Pressurized Shower Heater

[sanramon]

Thanks for the comments guys. Logan005 - My last post wasn't too clear - its not my family but a neighbouring Costa Rican family. We're good friends and help each other out. They bought the parts and I did the labour.

The hot water tank had been a bulk soap container inside that yellow barrel for bulk shipping apple pulp from Chile to Costa Rica, so aesthetics weren't part of the plan. I thought it looked pretty neat, complete with a green logo .

[Logan005]

Amazing, the panel looks great, the tank not so much, but is the only way. I am so happy you can provide your family hot water.

[sensij]

Thanks for the update, congrats on a job well done.

[sanramon]

LucMan - thanks for the vote - I will go with your suggestion. Keep It Simple... And after drawing more diagrams of solar angles, etc, I agree it wouldn't make enough difference to mount the second collector on the west side.

The family is ecstatic with the hot water shower! First in the house, in 30 years. I was surprised that the head available of only about 2.5 meters was sufficient to give a good shower spray.

If anyone wants drawings, photos, experiences with this type of project, just let me know.
Here's the finished project.

[LucMan]

Because of the 10 degree roof pitch it will not make much difference either way. I would go for the easiest piping arrangement.

[sanramon]

The now NON-pressurized shower water heater is installed. During a 3 day test before installation it reached 39.5*C with about 5 hours of direct sun - then tree shade took over. Temperature loss over 17 hours of non-heating evening and night was only 4.5*C. I am happy, the new owners are happy!

However.....I bin thinkin'... This system faces 60 degrees from north, and is at 10 degrees latitude. Southerly facing mounts are not possible. I feel it could use an extra collector. I see two options:
1. place a second collector beside the first on the east facing roof slope, plumbed in parallel or
2. place a second collector on the west facing roof slope, and again plumbed into the first and the tank with Tees.

The outlet to the collector is well above the roof ridge line, so there should be no blockage to thermosyphon flow. It does mean longer piping for the cool and heated water, though and 2 extras Tees.

Any helpful thoughts on this setup will be greatly appreciated - diagrams below.

[sanramon]

The project is built, tested and ready for installation tomorrow morning. Set up in my yard with sun available only from 6:45am-1:30pm, It reached 34, 36 and finally 39.5*C at noon on the third day. This may be a bit of an unfair test as I did not draw off any hot water, as would be done in real life. But also, the rooftop install will get more sun. Unfortunately the orientation is at 60 degrees from north due to roof angle. Collector tilt angle will be at 15 degrees, just a bit more than the 10 degree roof angle.

Temperature loss overnight (17 hours without sun) was 3.8 and 4.5 or just around 1/4 to 1/3 of a degree per hour. Not bad for broken styrofoam chips as insulation.

Total cost was about $350 US - a little more than I had hoped for, but I did use best quality parts like CPVC tube, brass valves and such.
Here is the test setup, it will look tidier on the roof!

[Mike90250]

Here in Panama your next door neighbor to the east, outdoor showers are quite common. Most are nothing more than a barrel painted flat black and elevated above the shower area. Others like me use a coiled 50 meter black PEX pipe and at times can be too hot.

Thats what we had before the house was built. 10-11Am was the time to take a comfortable shower, after 11am, the water was too hot.

[sanramon]

Hi Sunking, yes I have seen reference to this type of solar water heater. I understand they work great at the end of a hot day. I am hoping to be able to store enough warm water for a comfortable shower in the morning. And yes my project is more expensive, but then I tend to over engineer everything. Whether it needs it or not.

When I lived in Papua New Guinea in the 1960's, our home had a steel tank on the roof peak, painted black as you mentioned. As we lived on rain water collected off the roof and stored in tanks in the yard, a daily chore was to pump water up into that roof top "heater tank". If you forgot - no warm shower tonight! And the first person into the shower got the warmest water. Ah, memories. But now we have mains delivered water (yes, here in Costa Rica) and a 20 tube evacuated-glass tube heating system that can boil water. Now we are spoiled.

[Sunking]

Here in Panama your next door neighbor to the east, outdoor showers are quite common. Most are nothing more than a barrel painted flat black and elevated above the shower area. Others like me use a coiled 50 meter black PEX pipe and at times can be too hot.

[sanramon]

Work is continuing. The heading should now be "UN-pressurized shower heater. Tank has all the necessary holes in it and fittings installed. The ball valve has been built into the highest point in the storage tank to avoid having to build a separate filler tank. It means a storage of about 120 litres instead of 145 or 150.

Collector tubes are almost completed. I would not have thought it so difficult to round up 48 PET soft drink bottles of the same size and shape! Especially here in CR where there is no deposit and recycle program. It has taken weeks to get 'almost' enough. Tank stand, made of steel and collector frame, made of wood are complete.
Photos will follow soon. Then it is on to testing.

[J.P.M.]

Thanks J.P.M. I have read all of builditsolar.com, and even saw a simpler version built here in Costa Rica.

I'm not worried about using plastic as this project is for shower only. Costa Ricans do not use hot water in kitchens, or even bathroom sinks. I'd sure love to use copper, but unless I bring a roll down in my suitcase next visit - it won't happen.

Work is progressing!

You're welcome. If you can get/use copper at all, it'll be better overall for serviceability if used where you can't see or get at the fluid contact surfaces.

[sanramon]

Thanks J.P.M. I have read all of builditsolar.com, and even saw a simpler version built here in Costa Rica.

I'm not worried about using plastic as this project is for shower only. Costa Ricans do not use hot water in kitchens, or even bathroom sinks. I'd sure love to use copper, but unless I bring a roll down in my suitcase next visit - it won't happen.

Work is progressing!

[J.P.M.]

Late to this party. See builditsolar.com for a lot of ideas. For a lot of reasons, I'm not a fan of plastic for DHW or potable H2O at elevated temps.or where access is limited, but understand the costs and possible fab. limitations associated w/copper. The world is full of tradeoffs. I'd stick with copper were access/visibility/inspection is difficult as much as possible.

[sanramon]

Sensij, thank you very much for your sentiments. I do appreciate using civil, helpful forums (fora?).

For LucMan - the blue PE-HD storage tank will be covered with insulation and inside a painted metal drum - so no UV problems there. Collector tubing will be CVPC, with probably black PVC between collector and tank - again pretty safe I feel. Collector "glazing" will actually be PET drink bottles, and I see they can last up to 10 years in sunlight. (This is the design invented in Brazil around 2002.)

Perhaps I could move on to "plan B pt 2" - using a pressurized heat exchanger . Since copper tube is $12/meter, but black flexible PVC tubing is readily available here, it might serve as an affordable heat exchanger coil inside the storage tank. In most DIY systems I see, they use copper tube. My own commercial system uses 28 meters inside a 200 liter tank. It always exchanges heat faster than we can use with showers, dishwashers, etc. But copper is just too expensive.

So, now some thoughts. This storage tank will hold about 125 liters (33 USgal) below the float valve. Temperature is hoped to be around 50*C (120*F). Mains water temp here is about 24*C (70*F). For a low flow shower, perhaps about 15 meters of 3/8" tubing would give rapid enough heat transfer into the exchanger coil? I don't know what the water speed (feet/min) or thermal characteristics of the PVC are or how to calculate the heat transfer rate.

All ideas and suggestions appreciated.