Help provide a path forward, up north woods with backup

[skorch]

Hello, I've tried reading many posts, trainings, manuals, etc., but I seem to keep going in circles. Can someone help point me in a direction so I can decide to commit or that this is just not going to work out.

Location: Northeast Wisconsin, I live in the middle of woods. I've performed some solar path studies and should be able to get solar from 10 to almost 3 most of the year. I have to clear out some trees. Solar Radiation is roughly 6 hours for 4 months of the year down to 2.2 hours in December if I had no obstructions at all which I cannot get.

Usage: Average of 350kWh/mo. on one meter and 720 to 1720kWh/mo. on my dual fuel rate meter (dryer, furnace, A/C, Plenum Heather, Heat pump, water heater, all high 240V loads).

Netmetering system is next to nothing, $0.0035/kW.

My goal is to DYI a system that will lower my bill and provide backup on my 350kWh/mo. meter only. I realize there is almost no way to cover the other one and frankly the rate is so low it wouldn't pay anyway. My backup would include daily use of lights, devices, refrigerator (320W), Freezer 500W, and well pump (31.5A surge, 8.4A continuous). My well pump runs maybe 2-3 minutes at a time, mainly when family is taking showers. So basically looking at installing another panel, taking out all of those breakers and making a critical load panel, and leaving all the heavy loads on the existing main panel.

Panels: I am hoping a 6kW system will suffice. I will do ground mount, and try to adjust angle seasonally since I will need to squeeze all that I can to make the system worthwhile. I'm hoping to source metal to simulate the Sinclair system.

Inverter system: Looking at at least 7500W due to well pump. I keep dancing between efficiency of DC coupling, simplicity of AC coupling, and limited number of hybrid inverters. I am constantly going in circles and hoping to get direction in at least narrowing it down. I'm thinking optimizers might really benefit me (Tigo or SolarEdge), but have seen studies in which inverters like Fronius it doesn't provide much value. Please!! Constantly bouncing between Fronius, SMA, SolarEdge, Growatt, and Schnieder. SolarArk is pretty much out due to cost.

Batteries: I'm thinking of starting out small as I only need them for back up and my power doesn't go out much or for long durations. I know Lithium is preferred, but carbon is so much more affordable. I am open to building my own too, but I see mixed opinions if it really lowers the cost that much and depending on inverter communication between the two would be really nice.

If I cannot put a system together for under $14k, to perform these needs it really isn't worth it, but I'm trying very hard to make it work. I think that is everything. I greatly appreciate anyone that takes the time to read this and provide advice. Thank you a ton in advance. Any advance on sourcing equipment is greatly appreciated as well as I keep finding only the main sites so far.

 

[skorch]

I posted quite a bit of information my main questions are:

1. Does anyone think that this system with budget restrictions and variables described is doable?
2. Starting with a new system what platform is likely be to be best (hybrid vs coupled)?
3. What sites or companies has everyone had success buying new equipment? Been looking Unbound, Solaris, Bluepacificsolar, SunWatts, and others I can't think of at the moment.

The rest would be discussion points that I would just love to learn more. As I said I'm just trying to reduce the number circles I am creating during my research.

 

[Mattb4]

Due to

Solar Radiation is roughly 6 hours for 4 months of the year down to 2.2 hours in December if I had no obstructions at all which I cannot get.

I would suggest you need to do some experimentation before embarking on a solution. Buy a couple of panels, SCC, a battery or two and a simple pure sine inverter. Run a few loads during the year to see just exactly what you can get out of the setup. Armed with that DATA you then can do some serious number crunching before going further.

During the year of fact gathering read up all you can about battery types, hybrid systems and keep an eye out for good deals on panels, wires, breakers and such.

I know that is not a simple buy "X" and all your problems is solved answer.

 

[Danke]

You have two meters? Why?

 

[Hedges]

Running a multi-kW well pump for a few minutes drives a bigger system that otherwise needed.
You need to determine starting surge. It is probably 5x nameplate current.

Can you put in a pump with much lower power draw, run for extended time to fill a tank?
Run a portable generator occasionally to fill a tank with the pump you've got?

I have SMA. Likely no cheaper than SolArk (unless you pick up some of the liquidation bargains) but is possibly the best quality available.

Optimizers don't add value except in some situations of shading (other situations, string inverter by itself does best), or multiple angles per string.

 

[skorch]

You have two meters? Why?

Danke, as I mentioned my power company provides a dual fuel rate. In rare high demand circumstances the power company can shut off power to anything connected to that meter. In exchange my rate on that meter is less than half. The program is typically for heat. The customer has to show they have a back up source in my case propane. They allow you to connect a limited number of other 240V loads as an incentive as well.

 

[skorch]

Running a multi-kW well pump for a few minutes drives a bigger system that otherwise needed.
You need to determine starting surge. It is probably 5x nameplate current.

Can you put in a pump with much lower power draw, run for extended time to fill a tank?
Run a portable generator occasionally to fill a tank with the pump you've got?

I have SMA. Likely no cheaper than SolArk (unless you pick up some of the liquidation bargains) but is possibly the best quality available.

Optimizers don't add value except in some situations of shading (other situations, string inverter by itself does best), or multiple angles per string.

Hedges,

You have actually listed all of the items I previously stated. I measured in-rush current and listed it as 31A. This is why I stated at least a 7.5kW inverter.

I am surprised in your statement of SMA being the same cost as SolArk. That hasn't been my observations up to now.

The main variable of concern is shading as I stated my limited window of clear sun. This is why I'm asking for other experiences to know if they really do make a difference.

 

[skorch]

Due to I would suggest you need to do some experimentation before embarking on a solution. Buy a couple of panels, SCC, a battery or two and a simple pure sine inverter. Run a few loads during the year to see just exactly what you can get out of the setup. Armed with that DATA you then can do some serious number crunching before going further.

During the year of fact gathering read up all you can about battery types, hybrid systems and keep an eye out for good deals on panels, wires, breakers and such.

I know that is not a simple buy "X" and all your problems is solved answer.

That is one way to do it, but I'm afraid that it only adds time and cost. If I don't add solar this year, I likely won't as the incentive is barely making this feasible in the first place. I am aware that in the winter it will not be enough, and this is why I'm still connecting to grid on my more common low demand loads (minus well pump).

Wouldn't starting out with a medium system that lowers my bill as in my original statement be almost the same thing and then I can use that data to determine if I continue to expand later? I have also considered not having battery backup with the initial cost and adding it later.

 

[Mattb4]

Problem I can see with building a system based on a government incentive to do so is it still may end up not providing what you need. It is the old story that you do not save money by spending money.

Other than that all I can say is I have no way to give good advice as to if something that would work when your location acts as an unknown factor.

 

[Danke]

Danke, as I mentioned my power company provides a dual fuel rate. In rare high demand circumstances the power company can shut off power to anything connected to that meter. In exchange my rate on that meter is less than half. The program is typically for heat. The customer has to show they have a back up source in my case propane. They allow you to connect a limited number of other 240V loads as an incentive as well.

Oh, I see. When you mentioned “net metering” I though you were not participating as the payout was so low. I didn’t realize that is what they are charging you.

That is a hell of a deal! I am not going to do net metering where I live as they only pay $.04/kWh, and I have to limit the size of my system to 120% of last years usage up to 20kW maximum.

Netmetering system is next to nothing, $0.0035/kW.

If it is really that low, just get inverters and batteries and charge off of the grid.

 

[Hedges]

Hedges,

You have actually listed all of the items I previously stated. I measured in-rush current and listed it as 31A. This is why I stated at least a 7.5kW inverter.

I am surprised in your statement of SMA being the same cost as SolArk. That hasn't been my observations up to now.

The main variable of concern is shading as I stated my limited window of clear sun. This is why I'm asking for other experiences to know if they really do make a difference.

OK, 7.5kW surge, which you may get from a 3.5kW or so inverter.

SolArk 5k offered for $4.5k, 15k for $8.2k

Sunny Island MSRP $5700, street price $4700, may find one from the DC Solar fiasco on eBay for $3k +/-
U.S. model is 120V, 5.75kW, 11kW 3 second surge.
Either buy two, or use a transformer for 120/240V split-phase.

Sunny Boy 5kW to 7.7kW is somewhere around $2k

For grid tie with backfeed, you may need UL-1741-SA, newer model GT PV inverters.
For backup or off-grid, older model UL-1741 is good enough, sometimes available cheaper.

Old-stock and used transforemer, SI + SB + Xfrm might be as little as $4k
Retail, 2x SI 4x SB for 12kW from battery 24kW from sun, might be $18k


Sun from 10:00 AM to 3:00 PM is half the hours we usually expect, but most of the available power. You could check an insolation calculator for what you'll get during that window of time.

With equal sun on all panels, optimizers do nothing.

If you have a single series string of PV panels to each MPPT input (Sunny Boy has three), if a panel gets shaded the others push current past its bypass diode and their full power is harvested. Avoid shadows when other panels have near full sun; some manufacturers cheap out on diodes and they burn up, taking panel with them. If sun is off-angle for half the power when that occurs, much less heating from half the current.

If two parallel PV strings and shade falls on some panels of just one string, its Vmp is different. If 10% shaded, most power is still harvested. If 50% shaded you'll lose 50% of 2 strings rather than 50% of just one. Optimizers could help there, but better to arrange panels so both strings get similar percentage shading.

I like multiple PV strings in parallel but of different orientation; better utilization of inverter or SCC, more hours production and only about 2% reduction from what separate MPPT could do.
But your shade outside 5 hour window may mean single orientation is best. Or maybe, put panels near East side of clearing tilted West, and near West side of clearing tilted East?

 

[skorch]

Problem I can see with building a system based on a government incentive to do so is it still may end up not providing what you need. It is the old story that you do not save money by spending money.

Other than that all I can say is I have no way to give good advice as to if something that would work when your location acts as an unknown factor.

I completely understand thanks. I'm just looking for anything that I may have missed as a way of estimation prior. I couldn't find anything on how to gauge solar radiance down to hour or part of day to help with window without shading, just monthly. Which is understandable. Trying to make that decision of what rate of return I will see. I got some feedback some someone that has the same issue, but then they added more panels on their house. Thanks.

 

[skorch]

Oh, I see. When you mentioned “net metering” I though you were not participating as the payout was so low. I didn’t realize that is what they are charging you.

That is a hell of a deal! I am not going to do net metering where I live as they only pay $.04/kWh, and I have to limit the size of my system to 120% of last years usage up to 20kW maximum.




If it is really that low, just get inverters and batteries and charge off of the grid.

Maybe I'm saying it incorrectly.
One meter is roughly $0.12/kW, my dual fuel meter is $0.045, and they stated any solar fed back in the system would be credited at $0.035/kW. Solar system greater than 20kW has other special requirements. Hope that clarifies things.

 

[Hedges]

I couldn't find anything on how to gauge solar radiance down to hour or part of day to help with window without shading, just monthly.

Calculation of Solar Insolation | PVEducation

www.pveducation.org

 

[peakbagger]

Get to the root of the problem, far better to spend 14K reducing your electrical demand than to spend your money on backup system. Wood heat is definitely something to look at.

 

[Hedges]

GT PV hardware costs $0.025/kWh (amortized over 20 years and assuming average 6 hours of sun, a bit more than you'll get)
LiFePO4 batteries are as low as $0.05/kWh over cycle life (assuming they last the claimed life); add cost of battery inverter.

You can compare those, or your own calculations for selected hardware, to utility rates and energy efficiency improvements.

 

[skorch]

OK, 7.5kW surge, which you may get from a 3.5kW or so inverter.

SolArk 5k offered for $4.5k, 15k for $8.2k

Sunny Island MSRP $5700, street price $4700, may find one from the DC Solar fiasco on eBay for $3k +/-
U.S. model is 120V, 5.75kW, 11kW 3 second surge.
Either buy two, or use a transformer for 120/240V split-phase.

Sunny Boy 5kW to 7.7kW is somewhere around $2k

For grid tie with backfeed, you may need UL-1741-SA, newer model GT PV inverters.
For backup or off-grid, older model UL-1741 is good enough, sometimes available cheaper.

Old-stock and used transforemer, SI + SB + Xfrm might be as little as $4k
Retail, 2x SI 4x SB for 12kW from battery 24kW from sun, might be $18k


Sun from 10:00 AM to 3:00 PM is half the hours we usually expect, but most of the available power. You could check an insolation calculator for what you'll get during that window of time.

With equal sun on all panels, optimizers do nothing.

If you have a single series string of PV panels to each MPPT input (Sunny Boy has three), if a panel gets shaded the others push current past its bypass diode and their full power is harvested. Avoid shadows when other panels have near full sun; some manufacturers cheap out on diodes and they burn up, taking panel with them. If sun is off-angle for half the power when that occurs, much less heating from half the current.

If two parallel PV strings and shade falls on some panels of just one string, its Vmp is different. If 10% shaded, most power is still harvested. If 50% shaded you'll lose 50% of 2 strings rather than 50% of just one. Optimizers could help there, but better to arrange panels so both strings get similar percentage shading.

I like multiple PV strings in parallel but of different orientation; better utilization of inverter or SCC, more hours production and only about 2% reduction from what separate MPPT could do.
But your shade outside 5 hour window may mean single orientation is best. Or maybe, put panels near East side of clearing tilted West, and near West side of clearing tilted East?

Thank you very much for your post.

Please correct my if my line of thinking is incorrect, but I was just going to go grid-tie with backfeed due to the limited amount of hours I can collect. My thought is have batteries to harness overproduction during peak hours and backup when grid fails, and grid-tie with back feed for when I run out of solar due to my limited collection times. Once confirmed that things perform well expand at a later time.

My primary battery concern is to ensure that when grid goes out I can have running water and refrigeration.

I have to review code yet, but yes I believe I will likely have to have UL-1741 as well. I haven't got a good grasp at how much more complicated adding a transformer for split-phase will be.

I will try to find this insolation calculator to see if it provides more detail than the solar calculators I have used so far.

I didn't know if optimizers would benefit me enough as the sun is entering and leaving my window of peak solar. there will be almost a direct line from shade to solar once I clear some trees out. I did see that Sunny Boy has three MPPT channels and I was wondering what the best way to connect 18ish panels to them would be. Your explanation of panels to shading is very much appreciated. I might have to draw something up just to make sure I understood your statements correctly.

My panels will be ground mounted facing South. I'm planning a 6x3 grid as of right now. As the sun rises from the East, it would hit one side first around 10a.m. no shade by 10:30-11 on any panels until the opposite happens as the sun settles West and hits the next tree line. North South I will have clearance throughout the year. So it would be better to place each row of 6 on a channel so shade is equal on all three channels throughout the day? I could get by without optimizers?

 

[skorch]

Get to the root of the problem, far better to spend 14K reducing your electrical demand than to spend your money on backup system. Wood heat is definitely something to look at.

I have Electric, propane, and wood heat. Where I live definitely need to have heat covered. I'm not sure what the "problem" you are referring to. I am just trying to ensure that the dollar amount of solar I plan to invest in will lower my bill enough to offset the cost under 10 years AND have the benefit of not worrying about generators when power goes out for water and refrigeration.

 

[Mattb4]

Maybe I'm saying it incorrectly.
One meter is roughly $0.12/kW, my dual fuel meter is $0.045, and they stated any solar fed back in the system would be credited at $0.035/kW. Solar system greater than 20kW has other special requirements. Hope that clarifies things.

At those low rates, unless I am misreading you, 12 cents per kwh and 4cents per kwh on the reduced cost meter, I fail to see that you could ever save by going solar. For emergency backup or for a hobby it might be worth it though.

I assume they do not pay you for excess generated power but rather credit you against your Bill. In other words you never get a check even if you produce way more than you consume.

 

[peakbagger]

I have Electric, propane, and wood heat. Where I live definitely need to have heat covered. I'm not sure what the "problem" you are referring to. I am just trying to ensure that the dollar amount of solar I plan to invest in will lower my bill enough to offset the cost under 10 years AND have the benefit of not worrying about generators when power goes out for water and refrigeration.

The "problem" is your energy use . Reduce your use and you need less for backup. You are trying to come up with a backup solution for what looks to be a high demand. Talk to any long term off gridder and they run their lifestyles on far less power. DC off grid refrigerators are expensive but draw minimal power compared to a typical consumer unit which was sold on price not on efficiency.