Homemade Solar Hot Water Heaters

[Smithson]

I've been told solar hot water heaters are quite expensive.

The units sold here seem to be similar to those in Australia.

Considering that it's a hot country a solar hot water heater wouldn't need to be efficient, even in the North there's plenty of sun in winter and the temp is still between 25 - 30.

A home made solar hot water unit could be easily made, a quick search on the internet will show plenty of designs, from simple to complex.

Has anybody ever made one?

[elkangorito]

I've never made one but I've some quite good 'home-made' ones.

The best example;

Copper tubing (about 15mm) 'zig-zagged' & laid in a metal trough. Metal trough dims - about 2m x 1m x 25mm. Fill trough with bitumen (tar) until it just covers the pipework (20mm deep).

It takes a little while for the bitumen to heat up but once it's hot, it stays hot for quite a while.

Edited September 27, 2007 by elkangorito

[londonthai]

there is a website called thaicoolhouse.com or something very similar (don't saved it in my favourite - but there are many references to this site here on the forums) where somebody describes how to make one.

looks more like the classical one to produce electricity - so water tubing in a wooden frame with a black background and glass/plastic covering

[Riley'sLife]

Yep, I made one by simply laying down plastic hosepipe in the rear garden. The water got too hot at times and had to be mixed with cold water for showers. Total cost was about 1000Bt. Never ran out of hot water. I'm going to lay plastic pipes on the roof of the new house, when I get around to building. In this climate there's no need to store the water separately, in my opinion, unless hot water is needed in the early morning - just lay out enough pipe for a day's worth of use. Not many Thia homes have it as hot water isn't an important requirement. None of my Thai village neighbours would thank you for it. They all shower with cold water. The hi-tec silvered glass parabolic evacuated tube collectors, or even the matt black flat plate copper collectors with copper pipe are all way too costly and unnecessarily efficient for use in the Tropics for domestic hot water, in my opinion. Keep it simple. Give it a try, it works well. Don't use clear pipe though, it will shower you with the green algae that can grow inside.

[Smithson]

Not many Thia homes have it as hot water isn't an important requirement. None of my Thai village neighbours would thank you for it. They all shower with cold water. The hi-tec silvered glass parabolic evacuated tube collectors, or even the matt black flat plate copper collectors with copper pipe are all way too costly and unnecessarily efficient for use in the Tropics for domestic hot water, in my opinion. Keep it simple. Give it a try, it works well. Don't use clear pipe though, it will shower you with the green algae that can grow inside.

The black pipe on the roof should work well, if you ran it into a storage tank that had simple insulation you should have hot water for the morning. The whole think should cost more that B2,000.

I've also seen units with a tank sitting in a mini greenhouse. A plastic garbage can with some clear plastic in frame should work.

I know in Isan it doesn't get really cold, but it's still cool, especially in the mornings. What part of Thailand are you in?

In the North it can be really cool in the evenings and earlier mornings. Even some of the less well off Thais have those small electric water units, which would cost quite a bit more than a simple solar system.

Edited September 28, 2007 by Smithson

[Riley'sLife]

Unsure if you are asking me or the O.P. but I'm in Songkhla Province. It never gets as cold here as it does in the north. In another life I owned a Solar Energy Company in Europe, among other interests. Good business in the mid 70's when the oil crisis hit.

Cheers Rick

[Smithson]

Unsure if you are asking me or the O.P. but I'm in Songkhla Province. It never gets as cold here as it does in the north. In another life I owned a Solar Energy Company in Europe, among other interests. Good business in the mid 70's when the oil crisis hit.

Cheers Rick

Rick,

Thanks, I was asking you (I am the OP).

Do you see much future here for the solar? I've been told there are several industries making solar gear, it's something I'll be looking into if I ever build a house.

[ClaudeFeller]

I've been told solar hot water heaters are quite expensive.

The units sold here seem to be similar to those in Australia.

Considering that it's a hot country a solar hot water heater wouldn't need to be efficient, even in the North there's plenty of sun in winter and the temp is still between 25 - 30.

A home made solar hot water unit could be easily made, a quick search on the internet will show plenty of designs, from simple to complex.

Has anybody ever made one?

Dont forget that you need a well insulated tank!

[jaideeguy]

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.

[Gary A]

I have given this a lot of thought and decided what I am going to try. I have decided on a roll of the black plastic pipe like the village buries for the village water supply. It is very tough and has a one inch ID. I'm going to mount that in as tight a coil as possible on a sheet of heavy plywood. The pipe will be secured by drilling holes on either side of the pipe through the plywood then using galvanized wire to hold the pipe to the board. After the pipe is secured to the board, I will paint the whole surface area flat black. I still need to find a very small circulating pump for between the solar portion and the insulated fiberglass tank. My house water supply pump takes water directly out of the tank so there is no need for any complicated plumbing or electrics. The circulating pump will turn on when the sun is up and off when the sun is going down. If it looks like it is going to work well, I'll box it in and cover it with glass to protect the plywood and the flat black paint. I pretty sure it will work well.

[londonthai]

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

[Gary A]

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.

[ClaudeFeller]

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

[ignis]

Yes, I also made one by simply laying down plastic pipe on the lean to kitchen roof = hot water to wash up and to the washing machine

[Gary A]

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.

[chownah]

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.

Gary A,

Are you going to have the entire system pressurized....if so then you will require a pressure tank. If you use an unpressurized system then you will need a pump to pump the hot water to the shower and a float valve to control the injection of cold water into the system. The point of injecting the cold water is important in determining the temp of the water delivered to the shower. If the water is injected into the tank at low velocity so that there is no mixing then you will have more usable volume of hot water at a more constant temperature than you would have if the incoming water mixed with the hot water in the tank. If this doesn't make sense I can explain in more detail. Also...the placement of all four connections to the tank (two coil connections, one supply connection and one supply line) need to be placed with consideration to how they will effect the supply temperature and usable volume.

Chownah

Edited October 21, 2007 by chownah

[ClaudeFeller]

Normally, the pump needs 2 temperature sensors to switch on/off.

Normally, a pressure tank is expensive...

[elkangorito]

Firstly, Thailand is an ideal country in which to employ solar water heating technology.

Solar water heating systems (domestic & commercial) have been available since the late 60's in Australia. One of the most popular Australian brands is Solahart. Below is the link to their site.

http://www.solahart.com.au

The below info is available on the above site;

Thermosiphon system.

All Solahart systems, where the tank is roof-mounted, use the Thermosiphon principle to collect heat from the sun and transfer it to your hot water. The Thermosiphon principle is based on two naturally occurring phenomena:

* Dark objects absorb heat

* Hot water rises

All Solahart collector panels are coated with a dark, heat-absorbent surface. This coating absorbs the suns rays and heats the cold fluid in the collector panel. As the fluid heats, it rises to the top of the collector panel and into the tank where it displaces cooler fluid which flows in to the bottom of the collector panel where the process is repeated.

The greater the temperature difference between the fluid in the collector panels and the water in the tank the faster the flow between them.

In open circuit systems the fluid in the collector panel is water while in closed circuit systems a special fluid called, Hartgard, is used. When heated in the collector panel, it is circulated in a jacket around the tank to transfer the heat to the water inside.

In this way Solahart systems constantly soak up the sun's energy to ensure you have hot water, on tap, everyday.

Pumped Systems. (whay Gary A wants to use).

Solahart's Streamline is designed to give you, the owner, the maximum flexibility of installation locations. The low profile and unobtrusive Solahart collector panels are mounted on a North facing roof, whilst the storage tank is mounted at ground level out of sight. The electric boosted tank can even be installed inside your home. This minimises the visual impact of going solar, while maximising the potential savings from the sun.

With "Streamline", the water is circulated from the tank and through the collector panels by an electric pump called a 'circulator'.

Cooler water is pumped in a continuous cycle from the bottom of the tank and circulated through the collector panels where it absorbs the heat extracted from the sun before being returned to the top of the tank.

The circulator is regulated by a control unit on the water heater, when the controller senses an 8°C differential in temperature between the top of the collector panels and the bottom of the tank, the circulator is activated until the temperature differential falls to 4°C.

The below link is for a typical hot water circulating pump;

http://www.grundfos.com/web/grfosweb.nsf/W...rundfos%20alpha

Also, check this link. It's about water quality & sloar systems.

http://www.solahart.com.au/default.asp?V_DOC_ID=757

The below link has some very interesting semi-technical documents for download.

http://www.solahart.com.au/default.asp?V_DOC_ID=908

Edited October 21, 2007 by elkangorito

[londonthai]

place the coil before the tank (from the mains to the tank). To get the biggest benefit of your system you will need to run taps at your home often, every 10 - 20 minutes but for short time (10 - 20 litres) at time.

I would place the tank higher, several meter over the ground - it will have more exposure to the sun, take less space on the ground (if you have a little space around the house - as I do) and it would allow to use water on the ground floor taps even if there is power cut.

[Naam]

place the coil before the tank (from the mains to the tank). To get the biggest benefit of your system you will need to run taps at your home often, every 10 - 20 minutes but for short time (10 - 20 litres) at time.

another benefit of that method is the creation of additional employment for the chap (or lady) who runs around in the house opening and closing water taps 8 hours a day. never mind the increased water consumption. after all it is for a good cause!

[elkangorito]

place the coil before the tank (from the mains to the tank). To get the biggest benefit of your system you will need to run taps at your home often, every 10 - 20 minutes but for short time (10 - 20 litres) at time.

another benefit of that method is the creation of additional employment for the chap (or lady) who runs around in the house opening and closing water taps 8 hours a day. never mind the increased water consumption. after all it is for a good cause!

[londonthai]

In the largish house, with a family living in, the water is used often (kitchen, bathroom, cleaning, hands washing) even throuthout the day. If nobody home for all day some device will have to do the circulation

[Gimbo]

I noticed when I was working in Iraq that the showers in our hotel had hotter water in the cold tap than in the warm one. So hot that it was at scolding temperature.

Turns out that the cold water tanks where on the roof, and they where black PVC or simmilar tanks. The sun was enough to heat them up that much. So my idea was simply to put a big PVC tank on a small tower in the garden, and have the sun heat it up. Should have a nice warm afternoon shower from that allone.

We did have temperatures exceeding 50 degrees celcius in Basrah thouh. But most of the year it should be hot enough here in Isaan too.

Well, it's just my idea... the others here have posted more elaborate and probably a lot more effective ideas...

[ClaudeFeller]

The magic is not to have hot water on a hot sunny afternoon but also after a cold night or on cloudy season.

A vacuum tube collector in a thermosyphon system with a well insulated tank is the best and most cost effective choice for residential use.

[elkangorito]

The magic is not to have hot water on a hot sunny afternoon but also after a cold night or on cloudy season.

A vacuum tube collector in a thermosyphon system with a well insulated tank is the best and most cost effective choice for residential use.

No need for this Claude...well, not in Thailand anyway.

The Australian climate ranges from sub-zero to tropical & over the past 40 to 50 years, Australian solar hot systems have been refined & are therefore able to be used in almost all of these conditions. None of the Australian systems use vacuum tube collectors, although it is another possiblilty. They are quite fragile.

[Naam]

I noticed when I was working in Iraq that the showers in our hotel had hotter water in the cold tap than in the warm one.

same experience in Saudi Arabia in olden times. the hot water boilers were inside the airconditioned house (not switched on) and the water tanks on the roof. when i wanted a hot shower i turned on the cold water tap and vice versa. it was always big fun when guests complained about "switched water piping" and big surprise when i explained "why".

[ClaudeFeller]

The magic is not to have hot water on a hot sunny afternoon but also after a cold night or on cloudy season.

A vacuum tube collector in a thermosyphon system with a well insulated tank is the best and most cost effective choice for residential use.

No need for this Claude...well, not in Thailand anyway.

The Australian climate ranges from sub-zero to tropical & over the past 40 to 50 years, Australian solar hot systems have been refined & are therefore able to be used in almost all of these conditions. None of the Australian systems use vacuum tube collectors, although it is another possiblilty. They are quite fragile.

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.

[batami]

this debate reminds me of working in mexico on a building site; we had been given what can only be described as large balck hot water bottle with a tap "plumbed" into the bottom of it. We filled this rubber bag with water in the morning, hung it on a pole outside our hut, and when we came back in the evening we had hot water to shower and shave with (sometime very hot!!) The more enterprising guys taped a "rose" made from a perforated can onto the tap.

now, returning to the real subject, if my water system in the house is pressurised and I have a hot water tank plumbed into the system ( this tank is located in the roof space) that part of the system is likely to be rpessurised as well I guess . How can I tap a solar panel into a pressurised sytem? If I put a "T" piece into the in and out pipes to the hot water tank (which has a almost comletely unused immersion heater in it) will convection just heat the water and the pressure will have no effect??

thanks for any advice

B

[ClaudeFeller]

Batami,

if your hot water tank is under the roof there is no reason to have a pressure tank. Check it again!

Why there is an immersion heater? Because you only want to heat the water volume in the tank. If you dont want to heat it by electricity but by solar you have two choices:

1) You have a pressure tank: You must add an heat exchanger coil that is connected to your collector. That means you will have two water circuits: The collector circuit and the water supply circuit. The first one needs a pump/temperature sensors to force a circulation to the collector. You can keep the immersion heater for backup.

2) Your solar collector is lower than your non-pressure tank: You can make a thermosyphon system, no heat exchanger, pump etc. is needed.

[Gary A]

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.

Gary A,

Are you going to have the entire system pressurized....if so then you will require a pressure tank. If you use an unpressurized system then you will need a pump to pump the hot water to the shower and a float valve to control the injection of cold water into the system. The point of injecting the cold water is important in determining the temp of the water delivered to the shower. If the water is injected into the tank at low velocity so that there is no mixing then you will have more usable volume of hot water at a more constant temperature than you would have if the incoming water mixed with the hot water in the tank. If this doesn't make sense I can explain in more detail. Also...the placement of all four connections to the tank (two coil connections, one supply connection and one supply line) need to be placed with consideration to how they will effect the supply temperature and usable volume.

Chownah

This is NOT a pressure tank. It is simply a storage tank for warm water. The water pump for my house can take water from this storage tank or another storage depending whether I want the warm water or cold water from another storage tank.

Our village only has water for a couple of hours a day and my storage tanks are filled with village water during the time water is available.