[Greenbuilding] Solar microFIT installations (was re: 10 kW solar power plant production)

[RT]

On Sat, 30 Jul 2011 09:57:35 -0400, Frank Tettemer <frank at livingsol.com>  
wrote:

> Keith Winston keith at earthsunenergy.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).

> The Dager tracker is a single pole mount, holding 10kw, mounted on a  
> monstrous concrete base

> 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.


I would venture if one were to think about Keith's statement, (horizontal  
pipe oriented with long axis oriented East-West) his question would answer  
itself.

As mentioned in my response to Reuben's post the other day, the panels   
are attached to spars (4 panels per spar, not two as I had mentioned  
earlier in my response to Reuben's message) mounted perpendicular to the  
long axis of the pipe.

If the long pipe were in fact oriented East-West and if the panels were  
laid flat (ie no seasonal tilt), in the morning the panels would be aimed  
at the Southern horizon. Then as the pipe rotates, after a ~90 degree  
rotation, the panels would be aimed straight up, perpendicular to the  
Earth and then after a further 90 degree rotation of the pipe, aimed at  
the Northern horizon... which of course, makes no sense.

WRT Keith's comment about Kanata being at "those far north latitudes" ...  
my and my neighbour's (rural) Kanata location is at ~ 48.38 degrees North  
Latitude, practically within (but not quite)the Banana Belt of Canada,  
hardly the "Far North".  "North of 60" is probably what most MooseHuggers  
would consider "Far North".

				*
As I've mentioned on numerous occasions, I have pretty much zero interest  
in active solar (and that would include PV gizmology) so I know about that  
much (ie ~zero) about PV paraphernalia.

What I do know is that the Dager system with a 10 kW array mounted on a  
single pole (as described by Frank) sounds like a nightmare waiting to  
happen. I certainly would not care to have one anywhere near my home,  
regardless of how many govt incentives there may be, unless of course, one  
enjoys having to pick up the bits and pieces of the smashed array at least  
a couple of times every year, for the life of the installation (or until  
the insurance companies put you on their blacklist).

Even the first design for my neighbour's 10 kW array struck me as being  
ill-considered (horizontal pipe suspended 3 m (10 ft) in the air, mounted  
atop three vertical single pipes (steel well casings) planted 3m deep into  
the ground.

Fortunately, the design was changed to tripod supports at the ends and an  
inverted VEE support at the middle so that the support structure is not  
unlike that for childrens' playground swings.

As for the skepticism/doubts about the "up to 40% incremental production  
over identical but fixed-mount array" in the same neighbourhood, it seems  
that my memory was wrong (as it was about some of the physical details of  
the revised design).

Some days during winter, it was actually producing 44% more than the  
Enphase array.

I did quiz my neighbour about what the daily output curve for his array  
looked like and (IIRC, the email exchanges must be on one of my other  
computers ) he mentioned that it hit the peak almost as soon as the panels  
go on-line in the mornings (as compared to a gradual build-up to a peak at  
noon as would be the case for a fixed-mount array (as Frank describes for  
his fixed array).

Clearly, the benefits to have an array that tracks the sun over the course  
of the day is immensely beneficial however, IMO having that tracking done  
automatically with sophisticated controls and equipment
while nifty, is unappealing to me. Just more potential for failures and  
expensive fixes IMO. If I were doing it, I think I'd look at trying to rig  
up some relatively low-tech mechanical arrangement, perhaps not unlike the  
way people used to wind-up clocks every day, with an automatic-default,  
spring-back to "12 noon" orientation for those occasions when there's no  
one around to "wind up the clock".

I have put some images of the rig along with some relevant comments  
snipped from emails, into a PDF file "LlamaRanch PV" that I'll put into  
the FILES section, into the "Mechanical (and non) Systems" Folder at the  
YahooGroups SB-r-Us site.

For those who are not or can't be bothered to become members of the  
SB-r-Us List, if you send me a message *OFF-LIST*, (repeat OFF-LIST)  
paying attention to the instructions in my signature file) I'd be willing  
to send out the PDF file as a bulk email once all the requests are in. And  
if that's not perfectly clear, do not send your request for the PDF to the  
List and do not send a message to the List saying that replying to my  
edress results in your message being bounced. Such messages will be  
ignored. Hokay ? Hokay.



-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  c a >
(manually winnow the chaff from my edress if you hit "reply")