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Comment by dylan604 | Hacker News Reader

Am I reading this correctly? Vertically they produce 77% compared to 90% of the tilted panels? In what graph is the lower number better?

Also: "Specifically, [Dave] is using bifacial solar panels– panels that have cells on both sides. In his preferred orientation, one side faces South, while the other faces North. [Dave] is in the Northern Hemisphere, so those of you Down Under would have to do the opposite, pointing one face North and the other South."

Isn't that the same thing? Is one of the sides specifically meant to face the sun? Maybe I'm just not as knowledgeable about solar panels, but what sunlight is being harnessed by the backside of the sun facing panel? Are they catching reflected light, otherwise, they are directly in shadow.

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Bifacial panels usually have one side that's a bit more more efficient than the other. The backside can catch reflections, sky light on overcast days, ...

But it's usually more common to orient them east-west, so they have peaks in the mornings and in the afternoon/evening, which combines well with other solar panels that are mounted south-facing, or might even just match your electricity consumption pattern better.

> Vertically they produce 77% compared to 90% of the tilted panels? In what graph is the lower number better?

77% of the ’normal orientation’ per year, but the graph and 131% value is for a day in winter (January 15 this year). At least that’s my read.

I also believe vertical panels produce more than flat panels in the mornings and evenings, thereby giving them anti-duck curve properties.

So one day of the year is producing 131% yet still only averages 77% for the year? Yeah, that sounds like a good trade off. /s

I'm still trying to decide if the entire post is trolling or not. Nothing about it sounds sane to me.

So your problem is that during summer, average solar production is much higher than in winter in the first place. So to ensure that you have sufficient energy in winter, you can either overprovision heavily for summer use (lots of flat panels facing south) or you can sacrifice summer efficiency to gain winter efficiency - vertical panels do that.

It's not just about production, it's also about reducing maintenance costs (don't collect snow, less dust build up on panels) and land usage. If you can take that 77% average, but maybe stick a couple more panels on land to reach your energy goals in an overall smaller footprint with less maintenance work, then maybe it's a good solution to specific problems.

If you had a solar panel that produced half as much power as regular, but produced power at night that would be a massive win. This is a less extreme equivalent. It produces less power than a normal solar pannel, but it produces power at an important time (when regular solar panels don't produce much power).

The graph confused me for a moment, but then realized the graph is showing the winter with SNOW on the ground, not the general case. So in the winter the vertical panels produce more power than tilted panels in very specific conditions and depending on how often that occurs, it may make up for the loss in efficiency during other times of the year. I'm guessing the vertical panels gain some advantage of the sun reflecting off the snow and into the vertical panel that the tilted panels do not, especially when the sun is at low angles to the horizon.

> Isn't that the same thing?

Yes, it’s a joke.

If bifacial panels are made so each side is the same making orientation not an issue, then sure, hahahaha (not really. it's a lame joke). If there is a back side, then you absolutely need to reverse the orientation depending on hemisphere. It would be better stated that they need to be pointed towards the equator. If these are literally reversible, it seems like wasted money to me as one side will never produce as much as the reverse does.

You're assuming that the bifacial panels have their faces pointing north/south; they can also be highly effective oriented east/west, so that they maximize power production in the morning and evening.

(Also: if the panels do have a "preferred" orientation, you can offset that by installing them in an alternating pattern, or at random.)

The hemisphere talk is a joke, the situation being shown off here is one where there is snow in the ground, which greatly increases the amount of sunlight hitting the backside panel.

This is also in January, when the sun in Ohio is very low in the southern sky. So north/south oriented panels are much more ideal.

If you look at the far right hand bar the B-N/S says 131% which is the highest bar on the chart. So it's producing more than the standard tilted slightly south orientation from what I gather. The legend is a bit hard to read for sure.

> Isn't that the same thing?

I had the same reaction. I noticed the top comment reading "some of us live in the southern hemisphere" so maybe this was a quick edit and not thought through?

Unless one of the sides of the panel is meant to face north, but that doesn't sound likely

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