Kinematics for single axis solar tracking array?

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Kinematics for single axis solar tracking array?

Postby Dejay » Sat Apr 08, 2017 3:11 am

Warning: This idea has been niggling around in my head for for a while now so I mostly just wanted to "get it out of my system" and dump it here. I might be over thinking this or reinventing the wheel or maybe I'm just on the wrong track. Nothing to do with 3D printing either of course (except you could build it using 3D build parts and similar construction methods) but I think there is a bit of overlap in interest in photovoltaics and 3D printing and in kinematics from this forum especially (:

Solar panels can be 30% more effective if they track the sun in a single axis, or 36% if they track in two axis. But solar tracking is somewhat expensive. So I'd love to get some feedback or ideas on this idea:

A solar tracker that takes a single axis input but maps this movement to a curved path of the panels face instead of a linear one. A simple one axis solar tracker mounted on a single rotating axis would describe a linear path across the sky, not a curved one (You would still loose some efficiency between winter or summer because of the change in inclination but not as much).
Also the tracking is done via spectra lines (or rope resistant to UV and weather) so you would only need a single motor and no gears or linear joints.

[insert sketches of ideas for such a system...] ... on.svg.png ... 281%29.jpg


At the start of each season you could manually change the height of one joint of the panel mount to account for change in latitude height of the sun. Of course this requires roof access and maybe it's just enough to optimize for winter only, since it's then that you get the least overall solar energy and you spend the most energy on heating, light and staying indoors (computer). Over a single day, since you have a battery for mornings and evenings, optimizing for the least available energy might be optimal already.
Or maybe with an array of 5 or more panels the additional cost for a cleverly designed two axis tracking system might be negligible? Or maybe just group enough panels into a single plane?

Linear joints vs rotational joints, cost, maintenance, cleaning dirt.

Tangling of lines when panels tilt? Safety during strong winds?

Balance design for panel density with tracking space (max power), costs for tracking, economic and environmental costs of additional panels, and equalized power availability during morning / evening with tracking.

No sensors needed: system only needs to know the date. Adjustments for latitude and orientation to south need to be done mechanically, e.g. lengthen or shorten the arms of the tracking system to match the right date.

Personally I'm thinking about a flat roof surface to mount the solar panels (container home) but ideally it should work for slanted roofs as well.

A single motor and spectra line could drive a linear array of solar panels all at once. Environmental costs of parts should be kept low.
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Re: Kinematics for single axis solar tracking array?

Postby Nicholas Seward » Sat Apr 08, 2017 3:40 am

As cheap as panels have gotten, I personally would probably go for a static mount. Paying a 30% premium for no worries seem reasonable.

That said...if you are going to actuate it then you can actually help yourself in a few areas. Wind and cleaning are two areas that actuation can help you out. The actuation could also move the panels to a stored position that is safe from wind/hail while also wiping this surface free of dust. I would keep them defaulted to the stored position and only bring them out when the sun is bright enough (not storming) and the wind is gentle enough.
Nicholas Seward
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Re: Kinematics for single axis solar tracking array?

Postby Dejay » Sat Apr 08, 2017 5:43 am

Probably right, although I haven't compared prices. Of course I should also check the environment CO2 balance of manufacturing an additional solar panel vs manufacturing tracking and the additional battery capacity to even out a more "spiky" day. Environmentally a tracker might be better for the energy balance.

And I've thought about a stored position for strong winds as well as an advantage, although with fixed panels you probably have to worry about that less than with more simple fixed attachment. With conventional trackers you really only can make them horizontal at best. Any linear actuator is much more expensive than rotation and would get old and dirty fast. You could suspend them from 4 spectra lines for 2D tracking, driving multiple panels from the same 4 motors, and lower them on the roof when there is wind. But that is complicated and not secure in wind at all.

My initial thought was that the single axis rotation leading to a straight path is a problem, but reading more now that impact is really rather minimal. And due to airmass even with a 2D tracker you only get like 50% of the energy in the morning and evening compared to midday, compared to 25% with a fixed panel. Nothing you can't fix with more panels and batteries.
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Re: Kinematics for single axis solar tracking array?

Postby Cozmicray » Sun Apr 09, 2017 10:55 pm

Let the sun and shade do it for you

DIY solar tracking with pressure differential ... lideshow=1

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Re: Kinematics for single axis solar tracking array?

Postby Dejay » Mon Apr 10, 2017 5:40 am

Haha that is a pretty ingenious and a cute solution! Thanks a lot for the link :)

It does use a linear actuator, but it's a very simple one compared to reprap. And it saves on gears and motors and electronics. Their practical implementation shows that it works and it probably doesn't require any more maintenance than anything electronic. And you don't have to outdoor proof your electronics.

You could even expand it to two axis tracking with a tilt-top and two independent hydraulic cylinders and using ball joints. Or you could replace one more complex double acting hydraulic cylinder with two simpler ones that are opposite of each other. Probably also best to turn the cylinder upside down so any water or dust falls away from the shank.

Only small downside is that it requires some "unfamiliar" manufacturing and tech (soldering copper, hydraulics, freon) but this is almost like the perfect project to learn more about this stuff and expand your horizons. And that it makes your solar panel slightly bigger, which would require you to space solar panels slightly further apart to avoid shading in a grid.
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