Harness the sun to power a do-it-yourself space heater

By Hannah Pullen-Blasnik

Most people agree that steps must be taken to stop climate change, but often it seems like such a big task that it’s daunting to figure out what you can do to help. But what if you could spend one afternoon making a kid-friendly project from recycled materials that could actually make a difference in your home’s energy usage? It is possible with window box passive solar heaters.

Passive solar heating is heat generated by capturing the sun’s energy without using any mechanical devices, other energy inputs, or physical effort. With a smart design, it’s possible to capture the sun’s energy and transform it into heat without using a power source – providing you with a bit of free heating!

Imagine a car sitting out in a sunny parking lot in the summer. It can easily reach 120 degrees inside because heat from the sun comes in through the windows and gets trapped inside. In the same way, passive solar heating can be applied to houses – it’s all a matter of design.

The most common form of passive solar heating for houses is a passive solar building design. This is put into place as the house is built using elements like special windows, window orientation, and tiles for the floor that absorb heat well. But what can you do if you’re not planning to redesign your whole house? In this case, you can consider building a windowbox.

A windowbox passive solar heater is a mechanism for capturing heat from the sun. Put it in a window and, when the sun is out, more heat flows into your house.

It’s relatively easy to make one. The first step is constructing a box that can be placed in a window  similarly to an air conditioner. The box has clear sides across from each other and is filled with empty aluminum cans (e.g. seltzer cans, beer cans) that are painted black. The dark cans absorb heat from the sun, and as the heated air rises and comes out a hole near the top of the box, colder air is pulled in from a hole by the base of the box and, in turn, heated.

So, it is possible to make recycled materials into a passive solar heater. The question is, how practical is this, and who is it useful for? It works well as a way to save energy for someone who spends a good portion of the day in one room, such as in a home office. This way, the heat for the house could be significantly lowered while the room in use remains at a comfortable temperature.

The amount of heat produced by a windowbox heater is largely dependent on size, shape, and window orientation. It must be placed in a southern-facing window for maximum efficiency. An efficient passive solar heater can heat air an average of 20 degrees on sunny days. For example, if the windowbox heater is placed in a room that has a temperature of 62 degrees, it will heat the air that passes through it to 82 degrees.

Generally, a windowbox heater works best as an additional heat source, similar to a portable space heater. However, unlike a portable space heater, it doesn’t use any energy and is made from recycled materials. It’s also a fun activity for both kids and adults to enjoy!

For more information about passive solar heating, visit http://www.mnn.com/your-home/remodeling-design/stories/heres-how-passive-solar-energy-works

For example calculations by BTU/h from a windowbox compared to a portable heater, check out http://sunsystemdesigns.blogspot.com/2013/01/solar-window-heater-btu.html.

To see windowboxes as art for sale, check out the cool design of these products! Pre-made and ready for your window: http://www.heatstick.com/_AirMaze.htm