From: Neon John <johngd@bellsouth.net> Newsgroups: sci.engr.heat-vent-ac,alt.solar.thermal,alt.solar.photovoltaic, alt.energy.homepower,misc.rural,misc.consumers.frugal-living Subject: Re: A 16' cube Message-ID: <3AA6AAB6.BDBB883C@bellsouth.net> Date: Wed, 07 Mar 2001 16:40:06 -0500 Zentuck wrote: > > "Jeepers!" wrote: > > > > > What the hell did he say? > > He basically explained how much energy is available to use. Then > explained the best ways to use it. Provided the numbers involved so > that the person wishing to do the project can do a cost benefit > analysis. By providing such a detailed post the builder can assess the > finished product and see if it is working at a reasonable efficiency. > Such a detailed post is a wonderful resource given freely by an engineer > that understands what is involved and how to quantify the project. > > For me it is refreshing to see detailed answers that can be evaluated > and checked. While I do find much value in the posts that have a less > technical nature they can not compare to this stuff. > > I thought it was clear and concise. But hey I like numbers that can be > crunched! Yes, but with all the assumptions, it was little more than an academic exercise in GIGO. For someone who's going to actually try to heat with solar, a more practical-oriented answer would be much more useful. Instructions for how to make a few simple measurements along with advice on what steps to take to constrain the unknowns would be really handy. Following my own advice, here's what I did back in '74 to heat my 1200 sq ft house cuz I was a student too poor to afford utility heat. Right in the midst of the post-arab oil embargo hysteria, TVA had published tons of documents on solar heat. One I found particularly useful was on how to fabricate a solar collector using (mostly) ordinary building materials. The collector consisted of a frame of 1 or 2X4 pressure treated boards wrapped around a sheet of metal corrugated roofing. The roofing is painted flat black (fancier coatings were also listed in the paper but flat black paint is cheap and works well. Behind the roofing are bats of fiberglass insulation. Over the top is either glass or heavy plastic (I used salvage glass). Along the top of the roofing is a length of copper tubing drilled with holes so that water would spray into the grooves of the roofing. AT the bottom is a gutter to collect the water. The water is heated by being in direct contact with the black collector. I made a rough measure of the collection efficiency by simply measuring the flow and temperature rise of water flowing through a collector. Then using TVA's published insolation numbers for this area, computed what I'd need on the worst case day I wanted the system to work. based on that, I built sufficient collectors and installed them in my large rural back yard facing south. These would have fit on my roof but I'd have had to build a mount to angle them due south. For heat storage, I buried a 2000 gal septic tank in the back yard and insulated it with several inches of styrofoam board that I picked up salvage. No detailed computations done here - the 2k gallon tank and the styrofoam were what I could find salvage. To heat the house I modified a large condenser coil by converting it to once-thru flow. copper tubing headers were soldered on each end after all the elbows were removed. This was mounted in the same duct work that served my homemade wood burning central furnace. A solar cell, a mechanical time clock, some platinum RTD thermal sensors (from the boneyard at TVA where I worked) and some discrete logic/analog controls (no microprocessors yet.) drained the collectors when the sun went down and/or when the outlet water temperature dropped below the temperature of the water in the septic tank. This prevented freezing and prevented diluting the hot water with cooler water. I interconnected this control system with the wood fired furnace control system so that if the water temperature in the septic tank dropped below about 80 degrees, the furnace was automatically lighted and took over heating. I later installed water coils in the furnace to heat the water in addition to heating air. The furnace fired only very seldom - a cord of wood lasted all winter plus. This was a case of "turn it on and see if it worked". It did. I like to take that approach first and only if it doesn't work do the formal engineering analysis. I ended up adding a few more collectors as I could afford them. Total cost? I'm going to estimate under $500 plus a lot of (fun) work plus the favor I owed a friend for borrowing his back hoe. Figure 30 years of inflation and with some clever scrounging, this system could still easily be built for under $2k. I believe that the system is still mostly in place but is not now being used. I talked to the current owners of the house a couple of years ago. They're still using the furnace but they've removed most of the collectors to install a pool. It probably served this house for 20+ years though. This 'back of the match book' approach probably wouldn't work in Minnesota but it worked fine here in the Sunny Mid South. John -- John De Armond johngdDONTYOUDARE@bellsouth.net http://personal.bellsouth.net/~johngd/ Cleveland, occupied TN From: Neon John <johngd@bellsouth.net> Newsgroups: sci.engr.heat-vent-ac,alt.solar.thermal,alt.solar.photovoltaic, alt.energy.homepower,misc.rural,misc.consumers.frugal-living Message-ID: <3AA7212D.405D43AE@bellsouth.net> Subject: Re: A 16' cube Date: Thu, 08 Mar 2001 01:05:33 -0500 Zentuck wrote: > > Neon John wrote: > > > > Zentuck wrote: > > > > > What color was the insulation? This is a real question, I really want > > > to know if the insulation you used was yellow or pink? > > > > > > BTW, Man o man I loved your post too! > > > > Pink. > > > > Well heck, they do make the stuff right up the road :-) > > > > John > > John, > Did you have trouble with outgassing of the insulation? I was told > years, perhaps decades, ago that the pink insulation would outgas and > fog the glass or plastic. Word was that the problem would exist as long > as the insulation was in place. Every commercial panel I installed or > had any dealings with had yellow insulation. > > So did you notice a problem and if so how bad was it? I put the insulation BEHIND the corrugated metal. The metal is RTVed to the wood frame to make it water-tight so the insulation is not in the heated space. It simply insulated the back side of the metal. I did not attempt to insulate the wooden sides. I imagine the pink stuff would offgas. I used it to insulate the walls of an annealing kiln for my glass shop (after stripping the backing off, of course) and it smoked like HELL the first couple hours of operation. When it quits smoking, the fiberglass is just slightly on the grey side of white. The glass is stiff so it obviously has some sort of coating, probably to make it less itchy. When I need fiberglass insulation for a project now, I buy the stuff in the pink plastic stocking. Inside the pink plastic is pure white fiberglass wool without any apparent coating. -- John De Armond johngdDONTYOUDARE@bellsouth.net http://personal.bellsouth.net/~johngd/ Cleveland, occupied TN From: Neon John <johngd@bellsouth.net> Newsgroups: sci.engr.heat-vent-ac,alt.solar.thermal,alt.solar.photovoltaic, alt.energy.homepower,misc.rural,misc.consumers.frugal-living Subject: Re: A 16' cube Message-ID: <3AA7216B.16A8DFF4@bellsouth.net> Date: Thu, 08 Mar 2001 01:06:35 -0500 Sechler wrote: > > "Neon John" <johngd@bellsouth.net> wrote in message > news:3AA6AAB6.BDBB883C@bellsouth.net... > > > > This was a case of "turn it on and see if it worked". It did. I > > like to take that approach first and only if it doesn't work do the > > formal engineering analysis. > > IMHO, a little preliminary engineering analysis with reasonable assumptions > helps one determine a starting point, an order of magnitude, from which a > prototype can be built, tested, and expanded upon. I'm sure the TVA's > documents listed "rule of thumbs" that were based on previous engineering > analysis and testing. > > Joe Oh, absolutely. TVA spent $millions of tax dollars on this stuff. Which meant I didn't have to re-invent the wheel. John -- John De Armond johngdDONTYOUDARE@bellsouth.net http://personal.bellsouth.net/~johngd/ Cleveland, occupied TN |