How it all got started

by Phunguss  

 

A long time ago in a geek far, far away...

Well, not so far away.  The next state over. 

While in 5th grade, I somehow connected the math and science of a vehicle headlight to creating a solar collector.  Pre-internet research was primarily conducted through experimentation, library research, and encyclopedia references.  I learned about parabolas and Fresnel lenses in a headlight.  I then concluded I could use a parabola to do some solar collection/concentration.

I started with a 4x8 sheet of half inch plywood.  Using half of it as a base, the other half was used to create ribs.  This formed the base of a crude bowl that I covered with cardstock (posterboard).  I then used some Elmer's glue to adhere aluminum foil to the bowl.  A simple wooden dowel with a nail in the end was placed through the center of the ribs to act as the place holder for the focal point.

While this was crude, it got the job done, and managed to cook a hotdog or two.

Fast forward thirty plus years.  I found myself collecting various materials for a new solar project, but never the time to start on it.  I was taking some college courses, and one involved some project management.  I proposed my solar collector and after approval, I got started.

This is the photo blog of the process and progress.

 

FYI, version 2.0 will be much grander.

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Step one

by Phunguss  

Step one really has two parts.  Figure out what you want to do (solar collector), and how to do it (use a preshaped parabola).

Step two is generally acquiring enough materials to get started on the construction.

Poopy Dish

City wide curbside cleanup.  48 x 52 inches, lightweight fiberglass, parabolic with offset focal point.  Birds liked it, I liked it.  It sat in the garage for over a year, but someday...

 

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Renewable Power

by Phunguss  

Since this was a solar collector, improving effeciency means that it would have to move as the sun moves.  This means it needs some way to power the locomotion.  Solar collector, meet solar panels.

Solar Cells

Ebay, just under one dollar each.  I nabbed 60 because I really had no idea how much power I needed or would use.

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Dark power

by Phunguss  

So if it is cloudy or dark when you first set this thing up, how would it track to the sun if the solar cells were not facing the sun?  Well, leave that to a battery.  This one was salvaged from a UPS during a typical battery replacement.

Sealed Lead Acid

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How much is too much?

by Phunguss  

Well, with light power and dark power defined, we need them to interact.  We can't just hook them up and hope for the best.  It could potentially overcharge the battery, and that would end in all kinds of unhappiness.  So ebay found this inexpensive charge controller:

Charge controller

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Magic

by Phunguss  

There is no dark magic that will make the dish follow the sun with just a battery and solar cells.  You need a device that can tell which way the sun is compared to your current direction.  Ebay again found these Red Rock solar trackers that work wonderfully:

Red Rock trackers

Simply put power on one set of lugs, the motor on the other.  The LEDs work as detectors.  The onboard comparitor makes calculations and the transistors send power to the motor lugs in forward or reverse polarity based on the light input.

The sun moves in a straight line on our celestial grid, but since we are a little off kilter this causes the seasons, blah, blah, blah...  The sun does not move in a straight line relative to our single location.  Thus we need two trackers, one for altitude (up down) and one for azimuth (left right).

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Let's Reflect

by Phunguss  

The surface of the satellite dish is textured.  This means if we attached aluminum foil, a lot of the light will be dispersed, not focussed.  So mirrors then?  Well, I don't have an old closet door that I could cut up, so I opted for another polished aluminum surface:  Hard drive platters.

Stacks of hard drive platters

Shown are old CD/DVD bulk cases filled with hard drive platters.  These were accumulated over some time while trying to find a dish.  The first stack is about 125 3.5inch platters, the second is about 60 3.25inch platters and the last is about 20 2.5inch platters.

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Preconditioned

by Phunguss  

According to the solar cell provider, the cells work optimally if they are preconditioned for a few hours in bright sunlight without being connected to anything.  So here they are:

This was a winter project, so daylight was through a window.  I left them there a couple days, just to make sure they soaked up enough sun. 

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Spherical Geometry

by Phunguss  

I really did not want to do that much math... The dish is a curved surface.  The platters make a nice honeycomb pattern on a flat surface.  I tried to plan out how they would best fit physically, as well as avoiding bolt holes for mounting the dish and the focal arms.

Patterns

Note that if you touch a reflective surface too much with greasy fingers, you tend to leave a lot of smudges. 

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Move it

by Phunguss  

I know that some satellite dishes utilize linear actuators to align them.  This is basically a screw drive system that converts radial turns into linear motion (like a nut spinning onto a bolt).  Of course my first resource was eBay (scrapping in the winter has many hazzards).

Linear Actuator

Just like the magical device that opens/closes the tailgate on newer vehicles. 

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