Our first 50 kWh day!

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RegGuheert
RegGuheert Solar Expert Posts: 102 ✭✭✭✭
in General Solar Power Topics #1
Well, 49.6 kWh, actually, but it rounds up to 50! ;)

Our 9.87 kW array with Enphase inverters was first energized January 5. Production has been very good, but I didn't really expect to see 50 kWh until later in the year. But today was very cold (high was 24F) and windy with very few clouds, so production was high. Here is an image from Enlighten showing the total along with panel production at 12:05 PM:

attachment.php?attachmentid=1584&stc=1&d=1295659583

Notice that the system was pegged at 85% of rated DC output for about three hours.

But there is NO WAY all of the current limits on the inverters ALL happen within 0.5% of each other. I am convinced that these things were all at OR ABOVE 199W but that the modules do not ever report anything higher. Interesting, since that could potentially be an issue for NEC if you actually put 15 of these on one breaker. But since the most I have on a single breaker is 14 (in two branches of 7 to minimize voltage drop) I don't think it is an issue here.

Anyway, it's good to see production meeting and even exceeding expectations!
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #2
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    Re: Our first 50 kWh day!

    Pretty darn good. My setup did 57.5 today
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  • RegGuheert
    RegGuheert Solar Expert Posts: 102 ✭✭✭✭
    #3
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    Re: Our first 50 kWh day!

    Awesome, Dave! You have an impressive system!
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #4
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    Re: Our first 50 kWh day!

    Yeah we use high seer heat pumps to warm the house overnight, but we still had a 19 Kwh back feed to the grid day. This time of year is great for running up the on peak credits to the grid for our peak summer usage for the 6 tons of AC we have.

    Hopefully our annual power bill is net zero situation. The one caveat is the Chevy Volt we have ordered. We will have to profile it's usage upon delivery.
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  • RegGuheert
    RegGuheert Solar Expert Posts: 102 ✭✭✭✭
    #5
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    Re: Our first 50 kWh day!
    solar_dave wrote: »
    The one caveat is the Chevy Volt we have ordered. We will have to profile it's usage upon delivery.
    I came VERY close to ordering one of those, also! If it had included five seats instead of four, I probably would have gone for it. In any case, that is one of the motivations for the PV, since I do plan on having an EV in the garage one of these days.

    Please let us know what you think of it!
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  • Peter_V
    Peter_V Solar Expert Posts: 226 ✭✭✭
    #6
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    Re: Our first 50 kWh day!

    Congrats! Generating your own power is pretty cool aint it?

    I only generated 23 kWh today, but then my array is a bit smaller than yours. Still that's more than I expected to be making during the winter, the cool weather really boosts performance.

    I was expecting to go in the hole during the winter but instead I'm banking about 4kWh a day. I guess I need to get my act together and replace the batteries in my electric truck so I can start using up the kWhs I've got banked (almost 500 kWh in the last 4 months).
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  • RegGuheert
    RegGuheert Solar Expert Posts: 102 ✭✭✭✭
    #7
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    Re: Our first 50 kWh day!

    That's a really cool system, Peter! It appears that your system with about 1/3 as many panels as mine will produce about 2/3 as much electricity, on average. Very impressive! (From your Enlighten webpage I'm guesstimating about 22 kWh/day year-round average for your system and our system has a predicted average of 35 kWh/day.)

    I like the way your power curves quickly go to max power on each inverter and then stays there all day. Almost as if it was planned that way! :roll:

    Our system REALLY DID go over 50 kWh today: 51.2 kWh. No more rounding needed! :blush:
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  • RegGuheert
    RegGuheert Solar Expert Posts: 102 ✭✭✭✭
    #8
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    Re: Our first 50 kWh day!
    RegGuheert wrote: »
    I am convinced that these things were all at OR ABOVE 199W but that the modules do not ever report anything higher.
    I guess this theory is NOT correct. I see one module reporting 200W today at 1:25 PM.
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  • Peter_V
    Peter_V Solar Expert Posts: 226 ✭✭✭
    #9
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    Re: Our first 50 kWh day!
    RegGuheert wrote: »
    That's a really cool system, Peter! It appears that your system with about 1/3 as many panels as mine will produce about 2/3 as much electricity, on average. Very impressive!

    I like the way your power curves quickly go to max power on each inverter and then stays there all day. Almost as if it was planned that way!

    Yeah the trackers make a big difference, much more so during the summer. Of course being in Arizona helps too.

    The small tracker is home made and I only got the freon installed in December, I'm still fiddling with the counter weights trying to get the quickest wakeup while still tracking from stop to stop.

    With everything working right, I'm hoping to top 30 kwh on clear days in May and June.
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  • RegGuheert
    RegGuheert Solar Expert Posts: 102 ✭✭✭✭
    #10
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    Re: Our first 50 kWh day!
    Peter_V wrote: »
    The small tracker is home made and I only got the freon installed in December, I'm still fiddling with the counter weights trying to get the quickest wakeup while still tracking from stop to stop.
    I couldn't understand why your summertime production was only marginally better than your wintertime production. I was hard-pressed to convince myself that it was due to the high temperatures! That explains it!
    Peter_V wrote: »
    With everything working right, I'm hoping to top 30 kwh on clear days in May and June.
    Around here, the *average* insolation in June with a tracker is around 10 full-sun-hours. I imagine the peak days would be around 12. I don't know what a peak insolation day would be in Arizona: perhaps a little lower due to latitude. But if you can drive your inverters to their power limit even in the heat of the summer then you might see days over 35 kWh. We'll see!

    Again, very nice system!
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    #11
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    Re: Our first 50 kWh day!

    At 44 deg lattitude I didn't see my inverters max out until the temps got below freezing. From July to the end of October I got 70+ kwhrs per day (depending on the day), and now with shorter but colder days I've had a few 70's. A cold day in March if it's snowy might get over 80kwhr.

    In the heat of the summer the inverters were never maxed out...the efficiency of the panels degrade so much at that point that even over-driving a 190watt inverter with 230watts of pv leaves you below the max threshold.

    Ralph
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  • RegGuheert
    RegGuheert Solar Expert Posts: 102 ✭✭✭✭
    #12
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    Re: Our first 50 kWh day!

    Nice system, Ralph!
    Ralph Day wrote: »
    At 44 deg lattitude I didn't see my inverters max out until the temps got below freezing. From July to the end of October I got 70+ kwhrs per day (depending on the day), and now with shorter but colder days I've had a few 70's. A cold day in March if it's snowy might get over 80kwhr.

    In the heat of the summer the inverters were never maxed out...the efficiency of the panels degrade so much at that point that even over-driving a 190watt inverter with 230watts of pv leaves you below the max threshold.

    Ralph
    For me a big part of the issue will be that the sun never approaches the boresight of the array. My panels are on my roof at about 30 degrees elevation and the sun goes almost directly overhead in the middle of summertime, so I think the angle will be a big factor for me. In Peter's case, he is tracking, so that factor is removed from the equation.

    I cannot tell from the pictures: Does your system track the sun, or do you change the elevation seasonally? Something else?
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  • Peter_V
    Peter_V Solar Expert Posts: 226 ✭✭✭
    #13
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    Re: Our first 50 kWh day!
    RegGuheert wrote: »
    I couldn't understand why your summertime production was only marginally better than your wintertime production. I was hard-pressed to convince myself that it was due to the high temperatures! That explains it!
    July through Sept is monsoon season here, lots of cloudy weather.
    However, May and June are typically clear skies all day, they are also the hottest months here.

    The small tracker had the panels mounted but was at a fixed position. I figure I lost maybe 1 kWh a day from it not tracking.
    Around here, the *average* insolation in June with a tracker is around 10 full-sun-hours. I imagine the peak days would be around 12. I don't know what a peak insolation day would be in Arizona: perhaps a little lower due to latitude. But if you can drive your inverters to their power limit even in the heat of the summer then you might see days over 35 kWh. We'll see!

    I live in a valley between two mountain ranges. The Huachuca mountains are only about 1.5-2 miles to the west and raise over a mile above me, so I lose the sun about an hour before "Sunset".
    The Mule mountains are 15-20 miles to the east so don't have as much impact, however my neighbor's house and some trees on his property shade my array for about an hour in the morning.
    Add in another 30-45 minutes for the trackers to wake up and flip over.
    I'm not getting the maximum amount of daylight possible, but I sized the array with this in mind so I get more than enough.

    I actually got lucky. I ordered 220 Watt panels, but my solar guy had another order at the same time for 230 watt panels. It was cheaper for him to buy a couple pallets of 230s instead of partial pallets of 230s and 220s so I got a free upgrade to 230s.
    Again, very nice system!
    Thanks, I've been very happy with it. :D
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  • Peter_V
    Peter_V Solar Expert Posts: 226 ✭✭✭
    #14
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    Re: Our first 50 kWh day!
    RegGuheert wrote: »
    I cannot tell from the pictures: Does your system track the sun, or do you change the elevation seasonally? Something else?

    Seasonal elevation changes. The elevation bar has 5 holes in it, you just unbolt it, and push the array to the appropriate hole and reinsert the bolt. The array is fairly well balanced so it doesn't take much effort. The only down side is this adjustment is 10 feet up in the air so you have to do it while standing on a ladder. :roll:

    I looked into automatic elevation changes (two axis trackers), but the data I got from PVwatts indicated only about a 5% increase and that didn't justify the cost and complexity.

    The Zomeworks trackers don't cost much more than fixed pole top mounts, I paid about $1600 each for them.
    To get 2 axis tracking I'd have to use something like the Wattsun trackers at about $4,000 each.

    The Zomeworks are not only much cheaper they are also more reliable, no electronics or motors to wear out or break.
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