Ulr of this page: http://bit.ly/4qFVpM
http://www.cnn.com/2009/TECH/04/09/solar.oven.global.warming/index.html Bohmer's contest win notwithstanding, solar cooking with a cardboard oven isn't new. Two American women, Barbara Kerr and Sherry Cole, were the solar box cooker's first serious promoters in the 1970s. They and others joined forces to create the non-profit Solar Cookers International -- originally called Solar Box Cookers International -- in 1987.
Arched Fresnel Lens - Entech Solar Edit
Entech Solar - http://www.gizmag.com/entech-solar-energy-hybrid/12509/?utm_source=Gizmag+Subscribers&utm_campaign=e6e668ca37-UA-2235360-4&utm_medium=email - has 26 patents on innovative designs such as stretched Fresnel lenses over photovoltaic cells increasing their efficiency by a factor of four by focusing and concentrating the incoming suns rays. It is your right to hack their patents and sell products based on it in South-Africa.
None of this technology will be able to be commercialized by Eskom or Eskom approved companies at a reasonable price. Look beyond "approved by Eskom" hyperbole and focus on the technology like a tech geek understands that hacked Linux doesn't mean inferior technology. This link - http://bit.ly/sb1Uz - goes into details as to why "Hackers will save the world" as a .ogg video.
http://www.patentstorm.us/search.html?q=Entech+solar&s.x=0&s.y=0&s=s Fresnel lens designs from Entech Solar. Further details on Helios array mirrors here - http://bit.ly/4qFVpM.
- http://www.patentstorm.us/patents/6111190/fulltext.html Inflateable Fresnel lens
mirror designs Edit
http://www.solarfire.org/tech/helios/helios.html Best idea yet
http://www.solarfire.org/Helios,36 Design with bent mirrors plans given
silverized mirrors Edit
>The only way we know how to generate large scale energy is to get something >hot to increase its pressure and then expand it through rotary or >reciprocating devices (save the use of potential energy from solar energy in >hydro-generation). I don't see that changing much very soon ...
Another quality solar thermal design from feklar.
A supercharged heated air solar turbine.
North side: parabolic solar trough reflector.
South side: clear structural glass enclosure, either at ground level or elevated on cast structural glass pylons.
Let's use a 40 foot long section for example purposes. Also for the enclosure internal dimensions lets use, say, 2 feet high and 10 inches wide (N/S), by 40 feet long (E/W). Open to the air at the top @ 10 inches by 40 feet. Maybe with a little roof suspended a few inches over the top of the opening to keep the rain out.
Inside the enclosure, install a pipe and bearings, say 9 bearings for approximately (a little less than) 5 foot sections of pipe between bearings.
For the pipe, use, say, an 8 inch diameter. Made of clear structural glass, but with the inner surface coated with heat storage mass material. Or instead, have a rod of heat storage material affixed inside the center of the clear pipe, running the length of the pipe.
Given this setup, there will be approx. five feet of pipe between each bearing. The bearings are there because the pipe will rotate inside the bearings. Consider the interior of the enclosured shaped not as an extruded rectangle @ 2' x 10" x 40' but as an extruded 'd' or 'b' shape, with the pipe rotating in the round area and the air pipe being represented by the line. So maybe a 10 inch diamter circle of the 'd' or 'b' shape, the upright section is approx. two feet high by 8 inches wide, and the length, 40 feet.
When making the pipe, slot it. Cut slots in it so air can pass out of the pipe, and arrange the slots so they run in the direction of the length of the pipe, between the bearings. Orient or angle the slots so that if heated air escapes out of them at high velocity, the pipe will rotate, and the pipe will only be able to rotate in one direction. Your very basic, very elongated turbine.
Now take the approximately 20,000 solar watts you will get with about a 7 foot wide 40 foot long reflector trough, and focus it upon the heat storage mass material coating on the inner diameter of the pipe (or upon the inner rod if using a rod).
Cool air will be sucked into the open ends of the pipe as the heat storage mass material heats up and the air will be heated and escape out of the slots to the airspace within the enclosure. As the mass constinues to rise in temperature, the air flow because of the pressure increase of the heated air will increase and the pipe will begin rotating from the turbine arrangemnt of the slots and the force of the escaping heated air. Use shrouds on the open ends of the pipe to act as venturis or pressure enchancers to dictate the correct direction of airflow through the pipe. Obviously, you don't want a lot of the hot air to be blown out the ends of the pipe. While the pipe would be (in this example) 8 inches, the ends of the pipe may have reducers and convoluted entrance pathways (a small length of 1" diamter coiled pipe the replacement cool air must travel through, for example) to create smaller and more effective end openings than that.
The top of the enclosure is open to the air, and here the heated air escapes. At the top of the enclosure, install a "supercharger" Or in other words, a roller cage blower type fan running the length of the enclosure, or other type of exhaust fan system. Link the rotating pipe mechanically with structural glass welded pulleys at 2X rotation speed with the fan drive, probably as simple as using a v-belt at each end of the enclosure. As the fan rotates, the hot air is helped to be forced out of the enclosure. This should either guarantee the correct direction of airflow (out the top of the enclosure), or amplify it once it is established since it will improve the pressure / temperature gradient between the heated air and the replacement cool air. It will evacuate the waste heat from the exhaust area. It will lower the pressure within the enclosure and therefore assist in a higher rotational speed via the greater pressure differential between the enlosure and the heated inside of the pipe (which is why the term "supercharger" is appropriate). Note that the use of 2X exhaust fan speed is used here as an example, rather than a given. Note also that the cool air resupply is introduced into the ends of the pipe, never into the enclosure.
Next to each bearing, or every other bearing, or at just the two end bearings, install a magnetic stator onto the pipe and affix it into place so it rotates with the pipe. Then have sliding generator windings that can slide past the bearing to control the rotational speed. The higher the speed, the more of the windings are slid over the areas where the stators are rotating, and the more power is produced, and the more mechanical braking action on the pipe as a result.
This one probably has to be kick-started in the morning to get it running. Given the weight of the pipe and the friction of the bearings, there is considerable initial resistance at first, even with the windings disengaged from the stators... Not a problem if it is connected to the power grid, just reverse the power flow and use the windings as motors to spin the pipe up enough to overcome the resistance, then disconnect, reverse, and reapply as a generator (using fewer windings, at first).
It is highly likely that an impressive rotational speed can be achieved this way, once it really warms up. The bearings could be magnetically levitated, but I would think the method itself lends itself more to air pressure levitation using the same principle. Have small sections of the reflector trough focus additional energy on small heat storage masses inside the bearings with a venturi for an air supply inlet, and use many small air holes in each bearing surface for the pressurized heated air to escape, like an air hockey table. Given the high initial resistance to rotation, it is probable that sufficient pressure to raise the bearings will be applied before enough force is available to rotate the pipe. Another approach would be to not slot between the bearings, but only at (inside) the bearings, so that the escaping pressurized air from the pipe would levitate the bearings.
This might be an excellent choice to use in conjuction with structural glass biomass production greenhouses, since these greenhouses do not require 100 percent of the incident solar energy. In this case, install the setup on the roof of the greenhouses. Instead of a single large trough, use three panel reflector troughs with a foot or half foot or so if empty space between each trough, and instead of orienting striaght east and west, be off by ten or fifteen degrees. This will ensure adequate insolation inside the greenhouse, at the cost of a slight loss in power production efficiency.
This only applies if you want to get maximum land use efficiency. The angle of 10 or 15 degrees affects the insolation of the greenhouse just to the north of the trough. For maximum land use you want to pack the setups together east and west and north and osuth, so from sourth to north you would have greenhouse, trough,greenhouse, trough,greenhouse, trough,greenhouse, trough, etc... with as little space as possible between each pair. For large scale biomass / solar terraforming, in other words. For a backyard effort, obviously this probably isn't an issue.
At the ends of the pipe where cooler air is being sucked in, it may also be possible to install wind generators at each end to further brake the rotation and provide more power output.
The only specific potential problem issue here that I can see that needs further addressing is the bearing issue. Obviously, prolonging the lifespan of the bearings is of considerable importance. I do not claim to have produced the best possible approach by suggesting air levitation.
For the time being, just assume that I know a way to make everything out of structural glass for a ridiculously low cost. The troughs, the supports, the pipe, the exhaust blower fans, even the bearings. Everything except the iron ferrite and steel stator cores, and the copper windings of the armatures. Assume that no other construction materials can come close to being as inexpensive.
So don't discard it out of hand because it would cost too much or "more appropriate" materials would be available that would also make it cost too much for what the output and efficiency might be.
Deal instead with the principle.
ptaakhang...@sbcglobal.net subtract where I hang at to unmunge
The Amazing and Mysterious Powers of Mexican Females.
Chapter 1: Levitation and Summoning. http://www.angelfire.com/empire2/ptaak/images/mexwench.jpg