The Oil Drum: Campfire | Practical Passive Solar Renovation

57 comments on Practical Passive Solar Renovation - Part 1: Easy First Project

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Will Stewart on February 11, 2009 - 10:01pm

Craig,

Excellent work, we admire your initiative! The solar collector style you've referred to is related to tonight's project, and will be the subject of a future post (email me).

Could you estimate the savings you would realize if you would have heated with natural gas instead? What are the dimensions and how well insulated is the workshop?

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renofreepress on February 11, 2009 - 10:47pm

Dear Will,
Our slab is about 22 by 30 feet. The workshop is not well insulated, but we did put some fiberglass in the rafters.
The slab is uninsulated around the perimeter, so it really sucks out the heat. If we were to dig it up around the edges and put in some rigid foam down about a foot, it would help a lot.
Also, it's really hard to calculate because here at 4500 feet in Reno, we do get some outstanding solar days, but also lately (climate change?) often get many days where it's cloudy. We used to have sun most every day here when I was growing up. Nowadays it's hit and miss.
The second year after building the 1st four panels, I took off the glass and painted the BACK side of the metal flat black also. This I've read allows better heat transfer, but I'm not an engineer and my math sucks.
The sheet metal is BTW offset from the wall by washers to about half an inch. This gives, I believe, double the surface area of the sheet metal, instead of having the air flow only over the front side.
I measured 146 degrees one day static at the top of one panel.
It was a quick and dirty job, but cost very little, and didn't take a whole lot of time to put up. I did learn, however, before drilling 3 inch holes in your wall, be SURE to see that there is not a stud right behind it. Also any (live) electrical....

I'm excited about solar thermal. IMHO solar PV is for the wealthy. Using solar hot air and also solar hot water is far more $RO$I, than Photovoltaic, and it is much more friendly to community manufacture, and creating jobs and energy savings quickly.
I'm also very interested in building neighborhood sized focussing parabolic reflectors, which could in theory provide steam, or great heat for Stirling and Ericcson hot air engines, as well as providing hot water as a waste product from the engine cooling requirements.
I've got a 1 M parabolic, and it is truly a scary device.
I wouldn't be surprised if it were possible for a neighborhood group to build a large enough solar furnace to be able to smelt small batch aluminum and other soft metals.

Thank you folks for this Campfire post, this is the kind of stuff that I like to get involved in. I enjoy reading all of this site, but have no expertise in much of anything other than campfire.
Will, I'll email, thanks.
Also, Nate, Please forgive me, I really should learn a little more patience.... I apologize.
I love this site.

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