New large PV system proposal -opinions please « Alternative Technology Assn Forums

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New large PV system proposal -opinions please

(15 posts) (8 voices)

Started 12 years ago by ec175
Latest reply from bryan

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ec175
Member

Hi all,

I am currently looking at two different systems from installers with good reputations (as far as I can ascertain) in the Sydney area.

System one: 40 x Inspire Solar (Sunlink PV Co Ltd) SL220-20M 240 panels, Xantrex GT5 + Aurora PVI3600 installation and accessories for a total of 9.6 KW

vs

System two: 51 x Trina TSM185D, SB5000TL + SB400TL installation and accessories for a total of 9.4 KW

As I understand it, both systems use panels manufactured in China however Trina appears to have the longer manufacturing history and installed volume. Both panels seem to be quite efficient based on the specs and have industry standard warranties as well as reputable certification entities (both are on Aus CEC list of course). System one has a significant price advantage over system two which is around 12% more expensive after recs rebate offered however the components are assumed to be more valuable due brands reputation / history /?!

Both vendors are attentive (during the sale process anyway) and seem to know their products well and of course they are very convinced that their system is the only sensible choice.

Any sage advice that forum members can offer would be most welcome.

Posted Monday 21 Jun 2010 @ 11:01:19 am from IP #
rockabye
Member

One purely technical point is that a 40 module system has fewer connections than a 51 module system. Each connection is a potential point of failure. Worth considering.

Posted Monday 21 Jun 2010 @ 9:20:38 pm from IP #
ec175
Member

Thanks Rockabye. I had not even considered that aspect!

Posted Monday 21 Jun 2010 @ 10:52:48 pm from IP #
Russell Moore
Member

Also, if you have any shading issues, it will be easier to manipulate the 40 panels positions, than the 51 panels, to avoid shade.

Now would be a good time to check shading onto your roof for winter , keep in mind that the sun rises in the NE and sets in the NW now, and will rise in the E and set in the W over spring/autumn, and rise in the SE and set in the SW during summer. Of cause there are variations from this as the seasons blend into each other.

It is interesting how much shade you get onto your roof, and from objects you thought were too far away to worry about.

Posted Monday 21 Jun 2010 @ 11:16:04 pm from IP #
ec175
Member

Hi Russell. You are right and I have spent quite a bit of time on the roof in the last few days establishing the "best" location for the panels to avoid winter shading. North facing arrays (about 7.4 KW) will be in full sun from 08:30 till nearly 16:00 and the remaining 2.2 KW are on slightly north of west facing roof so they will not be in full sun at this time of the year until after 09:30 and through till nearly 16:00. This west facing array may be subject to some (hopefully minor) summer shading in the morning near the height of summer as there is a tall tree to the south east of the house on our boundary with the neigbhour. Do you have any good ideas or know of any relatively easy to use tools or calculators to establish the shaded area?

Posted Monday 21 Jun 2010 @ 11:45:18 pm from IP #
ghostgum
Member

Compare the efficiency of the inverters at their operating point. I've got an SB1700 and SB3000TL, and the SB3000TL does about 5% better. For you, that's the equivalent of an extra panel or two.

Posted Monday 21 Jun 2010 @ 11:59:29 pm from IP #
Russell Moore
Member

Under 'solar panel angle' ghostgum has a link to a site that will give you sun angles and positions for any time of the year. It is a bit convoluted, but you can get a lot of info if you are patient.

I would get a thick texta pen, and over the next few months (you will have lots of time waiting for the install!) mark onto the roof any shadows you are getting at different times of the day. I did this, by marking just the top edges of the shadows and writing down the time and dates onto the roof. Remember that spring shadows are the same as the autumn shadows, just add or subtact six months as needed.

Posted Tuesday 22 Jun 2010 @ 1:14:11 am from IP #
LanceTurner
Key Master

I take it none of those panels on the west roof are in the same strings as the north facing panels? They will affect the performance of them if they are. This is unlikely, but always pays to make sure! Personally, I would probably go with the first quote, if only given a choice of those two. If it were me though I would look at thin film panels, they make take up more space but they generate more energy over the course of a year than the same rated crystalline panel array.

Efficiency only determines the size of a panel for a given rating, it doesn't determine how they perform. What matters more, especially in Oz where we have high panel temps, is the temp coefficients of the panels. For instance, a common coefficient of a crystalline panel might be 0.4% per degree C above 25 degrees. So if the panels are running at 65 degrees, you lose 16% (or thereabouts). Thin film panels have much lower coefficienct, usually below 0.2% per degree C, so they perform better year round. They also generally work better with cloud, diffused light and partial shading...

Posted Tuesday 22 Jun 2010 @ 1:54:59 am from IP #
rockabye
Member

My friends 1kWp thin film 10 module system produced 1720kWH over 1 year compared to my 1485kWh from a 6 module 1kWp monocrystalline system. If I had had the available roof space I would have gone thin film.

Posted Tuesday 22 Jun 2010 @ 2:17:58 am from IP #
ec175
Member

Russel, had a look at the thread on panel angle and the link to the http://www.ga.gov website has resolved some concerns I had around the morning shading issue for the proposed west facing array. It looks like any shading will be gone by 10 AM even on the longest day.

Lance, the west facing panels will be on one string with its own MPPT in each case (PVI3600 for 1st system and SB400TL for second system). One of the north facing strings that is at a different tilt angle to the larger north facing array will use the other MPPT on this inverter.

Unfortuantely, my roof space is not large enough to have seriously considered thin film
this time around.

On the topic of temp coefficients, advertised values for Sunlink 240W panels give
NOCT 45 +/-2C
Voltage temperature coeff (Voc) -0.37%/C
Current temp coeff (Isc) +0.035%/C
Power temp coeff (Pmpp) -0.5%/C
Min power tolerance of +/-2%
Nominal voltage (Vmp) 30.1V
Nominal current (Imp)7.97A

For the Trina 185W they claim:
Nominal Operating Cell Temperature (NOCT) 47°C (±2°C)
Temperature Coefficient of PMPP - 0.45%/°C
Temperature Coefficient of VOC - 0.35%/°C
Temperature Coefficient of ISC 0.05%/°C
Power Output Tolerance-PMAX (%) 0/+3
Maximum Power Voltage-VMAX (V) 36.8
Maximum Power Current-IMPP (A) 4.9

On the face of it the Trina appears to be very slightly better (not sure if the higher NOCT offsets the lower temp coeff or not?) and the higher voltages coming from the 72 cell Trina vs the 60 cell Sunlink make it slightly easier to optimise the inverter fit for small strings (perhaps with some minor efficiency gains due operating point). That said, the Sunlink system starts with a 200W advantage, takes up less roof space and costs less upfront so it remains hard to discount it even if shiny new SB TL's with Bluetooth comms are on offer (by the way, has anyone used the free SB PC software that interfaces with the standard SB4000TL and SB5000TL?).Thanks for your comments.

Posted Tuesday 22 Jun 2010 @ 3:33:27 am from IP #
Inspector
Member

I'll second all of Lance's comments however the only drawback I can think of with having a mixture of panels is that you will likely need to use separate inputs/channels on the inverter (and separate MPPT) to the other (mono/poly) panels (plus keeping in mind Lance's first comment re: facing all panels of a string in the same direction).

The 51-panel system would also be dearer due to additional panel mounting rails required (possibly up to around $1000 more for parts and labour).

I'd also ask each company their accurate estimation of install time delay (inp articular, find out their equipment availability, as some inverters are in short supply) - if the dearer quote is going to be able to install alot sooner than the cheaper company, it's possible a fair chunk of the higher cost would be recouped from the system up and running sooner than the other.

I'd have to do some maths to work out the temperature coefficient differences between the two panels (someone else might already have an excel spreadsheet or software which works it out for them in the blink of an eye) but I'd say the 200W higher output of the first system would be easily overcome by the better temp-coefficiency of the Trinas. And then further calculate whether the cost benefit is there to go for that system (and how long before ROI of higher-cost system VS cheaper system when factoring-in panel efficiencies).

Roofspace would only be an issue IF the 10kw limit was ever increased, or you wanted space for pool-heating or solar hot water.

edit: re: MPPT - You posted while I was typing

Posted Tuesday 22 Jun 2010 @ 3:46:28 am from IP #
ec175
Member

Inspector, I have left room for my solar hot water system and will relocate the pool heating to a less "prime" location

Interestingly, the cheaper system has a firm install date available in about a month and I suspect that I will be able to get the meter on and connected more quickly with this installer as well if the feedback I have had is anything to go by. The Trina system installer seems to be preparing me for a longer wait to get connected and I wonder if this is due to the significantly larger number of installs that they are doing and some sort of "quota" for gross meters to installers? If this turns out to be the case, it will further skew the difference at the financial end as the revenue from the system is also significant. Your comments on the meter install and approval situation would be welcome if you have any to offer.

Posted Tuesday 22 Jun 2010 @ 5:23:33 am from IP #
Inspector
Member

I would expect all your metering questions to be answered here: http://forums.energymatters.com.au/solar-wind-gear/topic1069.html (if not in the first post, then certainly by the end of the thread ).

As for quotas, this is simply a matter of meter installers (usually completely separate to the solar company/solar inverter installer) only being allocated a maximum number of meters at any time (and not being issued any more until they return paperwork stating they've installed previously-issued meters). You *may* require an unusual metering configuration which may impact the time it takes for your metering to be installed (as the required meter may not be in stock). Make sure you have filled out and submitted an "Application For Connection" form(s) to EA stating you request permission to install solar-pv and gross metering (if you haven't already done so) as this can take up to 10 days to process - I did mine months before the system was installed, but most installers only fill this form in the same day they install the system (very poor customer service IMHO!).

Posted Tuesday 22 Jun 2010 @ 9:15:19 am from IP #
lurker
Member

Hi EC175 we might be dealing with the same people! If it is I had a 3kW system installed by them a while back and they were fantastic. I am in the process of obtaining quotes for my father for a large 8 kW system and noticed that the panels are the same Sunlink? However it may be a different crowd as we also have the choice of a 235w panel which is flash tested at factory for the same price. The voltage matching appeals to me using these panels and to my dad as he is a retired electrical engineer but I have been assured that the other panels are just as good. The coefficients are slightly better but most panels are within a few percent of each other so I would not worry too much about this. As I said I might be biased and if it is the same people then I wouldn't have any reservations about trusting what they say. I like their down to earth attitude and having dealt with them before I know that they will do a great job and go beyond if they have to. My terracotta roof was a bit of a nightmare but they didn't complain and actually repaired damage done by previous contractors that have accessed my roof. I have had a couple of cheaper quotes for my dads place and these are from larger companies and they are saying the right things but their reputation does not stack up. The guys I am dealing with have also offered to let me baby sit the Xantrex inverters until the install date when we do the paperwork! My dad also tried to trip them up with cell architecture talk and voltage coefficient design at high temp and low voltage and they were on the ball. He commented that these guys were on the ball and understood how to design a system correctly. Unfortunatley the majority of the other experts did not answer the questions and tried to talk major jargon which my dad understood but he said they really didn't make sense! He hasn't done any paperwork yet but he is going to sign on the line tomorrow I think as he wants the fastest install. He has been procrastinating for a long time on a system and now realises how much potential monies he has lost and could lose if he gets this wrong. One thing that I discovered in my travels is that the Trina 185w panels which we got quoted from a Melbourne based company are apparently being discontinued. The stocks of these will not be replenished when gone. This was confirmed to me by a number of installers. Also I am not sure if you know but the SMA TL series is rarer than hens teeth. We were told to be cautious of anyone quoting these inverters as they are delayed indefinitely. Again a number of installers told us this. BTW dads set up is going to be 2 Xantrex 5GT and 33 panels in 3 strings of 11 with a further 11 or so panels added to in the future. The larger watt panels have allowed for a great system with a future upgrade. I hope all goes well with your choice and install.

Posted Tuesday 22 Jun 2010 @ 12:40:01 pm from IP #
bryan
Member

Good Day Lurker and ec175

Would love to know name of your company, sounds the same to quote I had on weekend

Posted Sunday 27 Jun 2010 @ 11:10:47 pm from IP #

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