[NeilBlanchard]

I think that hydraulics and hydrogen suffer from some of the same problems: they are both merely storage mediums, and they both depend on an actual energy source in order to work. Electricity is an actual energy source, that has numerous sources; some of which are renewable.

Hydraulics may be a great transmission system, and it may be a good way to regain energy, but you still must have an actual power source. If it burns "old carbon" fuel, then it is not a long term solution. Things like steam or biodiesel can get energy from "short-cycled" carbon, and so they would be good long term solutions. Hydraulics obviously work well for very large, heavy construction vehicles and medium sized delivery vehicles. I wonder though, if a small(er) vehicle system would be viable, though.

Hydrogen fuel cell vehicles are really series hybrids; and they replace a larger battery or a small ICE with an extremely expensive fuel cell and a critical high pressure storage system. Since it takes a lot of energy to produce hydrogen, and it takes a lot of energy to compress it, and so you would be a lot better off using a fraction of that power in a bigger battery. Or, use a steam or biodiesel generator, which cost a lot less and have much higher energy density.

An ICE only vehicle only works as a long term solution IF it burns a "short-cycle" carbon fuel; like biodiesel. Otherwise, it is only a less bad solution -- the engines are a maximum of 37% efficient (or so) and they by definition cannot be used at peak efficiency for part of the time. They have to warm up, you have to have a stop/start system to eliminate idling, and because they are mechanically linked to the speed of the vehicle, they must use a transmission. And they cannot have any energy regeneration; only conservation. They require lubrication, which is petroleum based, and they need other regular maintenance.

Electric vehicles have many advantages: electricity is already widely available from numerous sources, electric motors are very efficient, they have no warm up time, they have maximum torque at 0 RPM, they inherently work for regeneration, they do not idle, they last a very long time, they require virtually no maintenance. Since electricity *can* come from renewable sources, any losses are not important in terms of the environment; only to the actual operation.

It is the batteries that are the limitation to EV's. But, some of the problems are easy to overcome -- they can be fully recycled, and if they have *enough* capacity for most trips, then it doesn't matter very much that they don't work for ALL trips, because there are other options; including public transportation, renting/borrowing a efficient car. OR, you can make an EV into a series hybrid, using a biodiesel of some other renewable fueled ICE.

Yes, currently batteries are pretty expensive to buy, but they are very low cost to operate. Energy costs are much smaller than an ICE, and the regular maintenance costs are virtually zero. Battery replacement costs will come down over time, and even if they do not, they are still similar to the lifetime fuel costs of an ICE. Plus, all the money you spend on an EV *stay* in your local economy. The overall carbon cost is much better than any ICE powered vehicle that burns "old carbon" fossil fuels.

And lastly, and EV or an electric series hybrid gives you regenerative braking -- an using a supercapacitor and "smart" GPS based control systems can increase the amount of energy you can regain.

Parallel hybrids are inherently more limited (than an EV or series hybrid) because they *must* use both motors in combination much of the time, and therefore they will weigh more, cost more, and they need a transmission. They gain some advantages, but they also have some of the limitations of both. Again, if the ICE portion of a parallel hybrid (like any other system that use an ICE) can come from a renewable source, but they are still going to suffer from the other disadvantages.