Solar Tracking System

https://www.youtube.com/watch?v=c6dcnCS1PQ0

I would use worm gears to help stop unintentional movement via wind and other forces...

Even if you rotate your solar array, you'll still see a falloff in output as the sun gets low in the sky due to Beer's law.

The absorption through the atmosphere (in dB) is proportional to the distance the sunlight travels through the atmosphere. The path length through the atmosphere when the sun is at elevation Φ is L = A/sin(Φ), where A is the length when the sun is directly overhead.

You have the seasonal variance as well....not to mention weather factors, wind, clouds, smog and other particulates...

https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law

I guess the point I was trying to make is that if you are doing a cost analysis, you can spend the same money on a tracking system (installation plus maintenance) or a larger solar array for the same number of watt hours per day. You have to compute how much more energy you get tracking the sun, even when it is low in the sky.

Cost wise, you may be ahead buying more silicon.

https://news.energysage.com/solar-trackers-everything-need-know/

This is a concentrating dish type collector.....I think he said....

https://www.energy.gov/eere/solar/concentrating-solar-thermal-power-basics

You're right, my bad. Belay my last...Thanks.

<...What is the most economical way to track the sun?...>

Shadow tracking is not a term I am familiar with but you may be looking for this:

Mount two light dependent resistors (LDR) about 200mm apart onto a bracket that moves co-incident with your moving dish. I shall call one LDR the reference LDR and the other LDR the control LDR. The reference LDR is mounted so that there are no obstructions close to it which will block light. The control LDR is fixed in the center of a 25mm vertical capacitor mounting clip which holds a 100mm length of 25mm plastic pipe/conduit. The two LDRs are fed to the inputs of a voltage comparator, the reference LDR wired in series with a low value biasing resistor. When the sun shines directly down the tube both LDRs receive the same amount of light and have the same (nominal) resistance. The biasing resistor sets the reference comparator input voltage lower so the comparator output is low. When the sun moves so that the control LDR is in shadow it's resistance increases, over riding the bias so the control input voltage to the comparitor now becomes lower and the comparator output goes high. The high output is used to switch the actuator to redirect the dish towards the sun. As the control LDR falls back into sunlight the initial conditions are reinstated and the actuator is stopped until the next movement increment. Lengthening or shortening the tube controls the time between increments and the step length. When pointed to the sun both LDRs see the same amount of cloud or reduced light at dawn/dusk cancelling out these variations. Mounting the LDRs and comparator in a common IP66 box with a plastic lid means that both sensors experience the same amount of dirt, dust and rain and keeps the installation weather tight.

It is important that you reset the rig regularly to account for variations in the sun's track at different times of the year.

Components and costs

Light dependent resistors typically type G15528 £1.44/10

Comparator module (comes in kit form so you have to assemble and solder it) Banggood DIY lm393 voltage comparator module kit, comes with everything including relay £3.15

Both the plastic box and the post and packaging will probably cost more than the components.

I use a three point mounting for PV cells. A single central mounting on the lower southern side (I am approx at 54^o north) and the other two mounts on vertical tubes with closed bottom ends. Each tube contains a float attached to the PV cell frame by a rod eye and clevis. The eastern float has a longer linkage than the western float. At dawn the east tube is empty and the west tube is full and the cells tilt to the east. At each movement increment a solenoid valve in a pipe connecting the base of the east and west tubes opens and allows some of the fluid to flow into the other tube, raising the east side and lowering the west side. At dusk both tube levels are equal and the cells tilt to the west. Each night a third light sensor registers darkness and pumps the fluid back into the west tube. (but this could be done with a bucket) The fluid medium is old engine oil and the pump is a recycled car oil pump. The systems was set up as a demonstration for NGOs who wanted a cheap, reliable system, that could be built in country, by semi-skilled people, with local materials, for third world countries to increase power output of existing systems at the lowest capital cost. Sets of tubes can easily be daisy chained together using a single sensor provided that are all at the same base level.

My brother and I built a parabolic reflector in the 6th grade to track the sun to cook hot dogs. We entered it in the science fair. We used a very simple wire and stepped design to track the sun. The parabola was constructed using foil, cardboard and Elmer's white glue. We received an honorable mention. The judges deemed it too advanced for the age/grade. It cost us about $ 5.00 dollars to build as we pulled most of materials from the trash.

"Does anyone know about "shadow tracking" systems?"

Sunflowers do!

Positional sensor glued to the centre of a sunflower and the data transmitted to an Arduino should do the trick.

I can't claim credit for this answer as one of my former H.S. students experimented with it and it worked well to move a mylar collector to track the sun.

One could calculate it. Given the local time, the local date, the longitude and the latitude of the location, there is enough data out there for a computer program to work out the bearing and the elevation of the sun above the horizon.

The method works even when the sky is overcast, or it is dark.

One could also use a link to this:

https://www.timeanddate.com/worldclock/sunearth.html

There is something I once noticed one day when there was about an inch of snow on the ground. The rails of a split rail fence had cast a shadow all day leaving a sharp snowy patch where the shadow had been. It turns out the fence runs almost exactly East to West so the shadow was stationary.

If you fashioned a reflector by bending a flat sheet of metal into a parabolic shape, you could orient it with the open ends East to West, and track the sun without moving it on a daily basis. The parabola should be tilted towards the path of the sun (south in the northern hemisphere) and a water pipe painted black run down the axis following the focus of the parabola to collect the suns energy.

https://www.sick.com/ag/en/industries/power/solar/position-and-motion-control/parabolic-trough-tracking-in-csps/c/p651793

The advantages of this are that it only has to be adjusted on a seasonal basis, not daily, and can be constructed without any compound curves.

I often wonder why people design solar trackers, to actually find the sun visibly and track it, as the sun, each day of the year, is at the same time (ignoring possible local summer time changes) each day, at the same angle to any point on the earth.

The only minor difference each day is the "height" of the Sun, and the points on the horizon, for both sunrise and sunset will also change daily.

Therefore, using some simple coding and an accurate 24 hour clock, the solar collector can be programmed to turn to exactly face the sun, even on days with heavy cloud or fog, from sunrise to sunset!

And when it gets dark, to allow it to reverse position to where the sun rises on the following day, though that can also be ignored completely, of the solar collector is turned each and every day, back to the position of the day in the year where the Sun is at its highest, and forget it. Also, tracking, even after dark, before sunrise and after sunset, when the Sun has set, to the point on that "longest day", mid summer, when the sun actually rises and sets!

No need to "see it!"

Even the "height" of the sun, can be read out of tables, for any point on the earth on any day, again, or the clock data could be used to get the vertical angle correct, from sunrise to sunset.

Not needing sensitive solar cells and electronics outside, year in year out, for tracking, with sun, wind and rain aging them, will improve reliability in that area!

K.I.S.S. being the operative word!

Note. If anything I have written is not understood, I will do my best to explain if needed.

Remember, boy Scouts learn how to find the various points of the compass, using an analogue watch for any time of day where the sun is visible! This works because the sun, as I mentioned previously, is at the same horizontal position, each and every day of the year!

See here:-

https://lifehacker.com/find-true-north-with-just-your-watch-5439089

Thanks everyone for the great ideas! I am hoping to turn the solar thermal collector carousel base with a clock type motor. I don’t think servos or motors that must turn on and off 600 times a day is practical. I would like one motor turning a gear down to turn the collector on a continuous basis, like a clock. I will raise and lower the angle towards the sun with a second motor that will also act like a clock. A variable voltage to the motors can be programed with the proper cycle, continuing to run all day then stow at night. This sounds like the most maintenance free type of tracking system. Any comments?

Perfect example of K.I.S.S.

Though you will have to let it urn 360° continuously, if i understood you correctly. That may bring other problems along with it for you to solve.....like how to "recover automatically after a power failure (me not remembering what you are collecting exactly!!)

Keep us all updated please.