So, doing some math.....
It would take (in an ideal world) roughly 3.7 million square feet to generate 500W. Or, 85 Acres. That's assuming that everything is absolutely perfect.
The best current technology is somewhere around 25% efficient, so multiply that by 4. (340 acres). And, figure that you only get peak sun, for about 6 hours a day, so multiply that number by 4 again (1360 acres). And, you need to figure out a way to retain all of that power, to keep the 500MW flowing when the sun goes down. And, that doesn't figure in any losses to deliver all that power to somewhere it can be used.
And, the best technology is hideously expensive right now - I could buy that prices will come down eventually. But that still doesn't take into account what happens when this hypothetical Solar farm, gets hit by a hypothetical hailstorm. :-)
Or, more practically, would you want to be the guy who has to clean the dust and birdpoop off of 1300-odd acres of Solar Collectors? They've got to stay clean, or else they're not a peak efficiency......
Solar - on a large scale - just ain't the answer. I've no idea why people keep sinking billions into a self-limiting technology, when they could be looking at other, "out-of-the-box" ideas. Heck, just revamping the delivery structure (power lines) could be done comparatively cheaply, with mostly off the shelf tech, and would improve efficiency dramatically.
Because they are scientifically and mathematically illiterate.
You said 500W in the very first part of your message. I was asking about 500 Megawatt plant.
I would really like to nail this number down. I appreciate the mental calculations you did.