An improvement on my previous low-tech way to rotate solar panels

[Brian in Victoria BC]

TL;DR Summary

Airlift pump/waterwheel/capstan drive to replace motors and gearboxes to rotate solar panels. It takes so little energy to rotate a solar panel that a motor is overbuilt and runs too fast to do it optimally.

Electric motors and actuators are commonly used when people do solar tracking. But there are some problems. The sun moves really slowly across the sky so the motors must be massively geared down. Also, wind stress is an issue so the motors have to be built strong. This increases the price of solar tracking and makes it uncompetitive with the cost of adding new solar panels instead.

One of my previous solutions to the problem was to have 2 floats in containers, and to pump water from one to the other raise one float and lower the other, these were connected with string to the solar tracker to rotate it. It worked well but it was bulky.

https://www.physicsforums.com/threa...rial-mount-tracking-for-solar-panels.1062171/

I already use low pressure air in my garden so my next attempt was to be a mini homemade waterwheel attached to a torn apart old oscillating desktop fan. with the plan being to use the worm drive of the fan gearbox to rotate the solar mount. But I thought the plastic worm drive was too weak. (It already was slipping a bit) so I took the gearbox right off altogether and used the bare shaft as a "capstan drive". The waterwheel was driven by an airlift pump that turned on automatically whenever the mount needed to move a bit. It worked!

And it has plenty of torque to easily move the tracker. I think the airlift pump/waterwheel/capstan drive combo might have other applications in control systems too. For instance, it might be able to raise and lower night curtains in small greenhouses in the winter. Maybe open and close vents, etc. too. and if a capstan drive doesn't have the range to do it, and if you want one way power, with no feedback, a worm drive gearbox for an awning might be a possible way to attach things instead of or with, the capstan drive.

I have done several videos, but nobody watches them, this one is a short, so it only takes a minute to watch.

 

[gleem]

Have you considered only making incremental changes in the angle like 10 deg during the day and then resetting when the sun goes down? You would only lose about 1.5% efficiency. The gearing issue is solved.
Use an Arduino to control the motor.

 

[Brian in Victoria BC]

Have you considered only making incremental changes in the angle like 10 deg during the day and then resetting when the sun goes down? You would only lose about 1.5% efficiency. The gearing issue is solved.
Use an Arduino to control the motor.

For that, I would have to buy an Arduino, learn how to program an Arduino, and buy the motor and the gearbox. I think my way is cheaper and it can put solar tracking in the hands of more people. Half the people in the world live hand to mouth, have little money and less education. All you need is an axle, a couple of bearings, piece of plywood, 18 plastic cups, a length of string and you are good to go. I feel that I am doing more with less, and that using an Arduino and 10 degree increments is doing less with more. And in any case, what is wrong with having several way of doing things? Edited to add. The other thing of note is you can still have an Arduino, and use it to turn and off the air for the airlift pump or to turn on and off a tiny water pump to run the waterwheel. That saves buying the expensive motor and gearbox.

 

[berkeman]

I think my way is cheaper and it can put solar tracking in the hands of more people. Half the people in the world live hand to mouth, have little money and less education.

I need to go back and read your previous thread, but the question was asked in it why you are discounting a simpler hand-moved solution. With good counterbalancing and some simple index marks, it seems like for your scenario a hand-moved solution is always superior.

 

[gleem]

so where are these poor people getting the solar panels, controllers, and inverters? You learn to program get funding for the motors and gearboxes and help these people. I think the tracking system is a lot less.

 

[Baluncore]

Make a square array of panels. Mount it by two points. Because I am in mid-latitudes, I would use diagonal corners, one near the ground, the other high up. That axis of rotation is parallel with the Earth's axis.

Make a bridge circuit from four panels on the array, two series strings in parallel. Advance two diagonal panels by 10 degrees, and retard the other diagonal pair by 10 degrees. Take the midpoints of the two series strings, the bridge output, and use that difference current to power the small DC motor with reduction gearbox that rotates the array.

 

[Brian in Victoria BC]

so where are these poor people getting the solar panels, controllers, and inverters? You learn to program get funding for the motors and gearboxes and help these people. I think the tracking system is a lot less.

Mine is running a solar cooker reflector. Its linked up above. But the idea is that the poor people buy the solar panels, and then get an extra 25% efficiency out of them from a few dollars of extra expense. Here in north America nobody does tracking because it is cheaper to buy extra panels than to track. The economics of tracking changes if people can DIY it without motors.

 

[Brian in Victoria BC]

I need to go back and read your previous thread, but the question was asked in it why you are discounting a simpler hand-moved solution. With good counterbalancing and some simple index marks, it seems like for your scenario a hand-moved solution is always superior.

A hand moved solution isn't superior. It might be acceptable for moving solar panels, but who would want to go running around every 15 or 20 minutes in the hot sun, moving reflectors a tiny bit? And for solar cooking, it has failed. The Dutch guy speaking here oversaw the biggest deployment of solar cookers ever (in a refugee camp in Nepal) And after the project was over, and even during it, people didn't want to do the hand moved solution, and it wasn't working well.

 

[Brian in Victoria BC]

Make a square array of panels. Mount it by two points. Because I am in mid-latitudes, I would use diagonal corners, one near the ground, the other high up. That axis of rotation is parallel with the Earth's axis.

Make a bridge circuit from four panels on the array, two series strings in parallel. Advance two diagonal panels by 10 degrees, and retard the other diagonal pair by 10 degrees. Take the midpoints of the two series strings, the bridge output, and use that difference current to power the small DC motor with reduction gearbox that rotates the array.

I think you forgot about seasonal adjustment, but how is that cheaper than my method? And it doesn't work on cloudy days. Mine goes at 15 degrees per hour and it is always pointed at where the sun will be (if there is a break in the clouds), so especially on cloudy days with sunny breaks, it will harvest lots of energy while your design will spend most of the time "seeking".

 

[Baluncore]

I think you forgot about seasonal adjustment, but how is that cheaper than my method? And it doesn't work on cloudy days. Mine goes at 15 degrees per hour and it is always pointed at where the sun will be (if there is a break in the clouds), so especially on cloudy days with sunny breaks, it will harvest lots of energy while your design will spend most of the time "seeking".

Seasonal adjustment of ±23° is not critical. You can do it once a month if you want to. I bias towards winter, since energy is more valuable then, and there is more than sufficient sun in summer.

It does work on cloudy days. If the array is balanced, then it only takes a few mA to track the sun. A slew rate of 1° per minute is more than sufficient to track the sun. That can be done using a very small DC motor, and a high ratio gearbox.

Time seeking is not wasted. It will be harvesting energy all the time. There is no advantage in aiming at the sun if there is a hill or a black cloud there. It is better to follow the brightest sky. I have surrounding hills and more often thick cloud to the west than the east.

 

[Brian in Victoria BC]

Seasonal adjustment of ±23° is not critical. You can do it once a month if you want to. I bias towards winter, since energy is more valuable then, and there is more than sufficient sun in summer.

It does work on cloudy days. If the array is balanced, then it only takes a few mA to track the sun. A slew rate of 1° per minute is more than sufficient to track the sun. That can be done using a very small DC motor, and a high ratio gearbox.

Time seeking is not wasted. It will be harvesting energy all the time. There is no advantage in aiming at the sun if there is a hill or a black cloud there. It is better to follow the brightest sky. I have surrounding hills and more often thick cloud to the west than the east.

I am doing solar cooking, so seasonal adjustment is critical. Also, I have seen numerous posts that say that time seeking wastes a substantial amount of energy. Frankly, I don't know where the hostility is coming from. We don't need to rehash the merits of that type of solar tracking, it has been available for decades and almost nobody uses it.

 

[Brian in Victoria BC]

Just to be clear, the thread name was changed, but this isn't an "improvement" on the previous methods to move the solar panel and solar cooker, it is a separate 3rd method to move them. I had the tracker where a cylindrical container would empty into another cylindrical container, lowering a float in one, and raising a float in another. It worked very well but was bulky. and another one where water was forced out of a lower closed barrel by air pressure into a half barrel, with a bigger float in it. This was attached to a copper pipe, attached to strings that rotated the solar panel/solar reflector as it raised up. This also worked well but it was bulky too. This one is a whole separate and different thing.

 

[Baluncore]

We don't need to rehash the merits of that type of solar tracking, it has been available for decades and almost nobody uses it.

I don't think people understand it. It takes very little energy. It tracks perfectly in bright sun, and is as good as any other system on cloudy days.

Vive la difference.

 

[AlexB23]

TL;DR Summary: Airlift pump/waterwheel/capstan drive to replace motors and gearboxes to rotate solar panels. It takes so little energy to rotate a solar panel that a motor is overbuilt and runs too fast to do it optimally.

Electric motors and actuators are commonly used when people do solar tracking. But there are some problems. The sun moves really slowly across the sky so the motors must be massively geared down. Also, wind stress is an issue so the motors have to be built strong. This increases the price of solar tracking and makes it uncompetitive with the cost of adding new solar panels instead.

One of my previous solutions to the problem was to have 2 floats in containers, and to pump water from one to the other raise one float and lower the other, these were connected with string to the solar tracker to rotate it. It worked well but it was bulky.

https://www.physicsforums.com/threa...rial-mount-tracking-for-solar-panels.1062171/

I already use low pressure air in my garden so my next attempt was to be a mini homemade waterwheel attached to a torn apart old oscillating desktop fan. with the plan being to use the worm drive of the fan gearbox to rotate the solar mount. But I thought the plastic worm drive was too weak. (It already was slipping a bit) so I took the gearbox right off altogether and used the bare shaft as a "capstan drive". The waterwheel was driven by an airlift pump that turned on automatically whenever the mount needed to move a bit. It worked!

View attachment 351052

And it has plenty of torque to easily move the tracker. I think the airlift pump/waterwheel/capstan drive combo might have other applications in control systems too. For instance, it might be able to raise and lower night curtains in small greenhouses in the winter. Maybe open and close vents, etc. too. and if a capstan drive doesn't have the range to do it, and if you want one way power, with no feedback, a worm drive gearbox for an awning might be a possible way to attach things instead of or with, the capstan drive.

I have done several videos, but nobody watches them, this one is a short, so it only takes a minute to watch.

I know nothing about solar tracking, but I like your concept. It is a little complex compared to motors, but as not many people in certain countries have access to a Raspberry Pi or an Arduino, this is a cool concept, brother. :)

 

[Brian in Victoria BC]

I know nothing about solar tracking, but I like your concept. It is a little complex compared to motors, but as not many people in certain countries have access to a Raspberry Pi or an Arduino, this is a cool concept, brother. :)

Thank you. I think eventually people will use the airlift pump waterwheel combo to rotate their solar trackers, and they will use little solar panels to turn on and off the air valves or to turn on and off a tiny water pump that directly feeds the waterwheel. The slowly increasing pressure lifting a float in a 4 inch pipe (that I currently use to control the speed of rotation) is just too big. The waterwheel can go really really slow, or relatively fast without gearwheels so it is pretty adaptable. And it is low tech enough that it is less likely to be stolen.

 

[AlexB23]

Thank you. I think eventually people will use the airlift pump waterwheel combo to rotate their solar trackers, and they will use little solar panels to turn on and off the air valves or to turn on and off a tiny water pump that directly feeds the waterwheel. The slowly increasing pressure lifting a float in a 4 inch pipe (that I currently use to control the speed of rotation) is just too big. The waterwheel can go really really slow, or relatively fast without gearwheels so it is pretty adaptable. And it is low tech enough that it is less likely to be stolen.

You are welcome. I am not sure if your design would take off due to competition, but it could be one of many solutions to solar tracking in impoverished nations. Can you calibrate the tracker based upon the duration of sunlight, as sunlight angles and duration varies with the seasons?

 

[Baluncore]

The economics of tracking changes if people can DIY it without motors.

That may be true for a solar cooker, or water heater, but it is certainly not true for photovoltaic panels, either on-grid tied, or off-grid battery charging.

You need to make it clear what type of panels you are steering, and how often the control system needs attention.

PV panels are not low technology. Servo motor systems are very much more reliable than water based hydraulics. If you value, or sell your time, "hands-on hydraulics" will be uneconomic.

 

[Brian in Victoria BC]

You are welcome. I am not sure if your design would take off due to competition, but it could be one of many solutions to solar tracking in impoverished nations. Can you calibrate the tracker based upon the duration of sunlight, as sunlight angles and duration varies with the seasons?

Can I calibrate it? Absolutely! It is on "equatorial mount" Calibration is just changing the declination angle to match that of the sun. In theory I get about 16 hours of sunlight in June, (48 degrees north) but in practice, I get maximum 11 because there is a tree and a roof that blocks the early and late light. In deep winter, I might only get 4 or 5 hours. I am still cooking "weed soup" or "steaming soil" every other day at the moment! (7 liter batches). I will use the soil and weed soup mulch in my greenhouse. I usually transplant Swiss chard and Welsh onions in to the greenhouse over the winter as soon as the tomatoes, basil and peppers die off.

 

[AlexB23]

Can I calibrate it? Absolutely! It is on "equatorial mount" Calibration is just changing the declination angle to match that of the sun. In theory I get about 16 hours of sunlight in June, (48 degrees north) but in practice, I get maximum 11 because there is a tree and a roof that blocks the early and late light. In deep winter, I might only get 4 or 5 hours. I am still cooking "weed soup" or "steaming soil" every other day at the moment! (7 liter batches). I will use the soil and weed soup mulch in my greenhouse. I usually transplant Swiss chard and Welsh onions in to the greenhouse over the winter as soon as the tomatoes, basil and peppers die off.

So, you use a declination angle table? Also, it is cool that you work on farming in your greenhouse. Nothing can beat (almost) free produce.