With this in mind, the clean energy conversation should center on practical improvements to materials and engineering.

FORBES: Solar-Powered Cars? Clean Energy Hype Needs a Sober Dose Of Reality

The result is that despite the strength of the materials, the process is too expensive to be practical.

FORBES: Caltech Researchers Develop Cheap Process for Metallic Glass

One of the ways that Chapman added lightness to his cars, the use of composite materials such as carbon fibre and glass-reinforced plastic, is not that practical either.

ECONOMIST: Tech.view: Unbearable lightness? | The