over sized

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kittysoman2013
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over sized

Post by kittysoman2013 » Sun May 24, 2020 5:27 pm

For an off Grid applications does it make sense to over say your pv array beyond the size of your inverter? I know the inverter will only make what it is rated for but should you not have an array larger then the inverter to cover days with low sun hours?
I would assume that this is how it works that you try to size your array to still be able to fit the bill in the worse conditions. I am thinking right now of a GS8040 with an extra charger controller and a total nominal wattage of 9450.
What say you??

fcwlp
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I also install and maintain grid-tied and off-grid systems, details will be given for these system if required
Location: 80 miles NE of Phoenix at 5500'

Re: over sized

Post by fcwlp » Tue May 26, 2020 9:24 am

Hi Soman,

The size of the PV array is determined by the size of your battery bank. For a FLA (Flooded Lead Acid) bank you want to charge at typically 10% to 13% of the C20 rate for a VRLA (Valve Regulated Lead Acid) bank the max charge rate is typically 20% of the C20 rate. With the cost of PV panels being as low as they are today, you should at a minimum meet the above values. However, you can oversize the array and limit the charge current using the charge controllers, allowing you to harvest more power on the poor PV days. How much you oversize is going to be a function of your location, weather, DOD (depth of discharge) and available funds. Make sure you do not exceed the recommended PV watts for the charge controllers used.

raysun
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Re: over sized

Post by raysun » Tue May 26, 2020 9:41 am

I have a 3kW Inverter and 6kW of solar panels on two 80A charge controllers charging a 350AH @ 48V battery bank. I never actually see full output from the array, as the battery bank is generally in Absorb by the time the sun is high enough in the sky to drive the panels to full power. On marginal solar days the array still manages to charge the battery. On heavily clouded days the array may put out as little as 1/10th of the needed power. About 8% of my power consumption is provided by a backup generator.

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Re: over sized

Post by JRHill » Tue May 26, 2020 11:22 am

You don't mention what kind of batteries you have installed. But you must also realize the batteries change in performance. Most discussions consider the best performance of everything. Your batteries perform best after "broken in" the first year and then drop year over year until not tolerable. While I agree with "fcwip" and "raysun" as to optimum sizing, that changes over the lifetime of the batteries. As the batteries age they will charge faster and deplete even more quickly. Why does this matter?

For example, with a new set of batteries I can go from March through Sept with no external charging. Even with extra over night loads at that time like the ceiling fans going continuously. Right now? Ain't no way on five year old batteries - they charge quickly and deplete quickly. It doesn't matter how big your inverter is or the C20 rate of your batteries. When they are tired, they are tired. No, don't think about a 2nd bank unless thoroughly proficient. Just know that things change year over year until not tolerable. And the batteries will probably be the determining factor.

Batteries are consumables. They are an ongoing cost of your system that has to be factored. Another example: You can't say "I saved $XXXX.XX on electricity this year" without adding in the cost of replacement batteries at the intolerable point. And add in the cost if adjusting for the mounting intolerance.

I don't want to be Mr. Negative but as we go year over year the battery budget is a wake up call for planning. I don't see that publicized - only the minute by minute savings. That's not reality over the years.

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EA6LE-ONE
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My RE system: System 1:
MATE3s, 3 x Radian GS8048A,
4 x FLEXmax 100, HUB10,
2 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 4 x FLEXware ICS Plus,
54 x PANASONIC VBHN325SA17 325W

System 2:
MATE3s, 2 x VFX3648,
2 x FLEXmax 100, HUB10
1 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 2 x FLEXware ICS
21 x PANASONIC VBHN325SA17 325W
Location: Providenciales, Turks & Caicos Isl.

Re: over sized

Post by EA6LE-ONE » Tue May 26, 2020 11:59 am

If you size the batteries correctly and have them in the right conditions and regular checkup/maintenance, they could last a long time.
But before you go off-grid or any solar installation do you research and ask around people who have solar systems for more than 5 years to know what is involved.
I don't think right now any off-grid installation done right in US will save you money. There are so many factors to account for a an off-grid system that will work for years. You will probably go off-grid solar because there is no grid power and no easy way to access fuel for generators.
My cost here is $0.40/kWh and experimenting with solar for 10 years I can say I can't break even. Grid-tie for us is with a catch and not really much savings. The one here that might work is to use solar only during the day complementing the grid power, I have't played with that as i am crazy and want to be self-sufficient.
So if your are crazy, want to save the planet, want to experiment with solar and have too much money then you can go for it and be sure you do your research.

Sorry to second JR, but the reality is not like fairy-tales you get from the solar salesman.

fcwlp
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My RE system: GS8048A, FM80 w/3,600 W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed
I also install and maintain grid-tied and off-grid systems, details will be given for these system if required
Location: 80 miles NE of Phoenix at 5500'

Re: over sized

Post by fcwlp » Tue May 26, 2020 3:25 pm

EA6LE-ONE wrote:
Tue May 26, 2020 11:59 am
I don't think right now any off-grid installation done right in US will save you money. There are so many factors to account for a an off-grid system that will work for years. You will probably go off-grid solar because there is no grid power and no easy way to access fuel for generators.
A number of my customers are off-grid due to no grid power. Propane delivery is available (5-20 miles of rough dirt/gravel roads when dry, 4WD only when wet), but generator run costs for one of my clients before we upgraded their system was $600-700 per month. System payback is in the range of 5 years.

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EA6LE-ONE
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Posts: 106
Joined: Tue May 05, 2020 7:51 am
My RE system: System 1:
MATE3s, 3 x Radian GS8048A,
4 x FLEXmax 100, HUB10,
2 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 4 x FLEXware ICS Plus,
54 x PANASONIC VBHN325SA17 325W

System 2:
MATE3s, 2 x VFX3648,
2 x FLEXmax 100, HUB10
1 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 2 x FLEXware ICS
21 x PANASONIC VBHN325SA17 325W
Location: Providenciales, Turks & Caicos Isl.

Re: over sized

Post by EA6LE-ONE » Tue May 26, 2020 4:06 pm

fcwlp wrote:
Tue May 26, 2020 3:25 pm
EA6LE-ONE wrote:
Tue May 26, 2020 11:59 am
I don't think right now any off-grid installation done right in US will save you money. There are so many factors to account for a an off-grid system that will work for years. You will probably go off-grid solar because there is no grid power and no easy way to access fuel for generators.
A number of my customers are off-grid due to no grid power. Propane delivery is available (5-20 miles of rough dirt/gravel roads when dry, 4WD only when wet), but generator run costs for one of my clients before we upgraded their system was $600-700 per month. System payback is in the range of 5 years.
How long the batteries will last? replacement cost? Maintenance cost? other equipment failure? Still this is one example where off-grid solar makes sense.

raysun
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My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: over sized

Post by raysun » Tue May 26, 2020 4:37 pm

Meter rates are always going to be cheaper than off-grid power generation, even here on Hawaii Island with some of the highest cost/kWH in the nation. Meter rates ignore some important factors in domestic power consumption, however, that may be of value to homeowners, like me.

I'm strictly off-grid. Though the power line runs 30 feet from my home, I had absolutely no desire to connect.

• My wife objected to the ugly feed wires spanning our front garden and view.

• She also did not want a recurring bill. We have none.

• I prefer to set my own service and operational levels. In the past 4 years, I have exceeded what the local power company could deliver. I'm the guy on the street that has lights on during the power failures.

• We live in an area potentially impacted by hurricanes, and installing our off-grid system did not take much extra effort to make it disaster resilient.

I'm not interested in a pencil and paper exercise calculating ROI, any more than I would on the prices of a fine dinner at my favorite restaurant. My satisfaction with the experience is the only metric that matters.

User avatar
EA6LE-ONE
Forum Guru
Posts: 106
Joined: Tue May 05, 2020 7:51 am
My RE system: System 1:
MATE3s, 3 x Radian GS8048A,
4 x FLEXmax 100, HUB10,
2 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 4 x FLEXware ICS Plus,
54 x PANASONIC VBHN325SA17 325W

System 2:
MATE3s, 2 x VFX3648,
2 x FLEXmax 100, HUB10
1 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 2 x FLEXware ICS
21 x PANASONIC VBHN325SA17 325W
Location: Providenciales, Turks & Caicos Isl.

Re: over sized

Post by EA6LE-ONE » Wed May 27, 2020 6:15 am

raysun wrote:
Tue May 26, 2020 4:37 pm
Meter rates are always going to be cheaper than off-grid power generation, even here on Hawaii Island with some of the highest cost/kWH in the nation. Meter rates ignore some important factors in domestic power consumption, however, that may be of value to homeowners, like me.

I'm strictly off-grid. Though the power line runs 30 feet from my home, I had absolutely no desire to connect.

• My wife objected to the ugly feed wires spanning our front garden and view.

• She also did not want a recurring bill. We have none.

• I prefer to set my own service and operational levels. In the past 4 years, I have exceeded what the local power company could deliver. I'm the guy on the street that has lights on during the power failures.

• We live in an area potentially impacted by hurricanes, and installing our off-grid system did not take much extra effort to make it disaster resilient.

I'm not interested in a pencil and paper exercise calculating ROI, any more than I would on the prices of a fine dinner at my favorite restaurant. My satisfaction with the experience is the only metric that matters.
Same here, living on an island being hit every few years by a major hurricane and be without power for weeks you start to look for better ways to have a normal life even during disasters.

I am still connected to grid power and set as backup. I have to pay a minimum of $14/month. During summer I save about $1300.00/mo with solar and in the winter is about $700/mo. I spent about $150k on the equipment and I did the installation myself. While I designed the new house I used everything I learned in the last 10 year I experimented with solar. I build a workshop where I have all the equipment installed in a temperature controlled environment. I have electrical conduits from main house and guest house installed underground and into the walls. Did my own brackets and mounts on the roof with support behind each panel hoping that they can withstand 250mph winds. So I am about $220k invested in this specific system (the installation is not included). Some of the high cost is coming from the spare equipment for redundancy: one extra radian inverter, 4 CCs, 35 more panels and couple more combiner boxes. Initially the system was designed to be 35kWh but the 24kWh installed up to date is more than sufficient in my conditions.

In my case you can call me crazy :)

pss
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Re: over sized

Post by pss » Wed May 27, 2020 8:46 am

150K on an island is a decent price for all you got. Here in So Cal, we just mosey over to a place called CED Greentech, a Walmart of solar at wholesale prices, everything in stock except concrete. As for being on the island, please take excellent photos of the before, because there is no solar panel that will withstand 250 mph winds. Even auto claved aerated concrete (AAC) will be at its limits. Here in So Cal we only rate for 110 mph winds and the code still called for 10,000 lbs of concrete with posts tied together with schedule 40 steel pipes and only 16 Solarworld 340s. I'm afraid that if your panels don't fly away, they will just crack from the air pressures. You may want to prominently paint your name on all of your equipment for the recovery effort. And yes, we lost a home to a hurricane in Florida and recovery took about 10 years. Now in So Cal, we concern ourselves with earthquakes,d fires and the Tarantula Wasp.

raysun
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Posts: 2240
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: over sized

Post by raysun » Wed May 27, 2020 9:13 am

pss wrote:
Wed May 27, 2020 8:46 am
150K on an island is a decent price for all you got. Here in So Cal, we just mosey over to a place called CED Greentech, a Walmart of solar at wholesale prices, everything in stock except concrete. As for being on the island, please take excellent photos of the before, because there is no solar panel that will withstand 250 mph winds. Even auto claved aerated concrete (AAC) will be at its limits. Here in So Cal we only rate for 110 mph winds and the code still called for 10,000 lbs of concrete with posts tied together with schedule 40 steel pipes and only 16 Solarworld 340s. I'm afraid that if your panels don't fly away, they will just crack from the air pressures. You may want to prominently paint your name on all of your equipment for the recovery effort. And yes, we lost a home to a hurricane in Florida and recovery took about 10 years. Now in So Cal, we concern ourselves with earthquakes,d fires and the Tarantula Wasp.
If there's 250MPH winds theres bigger concerns than where solar panels end up.

As long as we're being hyperbolic in disaster predictions I guess a magnitude 8 or 9 earthquake would make all that California concrete and sched 40 pipe so much debris. Kinda tough to get to Wallmart after that.

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Re: over sized

Post by JRHill » Wed May 27, 2020 9:39 am

EA6LE-ONE wrote:
Tue May 26, 2020 11:59 am
If you size the batteries correctly and have them in the right conditions and regular checkup/maintenance, they could last a long time.
Yeah, I have to admit that that my location is not prime for battery longevity as you mention. For between two and three months of the year we have to charge via generator as the sun sinks lower at the top of the canyon and begins to rise again. It is this time of each year that the batteries age prematurely as they are not getting a full absorb. I have a few techniques to make the best of the low sun season but there is really no substitute for a full recharge on a daily basis.

User avatar
EA6LE-ONE
Forum Guru
Posts: 106
Joined: Tue May 05, 2020 7:51 am
My RE system: System 1:
MATE3s, 3 x Radian GS8048A,
4 x FLEXmax 100, HUB10,
2 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 4 x FLEXware ICS Plus,
54 x PANASONIC VBHN325SA17 325W

System 2:
MATE3s, 2 x VFX3648,
2 x FLEXmax 100, HUB10
1 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 2 x FLEXware ICS
21 x PANASONIC VBHN325SA17 325W
Location: Providenciales, Turks & Caicos Isl.

Re: over sized

Post by EA6LE-ONE » Wed May 27, 2020 12:25 pm

pss wrote:
Wed May 27, 2020 8:46 am
150K on an island is a decent price for all you got. Here in So Cal, we just mosey over to a place called CED Greentech, a Walmart of solar at wholesale prices, everything in stock except concrete. As for being on the island, please take excellent photos of the before, because there is no solar panel that will withstand 250 mph winds. Even auto claved aerated concrete (AAC) will be at its limits. Here in So Cal we only rate for 110 mph winds and the code still called for 10,000 lbs of concrete with posts tied together with schedule 40 steel pipes and only 16 Solarworld 340s. I'm afraid that if your panels don't fly away, they will just crack from the air pressures. You may want to prominently paint your name on all of your equipment for the recovery effort. And yes, we lost a home to a hurricane in Florida and recovery took about 10 years. Now in So Cal, we concern ourselves with earthquakes,d fires and the Tarantula Wasp.
In 2017 we've been hit by Irma and Maria. with Irma we had 200mph wind and the house next to me lost half of the roof. I have 100w and 180w panels and none of them had any damage. That is at the old house. The new house is built even better. the code here for building is to withstand 200mph or more winds and we build with concrete and and cement blocks.

For the solar panels I made special aluminum brackets and mounting bars well anchored in the metal roof.I used stainless 316 screws and stop-nuts. I also installed some support for under the panels that will keep the glass from bending. see pictures.
ws1.jpg
ws2.jpg

pss
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My RE system: 8330 watts in three strings, Flexmax 60 x 3, Radian 8048A, GSLC load center, Mate 3S, Hub 10.3, FN-DC and 900 Amp, 48V Trojan T105-RE battery bank.

Re: over sized

Post by pss » Wed May 27, 2020 2:31 pm

When the big storm hits the island, it will be a historic video of those panels for Nat Geo channel. If I survive an 8 or 9 quake, my plan is to sit outdoors and live in my tent, drink my pond water and use my camping toilet until help arrives. One nice thing about a socialist state is they sell you good earthquake insurance at cheap prices if they can afford to pay off.

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