Reply to post: Re: Impressive

Tesla launches electric truck it guarantees won't break for a million miles

Anonymous Coward
Anonymous Coward

Re: Impressive

Petrol or LPG are great ways of storing energy. If we ever get a way of making them from renewable power, water and air (CO2) that is cheaper than digging them out of the ground.....

The cost of fossil fuels will need to treble at least before that happens, even though the cost of wind and solar has essentially bottomed out thanks to subsidies encouraging build out. The problem is the chained inefficiencies of renewable power to gas are very low, particularly because in the most obvious form, of dissociation of water into hydrogen, there's very low value in the oxygen, so it is released, and immediately you lose about a third of the energy of the molecular bonds you've just broken. Then you've got compression losses (for storage and transport) and decompression losses - individually not huge, but the chaining of inefficiencies is a real killer. There's further small losses if you are practical and decide not to fart around with H2, and methanate it to give you CH4 (obviously that's a whole lot easier to handle and use). If you can distribute by gas pipeline you lose about 1.5% in transit losses and system use, and then you'd have the modest efficiency of a spark ignition gas engine, similar to a modern ICE engine. You'd be lucky to see 15% end to end efficiency.

All of which amounts to saying that you'd need a vast number of wind turbines to power any fraction of your road fleet. I did some fag packet maths, and an artic uses about 50 MWh of energy a year, and so the 120k artic tractor units on UK roads are going to need about 5 TWh (allowing for 20k truck out of the active fleet but registered). At 15% end to end efficiency, that gives you a need for 33 TWh of generation. That would mean that merely to power articulated HGV tractors via wind power to gas, you'd need all of the existing UK wind power fleet, and you'd then need to double it.

You could perhaps use desert locations for truly vast PV arrays (with certain practical problems), but you'd then factor in either further losses - electricity transmission to Europe of around 10%, or 25% if shipping liquified gas via tankers. ICBA to do the maths, but I suspect that a desert array to power Europe's vehicles would be big enough for the albedo of the panels to be climate altering.

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