Solar One, to International Space Station; Move over I’m coming into Near Orbit.
By Corporal Willy, 6/6/09
Well, I made some more progress on Solar One; of Engineering.com and I intend to explain in this article what I have done. This time to give you a better idea of what the more finished heliostat will look like, that I’m making, I am posting screen shots of my conceptualizations. Of course things can change due to better ideas and suggestions and one came my way via a retired Naval Commander Charles Maxwell. His invaluable help and experience with wooden gears is to be believed and one quick look at his web site will tell you why. http://www.hardwoodclocks.com
I am going to let the cat out of the bag here a little bit. I intend to power the sun tracking mechanism of this heliostat with the stored up kinetic energy from a pendulum clock movement and escapement gear. I know how that sounds and I know what you must be thinking, but the key engineering word here is KISS which I am sure all the engineers out there will understand. Besides, the emphasis here is that this could be used in areas without electrical power. Sure I realize photovoltaic cells have been invented and they work well enough to power pumps and many other things but they also cost dearly too. I intend to use one pump powered by photovoltaic cells to take the heat from the hot box receiver and pump it into the thermal storage container. If I were to use the thermo-siphoning principle or technique I would not even need that one pump. I have utilized this principal on two other projects and believe it works well. One blew up on me because it created steam which was not planned for and my solar heated duplex birdhouse had to be shut down two weeks before official spring arrived because it had already reached 112 degrees inside (44.44 Celsius). No kidding. Well without any further adieu I will show you what I think it will look like in the future when I get to that step.
Yes, it does kind of resemble the Klingon Ship on the Star Trex series. Yes, I watched that series too. Gene Roddenberry was my idol and still is. This will be considered the upper portion of the mirror array. The round horizontal circle and up from there will be seen above the bottom half that has not been designed or planned to far ahead yet. That will be a box basically that will house the pump, safety valves, (yup this time I want one for sure) flex hoses, counter weights and a host of other wooden gears. Under all of that will be the Thermal Storage Container which was going to buried underground but for testing purposes I will leave it above ground so I can get a testing company to hook up a DAQ recorder and do all the independent testing of it, leaving me out of the equation so I cannot be accused of padding the heat obtained. That is something that I am still trying to work out. Moving along now let’s take a look at this down below.
Wooden gears were used in many examples of early engineers and scientists going back to DaVinci and so many others. I had to change my idea to this one up above here. My idea was to drive the horizontal tilting of the array with my originally done idea down below here. See I listen to all of you and this time this tip came from Skipper Maxwell.
So with the four pictures up above which was my idea, I went with the suggestion of someone who knows better and now the vertical tilt will now be driven this way with probably some other optimizations done in the final. The white pipe is the vertical pivot point if you haven’t already guessed it.
Let’s review some basics here because I have gotten some comments that let me know that some do not understood this whole concept. Solar radiation comes to earth from our sun in about 8 minutes and 20 seconds traveling at the speed of light of course, which is 186,274 or 272 miles per second depending upon which encyclopedia you might be using. High School level stuff so far, but there are many people following this series of solar articles that are not engineers or scientists or technologists out there. They are just like me. J Furthermore, let us take a look at a car sitting in the hot summer sun with all the windows rolled up tightly. 140-165 degrees Fahrenheit (60.0-73.89 Celsius) can easily be reached inside and unfortunately too many children die in parked cars like that, while mom or dad run into a store quickly. But heat builds up very quickly inside a car parked in the sun and you don’t even have to come close to those temperatures to kill a human child or pet animal. Many are not aware of that and it happens too often. But let’s take a closer look now at what actually happens and why the cars heat up fast. From books I read many years ago, I recall reading this information and now I am going to relay it to you. It should also be checked out before thinking what I am going to tell you is the Gospel Truth. However, the solar spectrum coming to earth is a miss mash of different wavelengths. Remember using those prisms that we held up to the sun to see the different wave lengths break apart? Anyway, the short wavelengths here are very important. They can penetrate “much more easily” through a window like the glass in a car. After penetrating the glass something has changed. Remember that you cannot destroy energy so after those short wavelengths go through the window it changes into a longer wavelength and it doing so it creates heat which is the new energy represented by that change in frequency. That heat keeps accumulating because it is much harder for it to escape now because the new longer wavelength that it has changed into cannot go back out that window as easily as it did when it came in at a different frequency. Remember that is from memory going back into the early seventies. I also cannot remember what I ate last night for supper.
Now let’s go look at the point of all of this work, planning and expense. The whole idea here is to get all those mirrors pre-focused onto that little metal box at the end of that long arm. Once that is done then I only have to keep the whole assembly as near to a perpendicular angle to our sun as possible. It will have to be about five degrees or so off from perpendicular because you do not want any shadows to be allowed to fall on any of the mirrors caused by the hot box receiver out in front. But remember every mirror is adjustable to a great amount, with many DOF (degrees of freedom) on the X and Y axis. So today I started to work on that very important part that is going to bear the brunt of this heavy heat load. Take a look at this box then I will explain what I did.
In the two pictures up above I decided to use an 8 inch square electrical outside box (20.32 Centimeters). It is much easier than making one that is for sure. Metal because this thing is going to get hot and wood or anything combustible might catch on fire. I don’t want any more surprises with my experiments. Now also you can see that there is 3/8 inch OD, soft rollout refrigeration tubing (9.53 millimeters) that I used for my copper coil. I had to make a decision in my local Home Deposit store. Could I bend ½ inch in a small enough diameter to get it inside of an 8 inch box? I did not think so, so I went with smaller tubing which was the right call there. What you see there alongside of the box top left is a 10 foot length of this tubing (3.05 meters). No kinks allowed in the tubing here and it was a fight all the way believe me. I remember watching my father do this one but that was his trade and expertise. I think he would have been happy with what I did here, but he would have been mad that it took me so long. J I could never win. Now at the very bottom of the metal box are two strain relief electrical connectors meant to hold rubber cord or round wire firmly into the box without allowing them to be pulled out. It fit perfectly on the 3/8 inch tubing but I will admit that was dumb luck. It also plugs up those two holes pretty good. Down below here I’m showing you that there will be a cover that I made out of ¼ inch thick Plexiglas (7.62 Centimeters). When I am ready, I will seal the glass into place with Liquid Nails. I built a right angled lip into the box so it would have this edge to rest upon and be glued to it. All those little bolts and nuts you see are to hold the glass in place securely on that lip.
What now needs explaining is the silver colored foil insulation. In order to prevent the high heat building up inside the box from escaping through radiation and convection, I am using a simple reflecting barrier to stop those actions somewhat and to help seal up any openings in the box. It took me awhile to figure out how to cut the insulation foil to fit inside the corners nice and tightly but I did. A kid in school would have been much faster. But I am very pleased in how it came out. I will make reflector shields to help guide any stray mirror reflections back into the window of the box. I am not sure if this step is going to be needed but that is a rainy day type of item. I did buy a little more insulation than I needed. I guess. The foil lining I consider to be an important step. Even the bottom picture on the right shows the ¼ inch machine bolts with washers poked through the insulation to seal up those holes that are used for mounting the box, from outside air. The object here is to keep the hot air inside. I do not have any idea how hot it will get but if this doesn’t work I will report on that as well so we can all learn from it.
Once the box is all done I will use automotive flat black high heat engine spray paint to blacken everything inside and outside of the box and the copper coil inside too. It really doesn’t need to be painted because it is not directly absorbing solar radiation but absorbing that very hot super heated air circulating inside of the box that already gave up its heat when it went through the Plexiglas. But something is telling me to do it anyway and I am not sure why but I will. A Marine Corps Axiom is, “when in doubt salute” so that is what I am doing here. It might pay off and it certainly cannot hurt anything. I won’t do the Plexiglas window unless someone out there can give me a reason why I should do it. Let’s talk about it. Some last ideas here. From the internet some facts for you:
A 9 square foot heliostat = 836 watts of potential solar energy.
Facts and constants that are used in figuring out some things as a standard for computational methods to figure efficiencies of the unit in question.
8.33 pounds per gallon of water
1 BTU raises 1 pound of water 1˚F
10 gallons of water
total of 83 pounds of water
60˚F temperature change = 4980 BTU
Watt-hours to BTU = Watts x 3.414