Thursday, November 15, 2012

Solar Beer Can Heater Results

First I want to say thanks to for linking up this project. They sent over 1300 people to MDR so far.

 I hooked up the heater using a 3" water heater flex tube. The flex was the only way to go because of the pivot motion of the heater.
You can also see the placement where I get the temp readings   

 The other end of the flex goes through the window of the shop. I made a block out for the window and sealed it off to keep the drafts out.
The out flow really needs to be higher, but I did not want to start cutting holes in my new shop until I did some testing first.

It was early in the morning and the ambient temp was around 40 when this picture was taken. The output air was already at 150 degrees.

The high readings for the day were,
Ambient = 55 degrees
Air Output = 180 degrees
 I could improve the output temperature a little by insulating the box. I really don't want it getting much hotter because I did not use high temp adhesive.
Right now I am loosing 20 degrees by the time it leaves the box and gets into the shop. The metal tubing is cooling the air back down a little. I will insulate the tubing to try and hold on to the heat a little longer during its travel into the shop.
Another step I plan to do is to attach an additional tube and bring the inflow from the shop instead of the outside. This way the air that is circulated will be from the inside and when the shop starts heating up it will be more efficient by circulating that same air.
Doing that I will have to build a filtered return air box inside and on the floor of the shop and put the outflow pipe at a higher level. The fan will also be placed inside the filtered return air box to increase the efficiency of the fan.
If I am going to go that far I might as well put the heater on a thermostat and go ahead and hook up a battery bank to it as well. That means I will need to increase the solar panel to a higher wattage to charge the batteries.
The one main problem to all this that the square foot of the heater will not heat the shop quickly or keep it at a constant temperature. The cubic foot of the shop is too massive for such a small heater. This design was made as an experiment to see if it would work. This heater would heat a well insulated room of about a 10'X8' with 8' ceilings. I originally designed this to heat the bathhouse.
This means to achieve the desired temperature in the shop at a reasonable rate, I will need to build one 2 1/3 larger than this one. That is a 230 can system. Or I could just build another one like this one and attach them together. I guess I need to call my buddy and have him start collecting cans for me.

Cost results,
Total out of pocket using junk on hand = $70.00
If I bought everything new = $200.00

I have seen some of these made using just 1/2 insulation sheets and sealed with duct tape and they work, but I wanted to build a heater that would last. The biggest cost if you have all the building material is the high temp paint and caulking.

That's all I got for now.


  1. Have you seen how this same system is being made using aluminum gutter down spouts? Seems much faster than cans.Youtube it.

    1. Thanks Adrianna, yea I have seen them and thought about doing the next one that way. It looks to get a lot hotter and yes, it would be easier than cans.

  2. Yes, very well done. I will have to go check out youtube too.

    1. Thanks becky. You tube has a lot of different designs to choose from. I studied them all and came up with mine.
      Good luck

  3. Nice job. Spray painting your flex tubing black might help cut down on some of your heat loss, as it continues to draw heat from the sun.

    1. Thanks Wendy. Yup, I thought of painting the pipe. I still have some black paint left so it would be cheaper than buying insulation, plus it would keep the flexibility I need. It wouldn't hurt to try it.

  4. Nice job. This is so cool (or hot as the case may be) I saw where your article got picked up on Homestead Survival as well. wtg!!!

    1. Thanks Sci. I just saw that. I am honored to be featured three times on their blog. I need to give them another shout out.

  5. Interesting. This could be a potential 4H project to heat the hen house with...... How difficult would you say this was, or maybe I should ask what aged child do you think could do this project?? 14? 15? Also, how did you drill the cans-how big of a hole and which direction? It looks like you used the larger cans, if someone used standard size soda cans would they need to increase the number of cans?

    1. April,
      Thanks for the comment.
      Yes, I think it would make a great 4H or FFA project. I think more schools and youth organizations need to promote projects like this.
      You can make this as easy as you want. The design I did does take skill but you can make it really simple.
      The holes are 1/2 inch in the bottom of the cans drilled with a wood bit and the cans are glued top to bottom. You don't even need to cut holes and just have the air flow over the front and out the top but the holes make it more efficient.
      The cans are the standard size 12oz cans just like a soda can.
      Youtube solar can heater and you will see many different designs with some simple builds and not using fans and just letting the natural heating of the air to control the flow.
      I hope this answered your questions. If not let me know.

  6. Another question......Think this would work on a roof or would it be better free standing beside the coop? This would be in an area that gets snow and ice. However the roof isn't so high that it couldn't be reached from the ground to brush it off should it become snow covered.
    Another kid is thinking it could also be used to heat a large sized dog house, but thinking they would need to make a smaller version so that the dog house wouldn't get too hot.
    And, child 3 is thinking of using this concept but with clear soda bottles connected by tubing to create a solar water heater, but he is first studying the effect of hot plastic on water for drinking purposes.
    I love young creative minds!

    1. April,
      Yes this can be mounted on the roof or on the side of the wall. As long as it can get full sun for most of the day it can be placed anywhere. I have mine free standing so I can turn it and receive 100% of sun throughout the whole day.

      For the second child, he needs to determine the square footage of the room to be heated. The capacity of heaters are given in BTUs per hour. You need to establish the correct number of BTUs per square foot for your room needed to heat it.
      At a bare minimum, you can use a figure of 20 BTUs per square foot and multiply this by the total square footage to be heated, but this does not take into account climate or the amount of insulation you have.
      In warmer climates, you need only 30 to 35 BTUs per square foot to heat your room adequately, while in colder climates, you may need up to 50 to 60 BTUs. In general, the further from the equator you live, the greater the number of BTUs per square foot you need
      If you have a 400 square foot room and a climate zone with a heating factor of 40 BTUs per square foot, you need a heater with an output of 4,000 BTUs per hour at 100%.
      How you figure the BTU your heater is producing is a whole other animal. In general you can figure, 1 btu = 1 055.05585 joules. It would take a very long post to tell you how to calculate joules from the sun but if you google it, you can find out how.
      In short this is what I have found out. A 100 can system in the exact angle of the sun, getting 100% exposure with an outside temp of 40 degrees will heat a 8x10 room. It takes about two hours to raise the room temp up 10 degrees and if the system recirculates itself it will warm up above that quicker. I don't think this would be very good in a dog house because at night it gives off no heat. I guess it could work only if the dog was put out during the day.

      For the third child, On my blog you can search solar water heater or bathhouse and you will see how I heat my water from the sun. If the child is persistent on using this design for water, then a detention time fracture has to be considered. Plastic and glass do not transfer heat as well as metal.
      I hope this helps