[philipkglass]

He's using a household solar inverter designed to convert low voltage DC to AC at standard wall socket voltage. It's not the most efficient approach, as noted in other comments, but it's an easy approach since these inverters are common and a laptop's power supply is already set up to plug into a wall socket.

[forkfork]

Yep! Inefficient, but it is what I have, and there is no risk to frying my moderately expensive laptop which I hope to keep running for many years.