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

[x98myers7]

okay.... so the title is a bit click-bait.... but hear me out.

my only goal for having a solar system is to be completely off-grid to power my second refrigerator and 3 freezers. I only need 2.8kwh daily confirmed by my kill-a-watt meter to achieve that.

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.

 

[Brucey]

okay.... so the title is a bit click-bait.... but hear me out.

my only goal for having a solar system is to be completely off-grid to power my second refrigerator and 3 freezers. I only need 1.8kwh daily confirmed by my kill-a-watt meter to achieve that.

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.

With a 500W array I'd expect maybe 500W total for the day in cloudy conditions.

You need to look at the detailed hourly results via csv export to actually see where there could be long stretches of crap followed by one of two days of full productions. Just taking monthly average and dividing it isn't going to capture those days or weeks of poor production.

Other thing when you have low production is make sure your inverter etc have a low zero load consumption, no point having inverter idle losses rob you of your hard earned production.

 

[SunDave]

Hi,
I believe you have some bad assumptions. I just ran PVWatts data for the middle of Michigan, 500 watts, no shade. The numbers said 25kWh for all of December, or 833 watts per day on average.

It is also good to remember that equipment has idle/running losses, and they affect smaller systems more. A few hundred watts a day out of 833 watts for example is a lot of loss.

I bet if you stick around and ask questions, you can improve your setup greatly.

 

[EPicTony]

I'm sure there are folks from Michigan that can chime in. You definitely need more than the lowly 500w of PV you have, but panels are cheap.

 

[Mattb4]

You need Brute force solar. Your system is not sized appropriately. If you need 2.8kWh daily and perhaps another 2.5kWh for operational overhead in a less than ideal location I would suggest about 4kW worth of solar panels and around 15kWh worth of battery.

 

[ITSolutions]

okay.... so the title is a bit click-bait.... but hear me out.

my only goal for having a solar system is to be completely off-grid to power my second refrigerator and 3 freezers. I only need 2.8kwh daily confirmed by my kill-a-watt meter to achieve that.

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.

I am from Michigan and would like to share my insights. First I agree that I would not expect much more than 500 watts a day on a cloudy day at best. You mentioned that it is a "redneck dual-axis" array, is this powered in anyway or do you mean "red-neck" as in you go out and move it? If there is any automation all your production is gone just trying to move it.

I currently have an 8k array that is very much not optimally located or positioned as it is on my garage with only 23 degree tilt and a SW facing with trees that shade it too early in the evening. In the Winter I average 2KW a day, not great at all. But as I said horrible conditions for it. Either way, with my experience I would say that if you want 2.8KW a day, year-round in MI I would say you need to get a min of 3KW of panels with 5KW battery or 2KW with a 10KW battery. I still think it would be tight some days, and way over other days, but that is Solar in a nutshell. No way to avoid it. I would also suggest maybe shutting off the freezers at night to reduce the battery load on the days that are darker. Any decent freezer should withstand 1-2 days with little to no temp rise as long as it mostly stays closed.

 

[x98myers7]

my total system is 2.5kw, 208 azimuth, 23deg tilt. the 500w array was just for reference. and yes, my redneck array gets moved manually by me.

even with a 20kw array, actual production would only be 800watts at 4% production that I see on normal days. I'm not spending $35k for an off grid system that only powers my fridge and freezers.

 

[SunDave]

Hi,
Well that's better data to work with. Then PVWatts says 3.9 average for Dec, if no shading at all, any time of the day. There are going to be periods with much worse production, and some with better. But having 3.9 on average, conversion losses, and idle/run of equipment will cut it down some. Snow on panels will make it worse of course.

If you have talked yourself out of it, then it is what it is. You are correct that with batteries, and the whole works, it takes a lot of planning and work to make a system cost effective. I would guess that it is most members 3rd or 4th system by the time they crack the code to cost effectiveness. Not sure I have yet!

 

[Q-Dog]

my only goal for having a solar system is to be completely off-grid to power my second refrigerator and 3 freezers. I only need 2.8kwh daily confirmed by my kill-a-watt meter to achieve that.

Something ironic about trying to keep freezers cold in winter.

 

[justinm001]

Michigan's a pretty big state. 500w doesn't seem nearly enough for 2.8kwh needs. 3watts seems pretty normal for 9am in the winter.

Is it just 1 500w panel or multiple small ones in a string? Since it seems that partial shade is your issue, I'm wondering if multiple panels/arrays would help when partially shaded.

Also while powering a fridge and 3 freezers, are you leaving the inverter and components on 24/7? I'd suspect turning them on/off every 3 hours would be more efficient. Save that idle consumption and maximize the efficiency of the inverter.

I have a fullsize home fridge in my RV and it barely uses electricity at max its like 50w. If running off a large inverter the efficiency has to be like 50%

 

[MattiFin]

You need Brute force solar. Your system is not sized appropriately. If you need 2.8kWh daily and perhaps another 2.5kWh for operational overhead in a less than ideal location I would suggest about 4kW worth of solar panels and around 15kWh worth of battery.

Sounds about right if compared to pvgis tool https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html

I’d up the panels to 3.5kWp with 20kWh battery. This would give monthly excess year-round with 2% of days withh empty battery ( 7 days per year)
5kWp panels and 15kWh battery would be little bit cheaper and give 0.2% days of empty battery(ie less than one day per year on average)

 

[OffGridInTheCity]

I'm in remote Southern Oregon and after 7 years.... it's absolutely clear I can only generate 15-25% in winter compared to summer. And over the years it varies significantly - I'm talking 350kwh/Dec has been my lowest with 500kwh/Dec highest.

It's all about cloudy/raining weather. Multiple days, weeks in a row with really thick cloud cover. Some days in a row so thick there is literally <1kwh for the whole day on 15kw PV array. I would need 300 panels instead of my current 48panels to get anywhere near what I need and then would still need a 7day battery capacity once in a while.

I LOVE solar panels and 300kwh is better than 0kwh but those few months in winter just aren't viable to power the house. Supplemental generator or just straight fuel based heat requires hundreds of gallons and is not sustainable if things break down - a major earthquake could cut us off for months. Because of where I live (much firewood) I'm looking into a water boiler for heat because I can harvest firewood myself.

But I am disappointed as my rose colored glasses made me so hopeful that heat-pump technology would be waaaaaaay more power efficient than it actually is. Not blaming heat-pumps - it just that I didn't realize how much power is actually needed to heat a large house.

 

[EPicTony]

Something ironic about trying to keep freezers cold in winter.

Yes, If he moves the freezers into an unheated area for the cold months the electrical load would be MUCH less.

 

[SunDave]

One other thing to note x98. Your area is rough for solar. The same system in Texas would double output in December. I don't know your exact setup, but if you were able to get to say 70 degrees instead of 23, it would produce 30% more power in December without buying more equipment. If they are roof mounted, that may not be an option. Getting the panels in a spot without shading is also critical. You have less sun to work with, so you have to make it count. Pointed as directly at the sun as possible, and minimizing shading.

As others said, if your freezers could be in a less heated area in the winter, you could stop fighting the temp bias as well. Good luck with your setup. If it works for 10 months of the year, it is still worth something, even if you give up on the idea of running that equipment off of 100% solar.

 

[x98myers7]

I would also suggest maybe shutting off the freezers at night to reduce the battery load on the days that are darker. Any decent freezer should withstand 1-2 days with little to no temp rise as long as it mostly stays closed.

yes... definitely. I have a 15amp rated manual timer that I need to experiment with, again. that was something I tried about a year ago, but got distracted and didn't do the data logging on.

 

[x98myers7]

2kw is roof mounted, but thankfully minimal shading.

the 500w mobile array was expected to be the kicker. in theory even at 1/4 the size it should produce nearly double my roof array, but there's just no sun.

 

[Mattb4]

my total system is 2.5kw, 208 azimuth, 23deg tilt. the 500w array was just for reference. and yes, my redneck array gets moved manually by me.

even with a 20kw array, actual production would only be 800watts at 4% production that I see on normal days. I'm not spending $35k for an off grid system that only powers my fridge and freezers.

I think your costs could be less. For instance I have routinely seen panels in the ~20-30 cent per watt range. For instance I bought 10-375W bifacial panels a few months back for just over $1000 delivered. I see 100ah 48vDC LiFePO4 batteries at around $600 so 3 (15kWh) would be $1800. Thus ~$3K for the panels and batteries. Toss in another $5K for a setup and you are ~$8K.

Also it will power more than your fridge and freezers a lot of the year. The secret is to have things needing to be powered when PV generation is high. I must admit I have not fully cracked the excess production utilization issue myself but I have nearly reached full Off grid capability year round.

 

[Brucey]

2kw is roof mounted, but thankfully minimal shading.

the 500w mobile array was expected to be the kicker. in theory even at 1/4 the size it should produce nearly double my roof array, but there's just no sun.

A 2 axis tracker array would be expected to achieve around 40% increase versus fixed mount of equivalent size, so not sure where you are getting your efficiency numbers from there.

 

[Offthewall]

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.

 

[x98myers7]

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.

that's definitely not the problem. the midnite 200 does just fine. it's a 24v system. there's the array mapping.

 

[quantum`]

my total system is 2.5kw, 208 azimuth, 23deg tilt. the 500w array was just for reference. and yes, my redneck array gets moved manually by me.

even with a 20kw array, actual production would only be 800watts at 4% production that I see on normal days. I'm not spending $35k for an off grid system that only powers my fridge and freezers.

Understandable. But it also depends on the technologies your panels have. The newest techs can gather incident (scattered) light through clouds most effectively. And the cost differential is minimal these days if you do your research.

 

[SunDave]

Sometimes the weather is just no good. Pulling 324 watts right now on 13.76kW of panels. Thick clouds and starting to rain. Overall though, it's been good. That's the trick with solar. It's good when it's good, but I have had multi week stretches of very poor production.

 

[Mattb4]

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.

 

[Offthewall]

that's definitely not the problem. the midnite 200 does just fine. it's a 24v system. there's the array mapping.

Am I reading that right???? VOC is 27.28 volts????

 

[x98myers7]

Am I reading that right???? VOC is 27.28 volts????

per panel