I'm still confused. The XKCD cartoon shows a single source - the Moon, Sun, etc. But what they are doing here has 149 sources of energy. So if you had a binary sun (hypothetically identical suns) with two lenses, each focusing on a single spot - wouldn't that be 2x the temp? Isn't that a better example of what they are doing? And if you get things hot enough, could you start fusion which would then release vast amounts energy?