Solar Box Window Heater
Written by Todd Fratzel.
Solar Box Heater
Solar energy can be used to heat your home in several ways including this easy DIY solution. The idea here is to put solar box window heaters in south facing windows during the winter to supplement your heat needs. The beauty of a solar box window heater is you can make one of these for about $100.
How Solar Box Window Heater Work
The basic idea here is that the cooler room air is drawn into the lower chamber and warmed as it passes over the black heat collector. As the air warms it rises and enters back into the room through the upper chamber.
The heat collector should be spaced in the center of the box so there is about 3″ to 4″ of space above and below the heat collector. The heat collector could be made from almost any material and painted flat black. A more efficient heat collector can be made from a thin aluminum plate painted flat black, mounted 3/4″ of a inch above a heavy foam board. You can use some 3/4″ shims between the aluminum panel and the foam board.
It is important that the bottom and sides of the box be well insulated to improve air flow and prevent heat loss. It is also very important that the entire box be weather tight to prevent moisture from entering as the moisture will reduce the efficiency of the box. The top of the box should be a clear top, either a sheet of clear acrylic plastic or better yet an insulated window pane.
This is one home improvement project that could help offset your winter heating bills and also help out the environment. This winter I may sit down and try to design one and build it to see how well it works. Some of the more efficient solar box window heaters can produce a steady 120 degree air flow on a sunny day.
If you found this interesting you may also like DIY Solar Panels.
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So, have you built one of these yet?
I’d love to have one or two for our cottage. What happens at night? Do you leave it in all the time? Can you leave it unattended, such as at a weekend ski house? I’m interested.
@ Campbell – I have not built one yet. I am thinking about building one this winter as an experiment.
Bringing solar heating to any home is a tremendous idea – no matter what form it comes in or whether you bought it or made it yourself. Unfortunately, I’m not a do-it-yourselfer…and not everyone is. For them the choice is to have someone build a window heater – or look for another solution. And one is out there.
Here’s the pitch from us.
SolarChoice passive solar heaters masquerade as vertical window blinds. Operating via natural convection, cool air is drawn into the bottom of each vane. Air travels along the sun-heated aluminum core at the rate of 1.7 meters/second and exits the top and re-enters the room at temperatures measured at 120 degrees.
The University of Minnesota helped develop this innovative passive solar heater and works on all product research.
An independent lab (Stork Materials Technology) assigned an R-value of 1.7 to the “blinds” – so they not only heat…but insulate as well. Bob Vila, Solar Thermal Magazine, NPR and Green Builder Magazine have all written about SolarChoice. Every one of their articles is on our web site.
Are SolarChoice Heaters the solar solution for everyone? No. But if you’re looking for a heating solution for your home – go solar in some way, shape or form.
[...] Re: Winter wind negating negative pressure A 40mph wind gust will easily overpower the air flow of yoru fan. You want to maintain a negative pressure in your room flow. Positive is like a balloon, negative is like sucking through a straw. Sounds like you know that part. So think of your door as the open end of the straw, the fan on the other end needs to be sealed to the exhaust/window so it can suck air out of the room in a controlled manner. In general a box or tower fan equals a huge fail when trying to maintain positive or negative pressure. It is already failing and if you try to isolate it, it will burn up. In no way do they work well with filters either. Tower and box fans are just for circulation, not pulling air. Plus you are now fighting convection. Warm air always leaves a space traveling towards colder air. So as the warm air passes out your open window, cold air will flow in to replace it and travel along the floor and through or under your door. Secondary air flow fail and codl tmeps bad for your plants. Bigger temp fluctutations too so you will potentially get condensation on the walls. Then there is the secuirty issue of an open and unlocked window. If I were venting through an open window 24/7, I would open it 2" to 4" max, secure it from going any farther, build a box to fit the width of the window. Seal it all up. Inside the box would hold the fan on one end, on the other end outside it would have a 90 degree downward bend and be bug, bird and mouse proof. There are similar designs out there for passive solar heating. You would just not make it a closed loop system, you would open it to the outside. Solar Window Box Heaters – Do It Yourself and Save [...]
A girlfriend had on of these in the late 70s. It worked great. We removed it each Spring.