Homemade Solar Hot Water Heaters

[pete_r]

I live in Sa Kaeo province. I just started experimenting with solar heating. I bought 3 30l black plastic jerrycans and put them in the sun for a day. By evening the water was 44 C and everybody enjoyed a hot shower and grandmother soaked her feet for half an hour.

I have lived in the centre if France and we used a spiral of black garden hose. Most of the days in summer and autumn the water was too hot to shower, we had to add cold water.

I really do not understand why people do not use this more in Thailand.

I have no idea how to work with those blue pipes, but I will enjoy learning it.

Thanks for these numbers: If 30l water can warm up from about 25C to 44C in a day, simply sitting in the sun, I guess we can be optimistic about the temperature a solar collector can reach.

I like the PVC blue pipes because they are cheap and easy to cut and put together. There's a good thread on joining PVC pipes here: http://www.thaivisa.com/forum/Water-Pipes-t58174.html

Here's how I joint the plastic pipes.

Your plumber should cut the pipe square (no slanting angles).

Then he should remove all the burrs from inside and outside the cut edges (Fine abrasive paper should be used)

Now he should slightly abrase the inside of the coupling with very fine abrasive paper.

Do the same to the pipe where the joint is going to be made (abrase all around the pipe and for a bout two inches from the cut end).

Make sure the mating surfaces are spotlessly clean and absolutely dry before applying a coat of the jointing compound to the 'whole' of the pipe jointing area (All around the pipe for a good inch and a half from the cut end).

Now push the cut end of the pipe into the fitting as far as you can force it and before the glue sets sets give the pipe and fitting a single twist through about a quater turn - this ensures the joint is fully made around all the jointing surface.

I support all joints against a solid surface, perhaps tieing them to a support or when burried in the ground I put them in a close fitting concrete channel (U shaped).

Make sure that the whole system is pressure tested with water before back filling any trenches or plastering over any joints.

I useually tie a piece of tissue paper around each joint and leave the pipework under pressure for a few hours then go check all the tissues are still dry.

Wath out too for stressed joints. ie Somchai the plumber is three inches short of pipe, so he pulls the ends of the two pipes together to make them close enought to join - They will then be under constant stress and will eventually break at the joint.

I pretty much agree with Guesthouse about glueing pipe....except I have found no need to sand the outside of the pipe or the inside of the fitting.....if they are clean and dry I just put a light coat inside the fitting (being sure it is wetted all the way around everywhere) and a liberal coat to the pipe (again being sure it is wetted all the way around everywhere) and jam them together (no need to turn but sometimes I do anyway). I've glued alot of pipe and NEVER had a leaker.

[whitfield]

I made a system with copper tube, in an isolated box.

Connected with a pump and an isolated tank. The tank contains 750 liters. When temperature in the collector is 7 degrees celsius or more higher then temperature in the tank the pump starts to run and fill, or if the tank is full starts to circulate. One hour strong sunshine is enough to fill the tank when empty, with water from about 60 degrees Celsius.

The whole installation costed about 100.000 Baht, but works more then 7 years without problems now.

Arjen.

Arjen this sounds much more like the system I require. Any chance of a drawing showing the plumbing and maybe a picture of the copper tube system. I think you mean insulated box and tank.

Where did you buy the pump and controls?

Thanks

[johnson36]

SOLAR HOT WATER USING BLACK WATER HOSE

[johnson36]

Can a large spiral of black pipe ( 50 metres / 100 metres etc ) be connected at both ends to a higher placed storage tank to make a thermosyphon system ? would the mains cold water would be connected to the bottom of the tank or joined with a tee into the black pipe ? How high above the spiral of pipe should the tank be ? would the circulate naturally ? How high would the tank need to be above a shower to give a decent pressure ( I suppose this also depends on the volume and weight of the head of water )

[ClaudeFeller]

We now focus on waste heat recovery, means catch the compressor heat with an heat exchanger. As AC are running mostly the whole year --> no extra costs for hot water. Of course should have a hot wate storage tank.

IMHO solar is not maintenance free, modern equipments with pressurized tanks needs too many parts.

[Naam]

We now focus on waste heat recovery, means catch the compressor heat with an heat exchanger. As AC are running mostly the whole year --> no extra costs for hot water. Of course should have a hot wate storage tank.

IMHO solar is not maintenance free, modern equipments with pressurized tanks needs too many parts.

i have installed a system 1½ years ago but i use it to heat my pool water. due to the corrosive pool chemicals the heat exchanger (Titanium) is bloody expensive. for normal water the price should be much more reasonable.

Edited August 31, 2009 by Naam

[ding]

The circulating pump will turn on when the sun is up and off when the sun is going down.

- Gary A

For Gary A's control, a phot eye would turn it off in daylight and on at night. *To flop this* he needs a relay with the same voltage coil as the supply voltage for the pump, 220-240Vs of course.

Supply voltage connects to the 220V photo eye. The power out of the photo eye feeds the realy's 220V coil. His pump is connected to the pair of Normally Open dry set of contacts on the realy (NO set of screws).

At night the phot eye makes (comes on). The relay's coil is energized. The Normally Open (contacts that are apart - not connected together) will CLOSE together (make connection).

But it does seem that since this is a closed hydronic loop that the tank would be pressurized to about the same inches of water column as the line. I think I'd go with that black plastic pipe on the roof with enough length to be the desired liters of stored water for morning use. Just tee off the house supply. There should be a thermal storage mass of some sort so heat is not lost overnight. Ideas?

A mixer valve like in my shower and kitchen sink at home would regulate the temperature and point of use just fine. Not ideal but better than nothing and pretty cheap & EZ!

[ding]

I made a system with copper tube, in an isolated box.

Connected with a pump and an isolated tank. The tank contains 750 liters. When temperature in the collector is 7 degrees celsius or more higher then temperature in the tank the pump starts to run and fill, or if the tank is full starts to circulate. One hour strong sunshine is enough to fill the tank when empty, with water from about 60 degrees Celsius.

The whole installation costed about 100.000 Baht, but works more then 7 years without problems now.

Arjen.

Is that 100,000 Baht? That's about $3,000USD! Not counting the pump's electricity cost. I wonder if you're at the point of payback yet as opposed to just buying an ELCB and paying the extra electric units. Any thoughts on payback period?

[kikoman]

Many Years ago in Mexico -Sonora desert-( house with Cement roof) We placed a 55 gallon drum on the roof,we connected a garden hose inlet to the intake at the top of the drum. we also placed a swamp cooler float valve to control the amount of water in the tank. We connected a outlet pipe an the bottom of the drum and ran the pipe into the bathroom, good water pressure operated on the thermosyphon system.

We later had to connect a cold water line to the shower head to, cool the water down to take a shower in the day or early evening.

The tank also supplied water for dish and clothes washing.

I wanted to set up a like system here, using an enclosed heating box on the roof, PVC pipe connected with Ts and painted black to heat the water connected to a Black plastic drum, here I would want to put a heat control relief valve on top to control the heat build up in the Tank.

My wife likes things the way they are, It still may happen!

[Gary A]

I was finally able to get a price for a solar hot water system for a small household. The solar collector is self contained and transfers heat to an insulated 500 liter tank using a coil inside the insulated tank. Sounds pretty simple doesn't it? The cost of that system is a WHOPPING 100,000 baht. That's about a 15 year break even deal. Even if I would pay that outrageous price, I would have to add plumbing because the water would be too hot and would need a cold water mixing valve added.

I can see why they hesitate to give even ballpark prices online. That totally turned me off.

[monty]

I was finally able to get a price for a solar hot water system for a small household. The solar collector is self contained and transfers heat to an insulated 500 liter tank using a coil inside the insulated tank. Sounds pretty simple doesn't it? The cost of that system is a WHOPPING 100,000 baht. That's about a 15 year break even deal. Even if I would pay that outrageous price, I would have to add plumbing because the water would be too hot and would need a cold water mixing valve added.

I can see why they hesitate to give even ballpark prices online. That totally turned me off.

Yeah, had some quotes as well, yours is actually not that expensive for a system with separate tank

At that price it simply does not make much sense, I'm actually contemplating a DIY system.

Efficiency would be much lower, but at the Thai climate I think that would be a non-issue. Most of those systems are designed for absolute maximum efficiency (read expensive) so they can be useful in less hot/sunny climates as found for example in central/Northern Europe! They even have electric heating coils in case of bad weather!

[Gary A]

I could use an extra 1000 liter tank anyways. It may be worth buying a tall tank and wrapping the black plastic pipe around the tank, painting the whole thing, tank and all flat black. Attach the black plastic at the bottom and near the top and see if it will thermosiphon by itself. I'd really like to eliminate any pump or electrics.

Added - It was a little strange that the solar water heater guy told me that saving energy wasn't just about saving money.

Edited December 4, 2009 by Gary A

[David006]

you don't need water circulating pump - the hot water will flow up and the cold fill from the tank

The solar collector will be on the roof and the water tank will be on the ground. I'll also need a flow control valve at the return line to assure that the coil stays full of water and in the coil long enough to collect the heat.

Please add a flow chart of your system! You are planning a forced cycle system - expensive and difficult.

Cheers from Samui,

Claude

Obviously I haven't explained it very well. Forget about the water supply to the house. This is an insulated tank at ground level. A small circulating pump pumps water to a coil on the roof through the coil and back to the tank on the ground. That is a simple closed system. The only complicated part is a timer to tell the pump when to run. Ideally it would be thermostatically controlled.

..maybe a solar powered (12v marine suppliers have 'em)pump?? Solar cell could be located so that it gets shaded at the appropriate time...just a thought...

[Olafur]

My idea for avery simple solar hot water collector:

 

Anybodyconsidered just running a straight water tube under the tiles along the ridgeof your roof?

 

Can anybodygive me some figures of what temperature to expect under the ridge on a sunnyday (e.g., in Isaan)?

 

I would run asingle loop along the full length of the ridge, fed by a small circulation pumpconnected to a storage tank.  I also thinkit’s a good idea to use the green color PB-type pipe, as it can withstand much highertemperatures than the ordinary PVC-pipe.

 

[JimShortz]

I also think it's a good idea to use the green color PB-type pipe, as it can withstand much higher temperatures than the ordinary PVC-pipe.

Can anyone tell me where I can get this PB pipe from on Chiang Mai? Or better still CPVC as used in western hot water installations. Is this available in Thailand? Any other suggestions of pipe that can withstand very high temperatures (for use in making a solar collector and piping potentially very hot water to a storage tank) much appreciated.

As I understand it PVC pipes (blue) are not appropriate and have a high probability of failure. Is this correct?

pete-r, how did you get on with yours? Is it in place and working?

A lot of questions I know. Any help (or sharing of experiences) much appreciated!

Actually - one more... I hear what people say about simply heating water up by leaving a black tank out in the sun, and this works for sure in Thailand, but useless for storing hot water for use in the morning. In the colder months I'd love to be able to have hot water for a bath or hot tub in the morning. Can any of you clever folk work out how to store that hot water for the morning? My only thought would be to set the first tank high on a scaffold, have a second insulated tank in the attic, and have the water transfer to that late on each day; but of course you would have to dump any water that was in the attic tank first (not very satisfactory) and get up on the scaffold to open the valve (not ideal!). This is all a bit too manual for me - I want easy hot water! Any better ideas?

[canopy]

Or better still CPVC as used in western hot water installations.

PVC is not suitable for solar. The reason is that PVC breaks down when exposed to sunlight. This process leaches toxins into the water. You don't want to take showers in poison. In the US it is a code violation for PVC to be exposed to sun. Also note if you want a sound design that even CPVC cannot take the temperatures you get with solar. There are other alternatives to PVC, but they are more expensive and harder to find.

I hear what people say about simply heating water up by leaving a black tank out in the sun, and this works for sure in Thailand, but useless for storing hot water for use in the morning.

This is called a batch heater. To have hot water in the morning the tank needs to be enclosed in an insulated box with a glass panel. There are countless DIY plans for these. Simple and effective.

[thaibeachlovers]

Simplest system that I've used in Thailand ( when at the beach ) is a plastic rubbish bin ( a few Baht ) of whatever size suits, with a black plastic rubbish bag over it out in the sun. At night, empty hot water into one of those insulated chilly bins normally used to hold ice. Sure beats a cold water shower in the morning.

[haveaniceday]

OK, great thread, been born again a few times now, so a 'nnormal' western storage tank is presurised, we are talking many times here of heating the water by day and storing it over the night. I presume to get good water pressure in the morning, you would need to pump that stored hot water.

Would you would need a dedicated hot water pump that will not over heat?

[canopy]

You don't use a tank with an open top for this, but rather a sealed tank. The water pressure coming out will be equal to the water pressure supply. No pumping or electrical needs.

[David48]

Just bumping this for others as it's a good read.

Some questions/issues never change.

[sirineou]

Very simple design that I made in my USA Florida home and plan to make in our isaan home as soon as I get enough free time from work to build a house there,

In Florida we have an insulated tank with an electric coil in it that makes hot water and the insulation keeps it hot, I think it looses a couple of degrees F per hr.

I simple took the cold water feed to the tank run it to the roof , connected it to a flexible coil of several loops of copper pipe that I painted back, and return it to the the hot water tank inlet, Since the water being feed to the tank is very hot from the sun the electric coil almost never needs to turn on but is there as a backup.

Most of the year the water in the tank is too hot for the electric coil to kick in, Only in the winter for a couple of months it kick in. It has cut my electric bill significantly.

Though I have not looked in to it, I am sure such electric water tanks must be available in Thailand, Here in the US they are very inexpensive, a 30 gallon one can be purchased for about $300.

[livil]

did a rough sketch and design for a termosiphon project in the house with an automated filling system . in the end i just bought a electrical water heater ....

.

[bbradsby]

Very simple design that I made in my USA Florida home and plan to make in our isaan home as soon as I get enough free time from work to build a house there,

In Florida we have an insulated tank with an electric coil in it that makes hot water and the insulation keeps it hot, I think it looses a couple of degrees F per hr.

I simple took the cold water feed to the tank run it to the roof , connected it to a flexible coil of several loops of copper pipe that I painted back, and return it to the the hot water tank inlet, Since the water being feed to the tank is very hot from the sun the electric coil almost never needs to turn on but is there as a backup.

Most of the year the water in the tank is too hot for the electric coil to kick in, Only in the winter for a couple of months it kick in. It has cut my electric bill significantly.

Though I have not looked in to it, I am sure such electric water tanks must be available in Thailand, Here in the US they are very inexpensive, a 30 gallon one can be purchased for about $300.

Just a detail note: since heat rises, for a thermo-siphon system, i.e., no water pump, the storage tank must be above the collector.