How To Build a Solar GeneratorAffordable solar power using auto parts could make this electricity source far more available.
Demand for solar power is rapidly heating up (see "New Solar Technologies Fueled by Hot Markets"). But constructing and deploying large photovoltaic panels to generate electricity remains expensive. Now two groups at MIT are working on alternative approaches to solar-based electricity that could significantly cut costs -- and put the ability to harvest electricity from the sun into the hands of villagers in poor countries and backyard tinkerers alike.
During a stint in the Peace Corps in Lesotho in southern Africa, Matthew Orosz, an MIT graduate student advised by Harold Hemond, professor of civil and environmental engineering, learned that reflective parabolic troughs can bake bread. Now he plans to use these same contraptions to bring power to parts of Africa baked in sun but starved for electricity. His solar generators, cobbled together from auto parts and plumbing supplies, can easily be built in a backyard. The basic design of Orosz's solar generator system is simple: a parabolic trough (taking up 15 square meters in this case) focuses light on a pipe containing motor oil. The oil circulates through a heat exchanger, turning a refrigerant into steam, which drives a turbine that, in turn, drives a generator. The refrigerant is then cooled in two stages. The first stage recovers heat to make hot water or, in one design, to power an absorption process chiller, like the propane-powered refrigerators in RVs. The solar-generated heat would replace or augment the propane flame used in these devices. The second stage cools the refrigerant further, which improves the efficiency of the system, Orosz says. This stage will probably use cool groundwater pumped to the surface using power from the generator. The water can then be stored in a reservoir for drinking water. The design uses readily available parts and tools. For example, both the feed pump and steam turbine are actually power-steering pumps used in cars and trucks. To generate electricity, the team uses an alternator, which is not as efficient as an ordinary generator, but comes already designed to charge a battery, which reduces some of the complexity of the system. And, like power-steering pumps, alternators, including less-expensive reconditioned ones, are easy to come by. As a result, the complete system for generating one kilowatt of electricity and 10 kilowatts of heat, including a battery for storing the power generated, can be built for a couple thousand dollars, Orosz says, which is less than half the cost of one kilowatt of photovoltaic panels. "You can't afford something that's designed for solar. You have to buy something that's mass-produced for something else -- that way the cost is reasonable," says Duane Johnson, owner of Red Rock Energy, in White Bear Lake, MN, who developed and sells thousands of the inexpensive LED-based sun-tracking devices Orosz uses to orient the solar concentrators. Most of the devices are used to position photovoltaic panels, he says, but some people are using them with old satellite dishes to concentrate heat and make steam. Sales of his devices have been growing 25 percent a year, a rate similar to that of the solar photovoltaics industry.
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Large-Scale, Cheap Solar Electricity
06/23/2006
Massachusetts Institute of Technology
Comments
07/14/2006
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I understand that sun rays hitting points on the parabola will reflect to the focus, thus heating the pipe carrying the liquid.
I found free sites on the internet that provide sun azimuth and vertical angles from any location, based on the time of day, any day.
I believe that a light weight hard, but flexible material covered with a highly reflective surface material could do the job.
What I’d like to learn is how a steam turbine would be connected to the feed pipe at the focus?
07/28/2006
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To solve for Y, divide X squared by 4* P, where P is the focal point. This will give you the parabolic curve for a given focal point.
08/07/2006
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Ways to draw an ellipse:
http://www.uwgb.edu/dutchs/MATHALGO/Ellipses.HTM
falk
10/16/2006
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2 Draw a straight line close to one edge (will call this the "base line")
3 Partially hammer in a nail some distance above the base line. this will be the focal point.
4 Obtain a framing square (the metal L shaped thing carpenters use).
5 Place the square so that the outside edge of one leg is touching the nail and the outside corner of the square is touching the base line.
6 Draw a line along the outside edge of the leg of the square not touching the nail, then extend this line to the edge of the plywood
7 Reposition the square to a new location that still meets both the criteria of step #5
8 Draw a new line as per step 6
9 repeat steps 7 & 8 many times, the line segments you draw will describe the parabola (in fact each of them is a tangent to it at some point)
john milton
03/02/2007
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If you can't increase the "suns" hitting the pipe then you just made a fancy batch heater so you'll get 150 degree water vs 400.
I just spent 1 week making 2 collectors using a freeware calculator, after checking it with a laser pointer it turned out it was for a solar stove.
It did focus 30 degrees onto the pipe and if exactly lined up I could get steam in 15 minutes
but if the rest of the parabolic dish actually hit the pipe steam would be almost instant.
jsixis
09/05/2008
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dinesh13
10/03/2008
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You only need a 'perfect' parabola if you need to focus to a perfect point/line. Your target is a pipe, something of sufficiently larger diameter, and it blocks a fairly wide angle of a poorly focused reflected beam.
Depending on the pipe size, the reflector can be somewhere between a half circle, a half elipse and a parabola and still work. If the pipe surface is dark enough (dark forest green absorbs IR very well, black is OK but also radiates a lot of heat) it will still capture most of the reflected beam.
You can approximate the parabola by holding/pinning the ends of a string as long as the width of your reflector sheet against the edge of a piece of cardboard, and just let it hang. The uniform weight-per-unit-length of the string causes it to sag in the shape of a parabola. Tilt the cardboard so the string is just touching to the piece of cardboard and mark the line.
The focal point for the parabola is on a vertical line half way between the two pins. (Draw the vertical centerline on the cardboard.)
Problem: You can make as many parabolic shapes as you wish with one string, by moving each end toward or away from the centerline (equidistant). However the focus of the parabola moves up/down the centerline with each change in width of the pins.
Now the amount of sunlight captured depends on the distance between the pins... and the maximum energy reflected is, of course a flat panel, but the focus is at infinity...which is not good. If you bring both ends of the string together the focal point is at the very bottom of the 'loop' of string. Maximum collection by reflection, but zero collection surface... also not good.
The "right answer" is somewhere between.
If you have a flexible reflector sheet, use the string to draw a 'good' parabola, say about half as deep as it is wide. Then hold the panel against the cardboard roughly pointed toward the sun and see where the 'focus' hits the cardboard (WEAR one or two pair of SUNGLASSES!!!!). Adjust the width/curve of the panel (moving both edges closer to or away from the center line) until you get the focused beam near the edge of the cardboard, centered between the pins.
That is close to optimum. Remember you will have a pipe there to collect the beam, not a point on the cardboard.
Practical Approach: To really play with it, draw a black disk or dark circle of paper the diameter of the heater pipe, centered on the line at the edge of the cardboard, and see how the beam collects as you change width of the parabola.
Theoretical Approach: Do a lot of math.
Pragmatic Approach: Look at someone else's design and take a few measurements.
Now it becomes a design/fabrication issue. Is your pipe going to be 'inside' the curve of the parabolic sheet so that the pipe must pass through the end support pieces? Then move the pipe 'down' closer to the curved sheet, move the
'ends' of the parabola closer and lose a little area of sunlight capture. Or do you want to keep the pipe independently supported so it is not locked to the parabolic dish? Then move the pipe 'Up' away from the reflector and widen the parabola. This increases reflective area, but exposes the pipe more to the air/winds. These are design/fabrication considerations.
Then when you build (at least your first unit), you should have some nominal adjustment of the pipe position, an inch or so up or down, so you can tweak its position on the focus line for optimum operation.
In the 1960's I built a solar hot dog cooker using a photographer's tintype and plywood ends. The wire for the hot dogs rested in notches in the plywood, The unit did not focus 'perfectly on the wire, but it did capture all the energy in the wider 'dogs'... it worked very well.
The largest variable in heating rate for it and for solar heaters is how well your parabola is pointed at the sun, so solar tracking is a must for optimum use.
Many years ago I saw an ingenious, home made, passive hydraulic solar tracking system. It used a set of four black hydraulic cylinders, positioned on a frame, one on each side of and behind the solar panel. When pointed directly at the sun each of the cylinders was halfway shadowed from the sun by the solar panel... they were all balanced at equal 'temperatures'.
As the 'sun' moved it would expose one or two of the cylinders more than the others, heating them up more and moving the frame until it was balanced again... and pointed directly at the sun. The unit had to be reset to point eastward each morning, but even that could be 'automated' with a few weights and an internal hydraulic 'leak'.
Has that been commercialized yet?
dannf
09/03/2009
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dinesh13
10/03/2008
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what kind of glue should i use to glue it to the formica
07/21/2006
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Romawat
09/27/2006
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07/15/2006
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Align was achieved by having two sensors in the sun, and two still in the shaded area of the sensor board.. think of it as a rectangle with a smaller square opening.. the output of the photo sensors drove relays to reversible electric motors.
Rob-in-texas
09/08/2007
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07/31/2006
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You could use an old satellite dish. You know, the old 6, 8, 10, or 12 foot dishes hardly anyone uses anymore. Set up correctly, the actuator (motor) on each one could easily track the sun. You could even run the plumbing through the center of the dish up to the focal point and back.
Just an idea. ;-)
MyTonyTiger
12/31/2007
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aymaneman
01/17/2008
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dinesh13
10/03/2008
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Kindly arrange to send details about Parabolic trough design and clock machanism for tracking.
I would like to fabricate parabolic trough in my work shop hence furnish the details.
Kindly send the reply on my e-mail ID - aditya1369@gmail.com
Thank you,
Dinesh.
dinesh13
10/03/2008
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It's not a technical problem. It's a social one. (Actually a bunch of them.) And as long as engineers continue to come up with new widgets that will solve it for sure this time, it will still be with us...
07/14/2006
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The idea is to bring those who are without, no matter what the reason, the ability to grow. It isn't a matter of race. If you have a doubt, check out the local trailer trash parks.
I hope they continue with their work.
07/14/2006
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07/17/2006
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I like too much your technology. I am from Inida now I am working in U.A.E.
I would like to implement your SOLAR GENERATOR SYSTEM for poor villagers in India and Site workers in. U.A.E.
I would like to get technical suport from you for the your greate new technology.
I am looking forward to hearing your replay.
Have a nice day.
Thank with Regards,
Gopakumar
Giffin Traffiks LLC
Section head- Electrical
Abu Dhabi
United arab Emirates.
Tel-00971 2 5553141
Fax-00971 2 5553992
Mob - 00971 50 5215644
Emai-goppikka@yahoo.com
www.signfab.ae
Gopakumar
09/27/2006
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marketofwgma...
02/04/2007
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watch a video on google video called "the money masters" or another called "masters of the universe"
07/16/2006
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It's good to read signs of intelligent life! Thanx...
07/15/2006
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I suggest do some more research on what these new technologies make possible.
KeithBK
12/12/2007
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This author gets my thank you
07/14/2006
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Dale
Raleigh, NC
07/14/2006
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Has already mentioned this idea. 10+ years ago.
07/14/2006
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http://matteranenergy.com/
See especially the animation pages.
07/15/2006
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produced by a mechanically driven
Stirling Engine can cool any project utilising a Heat Exchanger
07/15/2006
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I think it's a bit more challenging to build a dish that would properly focus on one point rather than a parabola to focus on a line... at least for a hobbyist anyway. And a dish also has to move more often to stay pointed at the sun. But cool technology, none the less. I want one on my roof.
08/03/2006
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, need to predrill holes for the pipe/collector(copper tube,or pipe
should be black to adsorb the heat
(can cover with thin plastic or film or leave open(to keep clean)(depending on how long, need a insert about every 2ft, depends on metal and how well bent), good luck, LFM
07/15/2006
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Link to build a solar generator from 1996, build off from there. You could focus the sun and power and middle gen. But the article states the basic philosophy behind it
08/10/2006
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I hope the man gets his patent and funding! That would be awesome.
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sandman
10/03/2006
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Engineering does not offer a silver bullet to these complex problems, it only provides options, but believe me options may be all that is missing to make significant difference in some communities lives.
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Where can I find plans to build this system???
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marketofwgma...
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maken
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Herald David
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sleepwalker
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http://www.ablamp.com
info@ablamp.com
ablamp
04/29/2007
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Thanks
leof
07/26/2008
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