Dave Liquorice wrote:
On Tue, 29 Mar 2011 00:01:32 +0100, Tim W wrote:

There is a lot of pressure on the motor industry to develop an electric
car which can charge up all night and run round town all day.

And what's with this facination with electricity. You could use
compressed air or liquid air. There is a "technology demonstrator"
for a small city type compressed air driven car somewhere and small
commercial scale liquid air power plants are being devleoped/built.

TBH I'm not quite sure how liquid air works as a fuel, it's down to
the phase change and expansion but I struggle with where the energy
comes from to liquify the air in the first place. I have niggly doubt
it's a bit like hydrogen as a fuel, you need to shove just as much
energy in to split water as you get back out later (less losses).

yes. All these thing are secondary energy sources. In fact there is only
really one primary energy source in the universe. The big bang.

Taking it locally, the prime energy sources in the Earth, are the big
fusion reactor in the sky, and the heat and energy still left in the
earth. We have dug up or pumped most of the low hanging chemical fruit
- carbon fuels - already. All that is left is nuclear fuel, but there's
a lot of that still left..although the low hanging fruit of Uranium 235
may not be in such abundance.


With a secondary energy source, what counts is cycle efficiency. How
much you get out later for how much you put in earlier. Batteries are
really very good. Plus energy density: How much your storage devices
weighs per unit energy stored. Batteries are not so good there.

We tend to use electricity as a transmission energy form, because its
very very cheap and easy to *transport*.

Its a bitch to store though.


We use heat in heat engines, to turn heat to mechanical or electrical
power because heat engines are simple and well understood.

WE tend to want to store energy in chemical ways because its a pragmatic
way to run transport and its easy to stockpile.

What we don't have are efficient ways to go from one sort of form to
another.


Ideally a back box that you shovel uranium,. CO2 and water in at one
end, and get diesel and oxygen out at the other, would be everyone's
dream come true.


Or a black box you sit in the middle of a desert by the sea, that takes
water, CO2 and sunlight and makes diesel..


PS I note that as of ten minutes ago, the total power output of all the
UKs metered wind was just 20MW . Its up to a whoping 24 now.