Grid tied system sorting through the options

NorthWalt · October 2010

I am new to solar and am trying to decide on system components for a grid tied system in southern Ontario Canada at 42 degrees latitude. We want to take part in the microfit, feedin tariff program and so expect the system to be in the 10kW range. We have some things that make this site different than Arizona and more like Michigan or Wisconsin; snow, wind and low light in the winter.

So I have a number of questions about things like:
Fixed or tracker?

We are rural and so have space for either.
Trackers supposedly get 40% more production yet they look like they are often in safe mode (flat) and not pointed at the sun. This seems to be because of the wind.

We get a fair amount of wind from OHIO- south or Michigan- west as well as lake effect weather because of the Great Lakes. Average wind speed is 4.3 meters per second and range is 5.3 - 3.1

Another issue with trackers appears to be whether they track by bright spot or GPS. The bright spot aiming seems to be hard to configure properly and the GPS may be aiming at the darkest area of the sky when clouds are approaching. Do these problems reduce productivity significantly? How close in productivity are these two types of trackers? Seems like either way would work better in Arizona;).

What repair and maintenance costs should be projected over the next 20 years?

Are these 40% improved productivity claims true? For this Latitude and weather?

Is a ground mounted single axis system a good alternative for dealing with seasonal fluctuations and reducing costs initially and repair too? How would productivity compare to the tracker?

Thanks for responding to this with your experience.
________

solar_dave · October 2010

Re: Grid tied system sorting through the options

A 10 Kw system is really pretty huge for northern climates, I have a 12.5 kw roof mounted system here in AZ and between the panel heating and the huge AC loads I am almost at a zero sum $$ situation.

It is best to understand you consumption first, then get an estimate of your production. I would like trackers but the added cost and complexity can be easily offset with more roof mounted panels. that kind of setup is pretty bullet proof.

dwh · October 2010

Re: Grid tied system sorting through the options

Around here, it's been discussed that trackers may not be worth the price since with the lower cost of PV modules (solar panels) these days, it can often make more sense economically to static mount and just add more PV.

Trackers also have a hassle factor since they usually need some maintenance (even if only a shot of grease now and again) and moving parts can become points of failure.

Average wind speed of 4.3m/sec is right at the bottom edge of where small wind power is generally considered to become useful - 10mph (4.5m/sec) - and up on a 20m or 30m pole, you might well have even a bit higher average wind speed. So for your location, adding small wind generation might work out as a nice addition to a static mounted PV array.

drees · October 2010

Re: Grid tied system sorting through the options

One thing to keep in mind is that with the Ontario MicroFIT they are limited to 10kW in size - so to maximize payments a tracker will often pay for itself and then some quite quickly.

At the very least, it seems that one should consider a system which can have it's tilt easily changed based on time of year if you are going to be building a 10kW system.

dwh · October 2010

Re: Grid tied system sorting through the options

drees wrote: »

One thing to keep in mind is that with the Ontario MicroFIT they are limited to 10kW in size - so to maximize payments a tracker will often pay for itself and then some quite quickly.

Ah, yea. They'd make sense in that situation then.

I guess adding more either in the form of PV or wind would be right out then.

Seems a bit silly to limit the size of the system...couldn't they have just put a cap on the amount allowed to be sold and let people build whatever size system they want?

BB. · October 2010

Re: Grid tied system sorting through the options

dwh wrote: »

Seems a bit silly to limit the size of the system...couldn't they have just put a cap on the amount allowed to be sold and let people build whatever size system they want?

They are giving away people's money anyway--does it have to make sense too? :roll:;)

Using PV Watts for 10kW system fixed vs 2 axis tracking:

"Station Identification"
"City:","Ottawa"
"State:","ON"
"Lat (deg N):", 45.32
"Long (deg W):", 75.67
"Elev (m): ", 116
"Weather Data:","CWEC"

"PV System Specifications"
"DC Rating:"," 10.0 kW"
"DC to AC Derate Factor:"," 0.770"
"AC Rating:"," 7.7 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 45.3"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:"," 0.1 Can$/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value (Can$)"
1, 2.86, 735, 0.63
2, 4.70, 1075, 0.93
3, 5.27, 1286, 1.11
4, 5.01, 1110, 0.96
5, 5.21, 1158, 1.00
6, 5.47, 1138, 0.98
7, 5.53, 1174, 1.01
8, 4.99, 1046, 0.90
9, 4.56, 962, 0.83
10, 3.54, 818, 0.71
11, 2.27, 505, 0.44
12, 2.60, 655, 0.56
"Year", 4.33, 11662, 10.05

"Station Identification"
"City:","Ottawa"
"State:","ON"
"Lat (deg N):", 45.32
"Long (deg W):", 75.67
"Elev (m): ", 116
"Weather Data:","CWEC"

"PV System Specifications"
"DC Rating:"," 10.0 kW"
"DC to AC Derate Factor:"," 0.770"
"AC Rating:"," 7.7 kW"
"Array Type: 2-Axis Tracking"
"Array Tilt:","N/A"
"Array Azimuth:","N/A"

"Energy Specifications"
"Cost of Electricity:"," 0.1 Can$/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value (Can$)"
1, 3.46, 897, 0.77
2, 5.78, 1324, 1.14
3, 6.70, 1661, 1.43
4, 6.83, 1553, 1.34
5, 7.43, 1706, 1.47
6, 8.11, 1747, 1.51
7, 8.41, 1847, 1.59
8, 6.84, 1475, 1.27
9, 6.00, 1300, 1.12
10, 4.29, 1006, 0.87
11, 2.64, 592, 0.51
12, 3.08, 780, 0.67
"Year", 5.80, 15888, 13.70

You will really "clean up" in the summer months that far north.

If you get higher rates during day--then more power will give you a nice payback during peak Time of Use periods.

I have been saying that tracking systems are not worth the effort...

But Dave Sparks has been saying that (especially for off grid systems that need lots of time to recharge a battery bank) that a little bit of maintenance with good hardware makes for a nice tracking system.

Dave Sparks wrote: »

Tracking offgrid is the number one way if your location supports it to get completely away from generator use. This goal is very hard to do on a reasonable budget but a tracker is the path. I can not tell you the absolute difference other than we went from 25 days our batteries did not complete charge down to 5 per year. The other feature is you are off battery power earlier in the day and can do more with a smaller battery system. Conversely you can run cooling in summer at 7pm long after the fixed array has gone to sleep.

There just are too many variables but I would tell you a 2KW or slightly less tracker will do for most couples what 4KW fixed would do in winter up here in the Sierra. Winter is where the design is done and since all I do is trackers now it is my business model. I do not want phone calls!!! From my experience there just are too many days when an hour of sunlight at 9 am and another hour at 2 pm happen in winter. There are other senarios of clouds and just plain weather that a tracked array is superior over fixed.

If you like cold starting generators in the snow/ dealing with surges, doing alot more maintenance, having a big footprint of panels to deal with, a fixed array is definately for you. I do like a fixed array with a tracker so I am reasonable! I probably would agree with most of the gridtie folks here except I tried it. Definately no going back!

I asked him what he found to be reliable:

Dave Sparks wrote: »

24V DC motors supplied as a package from Array Technologies i.e. The Wattsun !

-Bill

johnl · October 2010

Re: Grid tied system sorting through the options

I have to agree with the previous poster that PV Watts is a great way to compare the output of roof mount vs. fixed ground mount vs. single-axis vs. dual-axis. Just make sure to put in the right kwh rate, azimuth, and tilt angle for each type of system.

A few things to remember for the Ontario microFIT ....

1) For applications filed after July 1, you can choose between $0.642/kwh for ground mount (fixed or tracker), or $0.802/kwh for roof-mount. OPA suggests that the rate of return on your initial investment will be roughly the same under these price options for similar sized roof mount, fixed ground mount, or tracker ground mount systems.

2) Ontario building code requires a building permit and plans drawn up and stamped by a structural engineer for anything more than a couple of roof-mount panels. Generally there are no such requirements for ground mount, but check with your municipality to be sure. On the other hand, trackers mounts are generally more expensive to purchase than roof racks for the same square footage of panels, and you may need to bring in a soil engineer.

3) Regardless of whether you choose ground or roof mount, you'll likely want to look at Ontario-manufactured mounts to meet the domestic content requirements for microFIT. That means manufacturers like True North Power, Dyco, PowerFab, SunLink, Sun-A-Ray, or Sentinel. These manufacturers are generally not charging premium prices for their Ontario-manufactured products.

4) Similarly to meet the domestic content requirements, you'll likely want to look at Ontario-manufactured inverters from Solectria or Enphase (SMA is supposed to be coming soon). There is minimal extra markup being charged for the Ontario-made inverters compared to those made by Solectria in Massachusetts or Enphase/Flextronics in California or Singapore.

5) Keep in mind that if you are not going to reach commercial operation by Dec 31 2010, your pv panels will need to be Ontario-manufactured. You will pay a very hefty price premium for this.

NorthWalt · October 2010

Re: Grid tied system sorting through the options - Inverters

Thanks for all the replies.

We have come to the same conclusions that the Trackers seem to be a lot of extra cost initially and maintenance over the next 20 years. Initial cost here seems to be 40% more than ground mount. Add in the maintenance cost and it is not clear you that there is much advantage. The wind here had them all flat On Wednesday. Trackers produced about 4KWH while the fixed ground mount was at 8kWH. Yes it does look like they really need to rack up the energy in the summer when the sun rises well North of east and sets well N of west. That limits peak tracker production to 3-4 months.

Yes seasonal tilt seems to be a good compromise for the ground mount. We have heard that vertical or close to it in winter will help boost the numbers (pick -up of the snow) while in summer we can get close to horizontal. Has anyone seen this happen?

This is all grid tied. The roof is small and points 20 degrees east of due south

Fixed Ground mount can over glass and meet regulations if the inverters limit the output so we are seeing systems that have 48 x 230W panels with 2 X 5kW inverters. This seems to fit with the idea of cheap glass as a way to maximize output. October data seems to show this Trackers produce 1.3mW while 10kW fixed produces 1mW this month. This is not enough difference to the pay the bills but I can see Dave's point that it is enough difference to keep the batteries charges;)

Next question:

String inverters or Micro inverters?

It seems like micro inverters offer excellent trouble shooting and better continuous power even when leaves, snow, dust or shadows interfere. Are they as reliable. Do they cut in at low voltages and do they Manage the current well? I have heard that string inverters use MPPT to manage the electricity. Are they as efficient can Micro's deliver with minimal losses? Do Micro's deliver power at both high and low voltages and do they work well in hot and cold.

Another thing I am hearing is that inverters need to be matched to panels. What are the characteristics that need to match up between the inverter and the panel?
________

jcgee88 · October 2010

Re: Grid tied system sorting through the options - Inverters

NorthWalt wrote: »

Next question:

String inverters or Micro inverters?

As with many "what's best?" type questions, the answer is,
"it depends."

The biggest indicator for micro-inverters is if you have
shading issues, or your site is space-constrained in a
matter where you are forced to multiple strings. The micro-
inverters can provide greater yield in those situations.

[Space didn't seem an issue in your case.]

If you have a homogenous string with no shading issues,
a string inverter not only makes sense but will also be
much cheaper in the case of such a large PV array.

I like the micro-inverters' management capabilities, and
for me this would be an important factor, but I can see
that others might not find this feature to be worth the
extra cost in such a large array.

John

johnl · November 2010

Re: Grid tied system sorting through the options - Inverters

I think you've got a pretty solid idea about fixed ground mounts with seasonal tilt-adjustments to minimize installed cost under the current microFIT scheme. I'll mention that for a 5kw or 10kw microFIT system, the lowest price per kw on fixed Ontario-made ground mounts seems to be the Unirac ISYS ground mount - made of galvanized steel I-beams instead of the extruded aluminum used in most other racking systems. Adjustable tilt-angle does not appear to be an advertised feature of this system - you might have to rig up a few customizations on your own to make that work. True North's ground and roof mount systems have really slick tilt-adjustments, but will cost a bit more.

If you have shading issues where you intend to put your ground mounts that can't be resolved with a chainsaw, and you really need the Enphase micro-inverters, Enphase has a compatibility list of which panels work with their inverters located here: http://www.enphaseenergy.com/downloads/Enphase_Module_Compatibility_List.pdf

Otherwise if you can live without the fancy Enphase data features and their annual per-inverter fee, you may be better off with the less-expensive and more time-tested monolithic inverters. The manufacturers of these products generally have online tools called "String Calculators" that will tell you what configuration of a particular panel will work with a particular inverter. The Solectria tool is found here: http://www.solren.com/stringSizing.html .

You simply input the panel you are planning to use, the size of array you want in kw, the min and max temperature range you expect to see in your locality, and one or two other details, and the software tells you what configuration of panels will work with their inverter. (ie the number of "strings", each of which will consist of a number of panels connected together in series in order to match the expected voltage and current output of the panels to what the inverter can accept). Of course you'll want to make sure that the string size also matches well with the number of panels your ground racks will accept. For example, if I choose a Trina or REC or Canadian Solar or Yingli 230w panel and an array size of about 10kw, I'll find that 4 strings of 12 panels will work nicely with two 5kw Solectria inverters. If I choose racking that holds 12 or 24 panels per rack, it will be easy to wire two strings of 12 panels to each 5kw inverter. However if I choose racking that holds 16 panels per rack, it becomes much trickier to divide up the 48 panels on the three racks among 4 strings of wire going to 2 inverters. (It may still be doable, but more complex, with greater chances of a variety of issues occurring such as voltage losses from longer cable lengths or slight mismatches in tilt/azimuth between panels on the same string but in different racks.)

NorthWalt · November 2010

Re: Grid tied system sorting through the options Inverters

Can over glassing be done with micro inverters?
Another way to deal with the lack of a tracker seems to be to overglass. That is go up to 12 KW of glass and then meet OPA 10 kW requirements by using inverters that total 10kW namplate capacity.

Can over glassing be done with micro inverters? All the over glassing that I have seen so far is with string inverters.
________

NorthWalt · November 2010

Re: Grid tied system sorting through the options

johnl wrote: »

5) Keep in mind that if you are not going to reach commercial operation by Dec 31 2010, your pv panels will need to be Ontario-manufactured. You will pay a very hefty price premium for this.

Which panels are made in Ontario today?
________

NorthWalt · November 2010

Re: Grid tied system sorting through the options

BB. wrote: »

Using PV Watts for 10kW system fixed vs 2 axis tracking:

Thanks for doing the PV watts calulation

What is the Derate factor? What is the effect if it is .84 not the .77 you used. One potential supplier used PV WAtts with the .84 derate. They were selling micro inverters and trackers.

-
________

BB. · November 2010

Re: Grid tied system sorting through the options

You would just get more power:

0.84/0.77 = 1.091 times more power (~9% more)

-Bill

johnl · November 2010

Re: Grid tied system sorting through the options

NorthWalt wrote: »

Which panels are made in Ontario today?

Solgate/Sentinel Solar, Photowatt Ontario, Heliene

Several larger international manufacturers have announced plans to begin manufacturing in Ontario in early 2011 - Canadian Solar, SunTech, Siliken to name a few.

drees · November 2010

Re: Grid tied system sorting through the options Inverters

NorthWalt wrote: »

Can over glassing be done with micro inverters?
Another way to deal with the lack of a tracker seems to be to overglass. That is go up to 12 KW of glass and then meet OPA 10 kW requirements by using inverters that total 10kW namplate capacity.

Can over glassing be done with micro inverters? All the over glassing that I have seen so far is with string inverters.

If by "over glassing" you mean install more STC rated PV power than the inverter is rated for, then yes. Enphase actually encourages you to install a 230W panel on a 190W rated inverter (the inverter seems to max out at 199W in real life). There are a few 250W panels that are listed as compatible with the Enphase inverters.

anthem · November 2010

Re: Grid tied system sorting through the options Inverters

drees wrote: »

If by "over glassing" you mean install more STC rated PV power than the inverter is rated for, then yes. Enphase actually encourages you to install a 230W panel on a 190W rated inverter (the inverter seems to max out at 199W in real life). There are a few 250W panels that are listed as compatible with the Enphase inverters.

You should look at the PTC ratings of the panels. Enphase doesn't necessarily encourage you to use higher rated panels than what their inverter is rated at but to use what the panels will actually output. So unless you live in say a cold tundra (without snow) that can keep the panels nice and chilly for optimal efficiency - the reality of the STC output is more closely approximated by using PTC.

So that being said, they recommend the M190 for just about every panel up to 230. The exception to that is the Sanyo HIT panels and the Sunpower panels. Both are in the 16-17% efficiency levels and their 215 panels are rated at 199. Give you some PTC numbers (quoted from HomePower charts)

SunPower 215 - 19.5
Sanyo HIT 215 - 199.6
Rec 215 - 187.2
Sharp 215 - 185
Kyocera 215 - 189

So, you can see how many 215 panels only get about 185 (outside of the ridiculously expensive Sanyo/Sunpower), so a M190 can easily handle those panels (or even up to 225/230) as they rate to 199.

Enphase recommends M210 for the Sanyo/Sunpower panels as they apparently regularly achieve greater than what the M190 is rated to output.

techntrek · November 2010

Re: Grid tied system sorting through the options Inverters

Micro vs. large string... I posed this question a month or two ago, and even after a long discussion there wasn't a clear answer. A recent development has changed that - at least one manufacturer has announced a high-voltage charge controller. Why a charge controller on a grid-tie system? All of that solar potential is lost when the grid goes down, no way to charge batteries to keep the fridge cold and a few lights on. The new charge controllers would allow that if you have a single (usually high-voltage) grid tie inverter.

drees · November 2010

Re: Grid tied system sorting through the options Inverters

anthem wrote: »

Enphase recommends M210 for the Sanyo/Sunpower panels as they apparently regularly achieve greater than what the M190 is rated to output.

Actually - the real reason they spec the M210 is that the M210 is rated for higher voltages that the Sanyo HIT / Sunpower panels put out.

PTC ratings only change the measurement procedures and may or may not be closer to real-life conditions for you. PTC ratings do tend to work well in a lot of California, though.

A high PTC/STC ratio only indicates that the panel performs better when hot.

Regardless - the higher the rating of the panel, the more power you will generate as it's not long that even a 250W panel in the cold won't be exceeding 199W for more than a couple hours a day.

johnl · November 2010

Re: Grid tied system sorting through the options Inverters

drees wrote: »

If by "over glassing" you mean install more STC rated PV power than the inverter is rated for, then yes. Enphase actually encourages you to install a 230W panel on a 190W rated inverter (the inverter seems to max out at 199W in real life). There are a few 250W panels that are listed as compatible with the Enphase inverters.

For an Enphase microFIT system in Ontario, the magic number is 52 M190 inverters for 9880w to stay within the 10kw nameplate limit (with each inverter attached to as large a 60 to 72 cell 240w or 250w panel as the Enphase inverter can handle in order to maximize output).

And as NorthWalt suggests, with the way the Ontario microFIT rules are written, it makes sense to do something similar with large traditional inverters, as long as you remain within the string-sizing limits of the inverters. The Ontario rules allow for the system to be sized up to a maximum "nameplate-rating" of 10kw, where the nameplate rating can be either the STC DC rating of the panels, or the nominal AC output rating of the inverters. The idea here would be to install perhaps two 5kw "nameplate-rating" inverters and 11kw to 12 kw of panels by their DC STC rating. Just as with the Enphase units, at midday during very sunny winter days, the inverters would clip the output down to 10kw, but in more marginal weather conditions, the output (and revenue) would be higher than if using only 10kw worth of panels.

Ralph Day · November 2010

Re: Grid tied system sorting through the options

It's not just in the snow and cold that Enphase output is clipped. Look at my signature and follow to see the output for the 10kw system.

Ralph

drees · November 2010

Re: Grid tied system sorting through the options

Ralph Day wrote: »

It's not just in the snow and cold that Enphase output is clipped. Look at my signature and follow to see the output for the 10kw system.

If you ask me - it sure looks like winter up there to me! Last Wed looks like a perfect day for you - cool (60*F) AND a steady wind blowing - very good for PV generating and probably as at least as good as STC conditions during peak hours with your tilt!

anthem · November 2010

Re: Grid tied system sorting through the options Inverters

drees wrote: »

Actually - the real reason they spec the M210 is that the M210 is rated for higher voltages that the Sanyo HIT / Sunpower panels put out.

PTC ratings only change the measurement procedures and may or may not be closer to real-life conditions for you. PTC ratings do tend to work well in a lot of California, though.

A high PTC/STC ratio only indicates that the panel performs better when hot.

Regardless - the higher the rating of the panel, the more power you will generate as it's not long that even a 250W panel in the cold won't be exceeding 199W for more than a couple hours a day.

Drees - yes I know. The Sanyo and Sunpower are both a 'bit' higher than other panels that they officially support on the m190. However, that being said - I regularly see higher than 199 on some Sanyo panels (don't have access to the Sunpowers). So, yes, while its supposedly a higher voltage issue, I think its also an output issue. And yes in some higher climates (like say Denver), other panels can regularly max out the 199 that the m190 is capable of handling (flat lining for a couple hours) - but generally that is rare.

I think the PTC is a much better measurement because very few people will ever achieve STC as the panels/cells get hot from minimal radiance. PTC gives a better measurement of how panels work in closer to real world conditions. The only problem is that the better PTC rates panels (ones that work better in heat), have a 25% price premium on them as compared to the rest. 10% output premium for a 25% price penalty.. . . not the best option around unless you are real estate limited.

Ralph Day · November 2010

Re: Grid tied system sorting through the options

Hey Drees
Winter? Not yet, not for a few more weeks. No snow yet.

6 weeks the other side of the winter solstice (same insolation as today) with snow on the ground I expect to see over 80kwhrs generated. So far today 72kwhrs (nary a cloud all day).

The days that it is cloudy and rainy it looks like a giant has stepped on the power graph.

Ralph

drees · November 2010

Re: Grid tied system sorting through the options

Ralph Day wrote: »

Winter? Not yet, not for a few more weeks. No snow yet.

My comment was a bit tongue in cheek - the weather you have now is considered winter for most of California.

I am jealous of your array's capabilities. Wish I had the room for a system like that.

Well - I guess I do but I need prices to come down a lot more to make it worth while as my biggest roof surface faces the wrong direction.

NorthWalt · November 2010

Re: Grid tied system sorting through the options Inverters

I think the PTC is a much better measurement because very few people will ever achieve STC as the panels/cells get hot from minimal radiance. PTC gives a better measurement of how panels work in closer to real world conditions. The only problem is that the better PTC rates panels (ones that work better in heat), have a 25% price premium on them as compared to the rest. 10% output premium for a 25% price penalty.. . . not the best option around unless you are real estate limited.[/QUOTE]

I started looking into STC and PTC Ratings Thanks for the lead. What I understand now is that 220 is probably not 220 Ouch. At one site I also got info on temperature coefficient, and % Tolerances.

Next question Choosing panels

For grid tied fixed or grid tied tracking Sanyo seems to look awfully good Good in the heat, great efficiency per square foot. They seem to come in at a 18-20% premium $ Is it worth it? Will they generate 20% more per year? Will they degrade more slowly? Are they burned into start so initial degrading is low?

A buddy did a comparison using PTC numbers of Sanyo 220 +10% and Conergy 235 +- 3% Both have a low end PTC of about 204 and 207 So with Conergy being 30% cheaper it looks easy to choose. Does it really come down to which company will stand behind its warranty and speed of getting replacements. Is there something I am missing about the performance of lower cost panels? I see that around here there are so many different panels.
________

NorthWalt · November 2010

Re: Grid tied system sorting through the options

BB. wrote: »

You would just get more power:
0.84/0.77 = 1.091 times more power (~9% more)

-Bill

So how do you choose the right? derate. It sounds like a bit of sales trick to increase the power output by boosting the derate factor Or am I being too suspicious?
________

NorthWalt · November 2010

Re: Grid tied system sorting through the options

5) Keep in mind that if you are not going to reach commercial operation by Dec 31 2010, your pv panels will need to be Ontario-manufactured. You will pay a very hefty price premium for this.[/QUOTE]

Good to see you here John with the OPA perspective. My conditional offer ends in February so we are trying to get them in now. It appears that Hydro 1 is backlogged on connections. Have you heard what OPA plans to do about this type of situation where the everything is ready to go Dec 1but Hydro just can not get there by Dec 31?
________

NorthWalt · November 2010

Re: Grid tied system sorting through the options

drees wrote: »

One thing to keep in mind is that with the Ontario MicroFIT they are limited to 10kW in size - so to maximize payments a tracker will often pay for itself and then some quite quickly.

At the very least, it seems that one should consider a system which can have it's tilt easily changed based on time of year if you are going to be building a 10kW system.

That is interesting because once we changed panels to the cheaper Non Sanyo's/Sunpower, we saw that a tracker system could come in at 15% over the fixed ground cost and all of a sudden the payback works out.

I thought of single axis seasonal tilt too. Seems to be about 10% more productive than fixed but it also 10% more expensive than fixed and ends up very close to the tracker.
At that point tracker maintenance seems to be a great way to maximize production and gives us an option down the road of keeping away from a generator.
________

BB. · November 2010

Re: Grid tied system sorting through the options

On very good days, you can 85% (I get this a few times a year on my system in the SF Bay area--on the warmer side of the coastal hills. I always get at least ~72% peak... (this is just random checks during the day--I don't have my array logging data).

Take your pick... In real life, you are not going to be able to measure much better than 10% accuracy based on temperature/clouds/humidity/dust/etc. in the air.

My array is on a 2nd story roof and takes a good sized ladder to setup and wash--I do that perhaps once every year or so (remove the stains from the oak/eucalyptus leaf "tea" that builds up on the panels).

For a Grid Tied system--cutting things close may be the difference of $100 a year--or $10 per month power bill... But you always have power.

For my setup--Any excess power I generate is "zeroed out" at the end of the year (we currently do not get paid for excess power produced with our 1 year net metering plan). So, 5% too much is simply "lost" at the end of the year.

And--in point of fact, my 3 kW rated GT system does produce more power than I actually use. And I would do it again. I have a pretty good cushion that I don't have to watch every watt my wife and kids use (just keep track of the big stuff). It makes life a bunch more peaceful around the home (on a time of use power plan where summer peak charges run from $0.30 to $0.57 per kWH (use more power, pay more money per kWH).

For a off-grid system where you start with 52% efficiency and plan on 25-35% usage day to day--5-10% error in the day can be close to 1/4-1/2 of your daily planned loading (never plan on using 100% of the daily PVWatts estimated output for off-grid / no generator--Just is not going to happen).

Another reason I plan for the "worst" 9th month out of 12 as the "break even" point for off-grid systems. This is the month where the owner may or may not need to use the genset. The other 8 months--probably don't need to turn it on once. And the last 3 months, plan on using it several times a month. No major surprises.

I usually try to error on the 5-10% low estimate of usage (0.77 GT or 0.52% Off Grid) just because having a bit more power is never going to be a problem... Having bit too little power can be a pain--higher than planned utility bills for grid tied vs possibly running the genset 2x more than you planned on for off grid.

In the end--This is my personal point of view with a data set of 1 point (my personal GT system).

There are people here with a lot more experience that I with off-grid--and you can ask them for more specifics on what they would do/recommend/mistakes made and go from there.

In your case, you have MFIT payments of $0.85 or so per kWHr and the limit is based on the Array physical rating... Anything you can do to which will increase the output ("better inverter", trackers, heavy gauge wiring, etc.) is simply icing on the cake (Pure Profit).

I don't know if the installer would do it--but it would be interesting to see if they would guarantee output... I tend to think they would not--weather/cleaning/climate variation over time would make it difficult to guarantee actual output numbers over time--but it would be fun to see them squirm when they say they have 85% output and you try to make them guarantee it.

In the end, break everything down to dollars and cents. See how much an array will produce $$$/year and see if the difference in charges/costs are worth the extra returns.

-Bill

johnl · November 2010

Re: Grid tied system sorting through the options

NorthWalt wrote: »

Good to see you here John with the OPA perspective. My conditional offer ends in February so we are trying to get them in now. It appears that Hydro 1 is backlogged on connections. Have you heard what OPA plans to do about this type of situation where the everything is ready to go Dec 1but Hydro just can not get there by Dec 31?

Are you lucky enough to have submitted your ground-mount application before July 2nd, and therefore qualify for the extension announced in August:

Domestic Content Requirements
Eligible ground-mounted solar applicants who applied to microFIT before noon on July 2, 2010, will have until May 31, 2011, to install and request a connection for their projects at the 40% domestic content level.

http://microfit.powerauthority.on.ca/Program-resources/FAQ/FAQ-solar-Options.php

http://microfit.powerauthority.on.ca/Program-updates/ground-mount.php

Grid tied system sorting through the options

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