Homemade Solar Hot Water Heaters

[tango]

...between the solar portion and the insulated fiberglass tank....

For the insulated fiberglass tank simply purchase one of those large plastic ice boxes one sees in shops selling beer and soda on ice, or at markets in which they keep meat cool in ice. I am buying two 800 liter ice boxes @6000Baht here in CMai. 800L is the largest size, and will be painted matt black; these can be added to as the extended family grows. I managed to obtain a light alloy water tank used in passenger aircraft which I am having painted flat black at an auto shop [4000B and no rust]. This will be placed on the open top floor of a tower alongside my satellite dish. The tank will be backed by a glass covered V-wall; all of which will be covered w glass. The hot water will flow from here to the interconnected insulated 'ice' boxes on the second floor [along with an other (blue) insulated box for cool water], and from there to the house and pool. The interconnecting pipe will be the black pipes used by the municipalities these days. I will fit the 1 inch diameter pipe into a slightly larger sized one, running these as one, to the house, kitchen etc. Oh and the bottom floor of the structure will house the 'sak pha' room, a storage area, and possibly the dog kennel (6 Rotts). The idea for the V-shaped wall with instructions is on coolthaihome...(credit where credit's due). Just another approach for what it's worth, especially as electric costs continuously rise. Heating water with electricity is costly, to put it mildly. Hope this proves helpful:thumbsup:

Edited November 27, 2007 by tango

[Naam]

Heating water with electricity is costly, to put it mildly.

nobel prize in physics. no doubt about that.

[ClaudeFeller]

...between the solar portion and the insulated fiberglass tank....

For the insulated fiberglass tank simply purchase one of those large plastic ice boxes one sees in shops selling beer and soda on ice, or at markets in which they keep meat cool in ice. I am buying two 800 liter ice boxes @6000Baht here in CMai. 800L is the largest size, and will be painted matt black; these can be added to as the extended family grows. I managed to obtain a light alloy water tank used in passenger aircraft which I am having painted flat black at an auto shop [4000B and no rust]. This will be placed on the open top floor of a tower alongside my satellite dish. The tank will be backed by a glass covered V-wall; all of which will be covered w glass. The hot water will flow from here to the interconnected insulated 'ice' boxes on the second floor [along with an other (blue) insulated box for cool water], and from there to the house and pool. The interconnecting pipe will be the black pipes used by the municipalities these days. I will fit the 1 inch diameter pipe into a slightly larger sized one, running these as one, to the house, kitchen etc. Oh and the bottom floor of the structure will house the 'sak pha' room, a storage area, and possibly the dog kennel (6 Rotts). The idea for the V-shaped wall with instructions is on coolthaihome...(credit where credit's due). Just another approach for what it's worth, especially as electric costs continuously rise. Heating water with electricity is costly, to put it mildly. Hope this proves helpful:thumbsup:

Sorry, what you want to do with this set up? And can you include a drawing?

[pete_r]

Yes, i made one years ago and it was really quite simple.....with copper pipe soldered to T's making up a ladder configuration with the 'legs' being larger diameter than the 'steps', done so to get the 'header effect' [most efficient way to move water by theron syphon. then laid copper pipe assembly onto a 4'x8' piece of plywood with sheet metel and clamped tight and everything painted flat black and a 4'x8' sheet of glass over it. then it has to be placed at due south at an angle the same as our lattitude [18 degrees here] for maximum efficiency. like a ladder on it's side.

plumbing the out [of the header] to the top of the storage tank and the in [of the header] to the bottom of the storage tank, which was a hot tub and kept the water so hot at the end of the day that i had to cool it.

would have been easier to draw the design and will do if anyone is in question of the design.

i have thought about doing it here using the blue pvc pipe [painted black], but have doubts wether it could withstand the heat. copper is quite expensive and hard to obtain here.

If the "winter" stays long enough this year, maybe I will give it a try with PVC pipes and report the outcome here.

Some practical questions:

1. Is there an optimum ratio for the diameters of the "legs" and "steps" of the ladder?

2. How many "step" pipes should be fitted in the 8' length of the ladder? As many as possible, or are there other factors to take into account?

[jaideeguy]

using those blue plastic cooler tanks for hot water storage is not the best idea, as i used a big one for a 'home made hot tub' [with lpg water heater] and the heat has started to warp it out of shape in a year. they are meant for cold, not heat.

[jaideeguy]

"Some practical questions:

1. Is there an optimum ratio for the diameters of the "legs" and "steps" of the ladder?

2. How many "step" pipes should be fitted in the 8' length of the ladder? As many as possible, or are there other factors to take into account?"

mine had 1/2" steps and 3/4" legs [ 't's]

and, the more the better.....i think i had them spaced at about 3-4".

[pete_r]

Thanks for that, Jaideeguy. I find your description both straightforward and precise... much appreciated.

[chownah]

Yes, i made one years ago and it was really quite simple.....with copper pipe soldered to T's making up a ladder configuration with the 'legs' being larger diameter than the 'steps', done so to get the 'header effect' [most efficient way to move water by theron syphon. then laid copper pipe assembly onto a 4'x8' piece of plywood with sheet metel and clamped tight and everything painted flat black and a 4'x8' sheet of glass over it. then it has to be placed at due south at an angle the same as our lattitude [18 degrees here] for maximum efficiency. like a ladder on it's side.

plumbing the out [of the header] to the top of the storage tank and the in [of the header] to the bottom of the storage tank, which was a hot tub and kept the water so hot at the end of the day that i had to cool it.

would have been easier to draw the design and will do if anyone is in question of the design.

i have thought about doing it here using the blue pvc pipe [painted black], but have doubts wether it could withstand the heat. copper is quite expensive and hard to obtain here.

If the "winter" stays long enough this year, maybe I will give it a try with PVC pipes and report the outcome here.

Some practical questions:

1. Is there an optimum ratio for the diameters of the "legs" and "steps" of the ladder?

2. How many "step" pipes should be fitted in the 8' length of the ladder? As many as possible, or are there other factors to take into account?

The legs of the ladder are called manifolds and the steps of the ladder are called risers. One manifold runs along the bottom of the collector and one runs along the top....the risers connect vertically between the two manifolds. The water should enter at one end of the lower manifold and exit at the OPPOSITE end of the top manifold....this is important....this makes the length the water has to travel through the collector he same through every riser....if it is done the wrong way (the WRONG WAY is to have the inlet and the outlet on the same side meaning that the riser closest to the inlet/outlet side will short circuit the panel and water will mostly flow through it and the distant risers will have almost no flow at all) you will really really lose efficiency in that only a small percentage of your risers will have water flowing through them efficiently.

For copper pipe I have seen 1/2 inch risers and 3/4 inch manifolds used and supposedly this works fine in normal usage when riser lengths are long.

Generally speaking, to get equal flow rates everywhere in the collector (this is what you want; equal flow rates in all the risers) you want to have manifolds with bigger diametre than risers and long (rather than short) risers. I have read somewhere that you want the risers to be AT LEAST 70 times longer than their diametre. The more risers you use the more important it is to have a manifold diametre bigger than riser diametre i.e. make the difference even larger when more risers are used.

Properly designing this type of collector is not a simple matter and I have just presented some basic concepts. What kinds of pipes are used and what they are attached to are also important design elements....also the pumping rate and amount of sunshine striking the collector....and if the collector is insulated and if it has a glass cover.......

Edit: I found a US Dept. of Defence document that indicated that the flow rate for flat plate solar arrays should be about 0.007 to 0.034 L/sec-m2....but these are for efficient commercial units....it is doubtful that our homebuilt units will be so efficient so the pump rates should probably be considerably less than these figures for optimum efficiency....(assuming a system where you have a circulating pump which is used to transfer the hot water from the collector to a tank.) Of course optimum efficiency here in Thailand is not so important in that there is generally so much sunlight and the energy needed to reach shower temperature is so low that even really inefficient systems are likely to be adequate.

Chownah

Edited December 4, 2007 by chownah

[jaideeguy]

Thanks Chownah for fine tuning my previous post......

Do you think that the locally available blue pvc pipe [spray painted black] would hold up under the heat??? or any other cheaper locally available plumbing supplies??

other considerations are the orientation of the absorber. it should ideally be facing due south and at an angle the same as our lattitude which is 19 degrees.

and, i think that the top of the absorber should [the in to the storage tank] should be about a foot.

as cw said.....being so close to the equator here, there can be some room for error as total efficiency is not such an issue as if we were in the far northern lattitudes.

[chownah]

Jaideeguy,

I don't know if the blue pvc would work but it would be really easy to give it a try.....take a single piece of blue pvc of the type you think would want to use and paint it balck and install it like you would the entire system....then see if it holds up to the heat....you need to pressurise it if your system will be pressurised.....can't remember if yours will be or not. This is where the design of how your collector will be constructed is important....if you build a well insulated box with a double glazed cover and the water stops circulating for some reason (either planned or unplanned) and your system is pressurised then you will have the right conditions for failure of plastic pipe.....high temperature and high pressure. So....to test at max temperature and stagnation (no water flow) you could test a single pipe like I just explained. I've never built one of these things but I have studied their design quite a bit on my own so I'm not speaking from experience but from a fairly serious study of the design process.

Chownah

Edited December 8, 2007 by chownah

[pete_r]

Regarding the resistance of PVC pipes, I'm fairly confident they can last at least a few years. I see 2 risks, the UV radiations and the heat.

The resistance to UV seems ok, based on experience with some pipes connecting a pump in my garden, still holding after 3 years of daily exposure to the sun. Although I guess they will become brittle and break eventually.

For the resistance to heat, I think the PVC melting point is above 100 deg Celsius (maybe around 120 C), while the temperature of the pipes would remain below 100C in a non-pressurized solar heater (I don't expect water to reach boiling point!). So temperature should not be an issue either.

Of course theory always looks good... Reality may be different.

[chownah]

The black paint should eliminate any UV problems....an unpressurized system without extensive insulation or glazing should be safe even at stagnation. Keep us updated on how it goes.

Chownah

[jaideeguy]

i keep telling my self that i'll do it in my spare time, but lately i haven't had any........

[tango]

using those blue plastic cooler tanks for hot water storage is not the best idea, as i used a big one for a 'home made hot tub' [with lpg water heater] and the heat has started to warp it out of shape in a year. they are meant for cold, not heat.

Thanks Jaideeguy. You have saved me heartache,money, and a lot of extra work. Greatly appreciated. Hmmm...what to do now? The idea was to conserve the heated water throughout the evening and on cool days. I'll have to keep an eye open for alternatives. Cheers

[pete_r]

Tango, let us know if you find anything suitable to use as insulated tank. I was thinking of simply wrapping a layer of glass wool around a plastic bin, but I'm not sure this would be strong enough to resist outside conditions for long (my tank would have to sit outside of the house at first).

[klikster]

Tango, let us know if you find anything suitable to use as insulated tank. I was thinking of simply wrapping a layer of glass wool around a plastic bin, but I'm not sure this would be strong enough to resist outside conditions for long (my tank would have to sit outside of the house at first).

When thinking insulation, remember that insulation is mainly to prevent air movement. "Dead air space" can be pretty effective insulation.

[canuckamuck]

I like Gary's idea for the spiral; I designed essentially the same thing. What you need to do is have the tank up high, so there is no pump pressure needed to bring the hot water to the house. The mildly insulated tank will be refilled by tap water, by means of a float valve like in your toilet. Now all that is needed is a circulating pump to keep the water moving through the spiral and back into the tank. The circulating pump could be put on a timer, off and on every 20 min, but I would just leave it on all day, low flo pump, and have a photo sensor turn it off at night. Should be good enough for dishes and morning shower.

[Gary A]

I like Gary's idea for the spiral; I designed essentially the same thing. What you need to do is have the tank up high, so there is no pump pressure needed to bring the hot water to the house. The mildly insulated tank will be refilled by tap water, by means of a float valve like in your toilet. Now all that is needed is a circulating pump to keep the water moving through the spiral and back into the tank. The circulating pump could be put on a timer, off and on every 20 min, but I would just leave it on all day, low flo pump, and have a photo sensor turn it off at night. Should be good enough for dishes and morning shower.

I had a 3,500 watt heater and when it is cold up here, it wouldn't do the job. Since then I have replaced it with a 5,200 watt heater. I must admit to being lazy since I now have enough hot water and have not pursued the solar heater. I did go so far as to look for a circulating pump but they all move too much water and I didn't want to fool with a timer. I will eventually start on it. I intend buy a 1,500 liter fiberglass tank and wrap it with insulation then wrap the insulation with plastic film to keep it dry. I did fill a piece of the black plastic pipe with water and left it in the sun. The water got hot enough that I could hardly stand to put my hand in the water when I poured it out so I'm positive it will work.

[chownah]

Gary A,

For future reference, one way to make a low flow pump is to take a pump unit without the electric motor on it and put a large v-belt pulley on it instead and then drive it with a very small motor with a very small pulley.

Chownah

Edited December 20, 2007 by chownah

[jaideeguy]

A couple of ideas have come to mind in construction of solar heaters........

1] a friend suggested to contact an air conditioner installer with drawings of the solar absorber and they could construct easily....soldering copper is main part of instaling air-cons.

2] and the storage tank could be steel drum [or any steel tank] and wrapped with a couple or more layers of that 1cm flexible foil over soft foam used for insulation.

Just a couple of ideas for someone with time and motivation...both of which I'm short of at the moment..........

[Naam]

1] a friend suggested to contact an air conditioner installer with drawings of the solar absorber and they could construct easily....soldering copper is main part of instaling air-cons.

quite tedious work. rather take an old compressor/condenser unit (48-60k btu/h), remove casing, broken compressor, fan and spray fins as well as visible copper piping matt black. position max. exposure to sun, attach small pump and connect to insulated holding tank. wisdom and idea gained in the african bush, early 80s

[chownah]

automotive radiators

[MikeWill]

We sell both flat plate and vacuum tube - best value for money is definitely vacuum tube. Fragile? You don't have to jump on them (thats what the Thai Postal service did once ) we have no case of broken vacuum tube collectors.

Re: Solar Hot Water Systems

Do you sell them locally in Thailand?

Are they suitable for commercial use, and can be installed in Condos?

[pete_r]

The cold season is coming and the showers start to feel cold again... I bump this thread to add links to a step by step description of building solar heaters.

http://www.thesietch.org/projects/solarthe...panel/index.htm

http://www.thesietch.org/projects/solarthe...anel2/index.htm

[Eff1n2ret]

Thanks Chownah for fine tuning my previous post......

Do you think that the locally available blue pvc pipe [spray painted black] would hold up under the heat??? or any other cheaper locally available plumbing supplies??

other considerations are the orientation of the absorber. it should ideally be facing due south and at an angle the same as our lattitude which is 19 degrees.

and, i think that the top of the absorber should [the in to the storage tank] should be about a foot.

as cw said.....being so close to the equator here, there can be some room for error as total efficiency is not such an issue as if we were in the far northern lattitudes.

I wonder if since the above post jaideeguy or anyone else has made up a solar collector out of the blue pvc pipe? I can see where I could easily fit an open thermo-syphon-gravity system at our place, and the simplest way to make a solar collector with the most efficient manifolds and risers would be from the pvc pipe and fittings, and paint it, but I wonder how it would stand up to the heat. As I say, I'm thinking of an open storage tank circulation system, so there would be no pressure.

[jaideeguy]

No, I still haven't tried it....seems that the idel location for a unit on my roof is shaded by tall trees in the winter time [when I need it the most] and am not motivated to have hot water in the summer, when I prefer cold showers.

I still thinkthe concept would work and the pvc should hold up for a few years....maybe needing an occasional repainting of the black, which would protect it from the uv rays that break plastics down.

I may try it out to heat a hot tub that I could locate in a sunny area. I've done this before and a 4'X8' absorber panel will heat a 50gal tub too hot to get into.

[pete_r]

I wonder if since the above post jaideeguy or anyone else has made up a solar collector out of the blue pvc pipe?

Happy to say that we just finished one (see pic). My dad came for a visit, which helped to speed up the project.

I don't know how durable it will be yet, however some blue PVC pipes connected to the pump in my garden are exposed to the sun and elements and still holding after 4 years, without paint to protect them. So painted pipes should hold a fair amount of years.

By the way, a post on this thread suggested acrylic black paint to cover PVC, but the shop assistants at Homepro suggest enamel-type paint (typically used for metals)... Anyone has further opinions on which would be best?

The dimensions are ~200 x ~140cm, with 22 steps. The diameter of the steps is 1/2" and the diameter of the legs is slightly larger (3/4") as suggested by jaideeguy. We used small sections (~6cm) of 3/4" pipes to attach the T-junctions together. I also bought a specific tool to cut plastic pipes, which compared to sawing saves a lot of time and does not produce small plastic bits that need to be filed off. The cost so far is less than 1000 Bahts.

I'm also thinking of the size of the tank I should attach to it. Ideally I would like 80-100 liters at 40-50 deg C every evening, to provide enough warm water for the evening and morning showers for 2 people, but have no idea whether the volume of the collector (about 5 liters) will be enough to meet these requirements?

[Eff1n2ret]

Yes, that's exactly what I had in mind. Did you use any special glue or jointing compound? I seem to remember reading some posts that the standard stuff isn't too good.

[poldebol]

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.

[pete_r]

Yes, that's exactly what I had in mind. Did you use any special glue or jointing compound? I seem to remember reading some posts that the standard stuff isn't too good.

I used the standard PVC glue and will see how it holds. The important point when joining pipes is to avoid creating mechanical stress, which will weaken the joints sooner than later and results in leaks.