There are certain technology challenges which have waited in vain over several decades for a satisfactory solution. The economical storage of electricity is one of them. But intensive work in the meantime is driving advances along various avenues.

The first Formula 1 cars to be fitted with a controversial energy recovery system are due to race in this season's opening Grand Prix in Melbourne, Australia, on Sunday. But questions over the safety of the system remain unresolved in the run-up to the race.

Power lines stretching across continents would allow us to ditch fossil fuels for good

Algae are quickly becoming the most attractive successor to traditional biofuels feedstocks like corn and soybeans, and even to next-generation feedstocks such as switchgrass and jatropha, Although algal biofuels are not yet being produced or consumed on a commercial scale, a number of companies are working their way toward doing exactly that, possibly as soon as 2010.

Offshore structures that generate electrical power from ocean waves have been deployed but engineering challenges remain.