Comment by efields | Hacker News Reader

Comment by efields | Hacker News Reader

Specialty cut flower grower here. Backyard scale, but we're profitable and have received some grants so that means we have had a USDA relationship for a couple years. The rep I've talked to and am closest with is skeptical of agrivoltaics due to past dealings with solar companies (not sure what she means). There doesn't seem to be enough reliable public data to make it seem like the win-win-win we want it to be. In their mind, you're adding a non-ag industry to the land and that could have downstream consequences in a generation. Maybe you're scheming to get the land re-zoned for light industrial; I honestly have no idea what they're thinking, but they're averse toward it.

Most flowers in 7b don't want extreme sun. We use shade cloth frequently, so solar coverage would be fine and of course have the energy co-production. Cut flowers aren't harvested mechanically at our scale, so we wouldn't have to worry about tractor access.

Meanwhile, more and more food is produced under cover for a lot of good reasons. Polytunnels, glass houses. You might get some summer shade from solar but what about season extension at the beginning of spring/end of fall? Depending on your crop and location, that could mean 4-8 extra weeks a year. What if you do geothermal energy generation for the tunnel? Now you can grow through the winter and not need the same footprint as solar. That's more appealing to me.

Anyway, I'm forever mad at corn ethanol and we should at least replace all that with solar farms. That's probably the right place to start. But also, again, zoning...

Would also love to hear more about your project!

> Meanwhile, more and more food is produced under cover for a lot of good reasons.

(Disclaimer: I know nothing about farming)

I somewhat agree - dumping pesticides and fertilizer into the ground every year and then letting it pollute rivers is low-key insanity. But then you look at just how much farmland is out there and realize some crops just can't be put indoors, probably ever.

There are lots of variables for sure, but I do wonder how much more efficient indoor growing must get to overcome outdoor growing? Land value is vastly different between regions, so does labour, crop type, etc.

p.s. Tom Scotts recent video on strawberries was amazing - special mites to fend off other bugs and UVC light sanitizing was a bit of wow for me.

lol, you do know nothing about farming.

They aren’t talking about growing wheat indoors, and when they talk about tunnels it’s a bed crop in a field with plastic over it like you’d see over a box in the city.

Indoor growing has some cool stuff going for it, but you’re not going to grow row crops that we currently harvest headers wider than your greenhouse.

You’re also unlikely to put those under solar, if you’re going to do solar on that patch, it’s probably not worth farming a crop that produces 1000$ per acre under it when the solar is going to be producing way more than that.

If you sell corn you harvested right now you'll get $4.43/bu. Let's say $4.50 for ease of math.

My area averages about 175 bushels/acre for trash soil and closes in on 250/acre for prime River bottoms.

$1125 an acre without expenses is what you can expect in a GREAT year. But that's every year and it's insured against crop failure. The last years that we farmed, about 70% of our gross went to expenses. So figure about $450/acre in profit (mostly to pay for my house and food and what not).

Can electricity compete with that? I genuinely do not know.

> Can electricity compete with that? I genuinely do not know.

Here's the fun thing: if humanity were one united species instead of a bunch of tribes willing to fuck each other up every few decades, we might just go and grow crops where they grow the best, maybe with a bit of redundancy to guard against natural disasters and whatnot.

But unfortunately we are not, and so we have massive overproduction going on, which in turn means without insane amounts of subsidies (25% of the EU budget goes to farm subsidies!) farms could not survive.

If the subsidies were killed, even shit solar panels would yield more money than a lot of land could yield with growing crops.

Completely off topic but I'm fascinated with this. How much acreage do you devote to this?

I've done hobbyist exotic (legal!) mushroom farming for a while, at a scale that is more than I could use but not like 100x what I could use. I've thought about selling but it seems like a lot of hassle doing the marketing and business parts of it.

How do you sell? Do you have a distributor that purchases product from you or is it a farmers market type deal?

Very conservatively solar produces 30-50 times are much energy per acre as corn ethanol. I think if you consider just the ethanol to mix with gas vs charging an electric car with solar it's a 100 times more.

Something around 2500W of solar can provide enough energy to drive an EV 12,000 miles a year.

When it comes to zoning. The state should require offices to install chargers for employees cars when the solar share of electricity generation is highest.

I agree, but I always wonder: where do you store the energy from solar? Ethanol just goes into a boring tank. Electricity is expensive to store, especially at the scale we're talking. Carrying via cable all the way from the farms to the industrial centers is expensive aswell.

Ethanol goes into a boring tank, but to be useful that boring tank has to be pumped into a tanker and driven, using more fuel, to somewhere it can be distributed. That's way more energy-intensive than running a cable, so forget storage, just run the cable and let the grid operator take care of the storage at utility-scale.

The cost for the storage still exists and has to be paid by someone. And extending the power grid at this scale is a several decade long undertaking. These things don't pop up by sheer willpower.

> Electricity is expensive to store, especially at the scale we're talking.

An old XKCD what if: https://what-if.xkcd.com/128/

> What in my pocket actually contains more energy, my Zippo or my smartphone? What would be the best way of getting the energy from one to the other? And since I am already feeling like Bilbo in this one, is there anything else in my pocket that would have unexpected amounts of stored energy?

Which in part had:

> A container of butane the size of a phone battery could, in principle, power the phone about 13 times longer than the battery itself could. The obvious question, then, is "why doesn't my phone run on propane?"

...

Also http://www.jefflewis.net/blog/2012/01/how_much_gas_to_charge...

And while that's based on a study from Exon (no longer accessible)... but the math part is math no matter who does the math.

> So, the claim that there's enough energy in a gallon of gas to charge an iPhone every day for 20 years seems pretty reasonable (in reality, when you look at the efficiencies, you won't be able to put all that energy into charging the phone).

> An iPhone may not be huge, but 20 years is a pretty long time. It really just goes to show how much energy gasoline contains, and why it's so useful for powering vehicles.

"[lithium ion battery prices] declined by more than 99%. In 1991, lithium-ion batteries cost around $9,200 per kilowatt-hour — 33 years later, they cost just $78."

https://ourworldindata.org/battery-price-decline

The price of battery storage is dropping exponentially, just as the price of solar power has. Eventually, the price becomes pretty trivial.

The scale we're talking here is not just a shack with a couple of batteries. Even with low prices of today, we're talking several millions of investment for 10 MWh.

> The price of battery storage is dropping exponentially

We're at the flat end of things. Even if this trend continues, there won't be another 99% reduction coming.

> Eventually, the price becomes pretty trivial.

Only if you can scale manufacturing and materials the same way. Hopefully not with Lithium, because that's just not abundant enough.

> The scale we're talking here is not just a shack with a couple of batteries. Even with low prices of today, we're talking several millions of investment for 10 MWh.

1.78 million USD at current exchange rate. Before sales tax, but if you're buying at this scale, you claim that tax back anyway:

https://www.ladeengel.de/Batteriespeicher/Grossspeicher-ab-5...

> Only if you can scale manufacturing and materials the same way. Hopefully not with Lithium, because that's just not abundant enough.

1. Sodium is already cost-competitive with lithium, for batteries.

2. There's loads of lithium all over the place, the hard part of using it is that it's spread out everywhere rather than particularly concentrated. Like, we're talking 150 million tons of "reserves", 250 billion tons dissolved in the seawater, and plausibly 5 quadrillion tons in the bulk of the planet's rock.

Chinese companies are building salt batteries now.

Look at the graph in the article. The trend is clearly log-linear at the tail end in 2024, which is to say, still dropping exponentially. People said the same thing about solar for years, of course. Exponential decreases in cost are apparently hard for people to reason about. As others say in adjacent comments, there's lots of lithium around, and lots of promising work on salt based chemistries for mass storage. Plenty of room for progress.

I had never bothered to calculate the miles-per-year before. My very, very modest rooftop solar does in fact throw off 11,000 actual, real world miles per year for my actual PHEV - so very close to your number. That is a fun way to think about things. Alas, much of it actually goes to waste as the car that would be charged is at the office with me.

Reply on news.ycombinator.com