- Published: Monday, 19 December 2011
- Written by Jon Chandler
- Hits: 5214
In my article on the Irradiance Meter, I showed a picture of my friend Orris's solar panel set up for evaluation. I recently had a chance to visit and see the progress on this project. It's most impressive! Orris has been busy. Although not a exactly a microcontroller project, I think you'll enjoy seeing what a DIY-er can do on a large scale.
The array consists of 24 panels of 4' x 4' with a potential output of about 4 kW. The array features vertical tracking and will eventually include reflectors to direct more sunlight on to the panels. The panels are shown nearly fully elevated for the winter sun in the Seattle area (47° N latitude).
The panels are quite impressive. The framework at top and bottom is in place to accept the reflector panels. I believe the panels will add about 50% to the output of the array.
This array features vertical tracking to gain maximum efficiency. Orris learned that the panels can be tracked vertically (i.e., tilted) or horizontally (i.e., turned) with about an equal gain in performance. Doing both at once does not result in much additional improvement. The picture below shows the back side of the array which is fully elevated for the winter. The channel to the right corner is the flattest position for summer.
The tilt of the panels can be adjusted seasonally for optimum angle. Orris has designed the system for active tracking where the panels follow the sun throughout the day. After a lot of effort and research, the system is remarkable simple. The bottom edge of the panel is supported by delryn bearings rotating on chain link fence tubing. The array is positioned by a rack & pinion system connected to the top of the array. The racks can be seen in the photos above and below.
The pinion is ingenious. Orris found the manufacturer of this mechanism on the web. The pinions are mounted to a pipe which rotates to change the panel elevation. The bracket and rollers keeps the rack engaged to the pinion and allows using a relatively light weight rack.
The tilt mechanism is driven by a small DC motor. It output speed is immensely geared down by the triple-reduction chain and gearbox system. The final output of the gearbox rotates the pipe that carries the pinions, moving the racks and changing the array angle.
The bearings are simple delyn blocks. These handle the load and small angle of rotation well.
Concrete weights are used to counterweight the array and structure. The shape may be familiar.
Each solar panel is made from an array of solar cells sandwiched between sheets of tempered glass. Each panel has 49 individual solar cells.
This picture shows two solar cells of the panel.
The output of the solar array is converted to AC power by inverters and is sold back to the power company. There is no local storage or any ability to use the power directly.
A massive heatsink can be seen at the top of the inverter. Two inverters are required to handle the full output of the array.
The nameplate from the side of the inverter provides some information about the solar array. i believe this nameplate is for one half of the array.
Orris has put a lot of effort into this awesome system!
I almost forgot to mention that there is some microcontroller development going on for this system. the tracking system will follow the sun throughout the day. More accurately, it will follow the predicted position of the sun. Orris is using a Sparkfun GPS receiver to determine date and time for adjusting the position of the array.
If you have any questions about this system, ask them here or send them to me directly and I'll forward them on to Orris.