My brother just wrote an interesting post about hybrid cars saying how the current measures for economy we see aren't really effective.

He has a good point, but also what worries me about hybrid vehicles is the environmental impact of them over their life-cycle. Most hybrid vehicles have batteries, these batteries are often made with toxic chemicals and heavy metals. How long do the batteries last? What happens with them when they are expired? I know my laptop battery, after two years of heavy use, is now at half its' capabilities so how long will the very expensive batteries in a hybrid vehicle last?

Apparently if the KERS (Kinetic Energy Recovery Systems) used in F1 was applied to London Underground they would use 50% less electricity, but like in hybrid cars where would this charge get stored? Certainly not with conventional batteries because they can't absorb charge quickly enough and have trouble with the discharge power for fast acceleration; that said Altairnano and Hitachi both claim dramatic improvements in this area. Super capacitors suffer leakage so this wouldn't be very efficient for a standing vehicle. One of the most effective stores of energy is actually mechanical storage because conversion losses can be reduced substantially and this would be the best solution for London Underground. Fit a large spinning mass under the train and store the energy recovered in breaking deceleration directly on the mass, then couple the mass to the drive train during acceleration to give it that extra boost.

However, we can't all carry round a huge mass in our cars because it will have a worse affect on the efficiency of a car compared to the constant stop-start of the Underground train.

Some new technology is needed and I don't know where it will come from but, like mechanical storage, I think we will be surprised and it will come from the past!