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Comment by cjlars | Hacker News Reader

One issue with solar is where we put it all. If it turns out that a meaningful portion of farmland has an excess of solar energy, that takes a big bite out of the problem. Powering the US entirely on solar might take a land mass equivalent to 2% of the country... Only a small portion of the 40% of US land area used as farmland.

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This is a non issue. Rooftops alone are enough to power the US with solar, versus prime land. With that said, there is enormous potential in the roofs yet to have solar installed, parking lots with solar canopies, marginal land, floating PV systems at reservoirs, etc. Land is not an issue. At this rate, we’re constrained by pv module costs, deal flow, permitting, and install labor (a combination of labor and soft costs, essentially, with a healthy dose of supply chain issues).

https://pv-magazine-usa.com/2021/10/11/solar-deployed-on-roo...

Having PV above water is something we should do immediately.

As this article points out it seems to help with evaporation and evaporation is a big deal [1]

water out here and heading south just sits in concrete canals waiting to be flooded inefficiently onto crop land. but using way better irrigation is another topic.

[1] https://www.circleofblue.org/2013/world/report-evaporation-f...

There was a story on HN the other month about solar panels above irrigation canals in India. Something like this: https://www.bbc.com/future/article/20200803-the-solar-canals...

Love it. I also remember one a long time ago about filling a reservoir with floating balls. But solar does two things at once.

We already devote enormous tracts of land in the US for energy from solar for transportation, way way more than we'll ever need for PV. Fully 40% of the US corn crop goes to ethanol.

People talk about how bad solar efficiency is in turning sunlight into usable energy at around 20%, corn is only able to do 1-2% and then it has to be processed into ethanol. Thus, replacing corn for ethanol with solar would result in massively more energy available for our use (not that I think that would be a good idea or that we could even use that much solar electricity).

edit: And I should add that there's likely to be plenty of farmland becoming available due to water shortages. Think about it, say you are a farmer that has water rights and use it to grow a low value crop like alfalfa. You can put up solar panels and sell your water rights and you don't have to do any work. Or if you rely on groundwater, lease your land for solar for 20 years and let the aquifer recharge during that time.

Has this ever actually been a problem?

I think most of the recent progress has been in lowering prices, while the amount of power you can extract from a square meter of land presumably hasn't changed much. But I don't actually remember any serious commenter suggesting that running out of physical room was ever an actual consideration when it came to solar.

There has been opposition to greenfield developments on environmental concerns, much harder to oppose a dual use installation over farmland.

https://www.latimes.com/world-nation/story/2021-11-03/the-mo...

We'd have to solve some environmental problems with solar panels if we wanted to do that. Panels have been found to leak lead and cadmium into the environment. We should probably keep them away from our food until that's fixed

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5607867/

That paper doesn't support your claims. They didn't test for lead leaching, and they tested pulverized solar panels in strong acid. Moreover, they were cadmium telluride solar panels, which have been obsoleted by cheaper polysilicon. Polysilicon PV panels don't contain cadmium and don't contain a significant amount of lead.

We're really really far away from having difficulty with where to put solar.

That would be nearly enough to power the world; not just the US. Powering the world would take a bit over 115000 square miles, apparently. About 3% of the US landmass.

Residential roofs. As long as residents can sell the power back to the grid, it will be viable.

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