PV + PW in Japan

[charisjapan]

Hey All! I live in Yokohama, Japan, and am looking at Solar Panels and a pair of Tesla Powerwalls. Please understand I am a carpenter and mechanic, and know a bit about IT, but a newb about Electric Stuff ... please be kind.

Wife and I went to the Tesla Owner's Club All Japan Meet the end of May, and a fellow caught our attention. His spiel was pretty compelling, especially since Tokyo Electric (TEPCO) just announced some hefty price hikes, even to the late-night reduced rates. He got back to us with a plan for 8kW from 36 panels and two Powerwalls, and the numbers were quite nice. Our roof was done 4 years ago with Decra Senator, and that seems very compatible with PV installation, The panels, power conditioner, and associated is from Choshu Industies, made in Japan, and they seem to have a good reputation. Powerwalls and much of the other parts to the system to be mounted inside the entrance. Btw, I am asking for an additional 4 panels on the West Southwest side to get almost 9kW, but waiting for Choshu on that. I'll attach a few pics and a diagram. "a picture worth a thousand words" and all that.

If you got this far, and have any thoughts about this proposal, please share. In fact, practically any explanation about how all this works in layman terms, I'd really appreciate it. Oh, for background ... My wife and I (and two dogs) live on the 3rd floor, 2nd floor is classrooms, and 1st floor is a non-denominational church. And I drive a Model Y Performance. I've no idea why a Table Tennis Champion is advertising solar panles, lol.

 

[jjrandorin]

Welcome to the TMC energy subforum, @charisjapan

The main question I would put forth is, what is the driver for wanting solar + powerwalls, for you? that might help us help you work through the process of what you might or might not gain by installing solar and or powerwalls.

 

[charisjapan]

Welcome to the TMC energy subforum, @charisjapan

The main question I would put forth is, what is the driver for wanting solar + powerwalls, for you? that might help us help you work through the process of what you might or might not gain by installing solar and or powerwalls.

Hey @jjrandorin , thanks for the reply, and a very fair question. Maybe I'm still formulating that question in my head, and need more data? Well, that's not precisely the case, I DO want to get a more control of our energy costs, and not just be paying TEPCO whatever they tell me forever. The system above will probably not provide 100% of my energy at our present consumption ... but pretty close. I live in the middle of a gargantuan metropolis, so going Off-Grid is not my goal, but if another earthquake/tsunami hits (and our place is still standing!), we will have power to charge my car and help folks in the neighborhood charge phones, eat hot meals, etc. Not exactly a disaster shelter, but a bit of support. Finally, I'm 67, and while I can, would like to keep my abode as efficient as possible, within reason. Solar alone has been on my thoughts for years, but Powerwall put the package together, for me.

Hope that makes sense?

 

[jjrandorin]

Hey @jjrandorin , thanks for the reply, and a very fair question. Maybe I'm still formulating that question in my head, and need more data? Well, that's not precisely the case, I DO want to get a more control of our energy costs, and not just be paying TEPCO whatever they tell me forever. The system above will probably not provide 100% of my energy at our present consumption ... but pretty close. I live in the middle of a gargantuan metropolis, so going Off-Grid is not my goal, but if another earthquake/tsunami hits (and our place is still standing!), we will have power to charge my car and help folks in the neighborhood charge phones, eat hot meals, etc. Not exactly a disaster shelter, but a bit of support. Finally, I'm 67, and while I can, would like to keep my abode as efficient as possible, within reason. Solar alone has been on my thoughts for years, but Powerwall put the package together, for me.

Hope that makes sense?

Yes, it does ( wakarimasu )

In General terms, it typically is worth it to put as much solar on your roof as you can, if the main concerns are less reliance on the utility for energy. I dont know how resilient these systems would be in an earthquake situation (even though I am in California, which is also fairly active, seismically), but it would be a question I would be asking an installer if I was in your area.

Powerwalls (energy storage) generally dont "pencil out" from a strict dollars and cents / yen perspective, but can have the impact of having something similar to an auto switching generator, but with the fuel being the sun, and it being mostly silent operation. Powerwalls / Energy storage can pencil out if your utility has time of use rates, and there is a large delta between costs during peak and off peak usage.

Even if they dont pencil out completely with "pay me back", they allow you to use solar energy you generate during the day, at night, so can make it easier to absorb power outages provided there is sun the next day.

Based on what you said above, it sounds like having solar + energy storage (powerwall) would meet the goals you appear to have.

 

[charisjapan]

Yes, it does ( wakarimasu )

In General terms, it typically is worth it to put as much solar on your roof as you can, if the main concerns are less reliance on the utility for energy. I dont know how resilient these systems would be in an earthquake situation (even though I am in California, which is also fairly active, seismically), but it would be a question I would be asking an installer if I was in your area.

Powerwalls (energy storage) generally dont "pencil out" from a strict dollars and cents / yen perspective, but can have the impact of having something similar to an auto switching generator, but with the fuel being the sun, and it being mostly silent operation. Powerwalls / Energy storage can pencil out if your utility has time of use rates, and there is a large delta between costs during peak and off peak usage.

Even if they dont pencil out completely with "pay me back", they allow you to use solar energy you generate during the day, at night, so can make it easier to absorb power outages provided there is sun the next day.

Based on what you said above, it sounds like having solar + energy storage (powerwall) would meet the goals you appear to have.

Konnichiwa, @jjrandorin san, Arigatou!

"Pencil out" is a new term to me, but I've already read it about 10 times since investigating a solar harvest/storage system. It's fun to find out what's going on "back home." (quotes because after living in Japan 50 years of my life, I guess this is home, lol)

Indeed, I don't have a complicated agenda, just using my assets wisely. Few folks in town have unobstructed access to the sun in three directions, this much usable roof, and a place to put the batteries and other stuff. I also have a two car garage (in series), to home charge and even parking for a guest.

As to installation, I won't do it myself (any more) but I can vouch for a solid roof with no problem handling 600 kgs. In fact, it will still be lighter than the original shingles I installed (myself) 30+ years ago.

After the 2011 Disaster, we had a very nice plan for "All Electric" (no gas) that gave us VERY inexpensive night rates, but from June 1st that was changed. We still get an off-peak discount, but not near as much as before. It is time to change, so here we go! We will now have to tweak our lifestyle, like charging the MYP, hot water tank, washing clothes in the day.

I don't know how they got it so wrong, but I just went up and measured the roof, and here's the real layout. Looks like I mighjt get as much as 11kW, if they OK my ideas.

Thanks for the tips! Randy

 

[wwu123]

At first I thought how unusual to have a residential apartment above a non-residential business/organization, but then remembered we stayed in an Airbnb in Tokyo in April, that was a two-level house above a street-level nail salon . Makes more sense that in urban areas the street level is devoted to retail and the like...

I noticed the church has a white cross on the southwest wall, that looks like it will cast shade on that roof plane during the late afternoon. Have you considered the impact it could have on not just the panels partially shaded, but possibly the entire string production could be degraded during those periods?

 

[charisjapan]

At first I thought how unusual to have a residential apartment above a non-residential business/organization, but then remembered we stayed in an Airbnb in Tokyo in April, that was a two-level house above a street-level nail salon . Makes more sense that in urban areas the street level is devoted to retail and the like...

I noticed the church has a white cross on the southwest wall, that looks like it will cast shade on that roof plane during the late afternoon. Have you considered the impact it could have on not just the panels partially shaded, but possibly the entire string production could be degraded during those periods?

Hey @wwu123 , thanks for the reply.

Indeed, Japan authorities are conveniently blind to a lot of such situations. This property was owned by my late father-in-law's company since just after WWII, and was originally a woodworking shop and dormitory. I think if someone tried to start a business in 2023 and live on the top floor, it would not be allowed, but it's a legacy thing. I'm grateful! I'm just not sure if I'm living in the belfry (like "Alice's Restaurant"), or it's similar to "the church at Chloe's house," lol.

Yes, thank you for bringing up the cross, as my system guy was also concerned. He is now asking cic (Choshu Industriess Co) to clarify that issue. Just before sundown, one, possibly two panels will have that 40mm shadow cast. Would that affect the entire panel? One solution would be to lower the cross about 3 feet, which would then only affect the lower center panel for about 30 minutes before sundown. This would actually make the cross more visible to the folks walking 30 feet below. I am woefully ignorant about how the PV cells work ... as well as power conditioning, storage cycling, car charging from solar, "etcetera, etcetera, etcetera" (my favorite Yull Brynner line, btw). I think you will see more of me here to find out what I'm getting into/gotten into!

Cheers! Randy

 

[jjrandorin]

We have some members here who are pretty technical (I am not one of them), however, it seems to me that issues with shading seem to be addressed either with Optimizers, or with using micro inverters.

Micro inverters are small inverters that work on each panel or a couple of panels (not sure how many panels a typical micro inverter supports but its a very small number) vs a string inverter which is a more typical type of inverter where all the panels are cabled back to it.

Im not sure what company is doing your install, but if you are concerned about shading, before you start changing structures themselves (like the cross for example), you might ask them to investigate if either optimizers or micro inverters can mitigate that issue.

 

[hmcgregoraz]

We have some members here who are pretty technical (I am not one of them), however, it seems to me that issues with shading seem to be addressed either with Optimizers, or with using micro inverters.

Micro inverters are small inverters that work on each panel or a couple of panels (not sure how many panels a typical micro inverter supports but its a very small number) vs a string inverter which is a more typical type of inverter where all the panels are cabled back to it.

Im not sure what company is doing your install, but if you are concerned about shading, before you start changing structures themselves (like the cross for example), you might ask them to investigate if either optimizers or micro inverters can mitigate that issue.

Optimizers and MicroInverters help with keeping one panel being in shade from impacting the other panels, but it does not give you back the power that the shade is blocking.

If you can avoid the shade, great, but if you can't you just calculate it in.

We have a huge tree in our neighboors back yard, and we avoided putting panels quite where I would have liked them to avoid some of the shade, we still get some shade, just not quite as much as we would have.

-Harry

 

[charisjapan]

@jjrandorin and @hmcgregoraz thanks for the ideas of Microinverters and Optimizers. I watched a few Y-Ts by Gary Does Solar on the topic, and now have some (small) clue (Solar Panel Shading )

I haven't heard back from my project guy yet, but will definitely want to find out about these things, as well as Strings and panel Bypass Diodes. The Shadow of the Cross in question looked like the pic about an hour before sundown. Lowering the cross a few feet is just a matter of drilling three 10mm holes, so very easy.

Thanks and cheers! Randy

 

[zƬesla]

I have 50x 350kW LG panels separated into 5 strings of 10 panels each going into 2 SMA inverters. We have severe morning shadow in winter caused by trees. Even with partial shading on a panel though, it is still producing. There have been a few threads here about this w.r.t. newer panels. I would not expect the shadow shown in the photo to cause a substantial issue.

PS: This thread reminded me it has been way too long since my last trip to Japan and wandering the streets of Akihabara.

 

[charisjapan]

I have 50x 350kW LG panels separated into 5 strings of 10 panels each going into 2 SMA inverters. We have severe morning shadow in winter caused by trees. Even with partial shading on a panel though, it is still producing. There have been a few threads here about this w.r.t. newer panels. I would not expect the shadow shown in the photo to cause a substantial issue.

PS: This thread reminded me it has been way too long since my last trip to Japan and wandering the streets of Akihabara.

Hey @zTesla, thank you. It seems the panels I’m looking at are the Half Cell type with Bypass Diodes, which (according to YouTube, mind you) are a little smarter at ignoring cables and such. The cross is not much wider than a cable, so hoping for the best. it Comes off with just three bolts, so will be able to test empirically..

I live less than an hour from Akihabara, but not gone in years. Five decades ago, I went practically every week … but that was probably a different era, lol. I was hopping up slot-car motors, and tweaking electrical stuff, then three decades ago building PCs and even installing cutting-edge floppy disk drives. Hahaha.

cheers, Randy

 

[wwu123]

@jjrandorin and @hmcgregoraz thanks for the ideas of Microinverters and Optimizers. I watched a few Y-Ts by Gary Does Solar on the topic, and now have some (small) clue (Solar Panel Shading )View attachment 959934 I haven't heard back from my project guy yet, but will definitely want to find out about these things, as well as Strings and panel Bypass Diodes. The Shadow of the Cross in question looked like the pic about an hour before sundown. Lowering the cross a few feet is just a matter of drilling three 10mm holes, so very easy.

Thanks and cheers! Randy

Maybe replace the current cross with a shorter thicker one, that not only hides the brown wooden support post, but also has the crossbar covering that wooden stud sticking out sideways near your gutters? So just as visible to passersby, but even more aesthetically pleasing, and no shade on the roof....

 

[Matt-FL]

Your cross won't cause much issue, especially how thin it is. For more details on how modern panels handle partial shading, check out this very informative video comparing string to micro inverters. It was surprisingly minimal.

Would I have chosen micro inverters? It depends. If it was only $1 or $2k, absolutely. However, the difference for me was closer to $35k (changing from Tesla to a local vendor). That is far from worth it.

 

[hmcgregoraz]

I know there are a lot of fans of MicroInverters, personally I don't like having the electronics on my very HOT roof (Arizona summer), vs having the inverters in my less hot garage.

My roof is hitting 120-130F, and my garage right now is maxing at 107F and has no direct sunlight. Less extreme climates I can see some advantages for MicroInverters.

-Harry

 

[wwu123]

Your cross won't cause much issue, especially how thin it is. For more details on how modern panels handle partial shading, check out this very informative video comparing string to micro inverters. It was surprisingly minimal.

Would I have chosen micro inverters? It depends. If it was only $1 or $2k, absolutely. However, the difference for me was closer to $35k (changing from Tesla to a local vendor). That is far from worth it.

I think this one is a better video to watch, and in fact at the beginning references the other video to ask if that is telling the whole truth. Esp at 12:17, this one does a skinny mast test, which is more indicative of @chrisinjapan's thin church cross scenario:

I agree that these days, things are a lot more nuanced regarding string inverters vs micro-inverters, though I don't fully understand how all things work together - DC optimizers, MCI's, bypass diodes, half-cut cells, half-cut panels, MPPT curves... But while micro-inverters may be over-marketing shading benefits, it's funny how string inverters now do counter-marketing with very specific scenarios. First, invention of half-cut panels must have been the biggest boon to counter-marketing - why show the giant 3' wide leaf always only covering half of a half-cut panel? Because half-cut panels are essentially two separate panels, and right off the bat, they can completely avoid any effect on half the string.

Why don't we see what happens when the giant leaf covers parts of BOTH halves of the half-cut panel at the same time, or parts of all three bypass diodes simultaneously? Or what happens when a quarter of your entire array is shaded in a complex manner? Or a large tree whose shadow takes 3 hours to track across the entire array?

 

[charisjapan]

Maybe replace the current cross with a shorter thicker one, that not only hides the brown wooden support post, but also has the crossbar covering that wooden stud sticking out sideways near your gutters? So just as visible to passersby, but even more aesthetically pleasing, and no shade on the roof....

Hey @wwu123 , thanks for this and your later post.

Haha, this is turning into a saga! "The Story of the Cross" or "The Shadow of the Cross" ... Oh, wait! Those are on my bookshelf. That white steel cross is from our first rented place in '87, and after a few years of use was up in the attic for a couple decades. We put up a proper wood cross in '03 which served us until a typhoon broke it in'21 ... and the wooden support you see now was the bottom half. Now THAT made a big shadow, and a LOT of noise when it hit the ground 40 feet below! I restored the steel one, and it is not gonna break.

Back to shadows on PV panels, I am just going to take the cross down for the installation. After all is up-and-running and I get a baseline for energy production, then can easily bolt the cross back up to see the difference. I can just as easily lower it 16" and 32" (the bolt pitch) to see what that does. This solves the manufacturer's problem, as they don't want even a speck of dust on "their" panels. The installers say the cross interferes with their work. And the Project Manager just wants to finish the job and get paid.

My personal expectation is that "The Shadow of the Cross" is no big deal, and I'll have some hard data to help the next guy in a similar situation. My bigger concerns are 1) getting everything installed without a leaking roof! 2) using the 4 available Strings to my best benefit. 3) tweaking the system to give me the best balance of battery usage. And 4) tweaking our lifestyle (my wife and I with 2 dogs living here, and also the church and school here in the daytime) to adjust from a "use inexpensive off-peak power" thinking to a "make hay while the sun shines" thinking.

 

[charisjapan]

I know there are a lot of fans of MicroInverters, personally I don't like having the electronics on my very HOT roof (Arizona summer), vs having the inverters in my less hot garage.

My roof is hitting 120-130F, and my garage right now is maxing at 107F and has no direct sunlight. Less extreme climates I can see some advantages for MicroInverters.

-Harry

Harry, I hear you. While we have milder temperatures, we have immense humidity swings, pretty constant seismic activity , and typhoons. Unless I REALLY need more electronic gizmos with clear economic benefit, I want the simplest system possible. (who was it that said, "the best part is no part"?) The only possible shadow problem I have is only a few hours a day and only on a few panels. These "Japan Black" panels are modern units with half-cell and bypass diodes ...

cheers, Randy

 

[hmcgregoraz]

Harry, I hear you. While we have milder temperatures, we have immense humidity swings, pretty constant seismic activity , and typhoons. Unless I REALLY need more electronic gizmos with clear economic benefit, I want the simplest system possible. (who was it that said, "the best part is no part"?) The only possible shadow problem I have is only a few hours a day and only on a few panels. These "Japan Black" panels are modern units with half-cell and bypass diodes ...

cheers, Randy

You will most likely need optomizers (which are a lot more basic than micro inverters), as they also generally double as quick shutdown devices. The solar installer we worked with used to use a lot of LG panels, but they exited the market, and now most of their systems use sunpower panels that have a built in inverter and use an AC interconnect. The panels have a 25 year warranty including the built in inverter. I don't really like it myself, but I can see some elegance to the system too.

I don't know too much about electrical codes in Japan, but in the US the quick shutdown devices are now required.

I do know most electrical power in Japan is similar to US electrical, as I have dealt a lot with Data Center power situations in Japan.

-Harry

 

[zƬesla]

For us, the SMA inverters provide the rapid shutdown function required.