[RE-wrenches] Reference PV System

Mon Jan 3 13:09:45 PST 2011

Snow removal never seems to be an issue as in the winter the panels are at a steep enough angle to shed any buildup. Around the Mount Shasta (we got 6' in 3 days last winter) the only problem I have encountered is when there is so much snow so that when the slide off the modules builds up a pile tall enough to meet the bottom of the array, no more will slide. It then needs to be manually removed. This is why my pole mounts typically have the bottom edge of the array at maximum winter tilt at least 6' off the ground.

Todd

On Monday, January 3, 2011 12:19pm, "Jesse Dahl" <dahlsolar at gmail.com> said:

The snow removal system really interests me.  Being in northern Minnesota, we get a lot of it. I have one student that is responsible for snow removal now, but I haven't come up with anything else. I will be watching this thread intently!

Jesse 

Sent from my iPhone

On Jan 3, 2011, at 8:10 AM, "Jason Szumlanski" <[mailto:Jason at fafcosolar.com] Jason at fafcosolar.com> wrote:

One idea would be to put each microinverter on a separate A/C circuit and measure the current using a device like an eGauge or a revenue grade metering device. That would give you backup/redundancy for the Enphase numbers. With 16 modules/circuits in your system, that’s not too difficult to monitor.

For the second system, what about putting the system on a tracking rack that tilts to vertical once a day in the morning to dump snow. We don’t deal with much snow down here in Florida, so I’m not sure if that would 100% dump the snow off and how ice accumulation is dealt with… Born in Winnipeg, but left the snow behind many years ago…

Jason Szumlanski
Fafco Solar

From: [mailto:re-wrenches-bounces at lists.re-wrenches.org] re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Rob Harlan
Sent: Monday, January 03, 2011 1:25 AM
To: [mailto:re-wrenches at lists.re-wrenches.org] [mailto:re-wrenches at lists.re-wrenches.org] re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Reference PV System

I am working with the City of Edmonton, Alberta to develop a reference system.  The intent is to provide accurate data for owners of systems within the city limits to use to verify their system performance.  It is seen as a great way to insure quality installations under their municipal grant program, as well as a way to provide some real life performance data for system sizing and installation recommendations. The City is considering tying the dispersal of system grants to  verified performance.  (We are hoping to eventually have a municipal performanced-based FIT,  but until then...)  

At this point the plan is to permanently install modules at eight different orientations to imitate common installations:
True South 18.4 degrees ( Equivalent to a 4 in 12 pitch roof)
True South 26.6 degrees (Equivalent to a 6 in 12 pitch roof)
True South 45.0 degrees (Equivalent to a 12 in 12 pitch roof)
True South 53.0 degrees (Latitude)
True South 70.0 degree pitch (the estimated best angle for year round performance in Edmonton when snow is not removed)
True south 90 degree pitch (Equivalent to a vertical wall installation)
SE 18.4 degrees ( Equivalent to a 4 in 12 pitch roof)
SW 18.4 degrees ( Equivalent to a 4 in 12 pitch roof)
We will probably install two modules at each orientation to provide redundancy to back up possible equipment malfunction. Each module will have its own micro-inverter uploading data to a website.  The system will be installed on a municipal building, probably a firehouse.

We are also considering installing a second, identical system which would have snow removed once a day (at daybreak).  This would provide owners considering snow removal with comparative  data.  The challenge here is how to consistently remove accumulated snow.  We probably will not be able to get municipal staff to carry this out so we are looking into automated systems.

So gentlemen I would love to get your thoughts:

Anybody familiar with PV reference systems developed by other municipalities?   Have they been successful?
Have you found the Enphase Envoy to be consistently accurate?

Does anyone have a reliable automatic snow removal scheme with a track record?  We are putting it out to the University of Alberta mechanical engineering department to see what they come up with but I know this has been grappled with many times before.

Thanks much in advance for your input.
Rob
Rob Harlan
Executive Director
Solar Energy Society of Alberta
[http://www.solaralberta.ca] www.solaralberta.ca
[office at solaralberta.ca] office at solaralberta.ca
(780) 439-5608

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