Remember to keep control of the death-ray in the hands of people who will not point it at their enemies.
Or their friends.
Or threaten to do so.
Or their friends.
Or threaten to do so.
That's probably unfair. I assume they'll be spread across deserts and other places with low population density.
I thought maybe attenuation in the atmosphere would be a problematic amount of heat, but it turns out the Earth gets roughly 200,000 TW of solar irradiance so 100 GW would have a negligible (immediate) effect even if fully absorbed.