Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

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  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Now turning attention to daily solar harvest.

    In addition to fixed influences of solar PV system design, daily solar harvest will be affected by the same variable influences as maximum power: amount of cloud cover, humidity (how much water is in the air), and outside temperature.

    For daily solar harvest, it will additionally be affected by the time of year. For example, yesterday I produced power for 13 hrs, 12 min. and 15 secs. At the moment this time amount is getting smaller each day by about a minute or so.

    Here's the chart:

    DailySolarEnergyProduction2.png


    Here we see the highest daily harvest is in late Apr., at a little more than 45 kWh. It was a clear day with no clouds, humidity was low so there was less water in the air, and it's the most recent coolest day.

    Since late April, each day's solar hours increased until June 21st. Unfortunately it's also gotten a lot hotter here. It's pretty evident the high heat more than offsets (negatively) the longer solar days.

    With it being hot this summer, peak solar harvest days run at about 40 - 41 kWh.

    On a rolling 30 days basis (black line), the avg daily solar harvest is ranging at about 30 - 35 kWh. It's interesting to see how peak avg daily solar harvests occur in July and Aug., even though on a daily basis the peak was in April. This appears to be due to weather conditions. While in April temperatures are cooler, weather was not consistently cloud free. Right now, the 30 day avg daily solar harvest is again hitting a peak, at around 36 kWh. Even though it's blistering hot, we're going through day after day of near cloud-free weather.

    Clearly solar PV system design impacts harvest as much as or even more so than weather. The dashed magenta line illustrates this. This line is what PVWatts says should be my daily solar harvest, on a daily basis for each given month, at default 0.77 efficiency (default assumes all panels are at 180° azimuth, all panels are at a pitch equal to latitude, there's no shading of the panels, and local weather pattern is taken into account).

    Here we see that on a 30 day rolling average, only for a few days in Aug., and a few days in June, has the avg daily solar harvest exceeded the PVWatts 0.77 efficiency default. Clearly solar PV system design is influencing production - it's not just weather.

    Next: more on performance with respect to PVWatts efficiency estimates.

    Best regards,

    Bill
  • AntronXAntronX Solar Expert Posts: 462 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Is there a way for you to average out the zigzag-inness of the graphs? Maybe disregard night time temperature and humidity readings? Have you thought about adding solar irradiance meter as well? It would be useful to track both long term and short term degradation of solar panel performance. Also, how about placing temperature sensor on the back of solar panel to measure actual panel temperature? Logging AC line voltage would also be interesting.
  • jcgee88jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    With it being hot this summer, peak solar harvest days run at about 40 - 41 kWh.

    ...the avg daily solar harvest is ranging at about 30 - 35 kWh.

    Bill, thank you for this post, and for continuing to keep the
    community apprised of your experiences!

    I'd like to offer a comparison to my PV array, which was
    installed in mid-June, in St Louis, MO.

    You have 36 x 225 panels for an overall capacity of 8.1 kW.
    My array consists of 13 x 235 panels or 3.055 kW. So, your
    array has 2.6X more raw capacity than mine.

    [Note that my site is not "perfect" - I am 30 degrees off
    south, and there is some early morning/late evening shading.]

    You are at a latitude that gets 5 solar hours per day
    on average versus my 4.5 solar hours per day. In other
    words, you should be getting 11% more production
    than me on a unit basis. If we add that 11% to your
    2.6X, then you should be getting 2.89X more harvest
    than me per day, all other things being equal.

    I am averaging 15-17 kwH per day. Applying the 2.89X
    factor to that means that if your array were equal to
    my array, except for number of panels, then you should be
    getting 43.3 to 49.1 kwH per day on average. You are
    actually getting 42% less than that amount. Using a guess
    of $.15/kwH as your electricity rate, that's about $700/yr
    worth of lost power.

    I realize that you have zero capital investment in your
    array and you are not required to fund anything in it. Still,
    the way it is configured might be wasting significant
    potential harvest that you could capture by spending a
    little out of your own pocket.

    If I were in your shoes, I would see if I could get a small
    capacity inverter to spring your worse performing panels
    off of the main array. In effect, you would be freeing
    your best performers from a boat anchor. Perhaps your
    contractor would be willing to do a temporary experiment
    with a borrowed inverter? Alternatively, is there a way
    for you to measure kwH/day by panel to see whether
    you are experiencing gross losses? Let's say that you
    can install a smallish inverter with requisite re-wiring
    for $2000 (less $600 Fed tax credit)...the payback
    period is on the order of only 2 years.


    John
  • russruss Solar Expert Posts: 593
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    @ jcqee88 - quote: I'd like to offer a comparison to my PV array, which was
    installed in mid-June, in St Louis, MO.

    You have 36 x 225 panels for an overall capacity of 8.1 kW.
    My array consists of 13 x 235 panels or 3.055 kW. So, your
    array has 2.6X more raw capacity than mine.


    İf a0128958 - Bill - is exceeding PV Watts then maybe you should do some checking on how much you are really producing. Meter readings are not always correct possibly even more so the units supplied with systems.
  • jcgee88jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    russ wrote: »
    İf a0128958 - Bill - is exceeding PV Watts then maybe you should do some checking on how much you are really producing. Meter readings are not always correct possibly even more so the units supplied with systems.

    I'm not reading off a meter, my micro-inverter control
    unit is capturing the data. Assuming that Bill is also
    capturing the harvest data off his inverter, that would
    seem to be the best apples to apples one could have.

    I frequently* compare my output to other sites locally,
    done by the same contractor, and my output is in
    the comparable range. These other sites even have
    different inverter technology, which further confirms
    that my inverters are not being misleading.

    *part of the fun of being a relatively new PV array owner!

    I think PV-Watts is a useful tool for predicting the
    ballpark of what a site could produce. It doesn't have
    enough input parameters to model a site perfectly,
    though. For example, tall trees across my street block
    out some direct sunlight in early morning. PV-Watts
    has no parameter for me to express that. Anyways,
    I'm exceeding my contractor's original PV-Watts
    prediction, too. Bill exceeding his PV-Watts is only an
    indicator that he is in the reasonable range for output.
    Given his low kwH to capacity ratio, it would be hard
    to believe that that is the best possible, regardless
    of whether my own number was mis-reported.

    John
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Continuing to look at system performance relative to estimates from PVWatts, here's a different way of showing the previous chart, this time iluustrating daily efficiency performance.

    SolarPerformance.gif

    Here we see how continued recent relatively cloud free weather has now pushed the 30 day rolling avg for daily efficiency above the 77% PVWatts' default estimate (black line). What this says is, on average for the past 30 days, at the moment, daily efficiency is upwards of 81%.

    The red line illustrates the minimum efficiency expected by the utility company to ensure rebate. It is set at 80% of the 77% PVWatts' default, which is abut 62%.

    Overall, noting that daily efficiency, on a rolling 30 day basis, is maintaining between 69 - 81%, it says that, so far, the installing company's design of one central inverter (with panels and strings of multiple orientations, and with some panel shading) is meeting the expectations of the utility company to issue rebate.

    Next: Longer term performance on a monthly basis.

    Best regards.

    Bill
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Bill - nice charts - I notice that your PVwatts default numbers don't seem to change on a monthly basis for example on your daily harvest chart - shouldn't the line move up/down every month? Or is it flat enough that I'm just not seeing that?
    jcgee88 wrote: »
    I'm not reading off a meter, my micro-inverter control unit is capturing the data.
    The issue is that the Envoy is not a revenue grade meter so we don't know how accurate it is. Many inverters have been known to over report output by up to 10%. Funny - they never seem to under report output.
    jcgee88 wrote: »
    Assuming that Bill is also capturing the harvest data off his inverter, that would seem to be the best apples to apples one could have.
    Bill is using a WEL logger to monitor output. I don't know if he has compared his inverter's output to it.
    jcgee88 wrote: »
    I frequently* compare my output to other sites locally,
    done by the same contractor, and my output is in the comparable range. These other sites even have different inverter technology, which further confirms that my inverters are not being misleading.
    Right, but you wouldn't notice a 10% difference in output when comparing systems.
  • jcgee88jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    drees wrote: »
    The issue is that the Envoy is not a revenue grade meter so we don't know how accurate it is. Many inverters have been known to over report output by up to 10%. Funny - they never seem to under report output.

    It is entirely possible that the Enphase is not perfectly
    accurate. I'd say that 10% too high would be surprising.
    BUT, even if one uses 10% error, you'd still end up with
    his average harvest being 2.2X mine while his array is
    2.9X bigger.

    I used my number, which I consider to be realistic, to
    put Bill's production numbers into perspective. If you
    set aside my number, you can use Bill's just posted
    PV-Watts number to do the same thing. In other words,
    if you owned this array, would you be satisfied with 77%
    of PV-Watts' prediction (which is itself at 77% derate)?

    So, I am neither bragging about my number nor criticizing
    Bill's. I am suggesting that based on the data, it appears
    he has room for improvement.

    Bill said earlier that one string is shaded until noon, thus,
    my thought is that this shading is dragging down the
    entire array when you use a single inverter. Hence, the
    idea to spring that string. This should be fairly easy to
    test, and if the hypothesis proves to be correct, then
    it is "only money" to grab back that lost power. [This
    shading would negate some of the 42% additional potential
    that I highlighted in my original post.]

    Of course, Bill is subject to a financial model that is, well,
    strange to say the least. It may well be that increasing
    the yield has no net benefit to him. In that case, we as
    a community can merely rue the unrealized kwH's.

    John
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    jcgee88 wrote: »
    It is entirely possible that the Enphase is not perfectly
    accurate. I'd say that 10% too high would be surprising.
    Well, supposedly any CSI EPBB approved meters (which the Envoy is) are supposed to be accurate within +- 5% - unfortunately, they don't seem to publish any testing results of those. The Envoy doesn't meet the +-2% accuracy level which is required for the PBI rebate, however.
    jcgee88 wrote: »
    So, I am neither bragging about my number nor criticizing
    Bill's. I am suggesting that based on the data, it appears
    he has room for improvement.
    I don't think that anyone here disagrees with that, including Bill himself. :D
  • Ralph DayRalph Day Solar Expert Posts: 873 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    I've calculated the difference between what my Envoy registers and what my utility revenue meter registers and it's 4%. That falls within their parameters...and the Envoy doesn't pay you, the utility meter does, so why no rebate?

    The enlighten website if sometimes fun to watch, but it's usually 30 minutes behind actual.

    Ralph

    http://enlighten.enphaseenergy.com/public/systems/hY7W5536

    link to my 10kw microFIT project in Ontario
  • jcgee88jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    Ralph Day wrote: »
    I've calculated the difference between what my Envoy registers and what my utility revenue meter registers and it's 4%. That falls within their parameters...and the Envoy doesn't pay you, the utility meter does, so why no rebate?

    Can you clarify: your Envoy is 4% higher than your utility meter
    or 4% lower?

    Since the meter is revenue generating, my sense is the meter cannot
    be registering high, else someone would eventually sue the utility
    for fraud. However, it could be low, and no one would complain. lol
    Ralph Day wrote: »
    The enlighten website if sometimes fun to watch, but it's usually 30 minutes behind actual.

    It is not fun to watch, it is ADDICTING. :-O

    And, you're right, it lags by 30 minutes at a minimum.

    John
  • Ralph DayRalph Day Solar Expert Posts: 873 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Sorry, to clarify, Envoy reads 4% higher than utility meter.

    Ralph
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    AntronX wrote: »
    Is there a way for you to average out the zigzag-inness of the graphs?

    ... disregard night time temperature and humidity readings?

    Have you thought about adding solar irradiance meter as well? It would be useful to track both long term and short term degradation of solar panel performance.

    ... How about placing temperature sensor on the back of solar panel to measure actual panel temperature?

    Logging AC line voltage would also be interesting.

    Excellent suggestions.

    It's tough to average out the noise in some of the graph lines. I'm using a pretty inexpensive monitoring tool (WEL - $375) and thus my ability to do averaging is limited to doing good approximations. For example, for 30 day averaging, I don't have the real time storage for 43,200 samples for 30 days (1 per minute), with the ability to drop off the earliest sample as the latest sample is added, and do a re-average. Instead, I use a built in to the WEL feature to do good approximations of averaging.

    Yep, it would be nice to pull out night time temperatures and RH values, but, not going to be possible with an inexpensive logging tool like the WEL.

    I agree using a solar irradiance meter would eliminate having to use PVWatts estimates, and would thus make for more definitive conclusions. I've carefully looked at Micro Circuit Labs' SDL-1 Solar Data Logger:

    100_048701_1.JPG

    Someday I'll purchase it to improve the study of my solar PV system. It's just not something I can afford at the moment.

    Yep, putting temp sensors on the back of a few solar PV panels is a good thing to do, something that I'll do in the future.

    Logging AC Line Voltage is not something difficult to do with the WEL (although the sensor itself is expensive). I'm not sure what I'd do with the information, though.

    Thanks for the suggestions.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    jcgee88 wrote: »
    ...Using a guess of $.15/kWh as your electricity rate, that's about $700/yr worth of lost power.

    ... the way it is configured ... wasting significant potential harvest ...

    ... get a small capacity inverter to spring your worse performing panels
    off of the main array.

    ... is there a way for you to measure kWh/day by panel ...

    John, thanks for the comments.

    If there was a way to generate another 4700 kWh annually, at my electric rate (10¢), usage rate (81% - I don't have net metering), and export rate (7.5¢), that's a net savings to me of about $10/mo, or about $120 annually.

    The leasing company gets 4700 kWh * 10¢ * 70% = $329 annually.

    The up front capital cost to the leasing company would have to include adding another inverter, changing the DC wiring to the inverters, and changing from a backfeed circuit breaker to a supply-side tap. My guess is this is a few thousand dollars, including installation. Looking at what the leasing company would get in return ($329 annually) it doesn't look to me that it would be a good business decision.

    Nope, with a single central inverter I don't have any way of measuring individual panel performance.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    jcgee88 wrote: »
    I'm not reading off a meter, my micro-inverter control unit is capturing the data. Assuming that Bill is also capturing the harvest data off his inverter, that would seem to be the best apples to apples one could have.

    ...

    Given his low kWh to capacity ratio, it would be hard to believe that that is the best possible, regardless of whether my own number was mis-reported.

    I'm getting my kWh harvest numbers from my WEL instrumentation system. The WEL accommodates a field installed custom correction factor such that my WEL reported kWh harvest matches right on to what the inverter is reporting.

    My leasing company wasn't interested in best possible output without regard to cost. Instead, it was interested in best possible output with lowest possible cost (thus just one inverter in spite of multiple panel orientations, and multiple string orientations). What I've got is a system that produces, so far, somewhere between 67% to 82% daily efficiency, on a rolling 30 days basis, of what PVWatts estimates at 1.00 (no losses of any kind) for my particular weather pattern.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    drees wrote: »
    ... I notice that your PVwatts default numbers don't seem to change on a monthly basis for example on your daily harvest chart - shouldn't the line move up/down every month? Or is it flat enough that I'm just not seeing that?

    ... Bill is using a WEL logger to monitor output. I don't know if he has compared his inverter's output to it.

    Correct - it's flat enough during these June / July / Aug. months that change is hard to see.

    From PVWatts @ 1.00: May=1374 kWh, June=1340, July=1388, Aug=1370

    I have compared my WEL reported harvest numbers to my inverter's output. The WEL provides for a correction factor, and I'm using it. Thus, my WEL reported harvest is right on what the inverter says.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    jcgee88 wrote: »
    ... if you owned this array, would you be satisfied with (a) 77% ... PV-Watts' prediction ... ?

    ... it appears he has room for improvement.

    ... Bill is subject to a financial model that is ... strange to say the least.

    ... It may well be that increasing the yield has no net benefit to him.

    For my roof space, given today's panel efficiencies, and noting the leasing company's design objective was to produce maximum amount of kWh harvest that space on the roof and existing shading would allow, it's entirely possible I have a very cost efficient design. If so, I'd be satisfied.

    My leasing arrangement is pretty straight forward - don't think it's strange at all. Zero up front cost, the leasing company gets 70% of all savings, I'm always cash flow positive, and good is being done for the environment. Seems like a win - win deal for me, the leasing company, and the environment.

    Keep in mind that I only get 30% of any increase in yield benefit. And that's only if I can actually use it (versus export it). If I can't use it, then I get even less of any increase in yield benefit.

    Best regards,

    Bill
  • jcgee88jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    My leasing arrangement is pretty straight forward - don't think it's strange at all. Zero up front cost, the leasing company gets 70% of all savings, I'm always cash flow positive, and good is being done for the environment. Seems like a win - win deal for me, the leasing company, and the environment.

    Keep in mind that I only get 30% of any increase in yield benefit. And that's only if I can actually use it (versus export it). If I can't use it, then I get even less of any increase in yield benefit.

    Bill,

    Thank you for the various replies to my and others'
    recent comments!

    I referred to your leasing arrangement as strange, but
    a more appropriate word might have been "complex."
    It assigns various costs and benefits across three
    different three parties, and encourages/rewards some
    behaviors that are not germane for the traditional
    homeowner-financed solar array. I agree with you that
    as a profit-making venture for you and your partners, it
    is straightforward and has the benefit of being
    environmentally friendly.

    To me, the bad part of the arrangement is that the figure
    of merit, achieving 62% of PV-Watts prediction, works
    against maximizing yield percentage. If all the array has to
    do is hop a low bar, then doing so at the cheapest cost
    becomes the driving force for your contractor. And, since
    your slice of any improvement is disproportionally small,
    you have scant incentive to make any correction that
    has out-of-pocket cost.

    To use an analogy, your situation, that is, not pursuing
    maximum yield, is like an itch I can't scratch. Solar owners,
    I'd say, have "I want the most bang for the buck," in their
    DNA!

    By the way, here's my calculation of how adding a second
    inverter would cost $2K. A SunnyBoy 3000 lists for ~$1600,
    and $400 should cover a half day's labor (my contractor
    charges $80/hour). [There's also the Federal tax credit
    of 30%.]

    John
  • jcgee88jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    What I've got is a system that produces, so far, somewhere between 67% to 82% daily efficiency, on a rolling 30 days basis, of what PVWatts estimates at 1.00 (no losses of any kind) for my particular weather pattern.

    Bill,

    You use percentage of PV-Watts projection because
    of the terms of your leasing arrangement. Here are
    the metrics I use.

    Going in, my contractor did a PV-Watts projection
    where he set the derate factor from 77% to 72%.
    This reflected that I am not true south and have some
    modest shading effects. We used this projection
    to estimate a worse case dollar return. I didn't
    worry about kwH during the financial analysis part
    of my decision making process.

    Once the dollars looks ok, I asked my contractor about
    production and array efficiency. His reply back was
    in terms of the percentage of energy captured versus
    theoretical maximum of the instantaneous output
    wattage. He noted that the practical maximum is 80%:

    PV panels typically run 10% lower than their rated capacity;
    Inverter is 95% efficient, i.e., 5% loss;
    Line losses consume 1-2%;
    Other factors, for example dust on panels, take a "few" percent.

    This 80% maximum occurs only when the sun is directly overhead.

    So what I see after installation is:

    1. Typical sustained 75% during the two highest intensity hours
    from 11 am to 1 pm: 2300w of rated 3.055 kW.
    2. Peaks of 82%, but only for brief durations.
    3. Typical sustained average of 72-73% during the 10 am to 2 pm shift.
    4. Some non-uniform behavior between the strings (I have two) outside
    of the 10 to 2 shift.

    --

    Based on the above numbers plus the per panel performance
    data that Enphase is providing me, I determined that I have
    a potential of an additional 3% kwH increase by making a
    couple of tweaks, including changing one string's tilt angle.
    Alas, the cost of the tweaks outweighs the benefit. :-(

    John
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    jcgee88 wrote: »
    ... the bad part of the arrangement is ... the figure of merit, achieving 62% of PV-Watts prediction ...

    By the way, here's my calculation of how adding a second inverter would cost $2K. A SunnyBoy 3000 lists for ~$1600, and $400 should cover a half day's labor ...

    John, thanks for the comments.

    My leasing terms may be less complex than many of the leasing examples I've seen illustrated here recently. Mine only has 2 key provisions: no up front cost, and, I pay 70% of the savings (monthly) to the leasing company. That about it. (There are some complexities if I decide to purchase the system, with respect to purchase price, but, I'm not ever required to purchase the system.)

    I agree that minimum expectation of a 62% of PVWatts prediction is too low of a threshold by the utility company (to issue rebates). I was surprised my utility company goes this low. They're paying out millions in rebates - I would have thought they'd want the minimum to be higher.

    Keep in mind one additional cost item if my system were to be modified. I'm 'full up' on a back-fed 40A breaker for my solar produced power. Any additional inverter capacity would require switching the inverters to supply-side connections.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    jcgee88 wrote: »
    ... You use percentage of PV-Watts projection because
    of the terms of your leasing arrangement.

    Correct. And because it's an easy to explain analysis.

    Some day I'll have an irradiance meter to eliminate having to use estimates from PVWatts.

    Best regards,

    Bill
  • VicVic Solar Expert Posts: 2,815 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Hi Bill and all,

    Thank you very much for starting this thread, and to all of those replying. While I am not in the market for a GT system right now, this topic has been very informative.

    Bill, I respect your ability to roll with the feedback, and know that you are a technical person, and this part of your background has helped inform all of us.

    AND, Thank you No AZ Wind and Sun for this great site, and dedicating this amount of storage and BW for the benefit of us all.

    Great Site ! Thanks, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    16 month update:

    Here's the performance of the system for the past 13 months, rationalized to PVWatts (Dallas area) for apples-to-apples comparison:

    SolarPVefficiency.png


    For about 4 months in Summertime kWh produced is greater than PVWatts default (77% of nameplate). The system then goes through a Fall season drop, and then spends about 2.5 months below the Utility company's minimum expectation (80% of 77%) during the Wintertime.

    On a rolling 12 month basis, the system's at 71%, which meets the expectation of the Utility company (production at least equal to or better than 80% of the PVWatts' 77% default = 62%). The utility company paid about $20K (rebate) toward the installation of this leased system - they were just here recently checking up that the system is still working to their expectations.

    As well documented in this thread, this is a leased system. Estimated at the end of 2011, which will be almost 23 months of production, cash flow will be about $500, or about $22/month:
    original.jpg
    This is net cash flow - inclusive of all investments.

    So I think all three parties to the system are happy. As owner I didn't have any up front investment, was able to maintain positive cash flow from day one, and only pay for what the system produces. Essentially my electric bill is reduced, on avg, about $22 each month.

    The installing/leasing company was able to economically install a system that essentially performs about midway between PVWatts 77% default and the minimum Utility expectation, and has a perpetual cash flow for as long as the equipment is in operation.

    The utility company is satisfied that for a system they contributed $2.40 / watt, it's meeting their minimum expectation.

    On Oct. 1st, this system will be part of the annual DFW Solar Tour of Homes
    ( http://www.dfwsolarhometour.org ). Here's the summary writeup:
    large.jpg

    Best regards,

    Bill
  • System2System2 Posts: 6,290 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Good read, I am new at this, I want to know more. In London, UK, we don't really use solar energy.
  • stephendvstephendv Solar Expert Posts: 1,571
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    London wrote: »
    Good read, I am new at this, I want to know more. In London, UK, we don't really use solar energy.

    A what now? The UK has one of the most generous Feed in Tariffs (FIT) on the planet. You could be looking at making upwards of 7% annual return on your investment guaranteed for 20 years. Details here: http://www.decc.gov.uk/en/content/cms/meeting_energy/renewable_ener/feedin_tariff/feedin_tariff.aspx and this UK specific forum: http://www.navitron.org.uk/forum/
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    forgive my sidetracking here for the moment.
    very interesting as that's a nice sized forum i'd be interested in checking out. your general take on it as to how it may compare or differ with this one stephendv?
  • stephendvstephendv Solar Expert Posts: 1,571
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    niel wrote: »
    forgive my sidetracking here for the moment.
    very interesting as that's a nice sized forum i'd be interested in checking out. your general take on it as to how it may compare or differ with this one stephendv?

    Hi Neil,

    The two sites are similar in some respects. In comparison to wind-sun, the Navitron site:
    - is more focussed on the UK, there are a handful of members from the rest of europe
    - is more focussed on grid tied systems in the UK (optimise panels, payouts from leccy companies, check my quote for a solar install, etc)
    - has far fewer off-grid members
    - has more content about wind turbines
    - has more content about generators, combined heat and power systems, veg oil conversion etc.
    - also includes quite of a lot environmental, political and general discussion topics (which just serves to obscure the actually useful topics IMO)
    - doesn't have a "family friendly" policy, so can use language suitable for over 12's ;)
  • RevolutionaryRevolutionary Registered Users Posts: 13
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Bill;
    Very nice install, and what an incredible ammount of technical stuff you had to work through! I am thoroughly impressed!

    We installed a system this last year, but with nowhere near the complexity or stuff to work through that you had to deal with. Ours is a little over 7KW, and I posted a link to our article on it yesterday, I think.

    It's a great thing when it's finished, though, and power flows from the sun.....

    Good Luck with your system, I'm certain it will provide you with power for a long, long time!
    Chris
  • jimindenverjimindenver Solar Expert Posts: 59 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Dallas Area Urban Residence

    Wow what a great thread for those of us new to solar and considering putting a system up on the house. Seeing the whole process fro start to finish has been very enlightening. Thank you

    Jim
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Dallas Area Urban Residence

    You and all other readers are welcome. This 8 kW system has been running now for slightly more than 2 years. It continues to generate about $250 positive cash flow annually, with no ownership of the equipment and no expense of any kind invested into the system. It's been a no mess, no fuss, and absolutely zero maintenance leased system. The sun simply rises each day, generates positive cash flow, with no cost or investment ever required of me.

    The system's technical performance continues to to tracked and modeled here: http://www.welserver.com/WEL0043/ , using a monitoring system that does not have any monthly expense.

    Holler if any questions!

    Best regards,

    Bill
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