| I think that pretty much reflects a practical approach. I fully
| cost-competitive alternate approaches that work. Therein lies the
| most alternatives thus far, either 1) they are not cost competitive
| only will be if no maintenance is required and they last 20 years)
| they don't perform as well as what they are replacing -- either they
| provide the same quantity or require significant intervention and
| the part of the user.
| Looks like the panels you are putting in place are definitely
| problem #2, and most likely pretty close to fixing problem #1.
Well, they aren't the "magic bullet" that most people seem to crave.
They do a first rate job of producing heat during the daylight hours,
but they won't produce heat between sundown and sunup. Still, that
represents a significant portion of the heating requirement,
especially for people who're comfortable sleeping in a cooler
environment. I think it's possible to shrink purchased heating energy
requirements by a significant amount (30-70%, depending on local
climate and the particular residential structure.)
In combination with improved building technology - I've been hearing
about R-60 SIP panels - it should be possible to achieve 100% of the
heating requirement with solar in much of the USA.
A passive panel doesn't need much in the way of maintenance. Any
exposed wood needs to be protected with paint (just as with any other
wood component). There aren't any moving parts, motors, or controls to
fail - so those can't present problems. I think any well-constructed
panel that's kept protected against the weather should last as long as
the structure in which it's installed.
Payback period depends mostly on factors which are likely to vary from
site to site - latitude, weather, shading, etc., and the cost of
conventional energy over the life of the panel. My take has been that
anyone who eagerly spouts performance numbers either doesn't
understand or is full of blarney (or both). I know I haven't done
myself any favors with this, but I've refused from the beginning to
attach a Btu output rating to my panels. What I've done instead has
been to encourage people to install solar panels incrementally. They
will probably start out with too little capability, but they'll
certainly be able to recognize when they have enough - and they won't
have been conned into spending for more capability than they need.
For anyone who finds that disturbing, I've created a web page with
data maps from www.nrel.gov (National Renewable Energy Labs) for the
USA showing their 30-year statistical analysis at
www.iedu.com/DeSoto/SolarEnergy.html - and there's a link at the
bottom of the page for downloading a Win/DOS executable that makes it
easy to play with their numbers (and get outputs in Btu).
I've also attempted to catagorize passive air-heating solar panels by
configuration at www.iedu.com/DeSoto/SC_Types.html - which might be a
good starting point for anyone interested in designing their own
DeSoto, Iowa USA