They run on pure solar for generating all their electricity for just a little over an hour, and, as the video explains, their solar power policy hasn't gone without some significant teething problems, but those teething problems are all technologically resolvable with ever improving technology thus obviously will be ironed out eventually and this is still impressive news;
Looks like they really need to start thinking of large-scale off-the-grid energy storage if they are to do much better.