Why can't countries with vast deserts make solar farms to power the world?

Others summed these points up quite nicely, but:

The sand and remoteness makes installation and maintenance difficult.
Heat is hard on electronics.
At a huge enough scale, it would lower the albedo of the (normally very reflective) desert, heating up the local environment.
Transmission. This is the biggest factor. Transmitting tons of power a long way is tremendously difficult, dangerous, slow to build, expensive, and unavoidably inefficient.
On top of that, you'd want to buffer power (with batteries) or keep spare capacity (like gas generators) near the source to regulate the supply. This is less of an issue at smaller scales, where solar 'blends' into the grid.
Producing the things. It's easy to say 'just make more', but you'd need to massively scale up every section of production: the mining, the transportation of the ore, the transportation of the panels, the production of the machines to fabricate the things, educating people to make those machines, all in a frayed global supply chain.
Countries might feel uncomfortable being so dependent on each other for energy. Yes, the irony is tremendous.

It's not impossible. There are installations in the Atacama Desert (for instance), which is basically the best case scenario (ridiculously dry, high altitude), but you'd run into problems scaling it up to, say, power all of Brazil.

There are reasons power generation tends to be more localized. Adapting it to the local environment, a la carte, is kinda the way to go.

For point 3, I assumed solar doesn’t get as hot since it turns the light into electricity. Due to the conservation of energy and mass, it must reduce some of the heat by turning it into electricity, right?
Maybe solar is mostly tapping into the energy from the light, not heat? If LED lights are so much more efficient because they don’t generate heat, then that untapped heat must be a lot of potential energy we could use for the grid, right?
I have no idea what I’m talking about lol
- This is true to an extent, but the raw conversion efficiency is not that high:
  https://www.nrel.gov/pv/interactive-cell-efficiency
  At best, you're looking at 30% for the most expensive experimental cells, minus other efficiency losses like dust or transportation.
  ...In practice, deployed panels will be less efficient than that. And I think that number excludes radiation frequencies outside the panel's absorption range, yet hitting the panels anyway.
  What I'm getting at is the sheer 'darkness' of the panels blows out the effect of converting such a small fraction of that radiation to electricity. In aggregate, far more heat is absorbed by a field of panels than light sand.
  That's not catastrophic. It's not a contributor to global warming on the scale of greenhouse gasses or anything (and don't let Big Oil tell you otherwise), but it is a slight concern for the local environment, and possibly a cost factor.
- Solar panels use photons to create electricity, not converting infrared heat to energy. So the heating really isn’t a factor in the energy created. Sure, we could place a crapload of thermopile/TEG’s on a solar panel to soak up the heat and turn it into electricity, but they’re expensive and inefficient.

Some reasons to be discouraged making a solar farm in a desert:

Middle of nowhere, you need to transport all the hardware to the place
Maintanace, you need people on-site to support it
Desert sand is sandbladting your panels
(and this is the biggest one I think). You need to transport the power from where its generated to where is requested. Which is an imperfect proces, and every time you double the distance you also double the resistance

Also deserts are not even nearly lifeless. A solar farm of the size needed would wipe out a lot of habitat.
- Won't somebody think of the Fremen?!
400kv DC lines to the rescue!
Expensive though...
- Why just 400 kV?
  At least Ukraine has several 750 kV power lines. Decreases the energy loss quite a bit!
- Why DC? I've always been taught AC was better for long distances. What am I missing?
This is also why there is a lot of work being done on room-temperature (-ish at least) supervonductors.

power loss because of distance is the common factor being said. But there is active work on using the Australian outback to power 15% of Singapore and some of Indonesia https://en.wikipedia.org/wiki/Australia-Asia_Power_Link

More reasons: Sand and solar panels don't mix. Any build up on the panels has to be cleaned, and blown sand will etch the glass quikly and lower power output considerably. Additionally, you don't want to stop sand blowing around. Those air and dust currents are importand to the world. You can't have a rainforest in Brazil without sand blown in from the Sahara, for example.

You can't have a rainforest in Brazil without cutting it down either, but that doesn't seem to stop people

Solar panels don’t like sand. It’s coarse and rough and irritating and it gets everywhere.

Also the heat actually makes the panels less efficient. And a large solar farm in the desert also creates a massive heat island which negatively affects the local environment.

How do solar panels create a heat island? They shade the ground beneath them. There have been installations where panels installed on buildings saved money on cooling costs before the panels were even connected, due to the shading from the panels.
Am I missing something?
- They're black, duh. Yes, some 20% of incoming energy becomes electricity but the rest gets turned into heat. A reflective (white) material heats up way less.
- The only thing that makes sense is that they absorb heat that would otherwise be reflected away, right?
  in the building example, they're essentially insulated against a specific mass by air gap behind them, and in the heat island example, the area of concern is larger and the panels are included.
- Not sure how it works but the effect has been studied
  https://www.nature.com/articles/srep35070

Another reason no one else has mentioned yet is that countries want to have control over their own power generation. If you're power is all generated in another country then it can potentially be turned off by another country.

The exact problem with oil. No point in replacing it with an electric cartel.

Well ackshually ...

As others have mentioned pwoer transmission is a huge problem. You lose lots of power in the wires between here and there. So Australia has vast areas of desert, but if you put up an array of solar panels you can't really transfer the power to where it needs to be used.

However, there's a lot of investment presently in hydrogen tech. So instead of transferring power by wire, you use it to crack hydrogen out of sea water, and ship the hydrogen to where it needs to be used... in cars and houses.

There are problems in that hydrogen is difficult to store, but the industry is confident these problems can be solved or reduced. Hydrogen atoms are very small and will leak through most materials. It also makes containers brittle over time, so you need a strategy to manage that.

There's a number of water cracking facilities in progress in Australia right now. The WGEH is a gargantuan project, although presently just in the planning phase.

I'm sure a number of experts will be along in a moment to tell me all the reasons why this isn't really a thing that will happen. IDK why Hydrogen tech invokes so much derision. The story is that there's too many problems with Hydrogen and that these projects are just a way to delay proper action on climate change. We will see I guess.

Hydrogen takes energy to make, to move, to store, new infrastructure and from generation to use it is extremely inefficient.
Makes much more sense to just directly use that energy as electricity.
- Sure but, the critical question in this post is how to get solar energy from the desert to the market. You can't just string up power lines because too much is lost in transmission.
  In the immediate future, Japan is a target market for Australia's Hydrogen, and that's many thousands of kilometers from Australia's production facilities.
  Over this distance hydrogen is the least inefficient method of transport.

You can spend millions on building power lines over oceans and such. Or you could just spend that money on building your own power production. Might be more expensive (or not), but you get to control the production.

It's easy: Geopolitical bullshit

As others have said, the issue is transmission.

There are parts of the world where solar power is deployed to help with the power grid; the Southwest USA uses solar power a lot as peak solar generally aligns with peak electrical demand. However, there isn't the infrastructure to move west coast power to the east coast.

Power can only travel that far. Electricity gets lost during transport.
The sun shines everywhere.

So given these two things there is always a point where it is cheaper to build your own solar system than to get it from far away.

There are more renewable sources of power. Wind. Water. Heat.
The desert isn't an euphemism for empty. It's a climatological zone.
There is political power in having control over electricity/power needs. The wild swings in oil prices reflect this fact. Reliance and necessity makes it far more logical to maintain your own source of electricity/power.

Deserts aren’t barren. They have plants and animals that are already in a delicate state. Even foot prints can cause significant disruption.

You also need to transport the power to where it's needed, and transporting electricity over vast distances is a bit of a challenge that incurs inefficiencies such as power lost to heat.

More importantly though, if you install the solar panels in Spain, then pipe the electricity to Germany, where it's consumed in factories, then germany would effectively make itself dependent on Spain and every country between spain and germany (for the cables). That's a geopolitical risk, in case an international conflict ever breaks out again.

Slightly unrelated, but I used to imagine houses whose rooves were made of solar panels. I eventually thought of battery walls to store the extra power for when no sun, but that's a tad silly, innit? Can't build a house of battery walls. Prolly can't make it solar panel roofed either, other than perhaps covering the entire non-panel roof with panels. I wonder if such would work, and how expensive it'd be. In fact, I wonder how expensive solar panels are, and how difficult to work with they are.

I also had this idea for a phone case whose back was a solar panel. Leave your phone facing down, and get some sun charge (if sun). The case could have a plug near or instead of the hole for the charger. Not sure if such would work either.

I'd also enjoy having just a, idk, an extension, with many a sockets, just connected to a solar panel outside the window or something. Me computer just powered by the sun. Maybe roller shades made out of solar panels? Too sunny? Close the shades, get some charge. Again, not sure this would work. But it would be cool.

If anyone understands enough and has the knowledge needed, please rate my ideas and let me know why these obviously wouldn't work (surely, such great ideas have probably been already thought of and discarded. No way I could have a good, original idea)

prolly can't make it solar panel roofed either
Solar shingles are a thing now
- Holy based, Batman. It seems we've missed an opportunity to patent the idea. If only I had come up with it before 2005. Though I was but a wee feller

It's happening gradually, China now has something like 1TW of solar deployed, a lot of it in deserts. But, that translates to maybe 300GW of base load, because it's night half of the time (so no solar) and so on. And the other part is battery storage, which is also getting built fast. There is a lot of catching up to do though. And also, transmitting electricity over intercontinental distances isn't really a thing.

There are a few factors that stand in the way of this setup, but a milder version of this where we are generally trying to tie power grids together to transmit solar and wind power from places with favorable conditions to users is underway. I know for example of at least one large project where Singapore is installing large scale solar in Australia and building undersea cables for transmission (1). So we are going in this direction despite difficulty.

The main issues are:

Transmission is difficult and expensive. High voltage power lines especially undersea or very long ones are expensive things to construct, and still relatively uncommon and therefore specialized compared to regular grid infrastructure.
Oftentimes solar in the dessert is actually not that favorable in price especially if you factor in the transmission which is not 100% efficient. The site in the dessert might require security especially in places which are perceived as insecure or unstable and regular cleaning if the dessert is dusty. And solar obviously benefits from more sun hours and no cloud cover, but high temperature eats into that advantage somewhat, as solar cells are less efficient at high temperatures (2).
The management and bureaucratic overhead rises for larger projects and projects involving several countries which is an issue for both regular grid interconnection but also purpose specific generation and transmission involving 2 or more countries.