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Home Built Solar Heater

06/06/2015 10:24 PM

Last winter I built a pop can solar heater using mostly found items. I did this more for the challenge of it than anything. I'm considering building a much larger one and hopefully a better one although the first performed flawlessly.

A google search shows lots of YouTube videos, some that are somewhat helpful and others that are,well, useless.

I watched many videos, read articles, looked over several plans and then came up with my own. The heated air, which was pulled from inside the house and blown back in was consistently 100 degrees or more warmer than the outside temp save for cloudy days when there was no sun.

My question is has anyone else built one and what if any modifications have you done to enhance performance? Looks etc.. Not particular as to what you used for heat riser tubes, cans, aluminum downspouts etc.

I just find I'm hooked on these as well as other sustainable energy projects that a do it yourselfer can do and am curious as to what others are doing.

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#1

Re: Home built solar heater.

06/07/2015 12:02 AM

Can you describe what you have started with, because my dreams go wild.

Is it a pile of pop cans, eventually painted black, exposed to the sun and covered with glass, where you blow air through?

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#2

Re: Home built solar heater.

06/07/2015 1:17 AM

I made tubes from the pop cans to make the heat exchanger, they are siliconed together and painted flat black. The cover is a piece of 1/4" thick glass that was given to me for hauling away. I made my box 6" deep and have the heat risers suspended in the middle with a 1" gap between the tubes and lined the inside with aluminum foil to radiate the suns rays to the back sides of tubes. Boards on either end have holes that the tubes sit in to hold them in place. The air is pushed through with two old computer fans that run off my solar panels. One pushes and the other pulls.

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#3
In reply to #2

Re: Home built solar heater.

06/07/2015 12:44 PM

Most of the Air to air heat exchangers I know of are characterized by big masses, and/or a pretty sophisticated control system to keep the temperature within specifications.

The 2 computer fans are not going to heat your house and unless the cans are plenty, and filled up with stuff to create a heat accumulator of sufficient capacity to serve your purpose.

In this setup you can control the temperature by playing with the air flows and mixes.

The air in this scenario needs to tap into the box where the can are kept.

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#4
In reply to #3

Re: Home built solar heater.

06/07/2015 3:09 PM

Good thing you didn't tell me all this before I built it, I may have never tried it in the first place. I'm happy to say you are mistaken as to it's abilities!

The thin walls of the cans conduct heat easily, the box is totally sealed from outside air temps, and air from inside of the house circulates through the tubes themselves. The holes in the bottoms of the cans are roughly four times larger than the opening at the top creating a bottle neck, so's to speak and that air that is held back becomes extremely hot!

You can not hold your hand on the glass at the top of unit when it's working, in fact you feel the heat well before you get too close. A friend tried to suggest I was wasting my time untill he started looking into it, I heard him cuss when he touched the glass. Imagine getting into a car that's sat in the sun all day, same principle.

Between the mass of the 140 cans ( which isn't much!) the 1/4" thick 3'X6' glass plate and the one inch wood that it's constructed from it holds heat rather well and will warm air for several hours after sunset providing it receives enough direct sunlight during the day. It has a snap disk that turns the fans on at 77 degrees and shuts back of at around 75, I've measured heat up to 250 degrees coming out of it, it makes a difference. And I've watched the temp on my thermostat rise with no other heat source being used.

I've heard of claims of well over 300 degrees with a similar set up but find that hard to believe unless it was already extremely hot outdoors to start with and even then I would have to see it to really believe it.

You should know I did this in part to see for myself if they actually worked and supplement my house heating if so, not replace it.

The case cooling fans work much better than you give them credit for, since these units work on convection alone as the design is passive the fans are not actually needed, I only added them because I wanted a little more air flow. All in all I'm very happy with the unit but want to build another, a little bigger and a little better! Add more mass, thought of steel bars or pipes maybe filled with wax or oil to hold heat longer. I'm hoping someone else is out there working on similar goals and won't be worried about the nay sayers and share what they have learned.

In the first moth it hit ROI, which if you don't count the hours I spent after work assembling it was $50. In fact living in South West Kansas I didn't turn our furnace on until early December. My heating bills were cut in half throughout the rest of the winter months and now I have it set to pull warmer air out of the house.

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#14
In reply to #4

Re: Home built solar heater.

06/08/2015 1:28 PM

Did you also notice how fast your can is cold when the sun is gone?

It seems to me that you stabilize your comfort zone variations with your body mass and clothes.

Earlier I have installed a stack of heavy blocks in a greenhouse type roof and that keeps the collected heat for days. You can even retract heat from it during night time.

Your system is a jackpot (like heat profit in the sun, not when you need it the most) with near to zero storage and the other a long term profit rendering system.

You can easily calculate the heat (storage) content of your 250 soda cans, compared with a 25 tons perforated block collector.

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#17
In reply to #14

Re: Home built solar heater.

06/08/2015 5:30 PM

In case you didn't read my earlier comment. It often continues to warm air for several hours after sunset.

Since this unit is only meant to supplement my furnace there is no need for me to wear layers of clothing to stay comfortable and I can see no reason why you would make assumptions to such!

If only there was a way for my plaster and lath walls to act as mass and hold heat! It was meant to work during the day, the housewife thought it was great and didn't seem to mind the fact that the main heater would not kick on till well after we were in bed. And the thermostat was kept on 75.

From reading your comments it's readily easy to see you have never built or used a solar heater and have no clue what they are capable of! I'd suggest you do some research into them and maybe even build one before you knock them, you just might surprise yourself and learn something new.

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#19
In reply to #17

Re: Home built solar heater.

06/08/2015 6:16 PM

You are talking to the wrong guy, but I let you have your fun and insinuations.

You can indeed warm up your cans after sunset with sending the warm air of your house through it.

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#21
In reply to #19

Re: Home built solar heater.

06/08/2015 7:23 PM

I was addressing comment #16. Unless your trying to now claim you did not make it! Had I realized your first comment was meant to have been snarky I would have totally ignored you like I will from here on out. I'm only interested in having an intelligent conversation on the subject matter of solar heating and or other solar powered projects, and you don't seem to be up to the task! Have a nice day!

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#23
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Re: Home built solar heater.

06/08/2015 10:00 PM

I had no intention to be snarky from the beginning. Perhaps I should have suggested stack instead of pile, but that was lost in translation.

English is not my native tongue and not even my second, third or fourth language.

Praise yourself lucky that I opened the comment line on your non- informative post by asking some more information in a moderate and polite way. I read your post many times before I posted and only after your answer I switched to my my kind of sarcasm, but still allowing you to read and digest my answers. You do a lot of non relevant typing. Me too.

I have seen your picture now and you did a great job with the materials available. Congratulations.

Just don't inform the customers that are convinced of our solar product lines as they cherish:

"Supreme quality and unique performance exported to more than 70 countries all over the world".

Some of the countries we export to are: Germany, Italy, France, Spain, Canary Islands, Portugal, Netherlands, Austria, Belgium, Sweden, Bulgaria, Slovenia, Albania, Cyprus, Australia, N. Zealand, Oman, Bahrain, U.A.E., India, Thailand, Malaysia, Indonesia, Philippines, Korea, Argentina, Brazil, Chile, Bolivia, Venezuela, Grenada, Martinique, Nevis, St. Lucia, Dominican Rep., El Salvador, Costa Rica, Nicaragua, Panama, Malta, Morocco, Tunisia, Egypt, Libya, Algeria, Senegal, Ghana, S. Africa, Kenya, Botswana, Namibia, Zimbabwe, Tanzania, Zambia, Mauritius, Reunion, Madagascar and others.

Three years ago we introduced the line of products to get UL certification but decided not to export to the USA yet, since the production capacity is limited by the 76 employees, producing only 1200 units a day. Fits 15-32 containers. Also a case study with poll exposed that the US public in general is not that ready to implement solar.

As reason was given that the energy price doubled or tripled the pay back period for the systems' investment.

I forgot the Bahamas, also good for 300 installed systems. As you can see also colder areas are included.

They have higher efficiency with a selective coating on the heating body, and a low reflective tempered glass cover. (Increase in non powered applications from 82% to 91%)

Tests in the Bahamas proved the heating body (black matte) to reach over 120 degrees Celsius (248 degrees Fahrenheit) Our sun exposure setup shows 1.700 Watts per square meter and more. The selective coating only provided 3% increase because of the heat load restriction in natural circulation flow through the solar body structure.

And you are welcome to check my power bill for heating, A/C, cooking, washing and averaging $25.00 a month for a $0.42 per kWh area.

All Solar

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#9
In reply to #2

Re: Home built solar heater.

06/08/2015 9:28 AM

The placement of your fans maybe a problem! Pulling heated air out , I imagined the fan motor is also being heated since it is along the heated air path? By doing so not only shortens it's usable life but also may cause some fire!

It will be safer if you place them both bellow where cold supply air is derived from and to push that colder air into the box rather than to pull!

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#18
In reply to #9

Re: Home built solar heater.

06/08/2015 5:34 PM

The fan that pulls air into the house is current not being used. Between the one fan pushing and the Summer sun doing it's thing the air is moving right along but thank you for the thought.

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#30
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Re: Home built solar heater.

06/26/2015 9:02 AM

Also Pushing is always better and efficient than pulling!

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#5

Re: Home Built Solar Heater

06/08/2015 3:58 AM

Solar hot water is probably the most cost effective and easiest way of utilising solar energy.

Plenty of sutff out there and on CR4 if you do a search.

Del

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#7
In reply to #5

Re: Home Built Solar Heater

06/08/2015 7:56 AM

Del, didn't you post something that you worked on for solar heating.... luke may be interesting in it.

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#8
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Re: Home Built Solar Heater

06/08/2015 9:03 AM

Yeah. this is that last part of the project, which also has a link to the first part.

Del

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#16
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Re: Home Built Solar Heater

06/08/2015 4:40 PM

Del,

I enjoyed your comment about the "boot" gasket. LOL!!

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#24
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Re: Home Built Solar Heater

06/08/2015 11:40 PM

I like that! Very nicely done and easy to understand what your saying. Have you considered combining this with a solar air heater? My plans are to build my next hot air unit 8'X8' . By running a coil through it for the hot water it would also add mass for the hot air heater, or do you think the two should be kept separate? Here where I live I would want to run antifreeze through the lines. Thank you for sharing your project!

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#25
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Re: Home Built Solar Heater

06/09/2015 5:04 AM

I didn't really consider the hot air thing as the south of the house acts as a sun trap anyway. It has a big double patio door total length about 15' if the sun is out it's the place to be in Autumn, Winter or Spring. We need the blinds down in Summer* as it gets too hot.

Del

That's about 5 random days in the UK

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#22
In reply to #7

Re: Home Built Solar Heater

06/08/2015 7:25 PM

Thank you!

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#12
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Re: Home Built Solar Heater

06/08/2015 12:21 PM

It certainly is. With the short payback time. Have it for 16 years now.

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#6

Re: Home Built Solar Heater

06/08/2015 7:17 AM

Well, the ROI of a lot of the systems touted round here is about 20 years, so a month is great.

These are my favourite projects, they cost little, they may not be 100% efficient, but they are effective and free.

Since your project has worked well, perhaps a photo?

Also, could you turn your attention to the holy grail of solar; inter-seasonal storage, ie soak it up in summer, release it all winter... there is no right answer, there are strange answers, ie pump summer air into a cellar full of broken glass to store the heat..

hope the next project is as successful.

cnc jim

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#10
In reply to #6

Re: Home Built Solar Heater

06/08/2015 9:36 AM

I like the simple projects as well. I just read a story last night along the lines of subject you brought up. It seems there is a small group of homes in Sweden doing just that, they are pumping solar heated water 65 meters underground and storing in in a layer of granite. They claim they are currently replacing 25% of their Winter heating needs and think that may increase over time as the rock builds heat. Food for thought.

Years ago I had read an article that talked about digging a hole 8'X8X8' and placing 10,000 pounds of rocks in it with a glass cover that would be covered in Summer to act as storage for cooler air and uncovered for warm air in the Winter.

They didn't really explain it in great detail but I'd think it wouldn't be difficult to figure out.

I may be looking at it all wrong with the ROI but to me even if it's 20 years your paying yourself back instead of continuing to pad someone else's bank account. And that then becomes money you can use on other things well before those 20 years have gone by.

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#26
In reply to #10

Re: Home Built Solar Heater

06/09/2015 5:41 AM

I may be looking at it all wrong with the ROI but to me even if it's 20 years your paying yourself back instead of continuing to pad someone else's bank account. And that then becomes money you can use on other things well before those 20 years have gone by.

Well, if you had the money, you are paying yourself back. If you borrowed the money it's lining someone else's pocket.

Thanks for the photo, it looks smart, some look like old pallets nailed together. Well done.

Cnc jim

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#11
In reply to #6

Re: Home Built Solar Heater

06/08/2015 11:25 AM

I'll try to put up a photo this evening when I can get to my laptop.

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#20
In reply to #6

Re: Home Built Solar Heater

06/08/2015 7:06 PM

This is as I was fitting the glass to make sure it would fit.

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#13

Re: Home Built Solar Heater

06/08/2015 12:50 PM

Your system sounds more like the link below. I have heard of some that only use natural convection to move the air.
http://www.rreal.org/solar-powered-furnace/solar-air-heat-basics/

Drew K

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#15
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Re: Home Built Solar Heater

06/08/2015 1:59 PM

Mine is similar but it sits at an angle to the house. In my location being mounted vertically like that would be a non starter the over hang of my roof would have a majority of it in shadows all day. I ended up enclosing the sides and putting a small window and a cutout on the side protected from wind so our dogs also have a heated dog house. I mounted a temp gauge on the side so I could see what conditions were like on the inside and found it stayed about 60 degrees.

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#27

Re: Home Built Solar Heater

06/11/2015 4:21 PM

I think if you melt aluminum in an "inert" atmosphere, you will have molten aluminum.

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#28

Re: Home Built Solar Heater

06/24/2015 2:38 PM

Nice job! Convective solar air heaters work great when the headers are oversized relative to the individual tubes. Many don't need any fan assist except to prevent overheating on bright sunny days when there's snow on the ground. Many people try integrating them into their forced air systems, but it takes a modulating damper to gain the most.

As far as using an interior wall as a storage unit, you could look into an architectural element known as a Trombe Wall which has a deliberately high mass, and faces south. If you don't have the window area you can imbed duct work in it and exit your collector into it to warm the mass during the day and let it radiate the heat at night, a big solar flywheel.

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#29
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Re: Home Built Solar Heater

06/25/2015 10:33 PM

Thank you! Good idea on the Trombe wall! I'm gearing up for another one that will be much bigger. Years ago I had read an article which talked about digging an 8'X8' hole 8' deep and insulating it and filling with 10K lbs of odd sized rocks with a glass top and using it for heat in the Winter and cooling in the Summer. I can't remember exactly what they called it but it seems like a good idea..

I'd like to do something like that to go along with my bigger heater! Mine works without the fans but I put them in to move air a little better and I was a little concerned that excess heat may break my glass. Not sure that it could but didn't want to risk it seeing as how it gets very hot on a nice clear day.

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#31

Re: Home Built Solar Heater

08/28/2015 8:48 PM

tracking mirrors

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#32
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Re: Home Built Solar Heater

08/30/2015 3:51 AM

I think it would take someone with more experience than myself with such things to make it practical. I lined the inside of the heat exchanger with aluminum foil in an attempt to reflect the suns rays onto the backside of the heat riser tubes. Since this is still my first unit I'm not certain if it works as I had imagined it might or not. It does put out a good deal of heat and has enough thermal mass that it continues to put out warmth for a full three hours after sun down. I had considered putting the unit on a sun tracker like they do with solar panels but the plans that I have found so far to date seem sketchy at best and a commercially built unit is currently out of my price range. I do like your idea though!

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