The thunderstorm generator is a demonstration of transmutation of elements, in the process turning the exhaust of gas engines to breathable air, removing CO2 and other pollutants. There is a 20 minute fun introduction and update done by Funny Olde World – with some speculation you may or not believe. A more technical explanation (40 mins) has been done by Jordan Collins on his Alchemical Science Youtube channel.
And if you want to get more deeply into the science of low energy nuclear reactions (LNER) try this conference presentation by Bob Greenyer of the Martin Fleischmann Memorial Project.