These things will never reach economic viability until the governments of the world stop wasting taxpayers' money on boondoggles and let private enterprise figure it out; when private enterprise has its own skin in the game (rather than having the taxpayers' skin in the game courtesy of a government), it usually figures things out: either (a) that there is no way the subject-matter will be economically viable, or (b) how to make it economically viable. When governments run auto companies, you get the Trabant; when private business runs auto companies, you get things like the Prius (in addition to all of the much more useful products the private auto industry puts out).