It all comes down to the economic tradeoffs. Panels are cheap and everything else is expensive.

If you can get 75% efficiency for half the cost, your return on investment is 50% higher

What you lose with Erthos' approach is any possibility of using bifacial panels.

In regions that get snow, bifacial panels (that use light reflected onto the back of the panels as well as light from the front) get a lot better output in the winter, increasing the annual capacity factor and therefor return on investment. (Winter electricity can be more valuable too, in those regions.)

Horses for courses.

you can have a back mirror on this, they probably do

Solar in Texas seems like an obvious win in just about any configuration. But I wonder how this would work at higher northern latitudes in the winter. I suspect efficiency would be pretty bad with a 20 degree incidence.

Doesn't have to be effective everywhere for it to be useful.

the unintuitive part is that land is even cheaper than panels, so you'd think that spending more panels to use less land would be a losing proposition

the interesting question is whether the costs of racking, grading, cleaning, repairing, etc., go up or down, and if they go down, whether it's enough of a reduction to make up for the larger amount of solar panels per average watt, as they say it will be

Based on my calculations, at my latitude (40 degrees North), you would need about 16% more panels to generate an equivalent amount of energy per year. This isn't taking into account potential issues with snow buildup (which theoretically would be worse with flat panels) or the effects of cooling (which theoretically could be better due to contact with a thermal sink, the ground), but it's probably pretty close. Even if 20% more panels are required, that means capital costs are superior as long as panel costs are less than 5x racking material and labor costs. Currently panel costs are more like 3x racking costs and will probably continue to decline. Racking costs will probably not go down unless steel prices go down pretty significantly. The only thing that surprises me is that there are not more companies doing this. Perhaps there are factors that neither Erthos nor I am properly considering, but I think this is how most utility solar projects will be done in 5-10 years.

We put in 40 KW and in the racking was a nightmare. The government required soil analysis, reinforced racks, and cement pilings 4 ft deep. Probably could have put in double the panels if we didn't have to deal with the f*** racks

I think this approach has interesting applications for small-scale solar in rural environments if the permitting can be streamlined

I mean with erosion, flooding, and the like, I'm not sure this sort of mounting on the ground would be any less of a hassle...

Most of those things seem nonissues in desert climates with flat Terrain.

steel prices are probably not a significant component of racking prices; scrap steel costs 50¢ a kg

the numbers they gave make the pv module prices seem slightly higher than the cited racking prices (15¢ per watt) but it's a little hard to be sure because of the numerous kinds of watts involved

Panels may be cheap, maintenance / replacement is less so, because humans at work.

Everyone is talking about maintenance ITT. Is it that big of a concern? My parents have had solar on their roof for almost 10 years now with zero issues. I imagine newer panels last longer.

So what's the actual maintenance cost? I could imagine it's going to be cheaper to just install new panels every few decades than constantly maintaining the installation to be 100% capacity.

For a grid scale installation, let’s say 5% of panels are dead due to whatever failure. I am not sure the rational response would be to do any maintenance vs installing more capacity. Twenty years later rip out all of the old panels, replace with new. Repeat forever.

They use a robot for regular cleaning; looks like the design will make that cheaper too as it's basically a fancy Roomba.

Replacing might be cheaper as well without any mounting racks or tracks.

> If the panels don't point directly at the sun, then you lose much of the efficiency.

This is true for a single panel. But the amount of sunlight which hits an acre of land is constant. If the land is 100% covered with panels, the panels will collect 100% of the available sunlight.

Installations that tilt the panels have lots of space between the panels.

> This is true for a single panel. But the amount of sunlight which hits an acre of land is constant. If the land is 100% covered with panels, the panels will collect 100% of the available sunlight.

That is not true from my understanding. The increased solar angle of incidence effects how much of the energy reflects back into the sky. Having more panels next to it without a gap won't change that. Yes you can fit more panels in the same area without putting them on an angle but they will be quite a bit less efficient because more light will be reflecting back up per sqft of panel which is what matters cost wise.

There is a small loss of efficiency (<2%) at extreme angles, but it is not too significant[1]

[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6611928/#:~:tex....

The anti reflective layers and texture on the panels are usually pretty good, such that then reflection is less than the area loss due to the angle.

Yes, one of the many areas of improvement of PV modules in the last couple of years has been reducing reflections from the surface of the glass and from the glass-cell boundary in panels. Also changed cell technology (n-TOPCon) helps with reflections and recombination within the cells.

it's true that you get 100% of the sunlight that falls on the land, or near enough (albedo is not literally zero at any angle) but you need more solar panels per output watt

it'll be interesting to know if they're derating the nameplate capacity by cos(latitude) as they should be

Their agreements with their local grid operator will specify power delivery. Marketing numbers like an individual panel's nameplate output are not important at utility scale, which this is designed for.

probably the local transmission companies are interested in not only average ouptut but peak output, but also, there were a number of numbers in the article cited as "per watt" which look like they might be talking about peak watts

Sounds like they're pretty confident this isn't an issue:

>Our fees are based on the plant producing at its optimal performance. If the plant underperforms for any reason, we curtail our fees – creating strong incentive and perfect alignment with the long-term asset owner.

I don't understand why they cant dig some kind of trench or mound to put them on at least, to angle them more towards the sun. There's plenty of agricultural equipment designed to cultivate soil (first example I found[0]). That could take care of the drainage as well, although I don't know how much it rains in Texas.

[0] https://www.asa-lift.com/asalift/producttypes/bodenbearbeitu...

> why they cant dig some kind of trench or mound to put them on at least, to angle them more towards the sun

Trench will flood. Mound needs to be maintained. Cheaper to put more static panels flat than trying to get every electron out of them.

> why they cant dig some kind of trench or mound to put them on at least

Just use the rack then, it's exactly the same result.

I think using the dirt that's already there and building the structure with some kind of machine would be cheaper than having someone mounting them on a steel rack. See for instance large potato fields [0]. The point is instead of putting them on flat ground, make the ground have a better shape first.

[0] http://www.thompsonpotatofarm.com/common-tater/banking-the-p...

The racks are really easy, well known technology. That was my point. If you're going to give up the entire reason for laying them flat on the ground, you're going back to the way existing solar farms work, so just use the same proven technology.

You get the majority of the power when the sun is directly overhead. You can make up the lost difference by the space saving and just adding more panels.

The sun is never directly overhead except on the summer solstice at noon, assuming you're in roughly the part of your timezone.

And then only at the equator. Here in Iowa at 42' North, you'd want a panel tilted 42' South to start with.

Most utility scale installations don’t track the sun- too much cost. This takes cost-saving to a new level though.

Horizontal panels also collect dust, so they still need to be propping them on the north side.

They don't look propped at all in the photos. Also I think propping would be hard for the cleaning robot as it looks like is a super simple little robot with small wheels and just rolls straightened over them.

Yah its probably a case that designing a vacmop style device (possibly purchased off the open market?) and having it drive around on a flat surface is both cheaper and keeps the panels cleaner than a custom bot that doesn't clean as frequently because it costs to much.

My question is whether sitting on the ground itself causes problems with efficiency due to the panels getting hotter than they would with some airflow under them.

According to the research on their site, ground mount solar has better heat dissipation than roof mount solar, and isn't that far behind racked systems, so it's not really a concern. The ground ends up acting as a heat sink.

https://www.erthos.com/modeling-heat-dissipation-in-earth-mo...

Erthos spend quite a bit of time designing their own autonomous cleaning and repair robot.

All panels collect dust, but this setup is much more challenging to clean (and to generally service, i.e to replace a faulty panel)

They have a robot that cleans the panels. It's a big, flat surface so they don't really need anything much more advanced than a Roomba.

Apparently they also have special shoes that maintenance people can wear that distribute the weight properly so they can walk on them if they have to.

This seems much easier to clean? A gigantic flat slab is pretty easy to automate something vs disconnected racks.

(Modern utility scale PV installations are already using automated cleaning solutions).

It is much better from POV of the cleaning robot maneuvering requirements. It's also much better in terms of single robot can access the entire installation.

But it's worse in terms of how much distance the dust should be pushed before it's off panel (as I don't see any gaps there)

Alternatively if the robot is a vacuum or something of the like, it could just store the excess dust and dump it at a station on the edge.

Service trade-off seems pretty marginal. They say the panels aren't tied down to the ground in any way, so you might be able to just pick one up and disconnect it