How to build a simple solar hot water system
Just enter your email to download immediately. Integral passive solar water heaters, also called batch heaters, are the simplest of the passive systems, and their reliability and independence from external power lead to long-term production at a very low cost. Switching from a plastic to copper panel of the same area increases conductivity by times, and going from 0.
Come on, it will be fun. Think of it as plumbing That sounds less threatening. On the following pages I wish to compare and contrast two types of flat plate collectors, the parallel and the serpentine. Here is an example of a flat plate parallel pipe collector system: This parallel collector is designed to transport collector fluid from the bottom of the collector to the top via a network of parallel pipes.
Notice that the top and bottom pipes are larger than the vertical pipes. There is a reason for this. Fluid mechanics favors an increased flow rate for the end pipes.
This is because incoming fluid pressure is greatest at the base of the first pipe and outgoing fluid pressure is smallest at the top of last pipe.
If the top and bottom pipes are large the pressure difference is moderated and the flow rate in each of the parallel pipes is more uniform. These collectors may be connected in series because the top and bottom distribution tubes are so large. It is unfortunate that the flow rate is minimal at the center of the collector where most of the heat is concentrated. Other problems associated with the parallel flow with collector include cost and leaks. Half inch and two inch copper tubing is expensive, not to mention the dozens of special T fittings and all that solder.
One small, undetected leak on one of those T fittings could become catastrophic mess. The serpentine collector consists of one long continuous flexible tube so there is no problem with uniform flow rate. The size of this flexible tubing is an important consideration.
Quarter inch copper tubing is inexpensive, however it restricts the flow rate too much. Half inch flexible tubing is difficult to bend and fairly expensive. It has a reasonable flow capacity, low cost, and ease of fabrication. What more could one ask for?
The main problem with a serpentine collector is flow rate restriction.
Even the larger half inch copper tubing restricts flow rate too much and puts an unnecessary burden on the circulator pump. Connecting the serpentine collectors in parallel alleviates this problem. A two-collector system works fine. A four-collector system works even better. This will insure that the flow rate is uniform throughout the serpentine collector array hooked in parallel. You can take readings on the model with a light meter and get a quantitative idea how much for example a reflector is increasing radiation.
Here is a unique solar water heating collector array that tracks the sun. Its a nice, simple tracking and actuation system that uses readily available components. A parabolic trough solar collector you can build www.
More information on the tracker: Good Youtube Videos on the collector A very nice set of ganged, parabolic, tracked, concentrating collectors used to heat water. Can be made with common shop tools. George now offers plans for this collector -- my thoughts on these plans George has also done some work on comparing tracked and untracked collectors both concentrating and flat plate.
In a normal shower, you spend a lot of energy heating water from 50F or so up to F. The gray water heat exchanger uses the heat in the drain water to heat the incoming water. A calculator to estimate saving: These Heat Recovery Units are heat exchangers.
They pick up waste heat from your Air Conditioner just after the refrigerant is compressed and before it goes to the condenser. This recovered heat is used to heat water in your hot water tank.
The heat is "free", and also makes your AC run more efficiently. These units may may make sense for people who have long cooling seasons, and run AC a lot.
The saving depends on the size of your AC, its efficiency, how much you run it, and the length of your cooling season. While the yearly saving in water heating costs for these units is likely to be less than a solar water heater, they are also less expensive, and potentially easier to install. Thanks to Gary M. Heat Pump Water Heaters These are small heat pumps that basically provide a more efficient electric water heater. Heat Pump Water Heater A couple of many? They also produce some cool air as a byproduct that may be useful in the summer.
I'm not a big fan of electric water heaters because of the high CO2 cost of using power from our very dirty US grid, but if you have an electric tank, this is one way to make it more efficient. Tom goes through the fairly simple install, and also explains some other potential uses for the heat pump water heater -- very good. This cold air ends up having to be heated by your space heater, and this costs energy. This paper shows the way in which the Heat Pump Water Heater was hooked up in a Building America demonstration home to overcome this difficulty.
Pros and ConsAlex Wilson. Several schemes for heating water with compost here There are several schemes that can be used to heat water for domestic or space heating use are shown at the link to the left. These schemes generally use a pipe coil embedded in the compost heap, and collect heat that is generated by the composting process. I'd like to hear from anyone with composting experience on how workable this all seems?
Solar heated stock tank in Minnesota Karolyn's solar stock tank has performed very well through a cold Minnesota winter. This is a great idea from Art for keeping the drinking opening in solar heated tanks from freezing during extended periods of not much sun and lots of wind. This technique can be used on any of the tanks described here.
Very nicely done insulated and solar heated stock tank. This design uses a galvanized stock tank as a base and builds an insulating and solar heat collecting structure over the tank. Description and construction pictures here Very nicely designed and built insulated and solar heated horse watering tank. Good photos, plans and construction detail. Steven lives in a very cold climate even colder than mine! Super Insulated Stock Tank All the details on how to build it This is Scott's really nice design for a well insulated stock tank.
All the details on how to build it This is a fully insulated stock tank with complete how to build it instructions. The insulation should dramatically reduce, and possibly eliminate any need for a tank heater -- depending on climate. This is an actual implementation of the prototype described in the design in the entry just below.DIY Solar Thermal Water Heater! - COPPER PIPE Solar Water Heater! - Easy DIY (full Instr.) 150F+
A solar heated and well insulated horse watering tank. It provides gallons of water that is protected from freezing by lots of insulation and a solar collector that is built into the south wall of the tank. Glazed with very though dual wall polycarbonate. This tank should avoid most of the high electric bills and wasted CO2 emissions that go with electric tank heaters. Heating Water for Your Pig.
This is a pretty simple water heater for a pig from the Nateful. It uses an old pressure tank with some left over lumber and insulation -- costs practically nothing. Gary This is a first cut at a simple insulated stock watering tank that has an integrated solar collector on the south side to provide heat and prevent freezing. The tank basically a plywood box lined with pond liner, and with a glazed sout side for solar collection.
See also the entry just above for an actual version of this tank. Freeze resistant stock tank design from U of M Extension relies on earth berming and a small trickle of water in very cold weather to prevent freezing. I cut a board to cover the top of the tank.
In that board I cut a hole that is the diameter of a 32 gallon plastic trash can. The hole is cut to the size of the trash can such that the lip around the top of the can will not go through the hole. These trash cans taper from the top to the bottom of the can I imagine so they will come out of the plastic mold. I cut the bottom off of the can. I then slide the can minus bottom down into the hole that I cut in the top of the lid.
The lip of the can stops the can from going all the way into the tank. Next I fill the tank with water. Now the only exposed water area I have is the diameter of the plastic trash can. I then use the bottom of the trash can that I cut off as my floating cover. It fits in the top of the trash can pretty well because of the taper to the trash can and it limits my exposed water to only a small ring which is the diametrical difference between the top and bottom of the can.
All of the horses quickly learned to just push against the trash can bottom to drink. Thanks to Mark for sending in this idea! Amesco and o ther commercial horse tanks This is a commercial product to keep water tanks for stock from freezing. Seems like a build-it-yourself one would be pretty easy? Dark colored tank, insulation under and around back, Lexan for glazing, plywood housing? Elevate it, and you could make a nice summer shower out of it? Uses a combination of insulation and ground heat to keep water line from freezing.
This link to Pet Finders provides a list of potential solutions to keeping water dishes from freezing for cats, etc. If you have any other ideas, please let me know.
Passive Solar Bird Bath. Plans for a passive solar bird bath The Cattle Site has several schemes for freeze resistant stock watering systems. The systems include one that pumps water to a cup when it senses an animal, and drains it after the animal is done drinking. Another uses a very well insulated small building to insulate a large supply tank that feeds a trough that extends outside the building. And, another makes use of a large inductrial mining tire.
These two publications talk about the systems -- unfortunately, not a great deal of detail is provided. This is a very nicely done well house that is protected from freezing with a large Trombe wall.
The well thought out desgn uses a combination of the Trombe wall, concrete block thermal mass, and insulation to provide effective passive freeze protection. Lots of good detail on the build Making cheese requires lots of water heating for pasteurizing -- here is a way to do it with solar.
This solar shower design uses a flat box above the shower to store and heat water for the shower. The shower is a simple gravity feed from the box. The solar heated pipe coil is gravity feed from rain collection barrels. I found this at: You put it out in the sun for 3 hours, and get a 5 gallon hot shower. And, yet another solar shower http: Fill it with water, hang it on the pole for 2 or 3 hours, and its ready to shower.
A simple homemade solar shower made from a few lengths of 3 inch ABS plastic pipe. Economy Solar Shower Bob Battagin. Home Power Magazine article, issue 43 If you are looking for simple, this is it.
Here is an even simpler one -- the hot hose shower. Mother Earth News, Issue S simple homemade shower made from a car inner tube. The Hot Hose Shower A very simple one: And another one with more capacity: Black plastic pipe shower And another very nice one: These are plans for building a pretty spiffy outdoor shower. Its not a solar shower, but I thought the detail on constructing it and dealing with drainage etc were worthwhile -- converting it to solar is left as an exercise.
Please send pictures if you do. A Very Nice Solar Shower http: Very nicely done with its own solar batch water heater. A comparison of glass, corrugated polycarbonate, sheet polycarbonate, and other potential glazing materials for DIY solar collectors. If your pump is located in an area that can go below freezing, you will need to protect the pump and possibly other equipment and plumbing from going below freezing.
Here are some methods Home Power Magazine article, issue April 06 Good article on how to select and test a used solar water heating collector. Used collectors if in good shape, can have 20 or so years of life left in them. Information on Diagnosing solar water heating system problems. GoSolar Repair Guides www. Some helpful troubleshooting information for solar water heating systems.
Build a simple solar water heater
Introduction I've seen a few different designs for solar water heaters and I
A friend of mine in France made a similar system to feed his swimming pool. Well considered and argued.
However i have a suggestion. One could use high temp bonding heat paste to make the connection. I know you will have to increase the distance that the heat energy must travel from 0. Have you also considered using insulated glass units Double Glazed as the primary glazing cover?
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Once again, thanks for the article. Would that keep more heat in and make the system more efficient, or is the styrofoam better? Am i reading the sums wrong? In a conventional tube and fin design that is NOT the same as the conducting cross-sectional area. This is the disadvantage of a tube and fin design.
The conducting cross-sectional area is usually much less than the collector surface area, impeding heat transfer. In my design the two areas are the same. All that matters is R-Value the higher the better. I think you are doing a commendable job of enlightening those who are in need. My topic is discovering if a solar powered water heater can sufice for the daily needs of hot water of a family. I have done other research and it seems as though it actually can.
Please let me know. I have no data on how well this would hold up over time. I only built it as a proof of concept and did not install it. Before fossil fuels and electrical power were widely available in North America, solar water heaters DID suffice for the daily needs of families. Good luck with your project. It will just be a little heavier when filled so you will need to support it well.
You may also have a bit more trouble cutting wider slots in the header tubes but you can probably manage OK. I believe that another reason why copper is used in collectors is sanitation. Copper is naturally bacteriacidal. So, no bacteria growth in the collector, lines, etc etc. Plus, copper is a proven container for the safe storage of potable water, even when repeatedly heated and cooled.
Plus, biofilms bacterial growth on the surface of the plastics will occur and be maintained unless proper sanitary processes are conducted on a regular basis. Cool to make the hot water collector so inexpenisvely and with as high an efficiency as you observed.
Not so cool to potentially cause harm to your family. Get the facts, check out your plastics and go for it!!! This collector design is not intended to be placed in series with a potable water source.
Not only would nasty chemicals leach into the water, but the panel will not survive city water pressure. However, in Canada at least, even copper pipe collectors are not designed for circulating potable water. The water would freeze in winter and burst the pipes.
Therefore, antifreeze must be added to the water circulating through the collector and a heat exchanger such as a Solar Wand must be used to transfer the heat to a water tank containing potable water. Basically, heat water one day and use the following. I was thinking of using a solar powered pump, but thermo-siphoning costs nothing!
If I used a double glazed unit I have a couple lying around instead of the plastic sheeting would this create too much heat and indeed melt the corrugated plastic sheeting? I really hope that if you install a water heater of any type in your attic that you will make a proper emergency drainage system. There is no way that any type of drainage system could be more expensive than replacing your walls, ceilings, and carpets. Hi Westy, If you use double glazing you probably will get too hot for the plastic parts inside.
It is possible to design a system that will expel air automatically. You simply need to ensure that at any point in the system there is a path that rises continuously from there to the highest point highest water level in the system, and that the highest point is the surface of the water in the storage container which is exposed to the atmosphere. For me that would have meant drilling holes in the side of my cooler one at the bottom for the exit and one at the top for the inlet. Then air bubbles would simply rise through the system and be released to the atmosphere.
I did not want to drill holes in my cooler so I opted to bring the exit and inlet tubes in from the top which introduces the problem of trapping air and makes it necessary to take steps to remove the air in order to get thermo-syphoning to work.
When the solar collector is mounted higher than the storage container a pump must be used to circulate the water. If you have access to AC power, I would recommend using that instead of adding photovoltaics.
You might try an AC aquarium pump or a sump pump. But then you either have to turn it on and off manually, or design a thermostat to turn it on when the collector is hotter than the storage container. The air temperature is relatively stable, around 80 degrees F average close to the beach, with breezes, never less than 60 degrees F at night.
But are there ANY solar water heaters or electric panels in this area? How do they heat their water? ABS pipe is strong, cheap, and available locally. I was also thinking of putting the assembly in an insulated box, glass front, so that it would not lose much heat overnight. I think ABS can withstand some heat, but I am not sure how hot. I was thinking that the metal plate should be copper, blackened with sulfur, as it would be very efficient as a conductor, be sturdy, and anti-bacterial, anti-fungal.
Again, I think I would insulate the sides and back of the box. It amazes me that there are NO solar water heater of any kind or solar collectors anywhere in this area. Just those black cylindrical ABS tanks, which are about 5 feet tall and about 3 feet in diameter.
No separate hot water tanks except in some hotels that cater to Americans. This area is has not yet been discovered by tourists, though Puerto Escondido doe have tourists, and a new resort, Huatulco, is being built near here. But there are no solar systems in those towns either!! Anyone I talk to around here about solar systems of any sort results in a blank stare. I was thinking of selling some, since they would be cheap. Very backward around here! What do you think of my two ideas?? Hi Dave, ABS should withstand hotter temperatures than you want your water, so as long as it always has water in it, you should be fine.
If the water leaks out, then the ABS might overheat depending on how well insulated and glazed your panel is. It does not need to be a good conductor since the absorbing surface is in direct contact with the water being heated. The only issue with this design is that water may condense on the underside of the glazing reducing the amount of radiation transmitted. In the text is says the average distance heat must travel is 1. On average therefore, heat needs to travels 1. I am interested to add a solar water heater on top of our camper.
Since I also live in vancouver, BC would it be possible to meet with you and see your prototype? Where I grew up in Israel it is very popular mandatory actually… but those systems are too heavy and not mobile. I liked your use of plastic however if you check carefully, the acid rain might corrode your plastic so a glass cover is recommended. I also suggest you warn people not to drink those water!
It was never my intent that this design be used for drinking water. Thanks for the comment. Hi rob, this is aurelio i did start putting together the solar panel and i can not find the pl in california and arizona is restricted what other adhesive will you recomend, i did try different other bonding like abs bond,flex,windshield sealant,and even the weather roof sealent, white silicone etc and none of this have worked, can you please advice what other kind of adhesive can use.
Hi Aurelio, There are few recommendations for different adhesives from readers in the comments above if you search through them. Even the PL I used is not a great choice. One reader recommended this: Has anyone tried using air to transfer heat to a car heater core or aircon type of radiator?
Meaning make a enclosed box with black insides that heat the air, then use a small slow muffin fan to circulate the air past the radiator at the top of the boxand then move water through it etc. It might be as simple as painting the wood inside black or putting a black trash bag in there.
Maybe convection would move the air, but I think a fan would raise the efficiency and you could run that with a small solar panel. Hi Rob, This is a great idea, and the method of construction is well explained. I am from India.
I have seen people here embrace solar energy as long as the device is affordable. I will spread this idea to all those interested.
I try constructing one myself to demonstrate this idea. Thank you for your post Rob. Well, just one concern. I am worried about what Eric said about sanitation. I came across your plans in the instructables.
I hope to take the edge off of our Calgary winters with this. I hope you can fill in the blanks for me on a couple of questions:. Should I run my pipe direct from the collector to the sand-bed and then to the storage container, or from the collector to the storage container THEN my sandbed? Hi Tweac-It, To answer your questions: If you are using a sand bed to store the heat, there may be little benefit to having a large storage container for the water.
Both the storage tank and sand bed will be in the greenhouse and both will store heat. One thing to note though is that a sand bed will dissipate heat into the ground.
You might consider a couple inches of polystyrene underneath the sand bed to insulate it from the ground. This way I will always know the walking surface is in contact with the sand. I will insulate 4 sides and bottom. As for the location of the collecter vs sandbox….
Any idea if your design as posted and unmodified will be able to fend-off freezing inside a 12 x 12 hoophouse? It will depend on the outside temperature, the wind chill, how well the building is sealed, how the panels are oriented, and how much sunlight you typically get. For example, if you find Watts on average is enough, then you might get away with 4 collectors as described, assuming the collectors see sufficient sunlight for about 6 hours per day.
I came across your site a few months back while I was prototyping my own plastic thermal panel. I think plastic solar panels have the potential to completely revolutionize the industry by lowering the cost. However, you hit on the problem I was working on:. I think the efficiency may also end up being higher then commercial systems.
I built a prototype:. I just wanted to give you a big thanks for your website and the work you are doing. Its people like you that are going to save this planet.
Hi Alex, Your solution is brilliant. I posted more comments on your site… — Rob. Hi Mike, Your guess is probably as good as mine, but my guess is that exposure to the plastic is not an issue. I doubt the chemicals that leach from the plastic are any more harmful than the chemicals people typically add to their hot tubs intentionally.
I have read your blog and another one you commented on about using Coroplast for thermal collector panels with great interest. My wife tested baking a sample at degrees F and it came out feeling just about as rigid as normal. We also filled it with water and put it in the freezer and it did not deform from the ice.
I am however concerned about freezing problems, more due to glued joints at the ABS pipe at the top and bottom of an assembled panel bursting. I am planning to build a drainback system using these panels, and just painting them black. I also saw that polypropylene does not tolerate UV light well and will become brittle and break after long exposure. Coroplast can however be made special order with a UV absorber mixed in with the polypropylene.
I mean protect it with minimal costs and move forward with making it actually do something at home. From a guy who does this stuff a lot, I see problems. The restriction of flow will use more pumping power, calculate that in. You are going to have to insulate it in a box of some kind during the winter if you want heat enough to cover the costs of building it.
When you do insulate it, the box is going to get hot, maybe too hot for your plastic. Now the question is, did anyone read my above post about the hot box with a simple car heater core, or car oil cooler in it and a fan?
Using the air in the box to transfer the heat? Just a black box with fiberglass insulation and glass front. Repeating these comments I left on the instructables site for this topic. The relatively low temperature of the collector minimizes expansion and contraction of components, reducing wear and tear. The mass of the water in the system helps protect it from freezing and extreme high temperatures that can harm materials, which leads to long system life.
Research in Europe suggests that up to 20 percent of the water in the collector can freeze without damaging the tank, but keep in mind pipes are still at risk unless protected or drained. Locate your heater for maximum solar exposure.
Find a sunny, south-facing location, preferably close to the backup heater to minimize piping distance. You might have to do some calculating to be sure your solar collector will be exposed to the sun when you want hot water, but placement and orientation are the single most important considerations. Remember the sun is high in summer, low in winter. Specific optimum angles for your location during any month of the year can be found here. Next, determine where your heater will be installed — roof, platform, wall or ground — keeping in mind that a filled three-tank gallon system can weigh more than pounds when full of water.
A rooftop installation may be placed above a load-bearing wall or reinforced section of roof. Ground mounting is easiest, and eliminates the weight problem. Make the collector and storage tank s as efficient as you can. Tanks come in a wide variety of shapes and sizes, but long, thin cylinders are the most efficient they have the greatest ratio of surface area to water volume.
The cheapest and easiest of these to obtain are used electric water heater cores. A new one costs only a few bucks, and it will add measurably to the longevity of your system. Check carefully for leaks, and never use a tank that you have doubts about. Wire-brush it and paint it with rust-resistant flat black paint, or apply a selective surface coating if you can afford it. If you prefer new tanks, you can order glass-lined electrical water heater cores — minus the heating element, outer insulation and sheet metal cover.
Stainless steel tanks also may be available in some areas. Ensure that your system will retain heat.
How to Build a Passive Solar Water Heater
There are a number of options for glazing the top and the south-facing wall of your unit, including single- and double-paned glass or fiberglass and plastics designed for extended solar exposure.
In most cases, you should use two layers of your chosen glazing material with an air space between to provide maximum heat retention. Glass is generally a suitable glazing for owner-built heaters, unless you get severe hail. Twin-wall polycarbonate is a tough alternative. Be sure to flash the glazing carefully to avoid leaks and to caulk and seal the panes to avoid condensation, which can limit energy capture.
Size your heater appropriately. To determine the size you need, allow 30 gallons of hot water per person in your household a conservation-minded family might get by with only 10 gallons per person.
A smaller water-to-glazing ratio speeds up heat gain considerably but can increase the freezing risk. A smaller system will still provide economical solar water pre-warming and conserve nonrenewable energy and cash.
Batch systems with relatively small tanks and simple enclosures are common, and many are still doing well after 30 years, long after most of the more complex systems have disappeared. Make an efficient, freeze-resistant connection to the backup system. Minimize pipe runs and insulate the pipe carefully using foam or fiberglass insulation with aluminum jacketing. Build it to last — if you just use foam it will break down within a few years.
It can take up to 72 hours at 12 degrees to freeze an exposed water heater tank, but pipes are much more vulnerable. In a brief freeze, you can leave the hot water on slightly to keep the pipes from freezing. In very cold winter climates, drain the collector tank and pipes in the fall. Set the system up so you can turn off the backup heater and run solar hot water directly to users, and so you can bypass the solar water system if you want to drain it and shut it down in winter.
Make sure the connections are building code approved.
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