Cheap Solar Heat

Last winter my boys and I made a very cheap solar heater with a large south facing window in our second story computer/ homeschool room. We just hung a black plastic sheet on the inside of the window with curtain rods. This left about 1.5" for natural convection to take place. It draws the cooler air near the floor and the heat just flows out the top. This room would always get warm with the sun shining in, but with just this black sheet I was able to turn off my heater (forced air) and just leave the fan on to circulate this heat throughout the house. I also used a portable fan to move heat out of that room so we could stand working in there on our computers. On sunny days with below freezing temperatures outside , I could shut off our heater from 11:00 am to about 6:00 pm and stay perfectly warm and comfortable inside the house.

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Howto & Style

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• solar
• heating
• how
• to
• heat
• home
• energy
• cheap
• panel
• easy
• alternative
• homeschool

[thatdontmakenosense]

hmmmmmm. the science doesn't make sense to me since the energy coming into the window doesn't change because of the plastic. The plastic doesn't make more sun/energy come into the room. hmmmmmmmm.

[TheRoosterscrow]

@thatdontmakenosense

Dark colors are dark because they absorb light, rather than reflecting it. This absorbed light energy is converted to heat. Havent you ever noticed how much warmer dark clothing is with the summer sun shining on you? Or compare walking barefoot some sunny day on both concrete (light surface) and black top (dark surface) and this will be made painfully clear to you.

[antorise1]

great !!! i love the simplisity and practical of this. but if you want ultra cheap heat also at night you must build the FUELLESS AIR HEATER that is proven to work.

[quote4257]

I saw this project in a book about cheap solar energy projects. The key is the gap between the window and the plastic and making sure the bottom has a gap. Hot air rises; so the cool air is sucked in from the bottom and hot air is pushed out the top. Wonder if it would be more efficient if the sheet is dropped to the base of the window vs. just above floor level.

[centervilletn]

thanks for posting this video..the simplicity and inexpensiveness makes it a no brainer for anyone concerned about utility usage.

[boat6868]

@thatdontmakenosense you raise a good question, I don't know if the light energy keeps bouncing around until it is absorbed or not...I am nowhere close to understanding this stuff, I am just a guy admiring some of the innovative homemade solar stuff that people are doing in order to see if any of it would be practical for me.

[thatdontmakenosense]

@boat6868 ok, I'm not trying to be a contrarian here, and my understanding of physics is completely "lay," but the light that comes into the room (no plastic) is absorbed in the blue paint (say, only 40%), but the remaining energy doesn't go away, it bounces onto the dark brown desk (and it absorbs 80%of the reflected light), and etc. until all of it is converted into heat. The ONLY light that isn't eventually converted to heat energy is the light that bounces back out the window into space.

[thatdontmakenosense]

Well the problem w/ white plastic is that it would reflect the sun back out the window so you're right, there would be no gain. But with the window open the light is absorbed in the room and turned into heat eventually. I guess the true experiment would be to, on identically sunny days, shut the door and keep track of the temp, once with the plastic down and once with it up. I think the advantage of a solar furnace on the wall (as opposed to covering the window) is increase wall space.

[Nubeck]

Excellent! Simple, inexpensive, effective.

[boat6868]

@thatdontmakenosense...my layman's understanding is that the BLACK surface creates more heat than the lighter surfaces that are in the room (same idea that a black seat sitting in the sun will be much hotter than a white seat sitting in the sun. To your point...if the surfaces of the room were black then hanging the black plastic would not generate any additional heat in the room.