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Comment by vasco | Hacker News Reader

I don't operate one but back in university did some calculations around these and another factor is that efficiency goes down with rising temperatures. If the panels are all on the ground, during summer they will heat up and there won't be much air circulation beneath them to help cool them off. So efficiency will go down for sure, and I'm not sure the 20% one time savings will compensate a forever-less-efficient running operation. I guess it depends where in the world you install them, if more towards the north it might be ok.

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When experimenting with solar efficiency, I noticed that spraying the panels with water every half hour increases efficiency pretty dramatically.

The wet surface seems better at absorbing sunlight than the 'anti reflective' glass surface, and the evaporating water is a great cooler.

Since it uses so little water, I don't know why industrial installations don't do it.

In some areas, the water use just from cleaning solar panels becomes a serious issue (let alone using more water to cool them). It's not much water to spray on some panels you are experimenting with, but for a large installation it seems like it would be a lot of water.

The best areas for solar are hot, those are also likely to be the areas where water supply is the most constrained, so this is definitely a no-go solution

Sorry if this is too basic of a question but for places close enough to the sea, would sea water for cooling and cleaning be an option? Too much salt residue?

salt crusts are highly reflective, driving down light exposure pretty fast. Plus, salt water is corrosive.

> salt crusts are highly reflective

I think this will not be a problem, as the salt would be continuously washed away with new water. But the corrosion would be a problem indeed.

Maybe some plastic/epoxy/glass casing would help, but it might also hinder recyclability.

Now I'm waiting for the seaside solar power plant/salt works proposal to pop up!

Seriously: Maybe residue wouldn't be an issue if it was never allowed to dry, but the corrosion-proof construction, drainage system, and pumping costs would be considerable. Then there's the 100 problems we're not aware of yet...

This is in Texas which is hot but there’s water.

Additionally power stations use steam turbines which require a lot of water. Some cooling water for misters would probably be a rounding error.

https://www.eia.gov/todayinenergy/detail.php?id=50698

https://www.seia.org/initiatives/water-use-management

See my comment above. This water is being used to grow agricultural crops under the panels in Kochi airport in India.

https://www.newindianexpress.com/states/kerala/2021/dec/13/c...

Don't try this at home. Cold water can crack the glass or cause other thermal stress.

True. But most panels are rated and tested for icy hail to hit it on a hot sunny day with the panel surface at 70 degrees C.

But obviously doing this repeatedly might not be good for it - naturally hail on a super hot day is rare.

The water would need to be demineralized in order to not leave deposits over the long term. That alone probably makes the idea unprofitable.

I wonder how much of that is the water increasing the effective surface area of the panel be acting as lens?

>spraying the panels with water every half hour

Sounds like a job for center-pivot irrigation! Just choose a model that can rotate at 2 revolutions per hour.

I never really appreciated how brilliant these are until watching this video:

https://youtu.be/7j1lMs7fcIQ

For large deployments of Earth-mounted PV you'll need a grid of drainage ponds to buffer runoff water, so you might draw from those. A control system would monitor temperature, PV output, and water turbidity.

The latter is important, since there's no sense dumping dirty water on the panels! Give the suspended solids time to settle out, or even add flocculants via a dispenser.

In the Kochi airport in Kerala, India, the water used to wash the solar panels is used to grow fruits and vegetable plants right under the panels and these are harvested and sold.

The plants under the panels also reduces the heat under the panels and thus increases the efficiency of power generation.

This can be a nice way of getting additional income from the land and also tackles the problem of plants growing under the panels.

https://www.newindianexpress.com/states/kerala/2021/dec/13/c...

this is a very good point. would be good to see data for a couple of years of production and compare vs. traditional system. it's most of the time better to spend upfront for ongoing production increase. If 5% loss during 25 years, 20% upfront saving might not look that good anymore for a plant that pays back in 7 years or so.

The response of the company when the issues of heating, vegetation, snow, and rain is... I guess I am not impressed.

> The expert added, “I’m also concerned about the lack of airflow around the module in this system design. Glass-glass modules provide a good moisture seal, but I suspect the back of the module will have very high humidity with no airflow. Damp-heat testing will be important. Not sure what other organic stuff could grow back there, like fungus or mold or things that get in the J-box,” referring to the junction box that houses the equipment that carries electricity from each panel.

> Daniel Flanigan, chief marketing and product officer at Erthos, offered this response: “No developer is going to install an Erthos system without proper diligence and all of these issues…being resolved. Yet we are engaged in over a gigawatt of pipeline.”

Okay, got it. So because people are paying for it people should pay for it. Everyone knows something no one knows.

https://www.canarymedia.com/articles/solar/utility-scale-sol...

That's what they said about Theranos, too.

I agree. sounds like a red flag when they reply with "yeah everyone is buying it so your question is irrelevant" instead of providing a technical explanation/response. I am also skeptical on companies that raise too much funding (I can not imagine why they need $18million)

Consider the difference in borrowing costs now too. A 20% higher upfront cost means a 30% higher cost if you include financing over several years. So it will be good to see how the alternatives work out

They’ve studied the heat dissipation https://www.erthos.com/modeling-heat-dissipation-in-earth-mo...

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