The parabolic trough can be designed as roof-top arrays.
Parabola:
All points equidistant from a given point and perpendiculars to a given line.
So, to build a model, draw a horizontal base line, mark a given point (the focus), and then, with a ruler, mark all points that are the same distance from the focus and 90 degree lines perpendicular to the base line.
* *
| |
| * * |
| | | |
| | | |
| | o - focus | |
| | * * | |
| | | * * | | |
| | | | * | | | |
| | | | | | | | |
|__|_____|__|_______|_______|__|_____|__|
I am more of a "compass and straightedge" enthusiast. Actually, a "ruler" hack.
Now, cut several copies of this template, space them apart as ribs for the trough. Lay a sheet of polished aluminum within the ribs, mount a water pipe through the focus point and turn on the water when the sun comes up.
Of course it gets more complicated than this. Be careful to market these plans. They are too simple and cannot be patented. You can't patent a parabola. You will have to come up with a patentable gimmick. Plumbing is tricky. You may need to store a lot of hot water, install heat exchanger, and automatic valves. The price tag keeps going up.
I am planning to use auto thermostat as valve.
I am also scaling down on the size of the parabolic troughs so that a flat panel array is achievable. Each trough will be 2 to 4 inches in width and eight feet long, in arrays 4 feet wide on a panel. I am hoping to make the array one continuous sheet of stainless steel that is stamped with the parabolic troughs by a hydraulic press. Intake and outflow manifolds will cap each end of the panels which feed water in 12 to 24 parallel streams through the foci.
For east- and west-facing roofs, the parabolas must be slanted south to capture the declination of the Sun.
Ask a smart ass "what is the declination of the Sun?" and he will say:
The Sun's declination is equal to the inverse sine of the product of sine of Sun's maximum declination and sine of Sun's tropical longitude at any given moment.
Just subtract your local latitude from 90 degrees. That is the angle of the parabolas. It will only be perfect at noon on the summer solstice, but it will still work. A pivoted array table might provide finer adjustments each month as the Sun's arc climbs and descends in the sky. Whatever you put on your roof needs to handle 120mph winds (150mph is better) or expect lawsuit from your neighbor.
Avoid rocket science. You can't afford it. This is free energy, so don't be a pig. The focus doesn't have to be perfect. Perfection is for fools with a lot of money to spend on solar cell tracking devices, motors, gears and perpetual maintenance. All you need is 150+ F degree water coming out the end of the array. You can probably collect better than that directly off the shingles.
A variation of this design can be used to boil water for distillation, although the more prominent size of the parabolas will become a rooftop eyesore for all but the avant-garde and may produce too much lift. Distillation is a back-yard project.
My latitude (Tampa, FL) is 28 degrees, so the parabolas will pitch at 62 degrees on the east and west rooftops. Southern roof tops will require a focus angle that is relative to the pitch of the roof. The northern roof might be in the shade. If your house violates compass alignment, then you are tasked with diagonal construction of the arrays.
A dome house would be perfect. The arrays could curve in bands that trace the path of the sun. As the sun passes, one bank turns on as the previous turns off. I was building such a dome house when the home owner's association went to the dark side. Lost everything.
