Where to Buy High Wattage Half-Cut Panels with Microinverters or MX Technology

[eric@psmnv]

We have a partial shade problem. For parts of the day, nearby trees and a pipe chimney would cast a shadow across parts of our panels. I know this is a hotly debated topic, and I don't mean to start a war, but I've been reading up, and it seems to me that I either need panels with half-cut cells and micro-inverters, or panels with MX technology. I also want them to be pretty high powered, like at least 400-500W, and maybe higher of possible. Anybody know where a soul could purchase such panels? I've been searching but Google is just laughing at me.

[Ampster]

Are you limited in area? 500 Watt panels and micro inverters that can handle that Wattage might cost more per Watt than 300 to 400 Watt panels and micros.

[eric@psmnv]

Are you limited in area? 500 Watt panels and micro inverters that can handle that Wattage might cost more per Watt than 300 to 400 Watt panels and micros.

Yes, I have very limited space. I will have to pay a premium for panels because of it.

[J.P.M.]

Yes, I have very limited space. I will have to pay a premium for panels because of it.

Keep in mind that panels that carry a higher STC output rating will generally have a larger footprint.
A higher energy density per unit area will require panels with a higher conversion efficiency, not necessarily a higher STC wattage rating per panel.
You probably don't need higher wattage panels as much as you need high(er) efficiency panels.

What are your end goals for this project ?

If one of them is a lower electric bill, and you have limited area for an array, one way to get closer to that goal is by lowering your usage. That's also a more cost effective method to achieve that goal than throwing PV at an electric bill PV. Reduce your usage as much as your lifestyle and inclinations permit before any PV.

Also, and often something that the peddlers don't bring up, keep in mind that building code restrictions, and maybe even more importantly, access to panels for practical but perhaps unseen or unknown service considerations may limit usable array size to a lot less than may be thought of by packing an area solid, especially when you consider that micros will need service and so access paths which will reduce the packing density and in effect reduce available space for panels.

[eric@psmnv]

Keep in mind that panels that carry a higher STC output rating will generally have a larger footprint.
A higher energy density per unit area will require panels with a higher conversion efficiency, not necessarily a higher STC wattage rating per panel.
You probably don't need higher wattage panels as much as you need high(er) efficiency panels.

What are your end goals for this project ?

If one of them is a lower electric bill, and you have limited area for an array, one way to get closer to that goal is by lowering your usage. That's also a more cost effective method to achieve that goal than throwing PV at an electric bill PV. Reduce your usage as much as your lifestyle and inclinations permit before any PV.

Also, and often something that the peddlers don't bring up, keep in mind that building code restrictions, and maybe even more importantly, access to panels for practical but perhaps unseen or unknown service considerations may limit usable array size to a lot less than may be thought of by packing an area solid, especially when you consider that micros will need service and so access paths which will reduce the packing density and in effect reduce available space for panels.

Hi JPM,

We live off-grid in a wilderness area where building codes, if they exist at all, are not enforced. We use wood and propane for heating and refrigeration. We use electricity for lights, electronics, fans, and so forth. I'm in IT, so I'm on my laptop and 27" monitor most of every day. I've spent the past two years messing around with a Kill-A-Watt, trying to determine our minimal power commitment, and it is always around 3700-4000 Wh/day. The cabin is surrounded by trees on all sides, but we have an 8x8x24 tower about 50 feet from the cabin, which pokes out above the trees (mostly) and there are currently 4 old panels on top of it, I'm guessing about 80-100W each. They don't provide much power, so we end up running the generator 3-7 hours a day when skies are gray, which is often. I want to replace those 4 small panels with new, larger ones, and try to get closer to our daily requirement. I'm aware that the newer panels are huge, so I can only get 2 of them up there unless I build some kind of platform that allows the array to stick out past the edges of the tower, making it look a bit like The Flying Nun.

[bcroe]

Living on 3 or 4 KWH a day is pretty efficient, way better than I
ever did. It is pretty hard to do much solar on a tower. I do not
know the width of your clearing or the height of the trees, but if
the ratio is not too bad, you might do well with something like I
have used for 9 years. It also puts out substantial power under clouds.

I have an array on the west edge of my space, aimed to pick up
the rising sun as it clears theeastern treetops. There are enough
panels on the ground mount, to immediately go to full power. These
are effective till past solar noon. Then there is a mirror image array
(facing west) that picks up the sun from approaching noon, till it sets
behind the trees. This keeps power at near maximum the whole
unshaded day, not just around noon. Since the 2 arrays never are
at full power at the same time, they can just be connected in parallel.

Panels are cheap, with a ground mount you can use enough to get
the job done. This arrangement has a secondary benefit. With light
dispersed under clouds, ALL the panels are about equally effective.
My clouded output is double that of a simple array of the same peak
capability. Bruce Roe

[eric@psmnv]

Living on 3 or 4 KWH a day is pretty efficient, way better than I
ever did. It is pretty hard to do much solar on a tower. I do not
know the width of your clearing or the height of the trees, but if
the ratio is not too bad, you might do well with something like I
have used for 9 years. It also puts out substantial power under clouds.

I have an array on the west edge of my space, aimed to pick up
the rising sun as it clears theeastern treetops. There are enough
panels on the ground mount, to immediately go to full power. These
are effective till past solar noon. Then there is a mirror image array
(facing west) that picks up the sun from approaching noon, till it sets
behind the trees. This keeps power at near maximum the whole
unshaded day, not just around noon. Since the 2 arrays never are
at full power at the same time, they can just be connected in parallel.

Panels are cheap, with a ground mount you can use enough to get
the job done. This arrangement has a secondary benefit. With light
dispersed under clouds, ALL the panels are about equally effective.
My clouded output is double that of a simple array of the same peak
capability. Bruce Roe

The problem is, we don't have a clearing. The trees pretty much butt up against the house on all sides, except for a small driveway, but there isn't room for an array in it. My only choices, without clear-cutting a chunk of land, are the top of the tower or the roof of the house, which faces SE, but I've still got a partial shade problem over there. The tower is 8' x 8' at it's base and goes straight up 3 stories. The top story has a water tank. The panels are on the very top. Not much room up there, just an 8x8 slanted roof covered in asphalt paper with 4 panels attached to a DIY mount made of angle iron. We're roughing it, but we love it.

I've thought about doing what you suggested, and maybe you're right. Panels are cheap. Maybe I could put two panels on the east-facing side of the tower, 2 on the west, and 2 on top facing south, but we would still have a partial shade issue. Hence my question about MX technology.

[bcroe]

MX might help with an occasional branch here and there,
but against solid shade it will add nothing. Bruce Roe

[eric@psmnv]

MX might help with an occasional branch here and there,
but against solid shade it will add nothing. Bruce Roe

Understood. That's why I'm asking about partial shade. I'm concerned about branch shadows laying across the array in random patterns.

[J.P.M.]

Hi JPM,

We live off-grid in a wilderness area where building codes, if they exist at all, are not enforced. We use wood and propane for heating and refrigeration. We use electricity for lights, electronics, fans, and so forth. I'm in IT, so I'm on my laptop and 27" monitor most of every day. I've spent the past two years messing around with a Kill-A-Watt, trying to determine our minimal power commitment, and it is always around 3700-4000 Wh/day. The cabin is surrounded by trees on all sides, but we have an 8x8x24 tower about 50 feet from the cabin, which pokes out above the trees (mostly) and there are currently 4 old panels on top of it, I'm guessing about 80-100W each. They don't provide much power, so we end up running the generator 3-7 hours a day when skies are gray, which is often. I want to replace those 4 small panels with new, larger ones, and try to get closer to our daily requirement. I'm aware that the newer panels are huge, so I can only get 2 of them up there unless I build some kind of platform that allows the array to stick out past the edges of the tower, making it look a bit like The Flying Nun.

Thank you for the info. It's probably safe to say you're not going to conserve much more electricity than you're doing now. You are to be commended.

Whether or not they are enforced, it's a good idea to follow local building codes if for no other reason than safety, not to mention insurance claim denial if something bad happens.

Depending on the height of the tower, it's construction, the additional surface area added by new panels and a bunch of other variables, you'll have another consideration: Wind loading and checking the structure for that loading, keeping in mind that you will need service access to all the components.

Again, you don't necessarily need large panels. 2 ea. 250 STC W panels can easily be as productive as one 500 STC W panel.

Sizing and designing a grid tied PV system and doing it right needs consideration of several variables. Sizing an off grid system adds consideration of the probable sequence/patterns of irradiance and some probabilistic analysis of sunny/cloudy days and then design of the storage system based on the load and irradiance patterns over time, how much of your load you want to offset and how often you're willing to run a generator if/when the weather disagrees with your irradiance analysis.

FWIW, the STC power density for modern, quality panels is ~ 180 - 200 W/m^2 (~ 16.7 - 18.6 W/ft.^2).

There are publications galore about off grid PV design. Google can be a big help in finding them.

Good luck.