
Gravity-Powered Solar Tracker - davesailer
http://www.notechmagazine.com/2015/09/gravity-powered-solar-tracker.html
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sandworm101
Anything that moves will one day break. I hesitate to move away from the
reliability of a static panel. Adjusting the drip rate in this scheme would
also be constant battle of weather, temperature and season. You'd never get it
perfect.

Compared to a simple solar setup it may be more efficient, but compared to
more complex, yet still static, combinations of a panels and a reflectors I
don't think the improvements are worth the extra complexity of moving parts.
I'm thinking of rigs like this:
[http://www.builditsolar.com/Experimental/Reflectors/Reflecto...](http://www.builditsolar.com/Experimental/Reflectors/ReflectorBenefitVertCollector.htm)

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hyperpallium
Yes, tracking has got to be super-simple. Flowers do it; maybe one day we'll
use them somehow. Flower power.

But the efficiency difference is dramatic, especially for monocrystalline. I
got full power in the middle of winter near sunet (4pm) by tilting the panel
almost vertically.

Consider the effect of solar ray incidence on Earth: it's why the tropics are
hot and the poles are cold. It's the difference between summer and winter.

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TeMPOraL
> _Yes, tracking has got to be super-simple. Flowers do it; maybe one day we
> 'll use them somehow. Flower power._

Flowers are not simple. They're insanely complex devices built entirely by and
from nanomachines. We're barely beginning to understand what's going on. For
instance, we found solar tracking to be a set of clever photochemical
reactions that respond to particular wavelengths and disrupt the natural
growth of the plant in such a way that it follows the sun. Mind you, that we
know about those reactions does not mean that we actually understand them in
perfect detail.

Nature only _looks_ simple. In fact, the levels of its complexity are so great
that for the most of mankind's history we didn't even suspect what's going on.

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mchannon
This is called a clepsydra (water clock) tracker.

A group at New Mexico Tech added water pumps to the technology to take out the
need for manual refilling.

What people tend to forget about trackers are they cost money and have to be
massive to hold their angles in the wind.

They are also less space-efficient users of land than fixed mounts, which is
why standard PV's never tend to use them. It also costs less per watt to buy a
second panel and fixed mount than spend the extra on any kind of tracking
mount.

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sitkack
As you said, the price of panels relative to the price of trackers is such
that trackers don't make economic or engineering (complexity) sense.

I think we we potentially getting there with energy storage as well for off
grid installations. Rather than trickle charge a storage system that can
supply short bursts of massive power (think running a welder off of solar),
purchase more generating capacity and feed it directly into the inverters and
use storage for the minimal case. Excess can be shunted into a opportunistic
load.

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radarsat1
Ah, before I read the article, from the image I thought maybe it was bottles
on both sides, and using the sun to evaporate the water in the lower bottle
until it reaches the higher bottle, causing it to tip. Thought that was pretty
clever! But probably not accurate. Would be beautiful to design a closed
system that works well like that however.

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weinzierl
Actually there is a simple mechanical gear that can translate constant speed
rotation into a perfect two axis sun tracker. If you'd combine this with the
contraption from the article you'd get a gravity-powered two axis tracker.

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glibgil
A human has to refill the bottles.

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gkop
Another mechanical approach that is relatively cheap and doesn't require
refilling bottles is to use a closed system of a hydraulic cylinder and two
exposed freon tanks, one facing east and one facing west:
[http://www.motherearthnews.com/diy/solar-tracker-
zmaz77ndzgo...](http://www.motherearthnews.com/diy/solar-tracker-
zmaz77ndzgoe.aspx)

These mechanical approaches are generally awesome because they hold up well in
bad weather.

If you wanted to go all out I don't see why you couldn't combine the gravity
system and the freon system and track on 2 axes! (Anybody got a clever idea
how to make one system or the other neatly handle the axis corresponding to
the height of the sun?)

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biot
What about an array of photodiodes like this:

    
    
      o o o
      o X o
      o o o
    

This is in an enclosed box with a hole over the center. Here, "o" represents a
photodiode and "X" represents the center of the hole. When the solar panel is
pointed directly at the sun, the sun is at position X and no photodiode is lit
up. As the sun changes position, eventually it will light up one of the
photodiodes. That completes a circuit which uses power from the panel to drive
a motor, which is attached to a worm gear and rotates the panel towards the
sun. Eventually the sun will be pointed at the X position again which breaks
the circuit and stops the rotation. Each diode completes a circuit, driving
one or both motors (in the case of the corner diodes) rotating them
appropriately.

It'd be interesting as well to have some sort of mechanism which, when the
panel receives power, keeps it locked in place. When the panel has no power
for a period of time (ie: after sunset) the mechanism disengages and the panel
falls back to its default position pointing towards sunrise.

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mapt
Finding vertical & finding north is not a problem, you can get that trivially
in a tiny MEMS IMU if you don't want to do it manually, and from there
determine the optimal path for solar tracking without added variables,
supposing you have the timezone set by the distributor (or use a GPS for that
at a few dollars a chip).

The cost is in the rotating frame and the motors.

