7.9 kWh from 1000 watts of panel

Chris Miller

We got a small building moved that was blocking some of our evening sun and went from around 5.5 -6.5 kWh per day production to an average of 7.5-7.9 on a sunny day.

A lot of guys act like production like this isn't possible but I guess we just get a heck of a lot of sun here.

Our upgraded to 3750 watts of panel is going to be pretty impressive I think.

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ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

I don't know what your location is, but clear up here in the Frozen North we can get that on a good day - provided we got enough loads to keep the panels busy all day.
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Chris

Photowhit

Re: 7.9 kWh from 1000 watts of panel

Chris Miller wrote: »

A lot of guys act like production like this isn't possible but I guess we just get a heck of a lot of sun here.
Our upgraded to 3750 watts of panel is going to be pretty impressive I think.

Max voltage 57.4, Time in Float 0

Most of us don't want to see numbers like that, you may not be impressed by your added array, but it appears needed, unless I'm reading your display wrong...

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

Photowhit wrote: »

Most of us don't want to see numbers like that, you may not be impressed by your added array, but it appears needed, unless I'm reading your display wrong...

Actually, you can never make that sort of production if you're going to absorb and float batteries every day. You need the loads to keep the panels at full output all day, without a break. During absorb and float the controller is going to cut the panels back on power so you won't get max production possible.
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Chris

Cariboocoot

Re: 7.9 kWh from 1000 watts of panel

Cold temps, high elevation, reflected sun are some things that can push panel production above typical levels.

It's a good thing you plan to add panel: 225 Amp hours @ 48 Volts usually needs about 400 Watts more than you've got.
This brings up the possibility that your proposed 3750 Watts would be a waste without a corresponding increase in battery capacity. Typically that would be enough to support three times the battery capacity you've got.

BTW, that 54.7 Volts max showing there is too low for charging a 48 Volt system. It almost sound as though all your kW hours from the panels are being used up and the batteries aren't actually getting charged. I suggest you check the SG and maybe hit them up with the generator from time to time until you expand the array.

westbranch

Re: 7.9 kWh from 1000 watts of panel

Photowhit wrote: »

Max voltage 57.4, Time in Float 0

...

No Adsorb either.. backed up by what Chris said...

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

Cariboocoot wrote: »

This brings up the possibility that your proposed 3750 Watts would be a waste without a corresponding increase in battery capacity. Typically that would be enough to support three times the battery capacity you've got.

It does not have to be a waste. You don't necessarily have to add more battery capacity just because you got over-capacity on the generating side of things. If the batteries are adequate for the period of time when there's no incoming power the overcapacity in solar (or wind) can be used to just run stuff direct. We got way more generating capacity than our batteries can take but we use the excess for things like water heating instead of trying to store it in batteries.

Batteries = bad. The less batteries you can get by with = good.

What I see in the info on the controller screen is that there was some loads on during the day using up the power. The array generated 152ah, which would normally charge 8x T-105's. So the power went to loads.
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Chris

Cariboocoot

Re: 7.9 kWh from 1000 watts of panel

ChrisOlson wrote: »

It does not have to be a waste. You don't necessarily have to add more battery capacity just because you got over-capacity on the generating side of things. If the batteries are adequate for the period of time when there's no incoming power the overcapacity in solar (or wind) can be used to just run stuff direct. We got way more generating capacity than our batteries can take but we use the excess for things like water heating instead of trying to store it in batteries.

Batteries = bad. The less batteries you can get by with = good.

What I see in the info on the controller screen is that there was some loads on during the day using up the power. The array generated 152ah, which would normally charge 8x T-105's. So the power went to loads.
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Chris

All based on being able to use the power at the time of generation. Nice if you can do it, but if you can't - waste of panels.

I manage to charge my batteries, run some daytime only loads, and realize pretty good Watt hours by careful management. Essentially my battery capacity is sized to provide the power needed between charge periods, but it is not an easy thing to achieve first time out.

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

Cariboocoot wrote: »

All based on being able to use the power at the time of generation. Nice if you can do it, but if you can't - waste of panels.

That's just never the way I've looked at it. We installed additional solar capacity (in combination with the wind) for the bad day instead of the perfect day. On the bad day when those panels and turbines are putting out only 30% of nameplate, I need every single watt online. On the average day they're adequate. On the perfect day you have to design in aux loads to use it.

But fact is, we get one heck of a lot more bad and average days than we get perfect days. Since I believe in avoiding charging batteries with a generator like the plague, if you want to live comfortably in an off-grid home you need to throw enough generating capacity at it for the bad day.

3,750 watts is probably going to be pretty marginal for this system for the bad day when those panels are running at only 30% nameplate.
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Chris

Cariboocoot

Re: 7.9 kWh from 1000 watts of panel

Well right now it seems he's delighted with 7+ kW hours per day, and then he's going to increase the array size by 3.7. That's potentially over 21 kW hours per day. Lots of power for most off grid applications. But if it's all in panel and none in storage he's either going to have to come up with a lot of opportunity load or just waste the potential. Given his Arizona location he's not going to have the problem of short Winter days we get up here nor likely to suffer from a whole lot of cloudy weather.

It's pretty rare when you hear me say "you need more batteries for those panels".

Chris Miller

Re: 7.9 kWh from 1000 watts of panel

Cariboocoot wrote: »

Well right now it seems he's delighted with 7+ kW hours per day, and then he's going to increase the array size by 3.7. That's potentially over 21 kW hours per day. Lots of power for most off grid applications. But if it's all in panel and none in storage he's either going to have to come up with a lot of opportunity load or just waste the potential. Given his Arizona location he's not going to have the problem of short Winter days we get up here nor likely to suffer from a whole lot of cloudy weather.

It's pretty rare when you hear me say "you need more batteries for those panels".

We went with the additional batteries like you recommended. We now have 3 strings of Trojan T-105-RE's. Just waiting to get the panels up before I add the batteries. Obviously we're already using more than we're making and having to run the genny sometimes so I don't want to damage the batteries. Just hope to have the panels up this week so i'm not charging those new ones separately.

I was just happy to see that number. Didn't think about it changing based upon usage. I figured that's just what was collected with it all coming in. Didn't realize loads played into that figure at all.

I'm in Far SW Texas now.... Big Bend Area on the Mexico border

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

Cariboocoot wrote: »

It's pretty rare when you hear me say "you need more batteries for those panels".

Yeah, I know

In reality, even with the location I doubt you'll see 7 kWh/day consistently. There may be times of the year when it will do that (like March and April here). But I would bet that once you get into the heat season (it regularly gets over 100 degrees there) that the production is going to drop off and 15-17 kWh/day is going to be more normal from a 3.7 kW array.

I'm seeing 8x T-105's = a little better than 5 kWh storage for overnight cycling to 50%. If you can generate 15-17 kWh/day and have 5 for overnight - you can live in style off-grid, man 8)

Up here we have to have more battery capacity for winter time. But if we lived in Arizona or Texas I'd only have about half the bank we got.

Dealing with opportunity loads gets really tricky if you try to harvest every possible watt-hour. I just went to the utility room and snapped a couple photos to show an example. We got good wind tonight after several bad solar days in a row and we used up most of our stored hot water. The turbines were going to re-bulk the bank overnight, after the controller resets at midnight, and I don't want that to happen. It needs to stay in float all day tomorrow. So I had to turn on the AUX1 on the solar Classic manually to turn on the water heaters and put a 3 kW load on the inverter all night:

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This will keep the turbines busy all night instead of screaming up against the clippers at 140+ volts. If we get a good day tomorrow I don't what the heck we're going to do with it. Turn stuff on I guess and use as much as we can. The load will keep the system voltage from reaching absorb during the night. In the morning when we get up I'll go to the Classic and force it back to float so it doesn't absorb the bank again when it doesn't need it.

But the deal is - as automated as I have tried to make our system, I still have to intervene and do these things sometimes. And that's the tricky part about opportunity loads.
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Chris

westbranch

Re: 7.9 kWh from 1000 watts of panel

Breaker, Brrreaker Car 99....

Chris O. and Coot are both correct , in part, from what I see. The truth is 'out there somewhere'.... in the middle...

I think, as Coot said, you need more PV in order to recharge your batteries as it isn't happening right now.
How much may take some incremental additions to find your sweet spot with a buffer for bad days.

You also are near Chris O's optimum where your gen set is used to Bulk/Assist your batteries, now you just need enough PV to Absorb and Float as needed.

I wouldn't add 3.7Kw of panels in one go.8)

Enjoy...

icarus

Re: 7.9 kWh from 1000 watts of panel

The best I have ever done is ~ 2.2 kwh, and that was running everything I could to keep the battery in bulk all day. My limitation is that while my panels get sun from sun up, they are out of sun by ~2 PM sad to say.

That said, I gt ~1.5 kwh in a clear day, something around 1 or better in an averqge day.

Tony

YehoshuaAgapao

Re: 7.9 kWh from 1000 watts of panel

8 KW-h per day from 1KW of STC rated solar? Pretty good. I get 6.25 KW-h per 1KW of STC. You always get full utilization grid-tied. My 6.48KW produces just slightly more than the 4KW of community solar that I subscribe to. The community solar is single-axis tracking (altitude) in the open desert. My best day is 44KW-h. Hovering around 41KW-h now. higher temps, fixed tilt (late april is peak production).

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

I've always wondered how very hot conditions (over 100 deg ambient) affects solar output on an otherwise beautiful sunny day, compared to the 70-80 degree temps we have on the same day in the summer. I know it has to affect it because those cells don't like heat. But I wonder how much?
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Chris

Cariboocoot

Re: 7.9 kWh from 1000 watts of panel

ChrisOlson wrote: »

I've always wondered how very hot conditions (over 100 deg ambient) affects solar output on an otherwise beautiful sunny day, compared to the 70-80 degree temps we have on the same day in the summer. I know it has to affect it because those cells don't like heat. But I wonder how much?
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Chris

Well of course it drops panel Voltage but has little effect on current. Even though panels run hotter than ambient anyway, the higher air temp reduces the ability of the panels to shed heat (which they're not very good at either).

So you have a condition where if you're using a PWM controller and an array with sufficiently high Vmp to begin with you already have the "Voltage overhead" built-in and will still have enough to meet charging Voltage even in the heat. The result is that power potential is affected very little.

However with an MPPT controller that "Voltage overhead" can be converted to additional power on "cool" days and will be lost on hot days. So the power potential will go down. This is that "10% (or higher) more power with MPPT" you hear companies go on about when they're trying to sell you one.

The actual factor can be determined using the Voltage coefficient of the panels involved, but it's difficult to say "so many degrees ambient raises panel temperature so much". We have the reverse problem up North of course: factoring increased Voc in due to very cold temps causing superconducting of the PV's. But there we can use the worst-case scenario factor of 1.3 and be right 99% of the time. I don't have any sort of straight-forward heat derating rule-of-thumb.

On the other hand the people down South have the advantage of lower panel angle working better year-round with more consistent length-of-day too. They will get more hours of equivalent good sun as a result. Hence the OP's wonderful number of kW hours. Up here I couldn't do that even in 16 hour days of Summer because of the wild arc the sun takes through the sky. Of course in Winter it does this silly 'bob up' on the southern horizon which is hardly worth bothering with. :roll:

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

Cariboocoot wrote: »

Up here I couldn't do that even in 16 hour days of Summer because of the wild arc the sun takes through the sky. Of course in Winter it does this silly 'bob up' on the southern horizon which is hardly worth bothering with. :roll:

I got those numbers on a couple days in late March/early April from our solar panels - I attributed it to cold weather at the time and super clear sky. But I have them aimed in three directions with 3.75 kW facing due south at 30° tilt for summer, 1.5 kW facing due east at 22.5° tilt, and .75 kW facing due west at 22.5° tilt. From about March thru mid-October this three direction aiming scheme works really good. I don't know how it will work in winter yet.
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Chris

Cariboocoot

Re: 7.9 kWh from 1000 watts of panel

ChrisOlson wrote: »

I got those numbers on a couple days in late March/early April from our solar panels - I attributed it to cold weather at the time and super clear sky. But I have them aimed in three directions with 3.75 kW facing due south at 30° tilt for summer, 1.5 kW facing due east at 22.5° tilt, and .75 kW facing due west at 22.5° tilt. From about March thru mid-October this three direction aiming scheme works really good. I don't know how it will work in winter yet.
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Chris

I have a similar scheme in mind, although it pivots on getting some panels aimed easterly to catch early morning sun. The affect of the sun arc difference between seasons is a bit of a puzzler at this point, but it can't work any worse than the single set that are up now.

NorthGuy

Re: 7.9 kWh from 1000 watts of panel

Cariboocoot wrote: »

I have a similar scheme in mind, although it pivots on getting some panels aimed easterly to catch early morning sun. The affect of the sun arc difference between seasons is a bit of a puzzler at this point, but it can't work any worse than the single set that are up now.

I have such a big difference between summer and winter that if the winter is somehow covered, it'll be enough energy in the summer no matter what I do. In the mid of winter, days are so short that sun always shine from the south. It simply doesn't have time for east and west

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

Our 1.5 kW east facing section of the array provides a pretty huge "boost" in the mornings right now. The sun comes up in the NE and sets in the NW so the south facing array basically does nothing until about 9:30 AM and we've had 4 hours of daylight by then. The east facing section of the array comes up to almost full power by the time the south facing starts to "kick in" at 9:30.
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Chris

YehoshuaAgapao

Re: 7.9 kWh from 1000 watts of panel

The difference is about 8-10 volts between hottest part of the day (72-75v) and close to sundown (80-82v). 60-cell panels, strings of 3.

northerner

Re: 7.9 kWh from 1000 watts of panel

NorthGuy wrote: »

I have such a big difference between summer and winter that if the winter is somehow covered, it'll be enough energy in the summer no matter what I do. In the mid of winter, days are so short that sun always shine from the south. It simply doesn't have time for east and west

Good point Northguy! I am encountering the same issue and makes sense to have all the panels facing more or less south, due to the low sun in winter, just when you need the power the most. On sunny days in summer, I can not use all the power coming in from just 6 panels, as my usage is also way down. On cloudy days in winter, 3 to 4 times the number of panels will not be sufficient.

offgrid me

Re: 7.9 kWh from 1000 watts of panel

Thats what I did. 4.2k of panels at 55 degrees pointed due south. Keeps my winter generator run time to a minimum, only 20hrs in two years. I have power to burn all summer long and dont have to think about my usage. Sure I could get more production the rest of the year with a shallower angle but I was really only concerned with winter.
Ned

Eric L

Re: 7.9 kWh from 1000 watts of panel

Man, you guys need to move to a lower latitude. My best day ever was in February. On that day I got about 5 kwh per kw (STC) of array (I have some morning shading or it could have been higher). More importantly for my purposes, I get nice output consistency all year at 30 degrees latitude. With 5.5 kw of array for an 18 kwh battery bank, it's now a pretty rare overcast day when I don't get enough to charge my batteries sufficiently to make it through to the next day, although of course on those days no opportunity loads come on.

Even though I have a high panel:battery ratio now, if I lived further north I'd have no qualms about raising it even more for winter, even though a huge amount might be 'wasted' in the summer. Panels just aren't the biggest cost factor any more in off-grid systems, even after mounting and wiring costs. You can always set the controllers to clip output amps to protect the batteries against overcharging.

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

Eric L wrote: »

Man, you guys need to move to a lower latitude.

We sort of enjoy our mild, long summer days up here. We enjoy winter too, even when it's bitterly cold at -40°. I couldn't live in a place where I couldn't enjoy the beauty of the changing seasons and that first winter snowfall.

The fact is, up here solar is pretty much useless in the winter time, no matter what you do. Might get 3 kWh/day out of a 6 kW array, average, for the whole month on each side of the winter solstice. In January and February it's not unusual to not even see a glimpse of the sun for six weeks with day after day of heavy, dense overcast. You can sweep the snow off the panels to try to get a few watt-hours, and the next morning they'll be covered again. Eventually it gets to the point where you just give up on it because they don't make any power anyway.

People who live in the north, off-grid, either use wind power or a generator in the winter time for the bulk of their power.

Where solar pays in the summer time up here is because of the fact that we get longer days than you do down south. At the summer solstice our days are roughly 2 hours longer than yours.
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Chris

NorthGuy

Re: 7.9 kWh from 1000 watts of panel

ChrisOlson wrote: »

We sort of enjoy our mild, long summer days up here.

It also does not require enormous energy expeditures on air conditioning.

northerner

Re: 7.9 kWh from 1000 watts of panel

ChrisOlson wrote: »

People who live in the north, off-grid, either use wind power or a generator in the winter time for the bulk of their power.
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Chris

We receive plenty of sun in winter where I live in northern Alberta. The downside is that the suns appearance is shorter in winter and doesn't get nearly as high. So solar isn't totally out of the picture in mid winter, but I expect to have more generator run time for about 3-4 weeks on either side of the winter solstice. Also, we can get long periods of cloudy, snowy weather, but that isn't the norm here. My panels are tilted up in winter to about 15 degrees off vertical, so they shed snow well, but still need a regular brushing to keep them totally clear.

YehoshuaAgapao

Re: 7.9 kWh from 1000 watts of panel

NorthGuy wrote: »

It also does not require enormous energy expeditures on air conditioning.

The best place to live for low heating and air conditioning costs and Auckland or Whangarei New Zealand.
More solar friendly but warmer (might need AC but could get by with fans), but still great weather, is Townsville Australia, or San Diego or Los Angeles California. Too many taxes and Laws in California though.

ChrisOlson

Re: 7.9 kWh from 1000 watts of panel

We get a few days in the dead of winter when the solar panels make some power, but they are few and far between. We tilt our south facing panels up to 75 degrees for winter but I think that actually hurts them compared to having them more flat for gathering the most power from what I call "cloud shine". I hope to find that out this coming winter with our east/west facing sections of the array because I'm not going to tilt them for winter.

And yes, the AC use is limited here. But we still get some hot muggy nights when the AC is nice for sleeping. We've never had AC before and just put in a new central AC unit. Looking forward to some more comfortable sleeping this summer in July and August, and being able to come in the house for lunch on a hot day and relax for a bit in a nice cool house to take some of the heat stress off. The Trane XR13 unit we bought only draws 9 amps @ 240V so it's no problem to run it all night on battery power, with the compressor going steady, if the bank is fully charged at sundown.
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Chris

solar_dave

Re: 7.9 kWh from 1000 watts of panel

Hey Chris,
You seem extremely knowledgeable. Did you consider a mini split of some sort before you added the Trane? I have a pair of 3 ton XL16i and I think they do a great job, but still would have considered a mini-split had I know more about it at the time I replaced the old Lenox 10 seer units (one died and the other was hammering hard at start up). The ceiling cassettes for the mini-split may have been an option here and relocating them to the east side of the house in afternoon shade might have helped as well. I sure like the one I have in my office/shop.