Harvest the sun twice: Agrivoltaics promises sustainable food, energy and water | Hacker News Reader

Harvest the sun twice: Agrivoltaics promises sustainable food, energy and water

sheffield.ac.uk

186 pointsgnabgib109 comments

Agriphotovoltaics is largely a solution for a non-existing problem.

It is always brought forward as an argument when the perceived landuse issue of solar is brought forward. But if you do any serious analysis, the landuse impact of even utility scale solar is so neglegible that it's not an issue to worry about.

If you want to talk about landuse impacts of renewable energy, there's really only one issue to focus on: bioenergy crops. It can be as bad as 30 times less space efficient than generating the same energy with solar photovoltaics.

Talk about using the same space to make food and bioenergy. Use agricultural land for food, and utilize the residuals as good as possible. Stop making biofuels out of food. And treat the space needed for utility-scale solar as what it is: tiny.

(P.S.: If people can make agriphotovoltaics work, I have no issue with that. Great. Even tiny impacts should be reduced if possible. But I have an issue with the way this is discussed, because it makes up a problem with photovoltaics that largely doesn't exist.)

I think this implementation and purpose is slightly different. The climate they are testing in is East Africa. One harvesting is the photovoltaics for energy. But the second harvesting is for food crops. The partial shade provided by the PV panels allows the plants to lose less water from evaporation and protect against overexposure to sun so that food crops like beans and corn can provide higher yield in a normally difficult climate zone. I agree harvesting the sun as PV + biofuels is a step down, but PV + food crops in a difficult climate zone is a step up.

Great points

Some (very rough) numbers to give scale here:

Corn in the US covered ~90 million acres in 2024. Something like 40% of that gets turned into ethanol IIRC.

Based on solar capacity figures around ~200GW, the surface area of the PV panels themselves (not the installation) are about 250-300k acres.

Both solar and bio-ethanol render an energy output on the order of 250-350TWh/year. Broadly similar levels of energy, but using a tiny fraction of the land area and chemicals and industrial pollution for the former.

https://afdc.energy.gov/data/10339

Don't throw biofuels out, there are plenty of fuels you can make from the parts of plants that we do not eat. Corn stover, walnut shells, bigasse, olive pits, etc. are all unused components that can be converted into fuel sources through gasification, anaerobic digestion, fermentation, etc. into usable fuel. Many times it's better than letting these leftovers rot in the fields and release methane into the atmosphere.

Honestly, I'd like to see some of the excess solar energy put into up converting such waste streams into storable fuels that can be used as denser alternatives to batteries when needed (winter heating, air travel, etc.).

Also, biofuels have >10x the energy per unit of mass compared compared to even the best batteries in the lab (and some sources put that at closer to 100x). There are a lot of use cases for biofuels (as a replacement to petroleum) that batteries can't come close to handling.

Converting the waste stream from agrivoltaics into biofuels appears to be the best option: reduced land for "energy" crops, increased output for food crops, and biofuel to replace petroleum.

Converting waste to fuel is great.

Meanwhile, I’m pretty excited about this project to make it cheap and easy to convert solar power to liquid fuel. Starting with carbon-neutral natural gas.

https://youtu.be/cRg1ZVwttNU?si=JWK5ZUdlNWooNYtt

I feel like hydrogen is the answer to fossil fuels, not biofuels. Battery electric vehicles (BEV) are great for personal vehicles. But for heavy transport, batteries just don’t work. They are too heavy and can’t be “refueled” quickly for continuous operations. We are already having issues with having too much solar power and not enough demand. We could be load shedding that by using it to create hydrogen.

We have gas stations everywhere because individuals need that kind of convenience to operate comfortably. BEVs have the same infrastructure in that every outlet is a charging station. While the barrier to entry for hydrogen is too high for personal vehicles, the logistic hub nature of heavy transport would be much easier to convert, using hydrogen storage/filling stations at strategic location to support hydrogen powered semi-trucks, local delivery trucks, busses, etc.

The most effective way to store hydrogen as a fuel is in hydrocarbons. Hydrogen gas, as itself, seems at first blush, to be great because it combusts into water, but it doesn't store as efficiently or safely as hydrocarbons. The wax candles on your table don't spontaneously combust when you touch them with a static charged finger.

The fact that plants already will produce hydrocarbons for us without much over sight only makes things easier.

Now that being said, our current natural gas infrastructure can accommodate something like 10% hydrogen gas, so it would be great if we could store extra solar electricity within our own pipelines by generating hydrogen gas, back feeding it into the lines, and then deplete it later, with a molecular sieve to pull out hydrogen gas alone, or burn it with the methane.

I understand what you are saying but I disagree. Yes, hydrogen is not as energy dense and has different safety issues, but I think it is overall still the better long term option. Biofuel is not scalable in the same way as green hydrogen. The more biofuel we produce, the more agricultural land it competes for that could be used for food, timber or even carbon capture vegetation. The more solar and wind we add to the gird, the more load shedding issues we will have and the more opportunity we have to convert that to hydrogen.

ICE engines running on biofuel are about as efficient as they are going to get, whereas hydrogen power is a fairly immature technology and has a lot of potential efficiency gains as the technology matures.

I think biofuel from waste products will still be useful for certain applications, for instance in medium and long haul aviation, where the energy density of hydrogen would pose a significant challenge. But biofuels are just not scalable to the levels required for global demand vs land requirements. Using biofuels just for aviation would require cultivating land the size of Texas, California, and Florida. [0][1][2] It is just not feasible to scale as a primary fuel in a fossil fueless future. Hydrogen can scale with electrical capacity, which can come from nuclear, solar, wind, geothermal, hydro, etc.

[0] back of the napkin math/conversions based on 2 and 3

[1] https://its.ucdavis.edu/blog-post/making-policy-in-the-absen...

[2] https://www.theglobaleconomy.com/USA/jet_fuel_consumption/

I'm not talking about growing plants directly for the production of biofuels, that is a silly proposition when there are mountains of unused organic waste being produced annually by nature and by agriculture. Utilizing the organic "waste streams" that already exist to produce fuel is quite sufficient for our storage needs. Agricultural waste, poop, dead trees and branches, dry grass or other "wildfire fuels" to produce methane, hydrogen and oil through gasification , fermentation and anaerobic digestion is simply low hanging fruit that is available to us right now. I've worked in this field, doing gasification, so I'm quite aware of what is possible.

Would you rather we burn grass and dead standing wood in natural environments to curtail wildfires, or would you rather it was used to make clean energy that is carbon negative? Yes carbon negative. You put carbon back into the ground through the use of biochar, where it is stable for thousands of years, and actually improves the soil.

Anaerobic digestion of all of your household waste (including feces) is also possible for production of all of your stove and heating gas.

Internal combustion engines aren't at their end of technology cycle. You should probably look into supercritical CO2 closed loop turbines if you think that we aren't still innovating. Regardless, by using an internal combustion engines, or an external combustion engine (Stirling engine, or modern steam engine) instead of a furnace, one can produce heat and power all in one unit from within your house or district (depending on how you want to scale things).

I love solar, I really do, as well as batteries. But you need to use everything at your disposal if you want to get away from petroleum.

And the best way to get from hydrogen to hydrocarbons might very well be processes that merge H2 (from electrolysis) with low value biofuels (usually hydrocarbons with a low amount of hydrogen I think?) into higher density synthetic fuels. That way you can use the waste parts of food plants, not so much for their (low) energy content but for their convenient access to carbon for "repackaging" H2.

Yes, like hydrolyzing vegetable oil, you can pack more hydrogen onto a carbon chain. You can also use the Fischer–Tropsch process to make longer chains out of smaller molecules like carbon monoxide and hydrogen.

Correct arguments all around re: utility scale solar, but the incentives for an individual farmer to immediately adopt are huge: local generation makes power cheap, shading makes water use more efficient, etc. Obviously there is a capital cost for the system and costs for maintenance, etc., but given the trend of increasing global energy costs and the resulting burden on households (https://www.nature.com/articles/s41560-023-01209-8), it seems like a very nice idea.

The article's arguments don't revolve around landuse, and in fact the article doesn't discuss landuse at all.

In rural parts of Colorado, I have seen large signs on farm building protesting the use of agriculture land for solar.

Who complains about the land use of solar?

Obviously not a bottleneck? There's millions of desert acres.

The main advantage that I see in agrivoltaics is for the purpose of density. If you can get both power and food production in a more dense footprint, located closer to a population center, then that will be much more efficient for purposes of transportation. Both electricity transmission and food transportation get worse across larger distances.

Power transmission is really efficient, HVDC is around 3% per 1000km, AC is around 6%. It is more efficient to put solar panels in sunny areas and transmit across country than have less efficient local ones. Oregon where I live is bad for solar with lots of rain, it is better to put panels in California desert and bring up here.

Food is similar where transportation doesn't matter much. Staple foods can be shipped by train, barge, and ship which reduces the cost. Some places are better at growing food. The canonical example is that New Zealand is so much better in growing sheep that more efficient to ship lamb by air. Growing local only makes sense for vegetables that need to be fresh or don't transport well.

My brothers farm had an offer by a similar startup with different dimensions but basically the same idea.

Had problems though. First was moving parts. You can not expect a system to last outside with any in them. Budget for the whole affair is tight, large repairs undo the whole endeavour .

Second is crops riping at different speeds below.

Finally practicality of the frame for farming machines . Meaning the dimensions need to adapt to pre-existing machines. And ideally remain upright even if one post gets hit.

Finally honesty regarding erosion ..corn is one of the more erosion prone crops and then having water dumped on specific areas concentrated creates channels fast. So the idea does not work with no crops or erosion crops in rainy areas. There is a reason there is grass below most solar fields.

One good aspect they didn't push is that this is ideal for electro farming. We have hyper effective electric moisture traps now and electro nitrogen fixing- combine that and this can remove one need for driving trucks through.

In all other aspects i see this limited to orchards.

> In all other aspects i see this limited to orchards.

This study is for a very specific region: East Africa (Kenia and Tanzania). Their main problems are too much evaporation, no energy sources, no other sources of food.

I don't see how a solution that might work for a good share of humanity (Africa is huge: Kenya and Tanzania alone have 150 million people) gets dismissed as "limited to orchards" because it can't be used for industrial scale corn crops in my country.

Well, unfortunately "Africa" is only mentioned in the article's title (which got cut to fit into HN's character limit) and not repeated in the article itself.

But I can understand the concern: most agriculture (not only corn) is highly mechanized pretty much everywhere in the world except the poorest countries, so this would be limited to the crops that can't be mechanized.

Or this can be adapted to mechanized crops where it makes sense. Greenhouses where small fragile minihouses of 4x3 meters, made of wood and glass 100 years ago, used only in countries with harsh winters. Nobody in their right mind would use a tractor to work on them. Today they can be seen from the space and are mechanized... where it makes sense to do it. They turned a desert into a huge production of fresh vegetables: https://www.amusingplanet.com/2013/08/the-greenhouses-of-alm... .

Agrivoltaics could be something or nothing. But don't dismiss it because it today isn't already perfect for everything. Ten years ago the cost of the panels alone would make this projects 100% infeasible.

Those plastic-foil greenhouses spreading like cancer across the landscape in Spain should be shown (especially up close, where you can better see the dirty tattered foil and the waste they produce) to people who think solar panels or wind turbines are eyesores. I would definitely support replacing those cheapo greenhouses with something more permanent involving solar panels!

I wouldn't sum up the challenges if i would be completely dismissive , i think the potential is there, especially when it comes to in situ fertilizer nitrogenfixing and electro moisture harvesting (the breakthroughs there are insane, from peltier 50ml to condensator 500 ml recently). This is not a attack on the idea, just a lets strengthen this to solve alot of problems .

Vertical bifacial agrivoltaics system are a promising setup that addresses some of your concerns. Most importantly, tractors can easily pass through them.

Another good setup is to combine it while grazing sheep.

A problem with sheep is that they aren’t worth anything. Here is New Zealand we have replaced nearly all of them with cows. Much improved profits but destruction of the waterways. We call that a win.

Hot take: compress them all cheek to cheek in a warehouse, feed them corn and capture the methane they produce. Cover the roof in solar.

Call that an even bigger win...

Good point. I'm not really interested in farming animals, I really don't know enough about it. In the Netherlands we still slaughter little under a million of them per year, on a populations of circa 17 million that should still mean they are worth something.

But maybe grazing isn't worth anything at all and its only cost-effective if you put them in a big box and feed them grains or something. I don't know.

Or hayfields.

Here in the US, a field of hay might gross $500/acre/year. A PV field selling power at $0.02/kWh would gross 50x that. You'd optimize such a setup for PV, not for combined PV + hay.

Aye, the question I answered wasn't focused on optimal layout, but potentially compatible crops.

Definitely doesn't seem appropriate for cash crops harvested by combine harvester.

Most orchards and vineyards in temperate climates are attempting to maximize solar exposure, so would compete for space with the panels -- and also have their own trellising systems and so I struggle to see a fit there, too.

But I can definitely see the use cases for two places.

Grazing land for some ruminants, especially in hot dry climates. Provide shelter for animals, and shade for grasses.

Vegetables, market garden or even large scale. (e.g. my neighbour grows something like 20 acres of cauliflower and it's all planted and picked by hand.) Many market gardens are using walk-behind / two-wheel tractors (BCS, etc.) which are far more agile and could easily handle moving around panels.

Spill-off / erosion can be dealt with through building swales.

that's ok. Not every solution must work for all situations.

the point here is that agrivoltaics tends to work well, especially in certain conditions. In central Africa, those conditions are reducing evaporation and providing shade to certain plants.

In north america, those conditions are often sheep grazing, as is common in New York and Ontario.

Aside: There seems to be an uptick in sheep rearing in my area (southern Ontario, near Hamilton) all the sudden. In the last year, I've seen 3 farms local to me put up fencing to start grazing them. Which is interesting because it's actually very difficult to find Ontario lamb in the butcher shop, and it's not a very popular meat overall, so I'm wondering where the source of the demand is. The majority of the lamb in the local grocery stores is either frozen prepacked from New Zealand, or from Sun Gold foods in Alberta. But I find local lamb from this area tastes much better (less gamey), must be something about the grass vs whatever forage they're giving them in Alberta.

My two border collies would love it if I raised sheep. But my quasi-vegetarian wife could never tolerate raising them for meat.. and dairy and wool make no $$ sense.

My guess - immigrants are the source of demand. South Asian and Middle Eastern immigrants eat lots of lamb. I live in the area and buy my lamb from a local farm. You’re correct, it is not the most popular commercial meat.

Yeah that's my assumption to.

The little Halal butcher around the corner from my office in Oakville consistently stocks fresh lamb. Doesn't see if it's Canadian or not though.

Many years ago we used to buy, once a year, a whole butchered lamb raised on a friend's farm down in Niagara.

actually , the orchards need constant sun is a myth too. There is a very sharp cut going towards too much sun, starting near sicily and travelling north.

https://citrusindustry.net/2022/07/05/protecting-citrus-tree...

> One good aspect they didn't push is that this is ideal for electro farming. We have hyper effective electric moisture traps now and electro nitrogen fixing- combine that and this can remove one need for driving trucks through.

Could you tell us more about this? I remember seeing a user comment a few years ago discussing the prospect of dumping excess electricity into nitrogen production but I had assumed it wasn't feasible. Does this technology really exist?

https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/ad...

There is one experiment in kenia

https://www.youtube.com/watch?v=G2brxBRnRH4

high voltage moisture trap

> Finally practicality of the frame for farming machines . Meaning the dimensions need to adapt to pre-existing machines. And ideally remain upright even if one post gets hit.

I believe that the end-game for agrivoltaics must be a reversal of that relationship: not the panel scaffolding adapting to farming machinery, but farming machinery and panel scaffolding becoming one, the scaffolding doubling as rails for overhead machinery. The status quo in farming is that a lot of fertile ground is wasted on machinery tracks. Machinery is either narrow-wheeled and ruining the soil in the track through compression, or the wheels are very wide (for weight distribution) to cause less harm per square inch, but harming proportionally more.

When you have scaffolding, scaffolding that is strong enough to survive a storm or two, it will also be strong enough to carry machinery. Not the machinery you'd attach to a 600 HP tractor, but the entire incentive situation for machinery size is based on the amount of harvest lost to machinery tracks and that would be completely solved through scaffolding-based machinery. And the issue of machinery tracks (and ground compaction) only gets worse when you start considering decarbonization: batteries are heavy, and a grid connect right above your field would be just what you'd not even dare dreaming of.

I really don't get the hype around Agrivoltaics at all. It all kind of pivots of the idea that land for Photovoltaics is scarce. Maybe it is in the UK but in the vast majority of the world this is a non sequitur.

Cover the crop in shade cloth, and mount the panels on the ground / roof structures nearby. No need to over complicate things.

Do you have your own personal garden?

I'm excited about it because its a combination of many things I truly enjoy doing and get a lot of pleasure from - harvesting energy, growing food, seeing life in equilibrium.

The integrated growth-stands with full-spectrum solar -> plant -> fish -> soil process is really, really appealing. Healthier food, energy harvested in neat ways. If I can get carrots and radishes and salads from the same device that charges my cell phone in the next year or so, I'll be a happier human for sure.

> Do you have your own personal garden?

Yes, every season I grow ~20kg of vegetables on a 15m^2 balcony (tomatoes, cucumbers, peppers, celery, various herbs). They are grown vertically on a trellis system, using 11 liter hydroponic "bato" buckets and recycled/reused perlite (sterilized). Nothing fancy.

The main energy input is the chemical fertilizer. Electricity to run pumps/valves etc is very minimal and probably amounts to 5-6 KWh over the season. I use synthetic fertilizers but avoid insecticides/fungicides, instead opting to use biocontrols (shout out to Koppert! https://www.youtube.com/watch?v=AFPkAQUfYvo).

The future of agriculture (excluding cereal crops, which I dream might be replaced by synthetic starches one day) probably looks something similar to: https://www.youtube.com/watch?v=a_pR_HihCVo

Now this is solarpunk.

> Maybe it is in the UK but in the vast majority of the world this is a non sequitur.

Land near energy demand is scarce almost everywhere. This kind of local generation is ideal and both reduces transmission losses and makes the grid/society more resilient.

Rooftop photovoltaic can (and will) cover local needs. Bigger issue is local energy storage (eg. community batteries).

This is absurd. There's no limit to energy needs - they only grow.

Sure there are reasonable limits. Where, is another matter. For example, I can not imagine a reasonable use-case for 1MW power-line per single apartment.

I was required to wire each unit with 150kW panel. The original 1931 service was 240 x 200 Amps which I upgraded to 240 x 800 Amps in 2018.

I posted the best image I could of the original 1931 schematic which has 9 circuits for 5,000 sqft school.

It's the first image in this slide show.

https://www.icloud.com/sharedalbum/#B2dGIcgc2GugpW3

Interesting. That is like 52 sqm per unit, which is 2.9 kW/sqm — three times higher power density than the solar irradiance on earth surface. If this is used at full power, how are the rooms cooled? (most energy gets converted to heat in typical use-cases)

I’m not completely following your comment but in 1954 they added a 7,000 sqft addition. We are using mini-splits for HVAC.

Almost 100% of the electricity you use indoors will be converted to heat (with few exceptions like charging batteries) that needs to be removed from the room to be able to live there. 150kW is a lot of power.

I get that. The apartments are small studios created by placing an 11' utility wall that is the kitchen on one side and the bathroom on the other. The kitchen side has 13 129 Volt outlets plus 2 220 volt oven and dryer.

I purposely had all those outlets installed as joke to the 150 amps out.

I'm not sure that holds true in a local sense. I have an all electric 8 unit apartment building. I have been tracking the electric usage and it is currently growing but only because of the addition of 2 EVs. I believe the the usage of actual electricity for the building to level off after EVs become the norm. I expect my electric usage to drop after adding a solar thermal collector to replace a portion of the electricity used for heating.

> I expect my electric usage to drop after adding a solar thermal collector to replace a portion of the electricity used for heating.

Well, that's just harvesting more solar energy, not reducing your energy needs.

True. Although it is self-sustaining and doesn't require outside production. I also distinguished between electric usage and thermal collection to satisfy overall energy needs.

I guess I'm trying to point out that on an individual level power usage may have a maximum. This might not hold true for commercial ambitions.

I just don't agree. The energy we use today would be seen as absurd even 100 years ago, as will our energy use in the future.

I see the difference between the USA's electric usage today and 100 years ago is that barely anyone had electricity 100 years ago and our standard of living has increased dramatically today.

I expect a bump in our usage in the short term due to EV usage but from a household perspective I believe our electric usage will flat line. Heating and cooling are currently the highest usage of power in the domestic setting and large efficiency gains and alternative sources are available.

I look at the power usage as a distributed problem and increasing local generation of power will create efficiencies. I also believe that there is finite amount of power that a USA based family of 4 needs. I think the alternate opinions assumes that the power needs are infinite.

There's nothing absurd about local generation being able to fulfill/contribute to a large portion of the energy needs of a local residential area.

People with residential solar do it all the time with payoff in less than 10 years.

The energy needs of a local residential area will just increase in response to the economically available power, but that's irrelevant as we're talking about agrivoltaics and farms use enormous amounts of energy.

Energy use in the developed world is actually going down. Electricity use is expected to go up in the next decades.

In some parts, due to cost of supply and taxation. Demand for energy is higher than ever.

Do you mean your own personal energy usage? Or your family? City? Country? The world?

This is electricity use in the US from 1975 to 2023. Between 2010 to 2023 it has not changed a lot.

https://www.statista.com/statistics/201794/us-electricity-co...

This of course doesn't include things like gasoline or natural gas.

My personal energy use has decreased over the last 25 years. Increased insulation and new more efficient HVAC equipment has dropped by summer electric bill by 40%. My old car used to get 26 mpg on the highway and now I get 36. Work from home has dropped my gasoline usage even more. My computer would run 24 hours a day and idle at 180W and now it is 90W.

> Do you mean your own personal energy usage? Or your family? City? Country? The world?

All of the above.

> This is electricity use in the US from 1975 to 2023. Between 2010 to 2023 it has not changed a lot.

Due to the cost of energy ballooning, largely due to taxation. However, the pent up demand is higher than ever.

Land near energy demand is not scarce almost anywhere. Where "near" means "Within 1000km". And it doesn't need to be near. Transmission lines are cheap and highly efficient infrastructure if you have a sensible process of land tenure (whether via routinized/generous eminent domain, Harberger Taxation, or other means).

Moving electricity is among the cheapest, most efficient industrial processes that exist.

*With all due respect to the Maldives, Gaza, Hong Kong, et cetera

And don't be sleeping on the potential of UHVDC transmission.

This is like the potential of High-Speed Rail.

It isn't a theoretical, it's something China is 30+ completed projects deep on. The technology existed decades ago. We just treat infrastructure like it's an impossibility here.

https://en.wikipedia.org/wiki/Ultra-high-voltage_electricity...

What you and the GP are discussing are fundamentally different solutions to agrivoltaics. One is inherently decentralised (not only decentralised power generation, but also local nitrogen fixing and reduced water demand) and the other is Just A Better Grid™. Just A Better Grid™ is inherently valuable, but it's not a substitute nor is it in competetion with agrivoltaics.

Was in Northern China recently,

Got to say the shiny and non-rusted transmission pylons in Hebei got me more excited than was probably warranted. I don't think I've seen a shiny pylon before, I guess we mostly just stopped building them decades ago.

On the topic of agriculture I was very impressed by all the polytunnels we spotted from the high speed rail heading north out of Beijing. Every valley, and nook and cranny was full of them.

Took a couple photos of a small town in inner Mongolia that we passed, was amazing seeing green crops in the middle of a Siberian winter.

I believe this was a farm using recycled water to grow cut flowers https://imgur.com/a/kw1IDZ3

I think those might be a specific kind of greenhouse rather than a standard polytunnel. The back wall is essentially a solar heat store.

Here's an article on them:

Chinese-style Solar Greenhouses

https://ag.purdue.edu/department/btny/ppdl/potw-dept-folder/...

Yeah, this highly optimized passive solar design is one of those things that seems very obvious when energy is too expensive to waste on international transportation or excessive heating in a cold climate. Citrus production in 40 below zero.

By pursuing artificially inexpensive energy we are doubling down on a great number of wasteful practices that are largely avoidable.

Thank you! That's exactly what they are. Even "higher" tech than I first anticipated.

To realise the benefits of local generation, near means on the order of 1,000m, not km.

What benefits?

Decentralisation and low capital cost, the points made in the article.

Real estate cost (the opportunity cost of human occupancy) is capital cost. So is the material and labor for any of the more elaborate frame systems required to work on a non-flat surface.

Only about half of Africa has any home access to electricity, and very few have access to the sort of high current associated with HVAC or EVs. Much of the population are going to leapfrog over the phase of full expansive grid construction, access & maintenance, and go directly to a somewhat more decentralized mode of operation.

But that experience isn't all that relevant to the developed world, whose countries have invested tens of thousands of dollars per person in establishing almost universal electrical grids.

I think you should read the thread you are replying to again.

This depends too much on the specific grid topology to be generally true. For example, there is an underground transmission line that is one of the bottlenecks for about 30,000 people in my part of Pittsburgh. It's not too uncommon to have summertime glitches or outages due to overload on that one circuit. Any generation installed on the consumer side of that line helps - and that's several km.

There's a planned solar project on an old partially reclaimed slag heap that will add generation proximal to that line, for example. (It's land that is too polluted for just about any other use, which is a fantastic place to stick some utility scale solar while still staying within the boundary of the city.)

At least in Europe, building transmission lines is a much longer process than building solar. Partially because of the complexity of acquiring land from a large number of owners, but more importantly because of NIMBYs that do everything to oppose new transmission lines that might disrupt the landscape. And some of the NIMBYs own the land you need to build the transmission line. Building a 1000km high capacity transmission line is a multi-decade project in this part of the world

Roofs near energy demand is plentiful almost everywhere.

I am lazy, I like to start with the low hanging fruit first.

> I am lazy, I like to start with the low hanging fruit first.

Then you should be looking at agrivoltaics before rooftop, as they are much cheaper in developed countries where the cost of rooftop solar is dominated by installation cost.

Yes you could easily combine solar panels and poly-tunnels for example. We have the potential over the next few years to make everything work so well but instead the US seems to be cutting cyber funding.

I've read an article with vertical bifacial panels between long hemispherical greenhouses to catch reflections.

Photovoltaic "fences" are one of those bizarre ideas that might actually make sense.

Just read an article about one of these in the local newspaper.

They currently have some challenges with bureaucracy, at least in Austria:

Given that it is an industrial facility it has to be secured from unauthorized access, but as it is a field, it has to be accessable to small animals. So now it is fenced with barbed wire on the top but it's open at the bottom.

Not the case in Germany. Photovoltaic installations on agricultural plots are routine, in certain cases (I.e. the plot is next to a motorway) you don’t even need a planning/building permit, as long as the installation conforms to established building practices. Agrivoltaics is still a niche practice, but not because of bureaucratic concerns.

so called agrivoltaics will have certain very limited applications, and putting pv panels on the many very large agricultural buildings roofs, is much easier to integrate. A big risk with "agrivoltaics" is that they will in fact destroy the agricultural potential of land and then become the only source of income for the "farmers" , therby converting protected agricultural land, into purely industrial uses. Putting solar pv over canals is a better option, it reduces evaporation, while providing a cooler operating enviroment for the panels, in places that have no real constraints with developing them further.Also resevoirs can benifit/help in the same way with floating solar pv.

> putting pv panels on the many very large agricultural buildings roofs, is much easier to integrate

for industrial farming yes. This study is aimed at subsistence farmers in africa. ones that don't have much mechanisation.

> will in fact destroy the agricultural potential of land

Given that this study highlights the water conservation features of agrivoltaics, I'd say it has a greater chance of stopping salinisation of agricultural land from over irrigation.

> Also resevoirs can benifit/help in the same way with floating solar pv.

again, this is aimed at african farmers with limited infrastructure. this would be the stepping stone to getting cheap electricity

something similar came out a couple of years ago for growing lemons in the south of italy with solar panels providing shades from an ever increasing temperatures https://www.bbc.com/future/article/20230424-how-agrivoltaics...

If this is target at developing nations, theft of the solar panels will be a major hindrance.

This is a pretty dumb idea. This article is from researchers at a University. Has anyone done this for real without a grant subsidy?

I understand the interest in maximizing space utilization, but this just doesn’t make any sense.

Some replies indicate field setups for solar should take priority and tractor/equipment systems should adapt to these new systems.

Crazy stuff.

There's a simpler way: you may burn oats and generate heat/power without relying on problematic solar panels. It's already quite common.

Sorry, how is this better? The whole path of [grow oats -> maintain steam power plant -> ship and burn oats] seems much harder to me than using solar cells?

No, EROEI for this is just bad if not negative. Also you do not produce any food.

What's problematic about solar panels?

There's a reasonable amount of waste biomass generated by farms that can be used in various ways without growing it specifically for that use.

People just like using "problematic" as a content-free slur that's acceptable in "progressive" circles that bypasses critical thinking.

Mainly recycling.

Even if you couldn't recycle them, they'd be a much better solution than what they replace.

The fact that you can recycle them just makes them even better.

And the problem with that? Seems we can reasonably easily recycle the vast majority of solar panels, no differently to any other electronic good.

Comparing the landuse efficiency of corn-based biomass vs PV is about 60-75x.

It just doesn't make any sense at all to use crops for energy production.

The only case where it might be viable is burning crop waste; stems of grain and maize, for example. The UK runs Drax on (imported! in oil burning ships!) sawmill waste, but that's greenwashing to me.

It definitely is. Besides that, Drax doesn't only run on waste products (that's what they'd like to make us believe), they mostly run on freshly logged timber.

Most of it, imported from the US: https://www.biofuelwatch.org.uk/wp-content/uploads/Drax-brie...

And even if it only was waste that's burned, it's IMHO incredibly stupid. We should be happy about every single gram of CO2 that's stored somewhere and use this "waste" for building insulation, paper production, soil revitalization or simply bury it.

Burning simply shouldn't happen when we have way better, cheaper, more efficient, more environmentally friendly methods of producing heat and electricity.

In a post-fossil fuel age, that crop waste will be used as a carbonaceous feedstock for things like jet fuel and what are now petrochemicals. Burning it for power will be uneconomical.

Unless you start considering carbon capture: if some direct carbon capture folly exists and you replace that folly with capturing the output of some crops-to-energy setup, then that would surely be a massive improvement over the carbon capture it replaced.

Growing crops for fuel is so absolutely ridiculously inefficient it's amazing anyone does it at all (It's usually not even energy-positive: the only way it makes sense is if you want to make sure you have excess food production and have something you can do with the waste).

Oats don't like hot dry areas, such as kenya in summer/dry season.

plus, burning oats is really fucking expensive, the chaff is a reasonable feed, and the straw is good bedding/binder for building stuff.

Burning for power is really a poor use, especially as it needs compressing into bricks first. Plus you only get a tiny bit of energy once a year, compared to ~1kwhr per panel per day. (depends on panel size and positioning etc etc )

What does “problematic” even mean here?

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