Benefits of Solar Wall Heater
Question: My children are studying passive solar energy in school, and until I add some solar heating to our house, they will drive me nuts. Are there any inexpensive, do-it-yourself solar projects?
Answer: There are quite a few simple passive solar projects that you can build for under $100 in materials. These are excellent family projects, and the finished solar heater can produce enough heat to keep an average-size room warm well into the evening.
The simplest designs use the passive solar principle of thermo-siphoning. These designs rely on the fact that warm air is less dense than cold air to create the air flow through the solar heater. A lower inlet draws in cool room air from near the floor, and solar-heated air flows out the top.
The advantages of these designs are low material costs and the fact that they tend to self-regulate the air temperature. As the air gets hotter and less dense, more naturally flows through, so the outlet air temperature stabilizes.
An air-type solar wall heater, mounted flat against a southern wall, is the easiest to build and will help get your kids off your back. As long as the wall is oriented within 15 degrees of true south, it will be effective.
Simply, this design concept uses a perforated metal collector sheet (painted black) inside a shallow insulated plywood box. As the sun shines through a glass or clear plastic cover, it heats the collector sheet. Crystal-clear acrylic plastic sheets are the easiest to work with.
The perforated collector is mounted on an angle inside the solar box. This forces the cool room air to pass through the openings in the sun-heated collector as it circulates from the bottom inlet to the top outlet opening. The bottom edge of the collector should be closest to the house wall.
Make it roughly 4 feet wide and 6 to 8 feet long to minimize scrap lumber. If you install an electric blower for more heat, a 100-cubic-feet-per-minute blower should be adequate for this solar heater. When using a blower, the entire heater can be tilted more directly toward the sun.
Standard expanded metal sheeting is most readily available and easiest to use for the metal absorber matrix. Lath can also be used. Wire together three or four layers of it, staggering each one a little to offset the openings. This provides more exposed area to the sun with adequate air flow passages.
If you have a large south-facing window, without the greatest view, build an attractive brick or stone wall close to it indoors. This creates a Trombe wall. The sun heats the wall (thermal mass) in addition to the room during the day. At night, the wall continues to heat the room.
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Write for (instantly download https://www.dulley.com) Update Bulletin No. 997, do-it-yourself solar wall heater instructions, building tips for a Trombe wall and solar position charts. Please include $3 and a business-size self-addressed stamped envelope and mail to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244.