Converting electricity into heat is one of the most expensive uses of energy. If you’re not convinced, look at the power usage of electric appliances like microwaves, space heaters, water heaters, ovens, or coffee pots. The difference can be seen between your electric bill from a cold month, when you have to continually run your central heating, and during summer months, when the ambient temperature does not need to be heated.
If you live off-grid, you tend to be far more aware of what it takes to create electricity; you can literally watch your batteries’ voltage drop lower and lower when using an inefficient appliance. However, if you are tied into the grid, you should almost be extra vigilant as regards your power usage. Not only do you have to pay for it each month, but also the power plants that produce your electricity are rarely sustainable or environmentally conscious.
When considering the issue of heat, there are several green options, the best of which is the sun. Solar thermal energy can be harnessed in many ways to heat your water, food, or home. For the purpose of this article, we will be concentrating on an active thermal space heater to heat a room or house. The unit takes one person two days to construct, one day to install, and costs under $100. The temperature inside the unit easily reaches 160 degrees Fahrenheit on a 50-degree day, and can be blown into the house using a fan that pulls less electricity than a light bulb.
Please note that the unit should be installed on a south facing wall (if that is not possible, then a west facing wall will at least give you heat in the afternoon).
An additional advantage for rural Mexico is that the production of these units can create a local business. A couple of people could start making them with very few tools and initial outlay. Any new business in a rural area will increase the wealth of that community, as there will be more money being circulated locally. Furthermore, people can apply to their municipal’s Presidency for aid in putting them in schools and community buildings, to reduce the amount of firewood that parents have to provide. If you are interested in starting an environmentally conscious business in Mexico, please see our Spanish version of this Intructable.
For more information, view How To: Solar Heater
One 8’x4’ sheet of ½” foam insulation, with foil backing
One 8’x4’ sheet of transparent, corrugated plastic
Three 10’ pieces of 4” metal channel
Two pieces of 24” x 13.5” sheet metal (for shorter room-see step 1)
Four 8’ pieces of molding (1”x1/2 “)
16’x4’ of black screen (metal or plastic)
One 8’ length of 4” dryer vent tubing (for shorter room-see step 1)
Two 4” hose clamps 4” 100CFM fan (if fan is 12 VDC, you will also need a converter from an old computer or printer)
Screened vent Snap switch (45C action, 30C reset, Normal Open, Thermostat Temperature Control Switch, we use model KSD301)
10’ of 12 gauge stranded wire
Cheap extension cord (to reach your nearest plug)
½” metal screws
1” wood screws
12 x 2” screws and concrete anchors
60” of 1” wide metal, 1/8” or ¼” thick
Insulation for the dryer vent (optional)
Masonry drill bit (long as possible)