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 Post subject: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Sun Aug 17, 2008 4:00 pm GMT EthGMT 
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Minnow
Minnow

Joined: Tue Aug 12, 2008 10:41 pm GMT EthGMT
Posts: 19
Hi everyone...

I'm having a PV system installed on my house soon, consisting of 30 Sunpower SPR-225-blk panels and a Sunpower SPR-6000m inverter. I have a few questions about the inverter.

1) is the 6000m inverter big enough for my setup? I'm thinking it's not, but the installer says otherwise. Comments?

2) Sunpower is beta-testing a monitoring system with an in-home monitor and an on-line monitor with real-time data. I think Sunpower inverters are basically rebranded Xantrex inverters....do I have any good monitoring options from the start, or do I have to wait for Sunpower to come out with their own setup?

I'm a total noob at all this, so use small words when you reply!! ;)

Thanks in advance!

JimmyD

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 Post subject: Re: Sunpower SPR-6000m
PostPosted: Sun Aug 17, 2008 4:21 pm GMT EthGMT 
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Guppy
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Joined: Wed Apr 19, 2006 1:02 am GMT EthGMT
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Location: SF Bay Area
JD,

To size your system, you need to know your loads... Since this is an existing home(?) you can start with your last year or two's utility bills. And, you need to know how your local utility will be billing you with Grid Tied Solar (flat rate, TOU, 1 year net metering, 1 month net metering, differential rates between the power you buy and what you sell back, etc.).

A 6kW grid tie system is not small--but if you use a lot of power for A/C, it is certainly within the realm of a reasonable system.

Basic questions:

1. How much power do you use, per month, per year in kWhrs.
2. Where do yo live (nearest large city with similar weather as yours).
3. Are the panels facing south, and tilted to your lattitude?
4. Any shading (shading--should be none between 9am-3pm at least, winter/summer)
5. Utility company/rate plan/rates
6. Any other issues (not south facing, split East/West, etc.).
7. Anything else? (battery backup/off-grid).
8. Trying for rebates?

In the end, it is almost always better for you to spend your first money on conservation rather than generation. Depending on where you live, rebates, and your particular system costs & issues, your "solar power" system probably cost you around $0.20 to $0.35 per kWhr

For most people in the US, these kWHour costs--excluding interest, taxes and rebates--is still more expensive than their current electric power bill. So it is doubly more important to reduce you energy usage before/as you install solar grid tie.

If your heating costs are high (oil, electric heat, etc.) solar thermal heating (typically domestic hot water and radiant heating) is also something else to look at... The solar thermal systems are typically much less costly per watt of heat supplied vs solar electric--but it is also more of a pain (plumbing, tanks, leaks, freezing, antifreeze, maintenance, etc.).

-Bill


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 Post subject: Re: Sunpower SPR-6000m
PostPosted: Sun Aug 17, 2008 6:35 pm GMT EthGMT 
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Minnow
Minnow

Joined: Tue Aug 12, 2008 10:41 pm GMT EthGMT
Posts: 19
BB wrote:
1. How much power do you use, per month, per year in kWhrs.
Average is about 960kWh/month. I went back 2 years for the average.
BB wrote:
2. Where do yo live (nearest large city with similar weather as yours).
Oceanside, Ca. Basically, coastal San Diego
BB wrote:
3. Are the panels facing south, and tilted to your lattitude?
Facing south-southeast. Roof mounted, on whatever tilt my roof is pitched.
BB wrote:
4. Any shading (shading--should be none between 9am-3pm at least, winter/summer)
Virtually none. I'm removing a couple palm trees that would be in the way in the winter months.
BB wrote:
5. Utility company/rate plan/rates
SDG&E uses a tiered system. Don't know the rates offhand.
BB wrote:
6. Any other issues (not south facing, split East/West, etc.).
Nope.
BB wrote:
7. Anything else? (battery backup/off-grid).
Nope.
BB wrote:
8. Trying for rebates?
I'm doing the Performance Based metering plan for California. It's $.34 per kWh that my system produces.

Between myself and my installer, we've covered all the bases and the system we've come up with will be exactly what I want (and maybe a little over). I'm ok with a little over production, because we get our fair share of cloudy days (marine layer effect), so we factored that in, too.

My biggest question is is the inverter big enough for the 30 panels? I know the panels won't put out a full 225 watts each, but still....the 6000 inverter seems a tad small to me.

JimmyD

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 Post subject: Re: Sunpower SPR-6000m
PostPosted: Sun Aug 17, 2008 7:00 pm GMT EthGMT 
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Red Cobra Delta Guppy
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Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
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Location: Lakeland Florida
I think your right on questioning the installer, the inverter being under sized, 6750 watts of Sun Power panels will put the Sunnyboy 6kW into power limit everyday for sure. SPR-6000m

Someone has been down this path before you, check out this thread Another CA installed system with an undersized inverter with Sun Power Panels

If you change, I would recommend a pair of Xantrex GT4.0's ( whatever the Sun Power part number is as they are just re-labeled ) . This would also allow you to use SG-View for free and monitor , log and have web available data for free ... something you can't do with a Sunnyboy with out extra costs. A pair of GT 4.0's from here are $4348 or a SB7000 for $3755 would be another option, I don't know if the SB7000 is resold by Sunpower, the GT4.0's are for sure.

A Pair for GT4.0's will never power limit, will be near there peak efficiency and run cooler which should allow a long life for the inverters

Regards, do NOT let the installer put a SPR-6000m in a system with 6750 watts of panels. Sun power panels have proven they meet name plate power and in your location ( cool weather ) you will probably be push closer to 7kw more times than not


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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Sun Aug 17, 2008 7:21 pm GMT EthGMT 
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Minnow
Minnow

Joined: Tue Aug 12, 2008 10:41 pm GMT EthGMT
Posts: 19
That's what I was getting at. I'll check with the installer (we haven't ordered anything yet) and see about upgrading to a Sunpower SPR-7000m. I'd like to stick with Sunpower equipment for the efficiency and piece of mind. I hope I'm not a victim of advertising!! :roll:

The system designer is coming out Wednesday to survey my house, figure panel placement, etc. I'll talk with him then about the inverter.

Thanks! (I can't wait for the system to actually start going in!!) :lol:

JimmyD

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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Sun Aug 17, 2008 7:27 pm GMT EthGMT 
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Red Cobra Delta Guppy
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Location: Lakeland Florida
The Sun Power versions of the GT4.0's are SPR-4000x

http://www.gosolarcalifornia.org/equipment/inverter.php

And as far as efficiency, they are similar, you would have to find out the array operating voltage and typical power level to see if there is any real difference

SPR-7000m ~96+ peak depends on the array voltage

SPR-4000x ~95+ peak depends on the array voltage


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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Sun Aug 17, 2008 9:17 pm GMT EthGMT 
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Minnow
Minnow

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Thanks for the info, SG.

I'll discuss my options with the designer go from there.

JimmyD

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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Sun Aug 17, 2008 11:25 pm GMT EthGMT 
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Guppy
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Joined: Wed Apr 19, 2006 1:02 am GMT EthGMT
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Location: SF Bay Area
In terms of how much solar panels... 6,750 watts, San Diego, SSE (assume 150 degrees), assume latitude roof tilt, and Grid Tied power. From this solar calculator,

9,751 kWhrs per year or ~812 kWhrs per month.

-Bill


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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Mon Aug 18, 2008 12:00 am GMT EthGMT 
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Minnow
Minnow

Joined: Tue Aug 12, 2008 10:41 pm GMT EthGMT
Posts: 19
BB wrote:
In terms of how much solar panels... 6,750 watts, San Diego, SSE (assume 150 degrees), assume latitude roof tilt, and Grid Tied power. From this solar calculator,

9,751 kWhrs per year or ~812 kWhrs per month.

-Bill


That's about what my installer estimated. The system has a CEC rating of 5.93 KW (AC), with estimated monthly production of 837 kWh (10,049 kWh/yr)

JimmyD

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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Tue Aug 19, 2008 12:08 am GMT EthGMT 
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Catfish
Catfish

Joined: Sat Oct 20, 2007 12:34 pm GMT EthGMT
Posts: 38
Location: So. Orange County, CA
Great choice going with a Sunpower system!

The Sunpower 6000m or 7000m is a SMA/Sunnyboy inverter, so to go online you need to purchase the add-in networking card which was about $500 last time I looked.

I have a 5.5kw Sunpower system (27 205BLK's) at my home, running a Xantrax/Sunpower 5000x inverter. I considered the 5000m for my install and the -m series inverters are all very nice units. The pros are the clean design and good efficiency, better than the Xantrex I think by a hair. But the cons are the added cost to go online, and it is also a fan cooled design wheras the -x series is convection-cooled which seemed like a more robust design overall.

For sure you will need to upsize the inverter to either the 7000 or 2 4000x units, my setup has pegged my 5000x on numerous occasions and your install will be more so based on your design specs.

One other pro for the 4000x is you can get a hardwired monitor panel included (check the SPRx monitor link in the Sunpower website), your installer can probably throw this in the deal, again SMA makes one but it is rather costly and relies on WiFi.


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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Wed Aug 20, 2008 1:14 pm GMT EthGMT 
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Fish Eggs
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Joined: Wed May 21, 2008 1:38 pm GMT EstGMT
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If you check the SMA website (Sunnyboy manufacturer, maker of Sunpower's relabeled 6000m) they have a sizing tool available. It says that the 3 strings of 10 Sunpower 225's work. This seems to contradict some of the advise given in this thread.

There are 2 advantages of the Sunpower monitoring over other monitoring:

1. Indoor remote display that can be placed in a convenient location and give you the ability to check your system performance at a glance.

2. You can check your system performance from any computer using the website.

GT-View gives you a great amount of data regarding you system (My father produces detailed graphs and charts for his 20kW system on it) but it might be a little overwhelming for joe homeowner who just wants to make sure his system is working. But then again the price is right (Free)


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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Wed Aug 20, 2008 2:42 pm GMT EthGMT 
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Red Cobra Delta Guppy
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Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
Posts: 1158
Location: Lakeland Florida
The SMA string sizer has errors/bugs in it. I sent the info to SMA , they never responded

Use the Xantrex String sizer select a GT5.0 and the panels you are to use and compare the data.

One error I remember is that the SMA tool doesn't take into consideration running below the units minimum voltage input, is just scales the watts as V*I when in fact is not linear in the drop. Another poster in Mass. has an SMA installed system with to few panels in a string an was only getting 1/2 the nameplate watts. on the SMA string sizer it look OK


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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Wed Aug 20, 2008 4:05 pm GMT EthGMT 
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Minnow
Minnow

Joined: Tue Aug 12, 2008 10:41 pm GMT EthGMT
Posts: 19
Well, here's the scoop from todays visit with the design engineer.

For this area, he says that to figure out the realistic output, you would multiply the maximum output (30 * 225 watts = 6750 watts) by .88. This gives us 5940 watts, under the 6000m inverters limit. He says that if we had perfect conditions, the panels MIGHT produce more watts than the inverter could handle, but he claims that it my happen one or two days a year and moreover does NOT hurt the inverter in any way. (comments on THAT?) He said from his experience in real-life SoCal conditions, that he wouldn't hesitate to install the 6000m with my system.

They are going to give me a price on a 7000m inverter which would alleviate any possible problems AND leave a little room for adding 3 more panels, if I should choose to do so later. If the difference is only a few hundred dollars, I'll go with the larger inverter.

As far as the monitoring system, I want to stick with Sunpower's setup, because it's just what I want. They're still beta-testing the units, so I told my engineer to call Sunpower and beg them for one more unit. I'd rather have them install everything at the same time. We shall see if the guy is any good at sweet-talking Sunpower. ;)

Anyway...that's all for now. As always, comments are appreciated!!

JimmyD

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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Thu Aug 21, 2008 12:17 am GMT EstGMT 
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Catfish
Catfish

Joined: Sat Oct 20, 2007 12:34 pm GMT EthGMT
Posts: 38
Location: So. Orange County, CA
I guess there is an argument both ways, on one hand the 6000m will be working harder and maybe more efficient than a 7000m, particularly at the low end of the curve which will be greater with the 7000m. On the other hand, the 6000m will lose some watts during the times that push your system over the inverter max. For sure that will happen, and more than just one or two times per year. I am in South Orange County, Ca not that far from SD, and my setup has hit max watts probably 20x in the 9 months I have been online. Of course, it has been sitting at 4,100 - 4,300 watts peak during this last couple of months for the most part due to high temps, but even recently we had some clouds blow in that created the right conditions to max the inverter for a bit. Your setup will be more so than mine, since using the .88 factor I am at only 4,878 watts max which gives me more headroom than you will have.

I say, make them throw in the 7000m as part of the deal at your current contract price :mrgreen:


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 Post subject: Re: SB 6000U: SPR-6000m inverter sizing with Sun Power Panels
PostPosted: Mon Sep 08, 2008 11:03 am GMT EthGMT 
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Minnow
Minnow

Joined: Tue Aug 12, 2008 10:41 pm GMT EthGMT
Posts: 19
Thanks to everyone for the information. After discussing the system with my installer, I'm upgrading to a Sunpower 7000 watt inverter so I don't lose any power AND so I can sneak a few more panels if I should choose to do so later.
We also managed to get in on Sunpowers beta test for their new system monitoring hardware/software that they're working on. It basically consists of a small in-home monitor that shows whatever the LCD display on the inverter itself shows. And then there is a wireless hookup that feeds to the internet so I can access current and historical data on my system using a graphical display. That part is accessible from anywhere, since it's internet based. The company ALSO claims that they'll set up silent monitoring of your system and should the output drop for unknown reasons, they can have the installer go out and check on it. I seriously doubt they'll use the information for THAT reason, but from the companies perspective, getting to monitor your equipment in the field would have to be good for demographics use, etc.

I'm setting up a web site for pics etc. during the installation. When it's ready, I'll post the link here for anyone interested.

Have a good one!!
:D
JimmyD

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