Potential Changes to TEA Solar Air Heating Collectors

The collector/system design for the TEA system was developed in 1980 as a part of the very intense development that was occurring in the solar heating area during the 70's and 80's. It is certainly one of the most carefully designed and tested systems developed in this time period.

While the design is 30 years old, the system can be built today exactly as described in the construction manual, and will work quite well. There is surprisingly little to think about changing or improving, but here are few areas in which developments over the last 30 years might be worth incorporating:

In the design section, I would say that the home insulation levels suggested are too low for a cold climate home today. Today's homes should be built to better insulation and infiltration standards, and this will in turn result in a smaller collector area and less heat storage for a given solar fraction.
Rock bins for heat storage have come under some criticism over the possibility of health problems from mold forming in the rock bin. I'm not sure how valid these criticisms are, or how difficult it is to avoid the problem. I suspect that it may be highly dependent on climate, with dry climates being less susceptible.

Alternatives to using rock bin storage would include using something like the crawl space water container based heat storage schemes described in The Solar Air Heating Systems book, or the attic water container system used in this Norman Saunders home. Or, the collector can be sized small enough that the thermal mass of the home itself acts as the storage. A solar air heating collector of this type that produces too much heat at some times of year can simply be shut down, and will not overheat the house, as excessive passive gain might.
I believe that polycarbonate glazing has progressed since the manual was done, and is a viable choice for at least the wall collectors. Twin wall polycarbonate glazing with UV filtering coatings (such as is used in many greenhouses today) is a good material with high transmittance, good insulating properties, and long life. It is also very easy to work with compared to glass. Single wall corrugated polycarbonate glazing, such as SunTuf glazing could also be considered. More on glazing materials ...
The control system might well benefit from changes in electronic controls since the 80's.

Here is an example of one recent design that is based on the TEA design, but makes use of polycarbonate glazing

www.mofga.org/Default.aspx?tabid=488

Gary May 25, 2009