What is your daily Yield multiple? (In relation to panel ratingin)

System · January 2008

I'm looking at putting together a medium size array in Ontario, Canada; and I'm trying to get a better feel for what people in similar areas have. My Yield multiple, I mean the amount of power produced in one day in relation to your total capacity. For instance, 10kwh on a 3kw array.

Also, if anyone has an approximation as to what type of true increase you can see using 1 and 2 axis tracking that would be great!

So far, I've guessed at between a multiple of 4-5 during the summer and 3-4 during the winter, and a 20-25% increase using 2 axis tracking.

Am I way off here? (hopefully to conservative

)

Thanks!

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

You can look at this PDF file of solar data for Minnesota... International Falls is just about as far north. Don't know if lake effects and such make the comparison faulty or not...

Around 5 hours per day during the summer months, around 2-3 hours per day during the winter months (long term averages--the PDF file also shows the variation over the years too).

1 axis tracking seems interesting.... 4.3 hours vs 5.5 hours 1 year average sun hours per day...

My Grid Tie "multiplier" for the NREL data set (near San Francisco) using 5.4 hour average over full year (mounted at latitude, fixed, roof mounted array):

(9,701/2 years) / (3.500 kWatts (STC) * 5.4 hours yrly avg) = 256.6 kWhrs / STC kWhr per year

Or, about 0.70 kWhrs per STC kWattHour... Yours might be better or not as good as mine (I have pretty good weather, not too hot for much of the summer).

Your numbers will be different than mine--but it is probably a good floor (0.70 "PTC"-panel-Grid Tied inverter overall efficiency).

That is based on 2 year data, and my home facing ~SE with some morning/evening tree shading...

-Bill

icarus · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Where in Ontario are you?

Things are a bit different here in the north.

Icarus

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

I'm in Toronto, and we'll probably put the plant in the country near Sarnia or something as the solar w/m2 is the highest for Ontario there.

So BB- If I understand you right - the "5 hours" means the multiplier is 5 correct?

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Scot_J,

There are several multipliers. There is the derating for the Solar Panels (STC vs PTC--lab/marketing conditions vs more realistic PTC conditions used by California for rebates), there are temperature deratings (panels get hot weather, don't output as much power), there is Inverter losses (Grid Tied inverter for my case). There is mounting orientation and shading losses--etc...

For my system, my "System" derating was about 0.7xPanel wattage rating (vs the local San Francisco Airport station).

Then you have the "number of hours of sun per day"... If International Falls is close enough for a first estimate--then you look at the PDF file. Depending on tilt of the panels, tracking or not, month of the year, etc. you will get different numbers...

From the International Falls data; yes, the summer months for a Fixed 49 degree mounted panel averages around 5 hours per day (actual numbers for March through August are ~5.1-5.4 hours per day)... So for a 3kW array corrected using my SF site data and 2 year average:

3kW (STC) * 0.7 * 5 hours = ~10.5 kWatt*hours average per day from March though August

Will yours be more or less than that... I don't know--but it is probably within 20% of what your numbers will be (hopefully, my numbers are a bit on the conservative side if you have better siting).

Also, it depends on your local weather conditions... If I had my system 8 miles west--it would be on the Pacific coast experiencing a lot of marine layer (fog and clouds)--and probably generate only 1/2 the power (or less) vs where it is protected from the marine layer by a coastal ridge.

If you choose to tilt the panels up more in winter and less in summer, or using 1 or 2 axis tracking, you may average more power (see PDF file).

In general, most people these days recommend looking a non-tracking array vs tracking array because of the large amount of maintenance that most tracking arrays seem to require (plus the added expenses for the tracking mounts/motors/etc.). Many times, it is almost a wash on the costs of fewer panels with tracking vs more panels on a fixed mount (manual tilt may be very nice though--check the costs).

-Bill

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Ahh, I follow now - so around a multiple of 3.5 on average for that particular setup.

Where is this PDF file you are talking about, I'm a bit lost.

As for the tracking system, my aim is to find one < $2/watt for the setup, and if we can't keep the cost under that then I'll axe it. My main appeal to the tracking is that with a programable system, we can have it go to a 75degree angle during the evening to clear any snow that may have accumulated during the day, or evening; and with a fixed array that may be difficult. This project is going to be in the country, and not accessed easily, so as much automation as possible will be implemented.

That being said, how true are manufactures' claims that you can see a 20-35% increase in power production using a 2 axis tracker? A little far fetched?

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Duh... this PDF file (forgot to add the link on the earlier post)

Also, here is the link into the base web page with all of the states--PDF and TXT files...

Regarding the how much a tracker can add... Check the now present PDF link and you can run a quick spread sheet to check the costs for fixed mount, manual tilt, and tracking... If the units will be mounted near the ground (high enough to allow clear snow shedding--then manual seasonal changes will give you some nice power increases--on my 2nd story installation--I am too old to go up there...

I think we have a few people here from northern climates that change their tilts just 2-4 times per year and are quite happy with it. I am not sure that the "average tracker" (whatever that is) would be reliable enough for an unmanned installation (when they fail, usually it is not pointing at noon-time sun--and you can lose a lot of power until you get somebody there to work on it).

-Bill

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Wow, that PDF is an awesome resource, thanks!

By the looks of things I may be able to squeeze a average yearly multiple of as high 4, but most likely in that 3.5 range. I'm VERY happy that I found this forum.

Happy New Years all!

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Scot_J,

Are you going Grid Tied with Net Metering or will this be an off-grid/battery backed system... If you can go grid tie--it costs much less and has much better efficiencies (no 80% battery storage efficiency and 85% inverter conversion efficiency, more power than you can use in the summer and not enough power for the winter)...

I looked at an off-grid capable solar (for emergencies)--but decided a good quality 2kW generator was a better deal given we hardly ever have outages where we live.

-Bill

icarus · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Bill,

Use Detroit as an applicable comparison. Sarnia is just over the river and up a ways.

International Falls is 800 miles north!

Icarus

Trick question,, if go strait south from Detroit, what country would you come to first? Canada!

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Icarus,

I did not know where in Ontario he was at the time--just took a guess.

Anyway, I think he (Scot_J) has all of the basic information to do some estimates. And perhaps find some specific Canadian sources for solar irradiation that he can compare with.

-Bill

crewzer · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

You might want to take a look at this modeling tool: http://rredc.nrel.gov/solar/codes_algs/PVWATTS/version1/

The right hand side of the start page includes listings for “International” (non-U.S.) locations, including Canada. Just pick a location near you and launch the tool using the button at bottom right. You can then adjust model parameters to compare fixed, 1-axis tilt, 2-axis tilt, etc.

Note that this model is intended for grid-tie systems. I’d estimate performance of off-grid systems to be ~8% (VRLA) to ~15% (flooded-cell) less due to battery inefficiency.

HTH,
Jim / crewzer

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

I plugged in my data into Jim's link... Accepted the default of 0.77 derating factor (for grid tied systems), and using 150 degrees (~SE), it came out to less than 1% difference of my two year kWh production average...

This is probably close more by accident than by design--given that weather has such a huge effect on panel output--but seems to be very accurate (with my data point of 1).

Going to book mark that one.

I still like the old PDF files too (US only)--it shows on one page how weather, month by month, and mounting options can affect your total output with one glance.

-Bill

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Thanks again for all the info guys. I am going to do a grid-tie only system, and infact I don't even live at the location. We're taking advantage of the Standard Offer Program in Ontario.

As for the links, great thanks again; but any real world numbers would be great as well. I can do as many calculations as possible but would still like to know what people around the contenient are getting with their systems.

Much appreciated!

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Wow, and with that being said it looks like in this area (Sarnia/ Sault ste Marie), the average multiple is around 4.5 (using 2 access tracking)... Nice!

rplarry · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Scot_j
About a year ago I fabricated a 2 axis solar tracker for my off grid home. I've been off grid for about 9 years. Anyway I gained 40% in daily production ( over a fixed array) immediately because of the tracker. My array is very modest compared to your proposed array but 40% is still a substancial increase in my opinion. Trackers may not be right for everyone, they do require some maitainence, and some fiddling occasionally but the increase in daily production is impressive. Anyway it works for me since I can give it the time necessary to keep it working.
Larry

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

rplarry wrote: »

Scot_j
About a year ago I fabricated a 2 axis solar tracker for my off grid home. I've been off grid for about 9 years. Anyway I gained 40% in daily production ( over a fixed array) immediately because of the tracker. My array is very modest compared to your proposed array but 40% is still a substancial increase in my opinion. Trackers may not be right for everyone, they do require some maitainence, and some fiddling occasionally but the increase in daily production is impressive. Anyway it works for me since I can give it the time necessary to keep it working.
Larry

Awesome, great to hear good news about the trackers! I'm leaning towards a 1 axis because its < $1/w vs some of the more complex 2 axis are over double the price and have more things to break.

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Wow, forget Sarnia and the Sue; Trenton has a much higher yeild - 4.5 on a single axis tracker. Around 16,565kwh per year on a 10kw array.

Are there tools you can install at a location to measure the solar irradiance at a particular location?

Ralph Day · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Scot_J
Hello and welcome

Welcome to the real world too. The calculators and predictors always seem to me to be somewhat optimistic.

I live in Prince Edward County...about 20km from Trenton Ontario. Off grid, hybrid, 2.1kw pv (1/5 of your 10kw size) and my total solar harvest was 2152kwh from Jan 07 to dec 31 07. That only 65% of the expected/calculated/adjusted (for my system) output of your calculator. And last year was sunnier than the last 3 (except for December). If you're investing a lot of dough in solar...don't forget to add that extra grain of salt for the predictions;)

My 2.1kw pv is 12 Sharp panels, 10x175 watt and 2x180watt. 8 of the 175's are static with seasonal adjustment, the other 4 are on a manual tracker setup. No major maintenance issues with the old sattelite setup, but a new actuator motor will be needed sometime. I just hope they are still available when i eventually need one. Not too many of the old 10 foot satellite dishes around anymore.

Ralph

crewzer · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

I live in Prince Edward County...about 20km from Trenton Ontario. Off grid, hybrid, 2.1kw pv (1/5 of your 10kw size) and my total solar harvest was 2152kwh from Jan 07 to dec 31 07. That only 65% of the expected/calculated/adjusted (for my system) output of your calculator.

Ralph,

Those numbers don’t surprise me at all. The calculator used in PVWatts assumes that all derated energy generated is either used or sold to the grid.

Unlike utility-interactive systems, an annoying operating characteristic of off-grid systems is that a lot of PV energy can be “left on the table” whenever the controller is operating in absorb- or float modes. For systems properly sized to meet winter energy requirements, this behavior can be especially irksome in the summer when there’s lots of extra Sun and energy available but not necessarily harvested.

Accordingly, the PVWatts calculator probably won’t ever be particularly accurate when applied to off-grid systems, even if battery efficiency is factored into the equation.

I’ve considered this issue a bit as I plan my the PV system for my intended new home in Wyoming. For example, I may install two stoves: a gas unit for year ‘round use, and a two-or three-burner electric cooktop for use in the summer as a “diversion load” when excess energy is available.

HTH,
Jim / crewzer

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Ralph Day wrote: »

Scot_JI live in Prince Edward County...about 20km from Trenton Ontario. Off grid, hybrid, 2.1kw pv (1/5 of your 10kw size) and my total solar harvest was 2152kwh from Jan 07 to dec 31 07. That only 65% of the expected/calculated/adjusted (for my system) output of your calculator. And last year was sunnier than the last 3 (except for December).

I thought that Ralph was saying that he had a system that was an off grid system that was able to sell excess power back to the grid--unless he had another meaning for the "hybrid" description (hot water diversion load--or the other use of hybrid which is a generator/battery system to allow the generator to more efficiently supply variable loads)...

Assuming that it is grid-tie capable and operating normally, then there should be no "lost" solar collection like a true off-grid system would have (once batteries are near full, the charge controller cuts back on power used from the panels)...

-Bill

crewzer · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Ralph can obviously clear this up for us. However, past posts indicate that he's "cut the umbilical" (off-grid), and my interpretation of the "hybrid" label is that he's refering to his generators (one wind, the other diesel?).

Regards,
Jim / crewzer

Brock · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

My small system in Green Bay, WI, almost straight west of you and a bit north. Daily peak in summer I get 6 times its rated wattage and in the dead of winter I get about 3/4 of its rated wattage (almost none if it is snowing a lot). The best month is usually June and I get about 5 times the rating on panels and for the month and January it was just below about the rated wattage.

Mind you these are actual wattages out of my system including battery, charge controller and inverter losses. I am suppose to be in the 4 hours a day belt, but if you look at my numbers it is more like 2.5-3, then again my numbers are after losses.

westbranch · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

regarding you desire to track the sun, here is a very interesting link

http://au.youtube.com/watch?v=hQ5MiLqb5VE&NR=1

to a Discovery chanell piece on Youtube, titled Hybrid Solar Lighting. just near the start he mentions the use of GPS to move the multi directional tracker using a 9 volt battery. No metion of 110 vAC!
Thanks to ARTs' link re his PSP (?) charger, this was a related article that popped up...

EJ

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

The company is Sunlight Direct... Follow the link--but not too much more information than was in the video...

Interesting concept but I wonder about maintenance and complexity.

Obviously, it will take weekly cleaning of the mirror/fiber launch system. And the basic light fixture is a combination of "fiber" sources and florescent tubes (or halogen) under electronic control to keep a relatively constant lighting level in the room. Florescent tubes, at best, don't have shorter life when dimmed back (halogen bulbs can have 10-20x life under reduced power--but less efficient though).

To "power down" the solar light, they have to point the collector 5 degrees off sun... Sounds OK--but that may "turn off the lights" for several rooms--so to darken one room negates the advantages for the rest.

Sounds like it should not be a big problem--but in our local schools this has proven to be a big issue... Some of the 10-15 year old rooms have big skylights that now are all heavily shaded to block out the sun. Turns out it was a big problem to darken the room for films/tv/computer presentations and the next remodel is probably going to remove the skylights (or at least provide better light control).

-Bill

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Brock wrote: »

My small system in Green Bay, WI, almost straight west of you and a bit north. Daily peak in summer I get 6 times its rated wattage and in the dead of winter I get about 3/4 of its rated wattage (almost none if it is snowing a lot). The best month is usually June and I get about 5 times the rating on panels and for the month and January it was just below about the rated wattage.

Mind you these are actual wattages out of my system including battery, charge controller and inverter losses. I am suppose to be in the 4 hours a day belt, but if you look at my numbers it is more like 2.5-3, then again my numbers are after losses.

What is your total kwh output over the course of a year? (and the total rated cap of your panels?)

Thanks again all for the help!

I wish there was a registry of listed solar installations and their respective yeilds (atlas type of thing)

Ralph Day · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Sorry for the delay in responding, just the weekend.

Jim, i bought a single element coutertop electric "stove" and have used it as recently as 2 weeks ago. I'm not sure there'd be enough leftover power to warrant another entire cooking apparatus/stovetop. I guess it depends on just how much PV you install. Wyoming, thinking of wind as well?

Bill, yes, i did mean hybrid, as in wind, solar and genset...no grid. Maybe it's a Canadian english thing.

ralph

BB. · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Ralph,

Hybrid means whatever the last marketing guy put on the glossy (i.e., Prius gas motor/electric motor/battery car became, in the latest NGO glossies, a gas/diesel generator with inverter/batteries for off-peak loads when generator is inefficient).

Personally, I always thought Off-Grid was a mix of whatever you had (RE, fuel, etc.) and hybrid was redundant...

But that is just me. :roll:

-Bill

Brock · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

I had 449.1 kw in one year running 4 KC120's for a total of 480w.

So that comes to only 1230w a day over the whole year or 2.5 times the panels rated output per day.

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

BB. wrote: »

Ralph,

Hybrid means whatever the last marketing guy put on the glossy (i.e., Prius gas motor/electric motor/battery car became, in the latest NGO glossies, a gas/diesel generator with inverter/batteries for off-peak loads when generator is inefficient).

Personally, I always thought Off-Grid was a mix of whatever you had (RE, fuel, etc.) and hybrid was redundant...

But that is just me. :roll:

-Bill

I think there is just confusion as to whether one is talking about the generation method and/or the source of generation (grid or off grid).

System2 · January 2008

Re: What is your daily Yield multiple? (In relation to panel ratingin)

Thanks for the info. What is your install angle, and do you adjust quarterly or anything?

Brock wrote: »

I had 449.1 kw in one year running 4 KC120's for a total of 480w.

So that comes to only 1230w a day over the whole year or 2.5 times the panels rated output per day.

What is your daily Yield multiple? (In relation to panel ratingin)

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