<blockquote><cite>Posted By: ringi</cite>There are now small fuel cells giving 50% efficiency from mains gas to electric, use the waist heat for DHW and space heating….

Then use the unpredictable renewable to make gas to put into the mains gas storage system. It is a lot cheaper to store gas then electric. If wind come down to 1/10 of its current cost, the above maybe cheaper then shipping liquid gas round the world.

The price of gas will go up, as soon as we start using less oil (due to electric cars etc), as at present as lot of gas production if a by-product of oil production.</blockquote>

Completely agree with you but very few people are aware that the products exist.

http://www.tropical.gr/images/docs/brochures/NG-5.pdf

With so little discussion as to there actual performance in the real world.

Quoting FT 2 days ago:-
"also super-lightweighting via carbon fibre etc, which has square-law effect on energy required."

Can you explain that?

I wropte in full

Posted By: fostertomsuper-lightweighting via carbon fibre etc, which has square-law effect on energy required.
Indeed - power-of-perhaps-two-and-a-half effect, because with lower power, 4WD motor-in-wheel + regen braking becomes feasible, eliminating engine bay, gearbox/diff, driveshafts, the volume and weight of all those hence lighter body ...

Posted By: mike7Can you explain that?

OK I don't know whether lightweighting has exactly square-law or power-of-two-and-a-half-law effect, but certainly much better than linear (power-of-1-law) effect. Body lightweihting enables smaller lighter powertrain, which enables yet lighter smaller body, which enables the major eliminations described above, which enable radically smaller lighter body etc, perhaps not ad infinitum but certainly to a Sinclair C5 level.

Much discussion of the various aspects: http://www.rmi.org/ultralightlowdragautoskeysolutions

Whereas mainstream cars (even Teslas, McLarens etc) are presently tending to put on weight and power, despite incorporating a lot of lightweighting technology, the suggestion is that a reversal, to lightweighting and lower power, would deliver very rewardingly steep cumulative benefits, far better than linear.

Posted By: ringiDon't expect me to use a very lightweight car if there is any risk of a normal car driving into it!

That's a common misconception. It's the strength that matters more than the weight.

1/2 mass x velocity squared.

Once moving at any speed, mass does not make a great deal of difference. And it is linear.
The velocity makes the difference though, or more to the point, the changes in velocity.

<blockquote><cite>Posted By: ringi</cite>And the crush zone is all about reducing the changes in velocity per second.

If self driving cars every become common and we have separate roads for them, then we may be able to do away with crash zones etc.</blockquote>

You'd need to remove 100% of interactions with non-self driving vehicles though. Separate lanes on the motorway are one thing but you're never going to get a dual network in the city. And there are still crashes that aren't prevented by convoyed self driving cars - how about a deer running out in front? Or the classic 'drive into brick wall to avoid human' scenario.


<blockquote><cite>Posted By: fostertom</cite>I wropte in full<blockquote><cite>Posted By: fostertom</cite> Body lightweihting enables smaller lighter powertrain, which enables yet lighter smaller body, which enables the major eliminations described above, which enable radically smaller lighter body etc, perhaps not ad infinitum but certainly to a Sinclair C5 level.
</blockquote>

https://en.wikipedia.org/wiki/REVAi c500kg for the liIon battery model. Perfectly adequate for city commuting - didn't exactly set the world on fire though.

Posted By: fostertomOK I don't know whether lightweighting has exactly square-law or power-of-two-and-a-half-law effect, but certainly much better than linear (power-of-1-law) effect.

I doubt it's that simple. Low mass helps for start-stop driving without regenerative braking. Low weight helps for reduced rolling resistance but that's most significant at low speed. For higher-speed cruising the dominant consideration is aerodynamic drag where it's shape that matters, not mass and weight.

Best thing is to travel less.

Says he hypocritically, having just done a 60 km round trip in a big flat-fronted vehicle for a tool which is not urgently needed just to feel I've made some progress on my project today, though I did do a bit of food shopping while I was about it which put off the need for another trip for a few days.