Bonjour Jim,
To my opinion, a wood or coal-fired boiler is a "must", unfortunately, it is quite difficult to manage in a RC model boat.
I like indeed this little plant, thanks for sharing it with us.
Raphael, I'm going to have to get some of those BBQ briquettes to try out by smashing them into smaller pieces soon as I can't get any coal (even though Australia has one of the world's largest coal reserves).