Club swimming pool heater

Hi, first post.

We have a small swimming club in South Africa. Looking for alternative to electricity to heat pool. It is 25m X 9m and about 300 000L water. Temp is 25, but trying to get 27-28 (degrees C...sorry we are metric!) average midday temperatures for Heidelberg (gt) range from 16.6°C in June to 26.3°C in January.

Question: Has anyone used or know of using a rocket type stove mass heater to heat pool water? I'm trying to stay away from a pressurized system, so was looking at the "bench" heaters on these pages. Idea is instead of having the ducting to coil copper pipes in a tight spiral to form a "pipe duct" then thread this through the mass (clay/straw?) this then becomes the exhaust. So pool water then circulates through spiraled pipes and exhaust heat heats water?

I have no knowledge of metals etc. so not sure if chlorinated water will have impact on copper pipe, also not sure what heat will do to copper if directly exposed to exhaust. Have looked at the clips of the water heaters on these pages, but that is to heat domestic water for showers etc. Also still need to learn how to calculate all the stuff needed for energy/heating like BTU's etc.

In South Africa on many farms with no electricity people use a "donkey". Basically a drum with water and fire underneath. Coldwater goes in, hot water out, but not as sophisticated as some of the designs over here. No coiling of copper pipes inside the hot water tank part, no "thermal riser pumps" etc. Open wood fires with lots of smoke!

Plan is to play around and build small model. Idea to start needs to know if it is better to use water as the "mass" and heat a boiler, then run coils through that and run pool water through coils, or heat a "bench" with clay/straw or any of the substrates I read about here and run coils past exhaust gasses to heat water. Flow rates are also on my mind as to use a high flow rate pool pump or slower? But anyway just need an idea if I'm on the right tract?

Thank you for taking time to read this and looking forward to any replies with advice.

and i thought i was scratching my head over a simple bench. lol i have seen some neat things made on this subject, but nothing that large. i would think an instant water heater core type deal mite be best? just on a bigger scale. interesting subject. if you can heat a pool you can heat water for an entire small village!

Idea to start needs to know if it is better to use water as the "mass" and heat a boiler, then run coils through that and run pool water through coils,

This plan is better; water is a better substance for thermal mass than clay.

Thanks for the replies - yes due to size of pool heating with electricity starting to get expensive. In S.A. we were "lucky" that electricity was cheap, so we were never forced to look at alternatives, now with infrastructure under pressure and a lot of environmental issues, lots of people are trying to be less dependant on state resource and trying to become more self sustainable.

Will look more into using water as the "mass" but still worried about steam and pressure, don't want explosions! So still looking at a "no pressure" sysytem...

Regards,

Jabu

jabu; Have you seen geoff lawtons video on building a water heater ? ( https://www.youtube.com/watch?v=1oDpmmsqHwQ ) You would probably need to burn it quite a bit ,but it might work for you.

Thanks guys, yes had a look at most of the clips I could find on youtube, that process led me to this forum.

I suffer from analysis paralysis hence the questions. All the clips I could find were for domestic heating and I'm not sure if it can be scaled up to the size of pool I want to heat. I have found a commercial company in SA that builds coal fired boilers to heat water to heat radiators to heat large volume buildings for the poultry and tobacco industries, just not sure I want to support this option as coal is running out! But then again If I can burn it directly and more efficient than the power company then maybe it is not so bad?

Anyway they talk about 136 kW to raise temp by 10 deg celsius over 24h for 280 kL water. I'm still searching for the maths on this, but they seem to know their stuff! So not sure what the kW output are of the domestic water heaters based on rocket stove?

Kind Regards.

I'd start with something like this (google "institutional rocket stove"):


Either use it as a 'double boiler' with pool water going through tubing coiled in water in the pot*, or as an open (no pressure) system with the pool water able to freely overflow into the pool. A large vat with multiple burners might be needed at your scale.

*Make sure the pot doesn't boil dry, maybe with a float valve controlled supply.