Cheap and Easy Solar Heater

Too bad putting it right in your window will do absolutely nothing to add heat to your house. Any sun that is being absorbed by the box is just heat being stopped from getting to the rest of your house. Sure the box will heat up, but the rest of the house will be cooler. I don't mean to harp on this guy, but its no wonder we have an energy crisis when 99% of people don't understand simple science. Energy in = energy out. One thing that would work is putting the clear plastic over the south outside wall of the house to create basicallly a passive solar envelope that increases solar gain.

Yeah, Paul D. makes my point, the first law of thermodynamics (conservation of energy) tell us that this device is most likely just intercepting energy that would enter the room and warm the house anyway. The only arguable benefit would be that the black painted box has lower reflectance than the average average albedo of the room behind the box, but I think that is a very questionable value.

Simply having a black floor and black walls wherever there is sun exposure inside the home--would that be a more effective solar heater?

This to me is an interesting question, as I'm due to renovate soon.

There is one way to capture more energy, more sun light. If there was a mirror outside the window angled to reflect more light into the window that would increase light/heat like solar thermal electric power plants. Double pane windows might reduce heat loss.

http://www.solardev.com/SEIA-makingelec.php
First link from google.

This might be a better solar heat project. I'm a layman but this seems like a way to utilize sun light/heat the would normally be reflect by the side of a building.

http://www.instructables.com/id/Solar-Heater/

I've seen a few of these floating around the web, and I'm considering making one to help keep my ground-floor apartment warm this winter. While I agree wit Dr. Paul (there is, after all, not escaping the 2nd law), I'm wondering if the fact that it's painted black increases the amount of energy that gets converted into radiant heat?

Ideally, of course, you want to have the heater outside and either heating outside air or sucking inside air out to be warmed up before blowing it back into the building.

There are several similar designs out there, both home brewed and factory made. Ones that don't obstruct a window obviously have an advantage. I understand they are very effective. Homebrewed ones can be quite cheap.

Black surfaces absorb light which builds up heat, as a child living in the UK I use to see kestrels flying over the motorways, not only were the birds looking for prey but also heat thermals generated by the heat from the black tarmac roads. You must of seen a heat haze/glare from the tarmac while on the road on a hot summers day?

Light colours reflect light and heat. So I can't see why this Solar Heater would not work.

I for one have started to save my copper coins for the project.

Hmm, only problem is that I bet the pennies don't do that much. Only pre-1982 pennies have copper in them.

I've never heard of using pennies before. Interesting and cheap, but I did wonder how the heat would get to the rest of the room.

This does not seem useful. There is no way to store the energy. Most of the folks will need to heat the hosue at night and not during a sunny day.

For all the physics lessons that abound in the comments here, they miss a point. Sure, this intercepts heat that otherwise would enter the room. However, the heat in the room is also free to leave the room. So then your room would have a temperature spike while the sun shines, and then get chilly as the heat is lost through your walls and windows. The pennies provide a not very good thermal mass, which will help to smooth temperature peaks.

No more heat enters the room. You just save some of it for a time when you need it more.

Hey,

Great article - makes people think and that in turn will lead to innovation.

Congrats - and good luck.

Cheers,

Eric Dewhirst
Ottawa, Ontario Canada

Hey Ruben,
All the comments about how this is basically useless make sense, but your commetn about the pennies being a thermal mass... well, technically speaking yes, they are a tiny, tiny thermal mass, but the whole idea of a thermal mass is to have a large mass that absorbs and holds heat. Those pennies won't do squat. Sorry.

quarters actually contain more copper than pennies which are mostly zinc.

Either this was genius or complete stupidity - so of course, I had to try it. I had plenty of cardboard boxes lying around after xmas... so I decided to make a cheap-o version to put it to the test. It could've been better insulated, but here's what I did:

I lined a cardboard box with a scrap piece of copper flashing. Then covered the interior with black construction paper, cut a hole in the bottom and top and attached a sheet of plastic to the front. I attached legs so that cold air would have space to get up in my box's business. As a final touch, I added a handle so that I would be able to transport it to to other rooms. hahaha Actually the "handle" was installed so that I could dangle a few loose threads above the exit airhole. This way, I would be able to watch the threads bandy about wildly as heat bellowed out of the box.

I set my furnace in the window and success! The threads were wiggling - about 1/100 of a nanometer, but still, it proved that convectional forces were hard at work. The problem though, is that my kitchen is tiled and freezing so I'm sure any magic box heat gained is quickly consumed. Maybe by sundown, it will be a sauna in there! At least I have a solar piggy bank now. I can drop pennies or quarters or (whichever has more copper) into the top slot, and when they're warm I can fill my pockets with the coins and then sit under a blanket. When I give them away I can also make someone else feel warm. All, compliments of the sun. See - it DOES work!! I'm not giving up on the solar furnace just yet...

LA: Send us some pictures and we will do a post on it.

I didn't quite catch how to attach this heater to the window or how the heat gets into the reoom.
It didn't appear to vent into the room . What have I missed?

I re watched the video and paused it. Iwas able to see the window was attched to the inside of the window (duh). Which slit is for the coool air to come in at the bottom, the large or small slit?

I like others I must have missed the venting process.

I know the idea works to some extent as I tried it on accident once. While working graveyard shift I tried to darken my bedroom with thick, black visqueen type plastic.

I taped the black plastic up in my south facing window. Here is Utah the winter sun arcs fairly low in the sky.

It worked great on darkening the room but what surprised me was how well the light was converted to heat. Within minutes I could feel that warm radiant heat like you would feel off a hot wood-burning stove or IR-heater! It would warm my room for nearly 6 hours and from about 11AM to 2 PM I did not need any blankets at all.

Since then I have always wanted to buy a set of cheap aluminum "Vertical" blinds for one of my windows. If you laid out the vertical veins on the ground and painted all of them on one side a very dark flat-black or any real dark color I think it would work great. On days when you want to supplement the heat in your house your would turn the wand to rotate the black sides of the veins towards the outside. If your house is already warm you could turn the veins to have lighter or white side towards the sun.

Black verticals might not be too aesthetic but you could always hang another curtain in front or even add wood shutters so long as they allowed for venting however you might miss out on some of the radiant heat that I noted in my visqueen "experiment".

Also, don't think that light simply reflecting around the house off white walls and out windows is going to convert the same amount of heat as a dedicated solar heater with dark surfaces that absorb a broader spectrum of light energy.

Any school-boy can tell you light color cars tend to be cooler than dark or black color cars even though they are both bombarded with the same amount of solar energy.

The only other small criticism I would add is that most pennies are not copper anymore. However, like I said my accidental experiment surprised me with the copious amounts of heat through basically non-conductive plastic. Certainly the modern-day penny is more conductive than plastic.

Before you dismiss this try a few experiments,then tell us.

I am thinking of building one for the roof and using a small PV-panel to power up a small 12VDC computer fan to force air through and into the house. It would run only when there was solar energy and could have a thermostat(s) to prevent overheating the house in the summer or blowing cold air prior to actually warming up.