Optimum geometry of roof solar panels ?

[swampspruce]

The panels we use at work are roughly 250W each and measure 2.5 x 4 ft on a single inverter. Since this is used to charge a battery bank as a back up when the genset isn’t running using micro inverters would be a waste. They are either vertically mounted or on an angle roughly 15 degrees plus the latitude to maximize solar gain when it’s winter.

[SamuelA]

@swampspruce

The panels we use at work are roughly 250W each and measure 2.5 x 4 ft on a single inverter. Since this is used to charge a battery bank as a back up when the genset isn’t running using micro inverters would be a waste. They are either vertically mounted or on an angle roughly 15 degrees plus the latitude to maximize solar gain when it’s winter.

Why would the microinverters be a waste? In principle money per watt is money per watt, you need a certain amount of solar capacity to charge the battery backups at an acceptable rate.

If microinverters give you more watts generated/$, it is more optimal to use them, regardless of where the power is going.

Now, there is an option on Sunny Boy inverters called “Secure Power Supply”. It allows for using the solar panels to drive a load without a battery bank. This is useful, it gives an emergency capability to grid-tied solar systems.

But, only the Sunny Boy Brand string inverters offer this feature. This, to me, is a solid reason to use them rather than microinverters. For every other purpose, I assume microinverters are better. (with oversized panels. Use 280 watt microinverters with a 300 watt panel so that the inverter gets more utilization)

Here’s a page explaining the reason to oversize the panels:

https://www.yourenergysolutions.com/solar/inverters/enphase/

[swampspruce]

For several reasons:

1. We have the panels arranged in a single array.
2. The current set-up is almost ten years old now and as it is supplementary power, utmost efficiency isn’t required. Don’t let perfect be the enemy of good enough.
3. Simplicity of set-up.
4. The Outback Flexmax 80 controllers have been super reliable and are easy to datalog and set-up.

[mjmlabs]

@SamuelA

This would be a valid comment except there’s large tracts of land that aren’t doing much right now and the land is nearly worthless.

Bloomberg - Are you a robot?

Basically just grazing land, and I think it’s possible to keep using land with solar panels as grazing land (since water is the rate limiting factor, not sunlight) with the panels on poles.

@dtilque

There is a company (German, I think) that will put solar panels above farmland, so you can still grow crops under them. The panels are on a framework that’s like 3 or 4 meters above ground, high enough so a tractor can be driven underneath. You might wonder about how the plants get enough light. Well, the solar panels have enough gaps between them to let some light down. Plants don’t use anywhere near 100% of sunlight, more like about 2%. And some crops will actually grow better in those conditions. Also, having plants underneath keeps the panels cooler, so they don’t lose efficiency when it’s gets hot. I’d give a link, but I don’t remember the name of the company.

I dunno the German company, but here are a few links about agrivoltaics:

Nature

futurity.org

the Yale School of Forestry & Environmental Studies

And this story has a quote from a farmer claiming that solar panels yield equivalent $-per-acre, if not more, than the almonds and pistachios he used to grow there:

L.A. Times

Pretty interesting that growing crops underneath solar panels can actually improve crop yields and reduce irrigation needs. Sounds like a win-win-win, but I know nothing about the economics involved.