Need Advice/Recommendations on Panels etc.

System

Hi all!

I can't tell you how happy I am to find a good alternative energy forum that gets enough traffic for the discussions to be worthwhile. This is great!

Ok, I just moved into a house here in the Bay Area on the Peninsula. I have a large roof with relatively good southern exposure. A friend of mine came over with a Solmetric device, and told me that I have 15-20% shading. I'm fully aware that I don't have the BEST location for PV and that it might take a few extra years to pay for itself, but it's something I'm interested in, and I don't think the motive for doing PV should always be financial. Regardless, I'm doing it.

I'm an electrical contractor, so I'm going to install the system myself. I'm shooting for somewhere around a 3kW system.

I'm still reading through the rebate materials, so I know I have some work to do prior to actually buying the equipment, but I'm planning on using the standard Unirac mounts, and either a SunnyBoy or Xantrex inverter. Being able to monitor my system via the internet is very important to me, by the way.

How should I select which panels to buy? For some reason I'm leaning towards the Sharp 208w panels, but I'm pretty much open to any quality manufacturer. Can anyone recommend a good dealer here in the Bay Area, so that I can avoid paying for shipping?

What about inverters? I know that everyone has their own opinions, but can anyone discuss why you chose one manufacturer over the other, and which you chose?

Also, does anyone have a link to a good explanation of the math? Like, a 208w panel will actually produce X based Y number of hours of sun in my area, according to so and so chart.

Sorry so long and so needy, but I really appreciate the help!

(by the way, if anyone here in the Bay Area would like free installation help, let me know, I'm dying to learn!)

BB.

Re: Need Advice/Recommendations on Panels etc.

I have 20x BP 4175 panels, and a Xantrex GT 3.0 inverter installed on my home, plugged in on September, 2005. San Mateo CA (south of 92 near El Camino--so I am in a bit more sun than those north of me). About a 30 degree pitched roof and some shading in the morning/evening by trees.

3,500 watts of panels have generated about 4,800 kWatt*hours of power (Sept 05 to Sept 06--about 10% less than the installer estimated). I am using E-7 (PG&E) Time of Use metering. Other than some water coming in through the conduit (placed weep holes in the exposed J-Boxes), I have not had a problem.

I had about $285 in unused credit at the end of the 1 year net metering true-up (pays to conserve--plus I wanted to be ready for the plug-in hybrid).

You can go to the Xantrex calculator to figure out the panels and the California PTC ratings for rebate purposes.

http://www.xantrex.com/support/gtsizing/disclaimer.asp?lang=eng

Month by Month power generation (even though my array faces East of South--~155 degrees--about half of my power is generated after 12 noon):

512 kWhrs Sept 7th to October 6th (billing period):
365 October 2005
285 November
134 December
268 January 2006
354 February
313 March
470 April
523 May
558 June
490 July
495 August
394 September
343 October
297 November
224 December 2006

I have hit 2999 watts a few times, 2,600 watts sometimes, and typically 2,500 watts or a bit less (depending on time/weather/etc.). Notice the variability in weather-- September '05 vs Sept '06, 134 kWhrs in Dec '05 vs 224 kWhrs in Dec '06.

I used a BP/Home Depot program so that I would be sure to get panels... And there was a shortage of UV wire available when my install was scheduled. Probably paid more than I should--but I hope I have a few companies involved in case of component/install issues down the road. Got my California and Federal rebates without problems (took about 1 month or so for California to even process the request).

There is another web forum where people discuss panel vendors (not a whole lot of shared information on panels/vendors--but it is worth reading through once to get an idea of some problems) (forum owner is one of the design engineers for Xantrex GT inverter series and others). Solar Guppy also has a program and support for Xantrex inverters that people connect to the web:

http://www.solar-guppy.com/forum/

Went through City of San Mateo for building permits--they and PG&E did not give me any problems.

Regarding of connecting to the Internet--be aware that just running a computer to log the output can consume significant amounts of power--and with solar, you need to conserve as much as you can before you even connect solar panels--conservation is a whole bunch cheaper.

Regarding the power calculations, P=V*I works pretty well. The issue is how much sun on the panel, how much voltage, and how much current... And the solar panel's voltage (primarily, but current is affected too) is reduced as panel temperatures increase (the STC ratings are with 77 F degree panels--but as you know, place anything black in the sun and see how hot it gets). The Xantrex calculator can give you some samples of estimated voltage and current at different temperatures (it also give the minimum and maximum voltages for the Xantrex inverter/panel series / parallel connections).

There is also a web site that shows Sun Hours per day for various cities in the country and different panel mounts (angles/tracking):

http://rredc.nrel.gov/solar/pubs/redbook/

I would suggest you look at the PDF file for your state (bit more easy to read and understand) first before using the text files.

http://rredc.nrel.gov/solar/pubs/redbook/PDFs/CA.PDF (right mouse click to download)

As a start, you can probably just take my data and divide by 3,500 watts STC then multiply by your panel's STC rating--should get you close to a monthly amount of power using Grid Tied inverters... You might get 10-20% more if you have better sun and/or shading than my home.

-Bill

PS: Also look at trees/vegetation/buildings/power lines around your proposed solar installation... Trees grow and people build--and in my area, I can't even cut down trees without the blessing of the city--some of these things may not be in your control.

Solar PV panels respond very poorly to even light shading (power lines, and such)--usually by dropping output of an entire string by 50% or more... Don't convince yourself that shading during the middle of the day (9am-3pm at a minimum) does not hurt you--it will.

Roderick

Re: Need Advice/Recommendations on Panels etc.

Bay area, huh?

Firstly, be sure to get the CEC reservation paperwork filed right away.  It only has to be approximate, but will nail down your rebate at the present level, $2.50 / watt.  I don't know if you have to take the 15% self-install penalty if you're an electrical contractor.  Probbly yes, unless your company is certified to install photovoltaic, and will provide the required warranties.

Also, avoid the E-6 rate of PG&E like the plague.  With your shading, it would be even worse.  There was a temporary ruling the the PUC, forcing PG&E to offer the E-7 rate to NEW Net metering customers, but with an insidious loophole.  If you sign up under this provision, when the next E-6 gets implemented, you'll be forced to take it.  If your array is about 3 kW, and produces substantially all the electricity in your house, then E-1 will be better.  E-1 has a minimum charge of about $4.50 a month, E-6 is about $12.  If the new E-6 turns out to be actually good, you can always switch over to that in a year.

On mounts, if I got to do mine over again, I would configure the arrays as long horizontal strips, parallel to the ground, rather than vertical strips running up the roof.  With the horizontal strip, there's at least the future possibility of adjusting the array tilt without using tall, tall, legs that the building code would probably object to.

On inverters, you might want to consider one that has two independent DC inputs.  At 3 kW, I suspect you will have more than one string of panels, and if your roof is subject to partial shading at times, the shaded string would drag down the sunny string.  You could add bypass diodes, but in that case, the shaded string would simply not contribute much.  With a dual-input inverter, you'd have the chance to harvest something from the partially-shaded string, too. While I wouldn't base an inverter decision on computer interface, it sure would have been nice to have 802.11 wireless communication.

Panels, don't be afraid to shop the internet.  I think I got a better price shipping them from Southern California than buying locally.  And this store sponsoring this site, which is actually in Arizona, has pretty good deals, even after shipping.  Also, don't be afraid to get an inverter from one place and panels from another, if it ends up cheaper that way.

If you Google for "solar insolation nrel", you will come upon some historical data for almost any area in the US.  For where I live in the Bay Area, the map says between 5 and 6 hours of insolation per day, averaged over a year.  I do not live near the coast, where one should probably deduct something for the coastal fog.  I took the number to be 5.5 hours a day, multiplied by 365, multiplied by the PTC (not STC) rating of the panels, multiplied by the efficiency of the inverter.  This turned out to a spot-on prediction of how much power I'm actually getting.  I'm maybe 5% above prediction in real life, but who knows how weather can vary?  This is only what happened on my setup, I don't know whether it will hold true for another.

If you want to see my experience in detail, try

http://www.archive.org/details/DIY_self_installed_solar_photovoltaic_panels

and if you want the actual DVD, send me a personal message with your address.  I'd be honored to send you one free.

BB.

Re: Need Advice/Recommendations on Panels etc.

Also about PG&E with tiered rates... For me, I get about 300 kWhrs at baseline... If you are using a TOU type rate (E-7, E-6 or others)... Say you generate 300kWhrs from Noon-6pm (which is my E-7 time period). And you have an electric vehicle (or battery bank for load shifting) and use 300 kWhrs off-peak.

You would think that you are good.... Well, using PG&E's math, you have now used 600 kWhrs in terms of Baseline--pushing up you into higher rate tiers for consumed power (don't quite understand the math myself--you may need to talk with PG&E if this sounds like an issue for you)... It also affects those that may use the E-9 Alternative Fuel rate plan (somehow--there is one baseline for all meters at a home and the baseline usage gets shared among them all--to the worst possible way in terms for a customer). At least one guy with solar and an EV pulled his E-9 Meter because of the charges.

So, it is pretty important to understand your load/generation profile.

I too would think very hard before using the E-6 rate plan--partial peak rates go well into night time (duh, solar ain't going to help here), plus weekend partial-peak charges too. E-7 was a flat noon-6pm, 5 days a week program (pretty nice).

-Bill

mike95490

Re: Need Advice/Recommendations on Panels etc.

blackmountain wrote:

I'm an electrical contractor, so I'm going to install the system myself. I'm shooting for somewhere around a 3kW system.

Also, does anyone have a link to a good explanation of the math? Like, a 208w panel will actually produce X based Y number of hours of sun in my area, according to so and so chart.

If you pay yourself for the install, do you get the bigger rebate ?

I agree with Rodrick - if you have shade issues, use 2 separate inverters so the shaded one won't pull harvest down,
and get his DVD, it's a great one for installs.

I have 22 Sharp 208's and while they are essentially brainless, once installed, I do have one with a bad spot, the installer is supposed to fix it (swap out), right after Thanksgiving! ! !

Assume about 75% of rated panel power, for real life contitions, for the optimum sun angle months, and less in winter.

I'm not sure about the math, but I wonder if more expensive racks, to have the winter angle set, and squeeze as much as possible in the lean months, and loose a few % in the summer months?

System2

Re: Need Advice/Recommendations on Panels etc.

Thank you all for your informative responses! Does anyone monitor their system remotely via the internet? If so which inverter as you using?

niel

Re: Need Advice/Recommendations on Panels etc.

as you requested blackmountain, i have moved the subject matter here for you.

mike95490

Re: Need Advice/Recommendations on Panels etc.

Does anyone monitor their system remotely via the internet?

Click the center button, under my avatar, it's a link to my site, using a GT series inverter. Sometimes the wireless connection on my laptop is down, aside from the wireless, the GT & its software has been fine.
Another similar thread is here:
What are your GT-VIEW URLS?
http://www.solar-guppy.com/forum/viewtopic.php?t=491

System2

Re: Need Advice/Recommendations on Panels etc.


Isn't it a little cheesy advertising your business/solar site on a board
run by another company in the solar business?

brad

System2

Re: Need Advice/Recommendations on Panels etc.

I did not think it would be a problem after the customer was based in california. That is where our headquarters are. :evil:

BB.

Re: Need Advice/Recommendations on Panels etc.

I guess it was the ArizonaSolar.com user name and website address that confused me.

-Bill :evil: