Another Solar Tracker

[Xringer]

I don't think a plain flat array design could ever have panels that shaded anything but area in back of the mount..



My guess is, the opening 'gap', is to break up the 'Sail' or 'Wing' effect, in cause of wind gusts from behind..?.
It would allow air from the top section to flow between the two sections,
and maybe cut the 'Lift' of the array.?.

[Bosco]

Hi

Thank you all for your comments. I will try to answer your questions.

The central pivot is the differential (back axle) of a utility vertically bedded into concrete with the frame assembly mounted around a wheel (minus tyre and tube, of course!). The tracking (azimuth and elevation) is controlled by two MTM Scientific ST2HD units. The azimuth drive is through the differential pinion (i.e. where the driveshaft would normally fit) from a very small 12 volt electric motor with a reduction gearbox, sourced from China. The elevation drive is from a 24" satellite dish actuator on the top set of panels, transmitted to the lower set via a linkage.

The power for control and tracking is from a 12 volt car battery recharged by a seperate 5 watt solar panel, barely visible in the photo.

The apparent gap between the two sets of panels is to prevent shading of the lower by the upper. The maximum elevation of the sun here where I live is 81.5 degrees on 21st December so on that day the panels are almost horizontal, hence the necessary gap.

The two systems shown are necessarily seperated by a large distance to prevent shading of the 'south' system by the 'north' system in the middle of winter when the sun's elevation declines to 34.5 degrees. However, it's not the vertical shadow that causes the problem, it's the horizontal shadow, as the rows of panels are five metres wide.

An additional problem that I had to solve was the presence of backlash within the gears of the differentials and I was concerned that there might be damage from large wind gusts. To overcome this I built two double acting hydraulic dampers (one for each system) some 900 mm long and incorporated each one in a tensioned wire cable loop which runs around the wheel, through the damper and on to a pulley mounted some 1.2 metres directly south of the unit and back to the other 'side' of the wheel, so no matter which way the gust tries to move the panels, the damper will slow the movement. Control of the fluid through the damper is by an external bypass and a needle valve.

The supporting 'trainer' wheels and concrete track were necessary to counteract the substantial moments caused when the frame and panels were moved (like a see saw) by small wind gusts. The total weight of the moving structure including panels is in excess of 600Kg (1,322 lb).

I hope I have answered all the questions but would be pleased to discuss it further. The highest daily output I have had was 40.03 Kw on 26th December and the lowest in the middle of last winter was 7 Kw. It is 'grid connect' and we gain 47 cents for every Kw we feed into the grid as opposed to the 20 cents it costs us to buy a Kw. The take up of grid connect solar power systems was much greater than the state government had planned and they subsequently reduced the feed in tarrif to 27 cents but we have a five year contract at the higher rate.

Regards

Bosco

[Xringer]

"The apparent gap between the two sets of panels is to prevent shading of the lower by the upper.
The maximum elevation of the sun here where I live is 81.5 degrees on 21st December so on that day the panels are almost horizontal, hence the necessary gap."


I think I understand now. The reason for the off-set & gap is because
the dual racks are tilted individually.

If they were on the same carrier frame, then shading wouldn't be a concern..


I put a small gap in the middle of my little 500w array..
http://i46.photobucket.com/albums/f1...r/RedPlate.jpg
Now, I'm sorry that I did.. It catches the snow, a big pile of it...
and takes a lot longer to melt off..

[Bosco]

Hi

Here are a couple of photos which should clarify the layout:



Morning



Afternoon

Regards

Bosco

[Slidegate]

Hi
Very ingenious design Bosco. I was right about the spacing because of shading. I'm trying to pick out a spot for my 2nd array and that crossed my mind for early morning and evening. How are your ST2HD from MTM holding up. I upgraded to the ST2-HD-PIX cause my array would want to track every 15 seconds playing hell with the relays. The ST2-HD-PIX is programable and works great

[Bosco]

Hi Slidegate

I intended to PM you but don't yet have enough posts. Please bear with me

[Bosco]

I will keep on

[Bosco]

posting these short

[Bosco]

messages, for which I apologise

[Bosco]

until I reach