Tracker efficiencies - generalized [RE-wrenches]

[jeff.oldham at realgoods.com]

Hi Windy,
Yes, I am including passive trackers. Although I think the design of these
things is one of the most elegant of mans mechanical creation. I just can't
get past the "psychological wrenching" of seeing the sun on the backside of
the array for at least an hour in the morning! I replaced my two about 8-9
years ago w/a Wattsun and have been a lot happier. I work on the Wattsun
about once a year and as you said the Zomeworks rarely ever need work.
However, I, and maybe folks I know, pull them over in the morning and tie
them off 'til the sun comes on 'round. This is a lot like work. In my larger
installs w/multiple trackers they sure look stupid pointing all over the
place and these are commercial customers that care a lot what the install
looks like! I agree with you in that the best application (and probably the
only one) is for water pumping. I agree with Ian in that over the life of
the array tracking is not as economical as a fixed array. In my over 20
years in this field I'I've only had two clients pissed off at my designs
(knock on wood!) and both cases it was over trackers that I could not
satisfy them with. I'm "fixed" in my ways for good now!

Have a good weekend all.

-jeff

> 	From the Solar, Wind & Hydro Powered office of:
> 	Jeff Oldham
> 	Gaiam- Real Goods & Jade Mountain
> 	Design & Consulting Group
> 	11755 Mid. Mtn. Rd.
> 	Potter Valley, CA 95469  USA
> 
> 	Ph: 303.222.3814
> 	Fax: 707.743.1820
> 
> 	www.solardevelopment.com
> 
> 	"When you turn to face the Sun all shadows fall behind you"
> 	- Old African Proverb
> 


-----Original Message-----
From: Windy Dankoff, Dankoff Solar [mailto:windy at dankoffsolar.com]
Sent: Thursday, March 21, 2002 5:03 PM
To: RE-wrenches at topica.com
Subject: RE: Tracker efficiencies - generalized [RE-wrenches]


>.... Personally, I've about
>had it w/trackers. I'm willing to work on mine all of the time but my
>clients are at their wits end.
>
>Jeff Oldham


Jeff,

Are you including Zomeworks passive trackers in the above statement? 
That would be very surprising. They are extremely durable in my 
experience. You replace a shock absorber or two every 5 years or so. 
Leakage of the working fluid is pretty rare and can be fixed by 
replacing the cannister assembly.

UNIRack now has a passive tracker on the same principle.

To estimate the gain from passive tracking, you need to take the 
theoretical data you might get from NREL, and subtract a factor for 
less accuracy, less range of motion, morning wake-up delay, and 
occasional wind-shift. I would guess it's about 15% less gain.

We sell lots of passive trackers for water pumping systems, only 
discouraging their use in extreme wind areas or extremely turbulent 
sites.

Windy

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