To be fair, the authors did make use of parabolic solar collectors to funnel the sun’s energy into their autoclaves more efficiently. I don’t mean to give the impression that you could just sit a can of nanoparticle-containing water in a field somewhere and turn it into an autoclave. Still, once you buy or construct your equipment, you have no more material or energy costs. That should be an enormous help in many poor communities.
Oara Neumanna, Curtis Feronti, Albert D. Neumann, Anjie Dong, Kevin Schell, Benjamin Lu, Eric Kim, Mary Quinn, Shea Thompson, Nathaniel Grady, Peter Nordlander, Maria Oden, & Naomi J. Halas (2013). Compact solar autoclave based on steam generation using broadband light-harvesting nanoparticles Proceedings of the National Academy of Sciences of the United States of America DOI: 10.1073/pnas.1310131110.