Change my mind: Solar is pointless (for me in Michigan)

[Offthewall]

I was going to say…. 109v voc is ok but I would rewire to add another panel in the string to get it to 136.25. If its a 200v max, you should be good with 5s… 6s may be getting too close to max at extreme low temps

 

[Offthewall]

I was going to say…. 109v voc is ok but I would rewire to add another panel in the string to get it to 136.25. If its a 200v max, you should be good with 5s… 6s may be getting too close to max at extreme low temps

For my array, I have 1 string of 10x 400 watt panels and 1 string of 11x 400 watt panels. Its very cloudy right now and the 10 is producing 819w the 11 is producing 1.02kw. So that 1 panel is helping a lot due to the higher voltage. Also the higher voltage will help with voltage loss from the wires.

 

[x98myers7]

the SCC would handle it as far as voltage goes, but at a 1.25x factor for winter temperature correction, it's unsafe on my 10ga wiring amperage (30amps max). it's already at 27.7amps temp corrected.

 

[Offthewall]

the SCC would handle it as far as voltage goes, but at a 1.25x factor for winter temperature correction, it's unsafe on my 10ga wiring amperage (30amps max). it's already at 27.7amps temp corrected.

The amperage should stay the same, only the voltage increases.

 

[rodrick]

the SCC would handle it as far as voltage goes, but at a 1.25x factor for winter temperature correction, it's unsafe on my 10ga wiring amperage (30amps max). it's already at 27.7amps temp corrected.

Putting a panel in series will not raise amps only volts

 

[Offthewall]

Ok so you have 12 panels total 10 on the roof and 2 on a redneck tracker… how are they wired???

 

[seneysolar]

my system is sized appropriately and pvwatts estimated lowest production in January of 5.28kwh. For the past 3 years in a row, from December through mid-April, I get 0.5 to 1kwh daily solar production. As I type this, my "redneck dual-axis" rolling 500w array is making 3 watts. Yes, 3 watts. It's the "Great" Lake's effect on cloud production. This makes my solar system completely pointless because there's no amount of battery backup that's going to get me through multiple months of effectively zero solar production. I was naive enough to think that the pvwatts estimation was reliable and I would actually see near the 5kwh daily average at the lowest.

I've been debating for months to upgrade and add on more battery, but there's no math that makes it make sense for the above intended goal. what am I missing? change my mind.

Something is wrong if you are only getting 3 watts out of 500. Is this array on its own Charge controller? are you adding the 500W array to the 2000 roof array? If all the strings aren't the same it wont work the way you want.

I run a 24V system in the Upper Peninsula of Michigan on 700W of panels. It powers the cabin with lights, running water and TV. Generally I can count on 10% (70W) output on an overcast cloudy day, but then inverter idle consumption generally consumes that before I power any loads.

 

[Dagoth Ur Does Solar]

That seems like a really undersized system for this need.

For being totally off-grid for a system with no grid backup, I think the idea is the "proper sizing" would include multiple days of run-time. Some people would even say a week or more worth of battery.

The alternative to building it bigger is have grid backup for prolonged cloudy periods, or have a generator backup of some kind.

 

[teal95]

Roughly where in MI are you? The big lakes make a lot of clouds...

 

[x98myers7]

Roughly where in MI are you? The big lakes make a lot of clouds...

Kalamazoo

 

[teal95]

Lake effect clouds and snow really hammer you there. I'm just far enough east to be on the fringe of the snow, but still get most of the clouds. Winter really sucks here for solar.

 

[x98myers7]

Something is wrong if you are only getting 3 watts out of 500. Is this array on its own Charge controller? are you adding the 500W array to the 2000 roof array? If all the strings aren't the same it wont work the way you want.

I run a 24V system in the Upper Peninsula of Michigan on 700W of panels. It powers the cabin with lights, running water and TV. Generally I can count on 10% (70W) output on an overcast cloudy day, but then inverter idle consumption generally consumes that before I power any loads.

it was very cloudy and raining. right now, i'm hovering at 5-6% production on both arrays, it's slightly brighter but 100% cloudy and lightly raining.

yes, the 500w 5s1p is on it's own SCC independent of the main 4p2s 2kw array on the roof.

last month during the -4F temp deep freeze, clear sky and bright sun, my 500w array was producing 620w. it's not a matter of configuration. i've been monitoring the system for 3 years. in the summer it consistently produces at 95% efficiency. there's just zero sun.

 

[teal95]

Currently making 2 kW on a 20 kW array. But it's on a 4/12 pitch roof which actually helps on cloudy days.

 

[seneysolar]

it was very cloudy and raining. right now, i'm hovering at 5-6% production on both arrays, it's slightly brighter but 100% cloudy and lightly raining.

yes, the 500w 5p1s is on it's own SCC independent of the main 4s2p 2kw array on the roof.

last month during the -4F temp deep freeze, clear sky and bright sun, my 500w array was producing 620w. it's not a matter of configuration. i've been monitoring the system for 3 years. in the summer it consistently produces at 95% efficiency. there's just zero sun.

5p1s? In low light you might not be waking up the charge controller.

What are the panel Voc and vmp?

What charge controller?

 

[OzSolar]

Off grid solar is about as classic a case of the 80/20 rules as there is. For most people, regardless of where you live, it's relatively easy to get ~>80% of your annual energy from solar. As you try to get closer to 100% it gets increasingly hard. EG: 3X's the system and still need generator a few hours a year.

Most of us already know that of course.

 

[x98myers7]

had it backward... five 12v 100w panels in parallel, single series.

 

[seneysolar]

had it backward... five 12v 100w panels in parallel, single series.

Connected to your 24v battery bank?

5 panels in parallel will only be the voltage of 1 panel.

If string voltage doesn't get at least 5v above battery charge voltage (depending on the controller) it wont work.

 

[x98myers7]

you're right... it's super close. it's definitely not getting enough voltage on dark days. the SCC requires 30v minimum and on dark days the array is bouncing from 27-42v.

they're 22.12voc/19.23vmp. the array is 110.6voc. they're bifacials.

 

[Brucey]

you're right... it's super close. it's definitely not getting enough voltage on dark days. the SCC requires 30v minimum and on dark days the array is bouncing from 27-42v.

they're 22.12voc/19.23vmp. the array is 110.6voc. they're bifacials.

I would suggest using four of them in a 2s2p config.

 

[x98myers7]

I would suggest using four of them in a 2s2p config.

what's the theory? that would be lower voltage (but higher amperage).

 

[Brucey]

what's the theory? that would be lower voltage (but higher amperage).

The theory is you aren't hitting minimum voltage to set your scc to startup in overcast conditions.

Going to 2s will double your panel voltage and should allow for better low light harvest.

If you scc can handle 150V then having them in a 5s string would probably be best as you can use them all.

 

[MattiFin]

Its a very cloudy day today and my 11.9kw of panels are producing 3kw to 3.7kw depending on the amount of light that makes its way thru the clouds.

Im betting you dont have enough voltage running to your charge controller… ie need more panels.

There is cloudy days and Cloydy days. What I have learned from photography that us humans are really bad eyeballing the lightning conditions. Really dark rain clouds block something like 20x more light than totally overcast day.

 

[MattiFin]

I will say however that PV is not suitable everywhere. If your location is perpetually overcast, or the amount of bad days far exceed the good, or that you lack a unshaded panel location, than it is impossible to make it worthwhile.

OP location of Kalamazoo looks like excellent alternative compared to some fellow Finns here.
Kalamazoo gets about 10-20 times more sunshine in december than Central Finland. Not to mention some of the forum members actually above the arctic circle.

 

[x98myers7]

The theory is you aren't hitting minimum voltage to set your scc to startup in overcast conditions.

Going to 2s will double your panel voltage and should allow for better low light harvest.

If you scc can handle 150V then having them in a 5s string would probably be best as you can use them all.

they're already in a 5s string. array Voc is currently 110.6v. going to 2s2p means halving the array Voc. it will make the problem worse.

 

[Brucey]

they're already in a 5s string. array Voc is currently 110.6v. going to 2s2p means halving the array Voc. it will make the problem worse.

OK i thought it was 5p, my applogies.