Solar Hot tub Icb

[Chanireland]

 
solar hot tub

using these key parts that i have lying around. planning on bodging solar hot tub.

key parts

icb water tub 1000lt
black water pipe 3/4 inch 150mt
solid foam insulation 100mm could find some more...

So Black pipe solar collector  feeding 1000lt tank insulated with old solid insulation.

Have seen black coils as pools heaters on net using the pool filter pump,  and  also icb hot  tub being heated from wood-burner.

Think it will work, only pump i have hanging around is a submersible.

Can anyone think of  how to  get long pipe to thermosiphon without pump and keeping pipe pattern/conections to a minimum. But i am presuming  i will need the pump and if it work well enough some kind of controller.

Is this just a waist cutting good icb up and will never get very  hot/???

Any sugestions ?
 

[Justme]

Fix the black pipe to a board (or along a fence line) that you angle to the sun.

If the pipe is laid out so that it rises as it goes back & forth across the support then the water should thermosyphon into the top of the IBC then take the return from the bottom.

[dhaslam]

The area of pipe is  about 2.7 sq metres  which should gain quite a lot of heat in strong sun.   Probably about 5kwh  per day, enough to heat the tub by about four degrees less losses.      This means that insulation is critical.  Losses will be minimal close to ambient temperature but as it warms up it will lose more heat.  It may reach  35C if there are enough sunny days in a row.

[docka]

Hi 1st post, this topic caught my eye, it sounds like an interesting idea. I helped build a hot tub out of some pond liner, some pallets, old carpet, old radiator at an angle, straddling a log fire. Worked fairly well.

docka

[PhoenixAutosport]

Reflectors from flourescent strip lights mounted behind the collector pipes work well to increase the energy collected

[billi]

.... Leave the "ibc water tank  1000lt intact , insulate it , lay your black pipe so it therm-syphons  into the tank , lay your pipe on the ground ( if you have enough insulation, then lay it on the insulation) , buy poly-tunnel foil  and span it over your black pipe , built a ferrocement bath or get a bath tub for free somewhere lower than the tap   , and open the tap of your IBC tank to fill that , whenever water is hot enough

Billi

edit.... surely  paint the insulation black if your absorber is placed on

[Chanireland]

well im on a hill south facing so line would be possible but would be very long run.

4 degrees a day isnt to bad.. so if we had a great summer (Ireland) and average ambient temp was 14oC say in 6 days it could be up to 35oC.

I suppose using it as a pre heat and then the radiator over a fire for topping up would be ideal.

150 mt is allot of florescent reflectors, But i do have a massive pile of old corrugate iron roofing which gets pretty hot  just lying in the grass so laying it on them could be a good idea maybe on top  of a load of straw.

And yeh could wrap it all up with polly tunnel wrap nice and simple.
Like the idea of it being bigger than standard bath, also after the bath the warm water would be wasted and could not fit a wood burner booster heater if needed.

So options,
A/ spiral with pump.     compact no fittings BUT needs pump...

B/ 15 lengths of 5m.       compact enough But allot of fittings. No pump

C/ zig  zags 4m zigs      massive space needed, possible hard to get constant rise.

So Option B seems the bet for space and control with no pump. But all thoughs Ts are expensive..
just phoned local builder and 26 1in Ts compresion fitting is €160. (sure i could get a better deal but still )

Any ideas on any cheaper 1in Ts ? Or how to bodge some or make 2 manifolds (think thats the right word) 1 at the top and 1 at the bottom..

scrappy drawing

 

[Countrypaul]

Would it not be possible to use a combination of B and C, that is use say 4 lengths in parallel zigzags connectedat the top (and bottom) into a manifold or even just into 3 Tees?

[knighty]

also, you could always put your pump into the line on b or c, but leave it off most of the time.... it shouldn't make that much difference to flow...


that way you could just turn it on for the really hot days, or the days you want to use the tub ?

could even add a small (Cheap) timer to make it run for 2 min out of every 20 ?
(might need to experiment a bit with the timing, 1 min out of 10, 20 out of 20, 5 out of 30 depending how long it takes to heat up!)


also, remember not to put the return line too high in the IBC..... or it'll only work when the IBC is full !   - I can imagine doing something like this myself.... but they day I go to use it I find the water level has dropped a few inches in the ibc and all the water is cold !


EDIT/PS

what about building a tub, and lineing it with a pool liner ?  you could make it out of pretty much anything ? old railway sleepers ?  or just dig a big hole in the ground for it ?