Developments Since "Solar Air Heating Systems" was Written

The "Solar Air Heating Systems" book is (sadly) pretty up to date. The reason is that interest in solar heating dropped off when oil prices dropped off in the 80's. But, there are a few things that have happened since the book was written listed below.

If you are aware of any others, please let me know.

Glazing:

While tempered glass is still the Cadillac of collector glazing materials, Polycarbonate has come along as another choice with some good things to offer. Polycarbonate glazing has a good temperature capability (270F), is nearly indestructible (its the football helmet stuff), its easy to work with, and less expensive than glass. Its life (with a UV absorbing coating on the outside) should be good, but its still uncertain how good -- I think that 10 years would be a conservative estimate.

Polycarbonate is available as a single wall flat sheet, as a corrugated flat sheet (e.g. SunTuf), and as double and triple wall (as is used in a lot of greenhouses).

Thermal Storage:

In applications where thermal mass is needed, plastic barrels filled with water have become a popular choice. Filled with water, they have a high specific heat (hold a lot of heat for their weight), and don't rust.

At the same time, some people have developed some doubts about the potential for growing bad things in rock bin storage that is discussed in the book. Radon might also be concern for rock storage.

Ducting:

The book emphasizes metal ducting, and has a lot of good material on how to fabricate metal ducting. Since the time of the book, the flexible and pre-insulated ducting has become common, and offers some additional possibilities.

The book talks about sealing joints with duct tape. I think that duct mastic would be a better choice.

Flow Rates:

I find the flow rate table on page 84 that shows you how to correct flow rate for altitude a bit suspect, in that the flow rates go up much faster than the air density goes down. This does not seem right to me, and I wonder if the table does not overcorrect at higher altitudes?

Prices and Tax Credits:

Of course, the prices throughout the book are way out of date, and you should get look up new prices.

The same is true of tax credits -- which now seem to have come full circle.

Sun Charts:

The sun charts in Appendix 1 are fine, but you can also get one online that is built for your particular location here: http://solardat.uoregon.edu/SunChartProgram.html

Controls:

There may be some good digital options to the types of controllers and thermostats listed in Chapter 6.

Measuring Performance:

Appendices 4 and 5 talk about measuring performance of your collector. There are some ways discussed here to measure collector performance and even do a rough estimate of efficiency without some inexpensive instrumentation here:
http://www.builditsolar.com/References/Measurements/CollectorPerformance.htm

Gary 07/15/06