Solar array at Lāhainā Noon

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raysun
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Solar array at Lāhainā Noon

Post by raysun »

Screenshot_20220514-123424_Gallery.jpg
7kW PV array in full sun at "Lāhainā Noon", a twice-yearly event in Hawaii where the sun reaches its zenith (solar noon) directly overhead. A pole stuck vertically in the ground has no shadow at this moment, the angle of incidence on the nearly flat-mounted panels is 87°. So is the temperature in the shade, so there's heat-induced efficiency loss, but also greater than 1kW/m² irradiance.
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SandyP
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Re: Solar array at Lāhainā Noon

Post by SandyP »

Now you just need to find something to use all that free excess power :cool:
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raysun
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REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
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Re: Solar array at Lāhainā Noon

Post by raysun »

SandyP wrote: Sat May 14, 2022 7:56 pm Now you just need to find something to use all that free excess power :cool:
Still working on a free charging station for homeless Tesla owners.

Seriously, batteries are fully charged most days by 11:30. Today, I planned to disconnect the PV arrays at 10:15 to leave some room in the battery so I could resume bulk charging at noon to measure the PV output. Wouldn't you know it, I no sooner look at the system at 10:15 and it was finishing absorb. I disconnected the PV, let the battery discharge until 12:10 then reconnected and reran a bulk charge.

What to do with the extra energy? The struggle is real. 😄

I suppose I could be a reverse power pirate. Hook up a feed to the HELCO line out front and surreptitiously feed power to the grid.
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Re: Solar array at Lāhainā Noon

Post by JRHill »

Probably the same in many places? My batteries are often full by noon - at least full as I define full.

But in the winter I could triple my array and still have to run the generator for 2.5 months. It is what it is and where it is.
raysun
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Re: Solar array at Lāhainā Noon

Post by raysun »

JRHill wrote: Sun May 15, 2022 9:57 am Probably the same in many places? My batteries are often full by noon - at least full as I define full.

But in the winter I could triple my array and still have to run the generator for 2.5 months. It is what it is and where it is.
Yes, it moves so easily from feast to famine.
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Re: Solar array at Lāhainā Noon

Post by pss »

You should come to our property. We have produced as much as 125 kW in a single day and still consume from the grid over a 24 hour period.

Anyways I hope you laid your panels down completely flat for the solar noon event and took photos. I have visited Lahaina in the past, a very nice place to be.

In San Diego, we are now in the period of no rain and almost no clouds until October. Except the high temps and summer sunshine (when AC is needed most) reduce panel output beginning about mid June.

Also, beginning in June, our 4-9 PM TOU rate goes to $0.66/kWh, so that's when I'm most in love with our batteries!

In San Diego, EV owners charge at night and till 2 PM on weekends for $0.10/kW. PV not even worth it.
raysun
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REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
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Re: Solar array at Lāhainā Noon

Post by raysun »

Our panels are permanently mounted flat (actually a 3% roof pitch so rainwater runs to the gutter). We don't have the unattenuated clear skies San Diego enjoys. Its rare to have blue sky here all day. Rather, we have clear mornings and partial cloud cover by about noon.

We could squeeze more PV harvest out of the array by optimizing for the conditions, but we really don't need it, so don't bother.

The local electric grid is expensive (and fragile). There's no peak/off-peak pricing. Its all peak. Hawaii has an aggressive plan to convert to renewables, but the reality is the majority of power now is generated with imported oil (formerly from Russia) and coal.
raysun
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REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
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Re: Solar array at Lāhainā Noon

Post by raysun »

HPP - Hawaiian People's Problems
Today, July 27, 2022 at 12.29PM will be the second of two annual "Lahaina Noon" events in Ka'ū, south Hawaii Island (the southernmost area in the United States.)

"Hawaii stands alone in the U.S. as having this special event. It replaces the summer solstice, when the sun’s rays are most direct, and occurs both before and following the start of summer. Additionally, Lahaina Noon serves as a reminder of just how strong the Hawaii sun really is at our location south of the Tropic of Cancer. The word Lahaina translates from the Hawaiian language to mean cruel sun. Another ancient Hawaiian name for the event was Kau ka lā i ka lolo, a hoʻi ke aka i ke kino,” a phrase meaning high noon."
Beat of Hawaii

I've been wrestling with two competing issues:
• Curiosity to see how much PV power is generated with the sun directly overhead (see above for the spring pass). Usually, the battery is fully charged well before noon, so the PV arrays are disconnected for now.
• Burning residual gas from my backup generator. There's been an unbroken procession of enough insolation to meet battery capacity targets since February, so the Honda has been sitting idle with a full tank of (ethanol free) gas. Not good, and I've been determined to burn it off as there's no non-messy way of draining gas from the generator. I can't bring myself to just run the generator to no purpose, so have been hoping for a cloudy, rainy day. No such luck. Today dawned uncharacteristically cloudy, so I fired up the Honda and burned some gas. Then curses! The Lahaina (cruel sun) came out in full force. Seems silly to continue when PV should be engaged.

We'll see what happens after lunch.
ralphday224
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Re: Solar array at Lāhainā Noon

Post by ralphday224 »

Welll Ray, you could always pull a fuel line off the Honda, drain it into a jerry can and use it in a vehicle or lawnmower. Just burn out what is in the fuel system if you need to re-fill with fresh gas. My Yamaha sits empty and burned out until I need it (not often).
raysun
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My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
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Re: Solar array at Lāhainā Noon

Post by raysun »

Yea, I could have messed with draining fuel, which with me, would have been a mess. Besides, it was probably good to run the engine for a while.
It gave me a chance to revisit a long-standing issue I've had with the dual FXRs stacked in parallel: they do a poor job managing the AC input current limit. There's always a small "overshoot" on the Slave inverter. It corrects itself, but its repetitious and mildly annoying. Yesterday it became more actionable, the input circuit is 30A total, and that's the continuous rated output of the generator @ 120V. Each inverter is apportioned 15A. The Slave drew 21A while the Master was drawing around 15, and it tripped the circuit breaker on the input line. 🤨
raysun
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My RE system: Flexpower Two: (2) FXR3048A-01 - Parallel Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Solar array at Lāhainā Noon

Post by raysun »

20220731_115035.jpg
The sun has been directly overhead for the past few weeks and its been brutal to be out in it. Its a bit overcast today and cooler, so was going out just now. Took a look at the system, and yikes! 7kW array @ STC usually produces about 5kW this time of day, but the panels must be cooler, and the solar radiation no less intense than normal.
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