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Introduction to A TRACKING SOLAR CONCENTRATOR. Alterations and abridgements to the original 1981 text will be italicized
You are about to become one of the solar energy pioneers. In the following pages I will show you in great detail how the very successful solar concentrator and collector designed and built by Teton Engineering can be duplicated with commonly available materials and tools to be found in most well equipped home workshops. We are confident that the purchaser of this manual will make improvements on Teton Engineerings design when you build your own system. Each of you have access to materials, tools and skills that are unique. Our design was restricted to those materials and tools that most home or farm handymen have easy access to. If you follow the Teton design in detail you can be assured of a working system, but we highly encourage you to experiment and add to the pool of knowledge.
Solar concentrators are a rarity in the home or farm solar installations, while flat-plate collectors can be found everywhere. Ever wonder why? There is a lot of reasons- concentrators have to track the sun requiring electronics, bearings, motors and other gadgetry that tends to frighten many folks. It seems that this type of collector should fall in the realm of heavily financed, big energy systems. Indeed, this has been true. You won't find anybody or organization fooling around with flat-plates if they are building a system for serious energy collection. Teton's goal from the beginning was to develope a device that was efficient, usable in very cold weather, hot enough to scald the dishes and still be within the construction abilities of most of Americas back-yard mechanics. Obviously flat-plate is out, simply based on its inability to achieve high temperatures. It is also out based on economics and cold weather performance.
Collecting solar energy is very easy. Retaining it in order to build high- er temperatures for practical use is where the difficulty comes in. We've all gotten into the closed up car in the summer and suffered the effects of collected and retained heat. This phenomenon, commonly called the greenhouse effect works because the collected energy has difficulty es- caping through the glass and insulation of the car body. Open the windows and most of the heat cannot be retained It is lost through re-radiation and convection. An effective solar collector has to be insulated and glazed to permit radiation to enter, while inhibiting the long-wave re-radiation. Frequently, double or triple glazing (like a storm window) is necessary if any energy is to be retained at all when the temperature outdoors is low. This adds to the already expensive collector surface, and now the "high performance" flat-plate is running up to 20 or more dollars per square foot. If we can concentrate the solar radiation with a reflector that can be assembled for about two dollars or less per square foot and hold the active collector area down to a couple of square, then the econ- omics become obvious
In addition to the economics of construction, there is a big plus. High temperature is easy- even steam if you like. The outdoor temperature is hardly even a consideration. because the area of the collector is so small that the re-radiation and convection losses are very low. In many cases, glazing is simply dispensed with. Recovery efficiency can run up to 60 or 70 percent when the best that flat plates can do is up to 25 percent and down to zero as it gets cold outdoors. These figures are based on the assumption that temperatures of at least 125 F are needed for household use. Of course if you only want to warm the swimming pool on hot summer days, the flat plate will work great and without glazing too.
As we go through the various construction phases, I will toss in a little lightweight mathematics here and there for those who like it. Ignore it if you please or use it to modify the design to suit your needs. We won't get heavy at all. If you want an excellant treatise on the engineering as- pects, I suggest SOLAR ENERGY THERMAL PROCESSES by Duffie and Beckman- published by John Wiley and Sons. My copy was copyrighted in 1974 and was the major engineering referance for this project. They call this system a Fresnel reflector meaning that the reflector (concentrator is made up of many small segments rather than one continuous surface. Further inspiration to use the economical mirror tiles as the segments came from Charles Curnutt, Popular Science, April 1978. The rest of the system is entirely original to the best of my knowledge. The economical bearing and drive systems, and the all weather electronic control system draw heavily upon my years of experience as an electronic engineer with microwave and radar systems. I make no claims to original inventions, but rather I have simply applied basic knowledge of optics, mechanics,thermal processes and electronics to design and fabricate this device. Its uniqueness lies in the fact that you can so easily duplicate it. I cannot assure you that you will not infringe upon the patents of others, although I am aware of none, but traditionally, home construction for personal use is no problem. The only thing We have to sell is this knowledge and a few parts if you should have local procurement problems. The manual is NOT for sale. Consulation and parts are no longer available
Wayne Roderick P.E.
Teton Engineering Inc.