Observing the world of renewable energy and sustainable living

Designing the Ultimate Solar Hot Air Collector

We can’t say for certain when the oil age will end. It looks as if the ASPO crowd of 200x was too pessimistic and that perhaps even a ‘third carbon age‘ might be in the cards, for better or worse. Nevertheless, some day there will be no fossil fuel available or too expensive to heat your home. Than it is nice to know that there are alternatives for those living in the northern hemisphere. A few indicators first. An average electric heater can consume, say 2000 Watt. High above the atmosphere the sun radiates a whopping 1367 Watt/m2. In other words, a two m2 window worth of extraterrestrial sunshine would suffice to heat your living room. However, the atmosphere absorbs a lot. In the Sahara at the equator at 12:00, there is still ca. 1050 Watt/m2 left, but in the middle of the winter in NW-Europe merely 150-300 Watt/m2 remain, during the day that is. With a solar hot air collector efficiency of 60% and an average irradiation of 200 Watt/m2 you would need something like 16 m2 collector area to replace your 2000 Watt electric heater and have at least the living room heated. Fortunately, such a hot air collector is relatively easy to built, even by amateurs, as the video shows. So if you have a blank wall or garden with a fence more or less directed towards the south, go for it!

Video notes:

Unit conversions:
1 cubic feet = 28.3 liter
60 degrees Fahrenheit = 15.6 degrees Celcius
32 square foot = 2.97 m2
1000 BTU = 1.055 MJ
1000 BTU/h = 2932 Watt
40 CFM = 1.1 m3/minute

[wikipedia] – Polyisocyanurate (Polyiso)
[] – Super TUFF-R
[] – Tuftex

Optimum airflow: ca. 3 cubic feet of air per minute = 85 liter/minute
Optimum collector output temperature: 120 degrees Fahrenheit = 50 degrees Celcius


Here is another video referenced in the video above with construction details:


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