[Greenbuilding] PV tracking...

[Gordon Howell -- Howell Mayhew Engineering]

It appears that typically no solar PV tracking system is economically 
worthwhile.  This arises because you can install additional 
fixed-tilt solar PV modules to equal the same amount of annual energy 
as the tracking system provides, yet the additional modules cost less 
than the tracking system's costs.

This has been apparent for several years, and with the significant 
drop in PV module pricing the difference is even greater today.

There may be applications where a single-axis tracker is indeed 
worthwhile, if it is designed and constructed in a very simple 
manner, such as in an off-grid system.

I'd be interested in readers' comments on their own experience.

+Gordon Howell
Edmonton




Date: Sat, 30 Jul 2011 09:57:35 -0400
>From: Frank Tettemer <frank at livingsol.com>
>
>/Just for reference: normally on single-axis tracking collector systems,
>the axis is E-W, not N-S. Are you CERTAIN it's N-S? Also, single-axis is
>generally good for more like 20% performance improvement, not 30-40%.
>But at those far north latitudes it may be that my rules of thumb suck
>(terrible pun on thumb-sucking, for those who missed it).
>
>K/
>............................................................................................................
>I agree with Derek and Kieth that these trackers, at best, will improve
>productivity, by (perhaps) 30%.  However, for a gambling man, this means
>their added initial cost will pay off the installation costs about as
>quick or quicker than the fixed mounts.  The carrot to this is that
>after the installation is paid off, the daily production is greater and
>thus the owner's income per month is also greater.
>
>Yes, I've seen quite a few of these North-Southhorizontal pole mount
>trackers.  They've become quite common trackers in the Ottawa Valley,
>Ontario. Talking to an installer/purveyor of these devices from
>Pembroke, and he says they cost 50% less than a Dager tracker, which
>seems to be the other common microFIT tracker in this rural area.
>
>The Dager tracker is a single pole mount, holding 10kw, mounted on a
>monstrous concrete base, and the actuators are two axis tracking, thus
>keeping the PV's at 90 degrees to the sun shine from early AM to late
>PM. They are definitely the most productive of the tracking devices,
>compared to the North-South horizontal pipe mounted thingies.
>
>My wife and I have built and installed our own microFIT, using eight
>steel poles, no tracker. These mounts can be adjusted seasonally, to
>optimize production but definitely have a production curve that begins
>low in the morning, goes to full production mid-day and drops off in
>afternoon.
>What we've done is mount 13,000 watts of PV's, to sell 10,000
>watts/hours.  As Derek has talked about, we've spent our money on more
>fixed mounted PV's, to get a greater daily yield, without the
>difficulties of maintenance of a tracking device.
>
>Two Reasons being:  I've seen one of these North-South horizontal pole
>mounts tipped to the East, and stuck there, for a full month, because
>the installer was too busy installing more of them to come back and fix
>the broken one.  This was a turn-off.
>
>And secondly, a Dager tracker holds 10Kw on one pole. That is One Huge
>Sail.  The one I'm aware of in Southern Ontario was blown over in a huge
>wind, and I'm told it wasn't a pretty site. (PV's contain very large
>sheets of glass.) Yes, they broke.  And how did they re-erect that huge
>tracker?
>
>I like the simplicity of a fixed mount, where I can go out four times a
>year, with a pair of wrenches, and manually adjust my mounts.  It adds ,
>maybe, eight total hours of labour per year. I can do that.
>
>Frank
>
>Frank Tettemer
>Living Sol ~ Building and Design
>www.livingsol.com
>613 756 3884
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