Solar energy is great! And its going to be the future energy, you can't live without sustainable energy, there's no way around.

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How they work:

Solar panels need sunlight in order to do their actual job. The photovoltaik cells (PV) take the sunlight and transforms them to direct current (DC). Now there are inverter which transform direct current electricity (DC) to (AC) alternating current. Now you can use it to power whatever you have connected to the panel.

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If we go with a demand of 400Kw per square meters we get a total of 496805 square kilometers. This 496,805 square kilometers is equal to the size of spain.

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This Picture describes it perfectly!

(though I'd add a few km) )

South of Italy, there is a large area with lots of lots and lots of space untouched, warmed extremely and almost 24/7.
This area will definitely be enough to serve us energy and its not that big to be honest!
In the upper corner you can see spain but as I said I'd extend the 'world' red box a little bit like this:

Then why don't we do it?!

1 . costs: This is not a cheap millions of dollars investment and to be honest looking at most billionaires right now it looks like they won't pay for it because of risks, greedyness, something.

1. Maintenance : This is a big problem. If you have a ton..... A TON of solar panels just laying around in the burning hot dessert, you must keep them repaired and clean all the time though I'm sure we could solve this by putting them a little bit higher from the ground and dust protection would help aswell.
2. time and efficiency:
   It will take a ton of (workers) time to mount them all in place but aside that the efficiency rate is a trouble aswell.. Even monocrystalline panel aren't able to get as high as the new discovered solar panels with an efficiency rate of 30%!. So imagine mounting monocrystalline panels and realizing that we're about to archive 50% efficiency rate. Yea it wouldn't look great for your company (;.