Solar Power & Energy

Gary Reysa of BuildItSolar.com states that “Solar space heating can be 25 or more times more cost effective than solar electric (PV) systems…” There are several ways to build solar space heaters, and most of those follow very similar designs which are generally easy and inexpensive to create.

Passive or Active
Solar space heaters work by allowing sunlight in through glass. The sunlight heats up air in the space behind the glass, and the glass prevents the generated heat from escaping.

Passive solar heating systems require no moving parts or electricity, while active systems have small fans to help circulate the heater air.

Passive systems work on a thermosyphon–or convection–process. Because hot air naturally rises, a passive solar system allows cool air to enter at the bottom of a heater, and once it has been warmed by the sun it escapes into the home out the top of the heater.

An active solar heating system uses small fans to help draw the warm air out of the heater and back into the room.

Direct Gain
The easiest, quickest and least expensive way to take advantage of solar space heating is through existing windows. If you have south facing windows on your home, simply open the curtain wide–or remove them entirely–while the sun is shining.

Direct gain solar heating systems work best in homes that have thermal mass which can be warmed by the sun. Thermal mass includes water, concrete and brick among other materials–these materials collect and store the heat from direct sunlight, then release it slowly into the air of the home throughout the night.

Windowsill Heater
A windowsill solar heater is attached to the lower part of a south facing window. This allows the window to continue letting in heat and light from the sun directly, while also releasing heated air into the room.

A windowsill heater is a shallow wood framed panel which is the width of the window it’s made for, and several feet long. Inside at the center of the wooden frame is an insulated panel. The back side of the internal panel is insulated and the top side is painted black to attract more sunlight.

The front or topside of the heater is covered with glass or other clear material which allows sunlight to enter. The sunlight enters through the glass and heats air that’s trapped between the glass and the black part of the center heater panel.

Cool air from the room enters the heater on the back or bottom side of the heater opening at the windowsill and travels downward in the heater. As the cool air reaches the bottom of the heater, it encounters the heating side and begins to warm up. As it warms it naturally rises, and once warm enough it will escape back into the room through the top heater vent at the bottoom of the window.

Wall Heater
Solar wall space heaters work almost exactly the same way as the windowsill heaters do. Instead of being mounted to hang off the lower part of a window though, these are generally mounted on the outside of a south facing wall.

Holes are cut into the wall itself to create the intake and outlet air flow vents, and an insulated solar heater frame is attached to the wall where the holes were cut. This space heater also has a glass cover to allow sunlight in, and the wall side of the heater is painted black to help collect heat from the sun.

Cool air from the room enters the wall heater through the lower vent and starts warming up. As it warms it rises naturally, until it’s heated enough to escape through the upper wall vent back into the room.

Resources:
Passive Solar Energy
Solar Space Heating Plans