Alternative sources of electric power have not been the quick solution many people once hoped they would be.
Wind power has proved to be both disappointing and divisive. Tidal has not met the technical challenges. Nuclear power faces popular opposition in some countries.
Even solar, long the most promising type of "green" energy, has stumbled; specialist companies in the West, unable to move fast enough despite fat government subsidies, have been put out of business by cheap panels from China. Installation rates have been slow.
But it is important to keep a sense of perspective. From railroads to computers, new technologies have always needed decades to develop, expand, prove themselves, become efficient and spread their wings. So it is with new energy sources. And this week brings news of another step forward for solar power, one that promises dramatic implications.
What if solar panels could abandon heavy, costly glass and be made of plastic foil, thinner than spider silk and flexible enough to be bent around a human hair? That is just what researchers from Austria and Japan unveiled this week, in the online journal Nature Communications.
Flexible and almost weightless, this material could be used - within five years, the researchers hope - in many applications for which normal solar panels are hopeless. Progress is coming, one step at a time.