to a series of corrugated tin roof panels... water round down the panels and then pumped back to pool.
This was surprisingly effective from June onwards. The pool was not bath temperature tho
Combine this with fastidious use of heat retaining covers
Google “hot horse showers” for £150 portable gas boilers. Just add filters, pumps and gas cylinders etc. Also safety cage to keep them away from people, pipes into the pool to extract and return water at different ends and heights to ensure mixing, insulating and trip safety covers on the pipes, etc...
Or lots of black MDPE piping run back and forth between glass sheets with all the other bits from above for solar heating.
Or a bunch of extension leads, isolating transformers and immersion heater elements...
You can get £400 wood burning boilers for hot tubs....
*but* hack anything in and you don’t use all the filtration and cleaning stuff in the boiler’s loop that’s really quite important.
Buying some wetsuits is probably cheaper than any other scheme, and failing that people adapt to colder water after repeat exposure - twice daily for two weeks would do it.
If the school doesn't have a contingency fund to cover a mere £7k, I suggest you need a new bursar* rather than a new boiler.
* Or whatever the primary school equivalent is.
Some straw, a few hundred meters of hose, some black plastic sheeting, bubble wrap/clear sheet and roofing batons makes a big cheap solar panel. Various more robust solutions exist without resorting to expensive evacuated tubes. Might be a wise investment anyway since it'll drive down running costs once the boiler is fixed.
UK summer insolation is ~1kW/sqm, efficiency of such a crude collector is likely about 10% so 100W/sqm, 10x10m gives you 10kWpk, probably 50-100kWh/sunny day. Cost is low, educational value is high and ongoing savings worthwhile if there is space. Worth a thought.
It'd help sizing the heating if you knew the rate it cooled at and under what conditions.
Alternatively find a way to borrow the money bearing in mind there might with some creativity/flexibility be some grant funding available. Not fuelling a heated outdoor pool should speed the saving process!
I´d go grovelling around the local heating guys and put the arm on them (alternatively take a few weeping little kids). An old oil heating plant that´s still serviceable is worth about 200 quid and most of the guys around here (in Germany) have one already on wheels for emergency use when they are repairing someones heating. I´ve got one as a back-up to my main system which is heating my pool at the moment.
What is the rated output of the old boiler?
Or if it's on a separate meter, what was the energy bill last year?
Get some old radiators that someone's chucking out (rinse the gunge out of them), paint them matt black, buy a pump and just circulate the water through them.
Low tech solution?
Could you keep it open as an unheated pool though the summer? At 1m deep I would guess that with the weather we've had recently it would be quite pleasant for a dip, allow wetsuits which these days are pretty cheap to pick up.
> Could you keep it open as an unheated pool though the summer? At 1m deep I would guess that with the weather we've had recently it would be quite pleasant for a dip, allow wetsuits which these days are pretty cheap to pick up.
No reason not to have it unheated, but worth sticking up warning signs about cold water immersion if it's not lifeguarded
Assuming the amount of time the pool is in use is relatively low and that it's covered when not in use simply replacing the existing insulating cover with black plastic floated on pool-noodles gets you 100sqm of crude solar heating during the day while still suppressing evaporation. That's probably worth 50-100kWh/day at 10% collection efficiency through the summer months which is what, at 6p/kWh between £30-£60/week, taking the low figure maybe £400/summer, £600/year saved and easily enough to take the chill off it through the warmer months especially if the filtration is set to only draw from the skimmers removing the warm top layer and mixing it in lower down.
Air source heat pump.
It's what I'm going to use on mine when I put one in the garden in a few years. I've got one on my house at the moment and it's great.
Maybe worth speaking to these guys http://eco2solar.co.uk/severn-leisure-centre/ I was involved as a project officer for this project amongst other things in a different life.
There maybe a grants officer at the local council that can look at available grants or loans for the use of renewables. The other thing to invest in are pool covers. The use of liquid pool covers can reduce heating bills too http://www.liquidpoolcovers.com/faqs
> with black plastic floated on pool-noodles
Aside: If I ever build the pool it’s having a professional rigid cover anchored at the sides - plastic can be a death trap.
The problem with surface heating on an unused pool is that the temperature stratifies insulating most of the water and heating the surface to the point it looses much efficiency of receiving solar radiation - more convective losses mainly. You need aggressive mixing pumps.
Snowflakes, just throw them in. We had an unheated outdoor pool in school and were forced into in November (in the snowflakes a couple of times).
Did make our lips go blue and put us off swimming for life and school in general
I don't think throwing snowflakes into the pool will warm it....
> I don't think throwing snowflakes into the pool will warm it....
If you threw a load of snowflakes in, then could harness the indignant energy they generate posting on twitter about it, that might work.
> If the school doesn't have a contingency fund to cover a mere £7k, I suggest you need a new bursar rather than a new boiler.
Remember this is against the background of huge funding shortages for schools. Heads are having to cut staff hours and halt all extended services.
I imagine that recruitment issues in teaching and a sharp increase in staff sickness across the country are having big impacts on available contingency funding, as are more vital building works that need doing due to under-funding in school improvements over the past 10 years.
If I was a head and had to choose between £7k for a new boiler and ensuring my school had adequate staffing and learning environments I know what I would choose.
Under the new funding formula schools are having to run at significant losses - hence £7K becomes less easy to find.
Tell me, do you visit this planet often? As a member of SLT and a governor sitting on the Finance Committee, I’m struggling to remember the last time our school finances ran to the extent that £7K was a mere trifle when compared with our massive surplus.
A solar pool heating system sounds like a really fun science-come-design technology project for the kids.
No labour cost either :^)
I think the long 'black pipe' idea is best seeing as it's summer. Use low diameter pipe for best heating efficiency - a quick google tells me 50m of 20mm pipe costs £21. Alternatively, use the downtime to take stock and consider building a simple enclosure over the pool and installing solar thermal heating on it to improve things in the long term. My primary school has its pool in an old greenhouse which made a huge difference to other school's pools - it can be used in any weather and heating costs are reduced.
Thanks to everyone for the responses to date. Some good thinking out there. I'll get my compass and protractor out at the weekend to figure out which of the areas around the pool get full sun in the middle of the day. The pool itself is mainly shaded by large trees, which are very attractive but rubbish for solar. If there is sufficient sunny m2, then I'll suggest a low cost solar option. In the meantime I'll look at hiring a portable gas boiler.
Regarding the £7K - it's a lot of money for the school. No doubt the PTA will want to raise much of it via donations. Pool party?
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