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Comment by goodcanadian | Hacker News Reader

I would caution that deserts are some of the most sensitive ecosystems in the world. Covering up large areas of a desert with solar panels may be more harmful than you realize.

That said, I am a strong solar advocate; I simply believe we should start with the roofs of warehouses. These are huge areas of relatively flat space where the ecological damage has already been done.

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I agree that we should use caution in setting up solar panels. That said the ecosystem in most of northern Chile is dirt. Not sagebrush or cactus with a few insects, or dormant seeds waiting for the next rain. Just dirt, sometimes rocks. If ever there was a place for solar panels it's northern Chile.

https://en.wikipedia.org/wiki/Atacama_Desert#/media/File:Ata...

I don't mean to disagree, just share a fun fact: the Atacama is actually so dry, parts of it are barely an ecosystem at all. Obviously, the life that does exist there is quite sensitive, but there's large swathes of desert that are some of the only places on Earth where no life has been detected whatsoever; the land is literally just rock, without even bacteria living in it.

Covering up large areas of a desert with solar panels may be more harmful than you realize.

I've heard & use the term solar strip-mining.

Solar power maxes out at no better than 1kW/m^2 (sun at zenith, clear day, practically 100% efficient conversion), we're talking an absolute minimum of 1 sq km to match a baseline 1GW power plant ... and likely 100 times larger for real-world scenarios (10% efficiency, night/clouds, non-zenith air densities, dust, etc). So yeah, the net effect is "strip-mining" a vast area by removing all (or a seriously impactful percentage) natural power input and thus killing everything off.

Rooftop solar should indeed be the focus. There's even solar panels intended as road/pavement surfaces, super-durable interlinked hexes grabbing power where we've already wrecked the natural surface.

> 1 sq km to match a baseline 1GW power plant

Does that sound like a lot to you? A single airport runway is much larger than 1 sq km.

As I noted: real-world conditions demand 100x as much space.

Uh, no. Chicago Midway happens to fit very nicely inside 1 mi² = 2.56 km². Its main runways (5 of them) with feeder ramps collectively take up at best ½ the space, so a single runway itself is not 1 km² but more like .2-.3 km².

Midway is an airport for ants. 10/28 at SFO is 2 sq km, and there are two of them, and 1/19 are 1.5 sq km, and there are two of them. Then you also have OAK and SJC.

Point: a square kilometer to generate 1GW peak of electricity would be an obviously excellent trade off, well within the cost parameters that humans are willing to spend on far less useful endeavors like runways and parking lots.

Wikipedia says that 10/28 is 3.618 km. For the runway itself to be 2 km², it would have to be 0.552 km wide. A quick glance at an aerial map indicates that a width of 0.552 km gives approximately the width of both runways, relevant taxiways, and the surrounding ground. Wikipedia says that the runways are in fact .061 km wide, for a total per-runway size of .221 km².

I picked Midway because it's a very conveniently sized airport, being almost exactly 1 mi² in a square-shaped with obvious meter marks (due to surrounding grid system).

Ok you got me. Bad at math.

Except that 1GW/km^2 is the absolute upper limit. As dreadmorbius computed, reality gives ~1.5% of that.

Why do you assume 10% efficiency? That seems awfully low?

I agree with regards to rooftop being an important part, though. It makes sense to use land that is already occupied to a large degree.

The efficiency of modern commercial photovoltaic solar cells is about 10-20%.

If you start looking at effective achieved energy delivery from solar, 10% is exceptional. Consider that plants are lucky to return 1-10%. Algae, under exceptional conditions, may also reach 10%, but that takes some doing.

Insolation: 1 kW/m^2

Panel efficiency: 10-20%, nominally 17%. Maximum for a single-layer cell is 37% for quantum physics reasons, with an "infinite" layer panel, 87%.

Capacity factor is the amount of time a panel actually recieves sunlightlight. Typically 20-30%, with 30% as a peak.

Spacing factor. PV doesn't work if shaded -- the entire circuit cuts out. So you have to angle and space your panels. On net, this reduces availble area by about 50%. Less near the equator, more at high latitudes.

Degredation. For numerous reasons, solar panels degrade with time, mostly due to physical wearing (broken cells, wiring, hazing of panels, stone and hail damage, etc.) When nominal output falls to about 85% new, panels are deemed due for replacement. This is about 20 years based on multiple studies. So you're replacing 5% of your stock every year, and losing a few percent of output.

Inverter losses. Converting panel (DC) to transmission (AC) power costs about 10%.

Transmission losses. Another 6% or so for high-voltage transmission.

Multiply all that out, and your 1 kW/m^2 * 0.17 * 0.50 * 0.9 * 0.9 * 0.25 leaves you with 17 watts of 24/7/365 capacity per square meter. Or about 1.7% net efficiency.

This doesn't account for storage which can cut into that some more.

> roofs of warehouses

And parking lots.

Parking lots are dangerous to build over, for two reasons:

1) people cannot drive. The amount of dents or other damage from incompetent drivers done to a concrete-built park house is crazy, I don't want to imagine the damage they'll do to tiny aluminium/steel constructions holding the panels

2) people cannot drive. They underestimate their vehicle height all the time - just google for "can opener bridge". Just a couple days ago a truck driver massively damaged the lighting in a Munich tunnel because he forgot that the excavator on the flatbed was higher than the truck...

> They underestimate their vehicle height all the time

There's a simple way to fix that: Have a solid steel bar slightly lower than the max clearance at the entrance. People that can't drive will notice there without causing further damage.

Not to mention multi-level parking lots, which have height restrictions imposed by the structure itself. I'm sure most people wouldn't mind having the top level covered as well.

There is no reason to make them tiny: http://solairegeneration.com/project/rutgers-university/

You just build the solar panel mounts like you would usually build lighting mounts (big concrete bases).

Height is less of a concern in some parking lots (where it's virtually all cars)

I agree. They should start by deploying local solar in the huge and already impacted active mining areas.

Solar panels are large compared to a house, not large compared to a desert.

Here is a couple of square miles of solar panels in the Mojave Desert. If you zoom out, you'll find quite a bit more nearby. Whether or not you count this as large, the impact is not negligible.

https://www.google.com/maps/place/34%C2%B048'44.1%22N+118%C2...

EDIT: To be clear, I am not fundamentally opposed to such installations just as I am not fundamentally opposed to new hydroelectric projects, but we need to be aware of the impacts, and we need to make conscious decisions about when the costs are worth paying and when they are not.

Traditional power stations aren't exactly small, either. In fact, people will think you're a lunatic if you start talking about nuclear or coal in "per square meter of land" terms.

For context: my local nuclear power station is about 600 W/m^2, unless you count the purpose-built lake it relies on for cooling water, in which case it's 50 W/m^2. The 17 W/m^2 estimate above for solar doesn't look as bad as I would've guessed.

Think I point out is there is a perception issue. When people thing 'power plant' they think of a large concrete building with a bunch of machines in it. But they don't think of all of the supporting infrastructure. (Comment I've heard about nuclear power in France is on hot days it's partly limited by the need to avoid dumping too much waste heat into the rivers. Coal fired plants seem neat and tidy until one thinks of the strip mines. Gas fired, the massive network of pipes needed to extract the gas and move it to where it'll be burned.

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