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Dear Alistair, I'm no expert but these figures should not surprise. Modern internal combustion engines have been designed for many other capabilities other than fuel conservation. When this is the priority, for example in the range of fuel economy competitions popular in the US, vehicles have been designed that can achieve 10 times this efficiency (albeit Heath Robinson look-alikes) http://www.autobloggreen.com/2008/04/13/new-record-at-shell-eco-marathon-2-843-mpg/ If an engine is designed to work at just on constant speed eg charging a battery, it can yield far more fuel output efficiencies than one that has to produce outputs that vary from stationary to 100 mph) These super competition records are being achieved by cars that neither, stop start or change gear - but some of their findings will filter into standard car design. We are already seeing new ways of rechanneling energy normally lost through breaking but once car designers stop creating transport boxes as willy extensions and move towards systems designed to maximise fuel economy and using new methods - we are likely to see fuel ecnomies which seem astonishing by todays paltry standards. Steve ________________________________ From: Discussion list for the Crisis Forum on behalf of Alastair McIntosh Sent: Wed 12/08/2009 10:14 To: [log in to unmask] Subject: The Herald - GM's 230 MPG claim - does anybody understand the thermodynamics? http://www.theherald.co.uk/display.var.2525038.0.0.php?utag'076 Fascinating concept here from GM. But does anybody understand the thermodynamics behind this? How does using an internal combustion engine to charge a battery give such efficiency? It seems to me contrary to the normal entropic laws where you'd expect energy losses at each level of the system - from the engine, the battery, and the electric motor - rather than just from the engine as would be the case with a conventional direct drive system. But maybe it's to do with the charger engine being able to run at a steady state rather than being put through all the rigours of acceleration and deceleration. Does anybody have an angle on this? Also, at some point, if you're going to be carrying a ton of metal around as your means of conveyance, you have to hit on the thermodynamic limits of the energy contained in a gallon of fuel. Beyond that limit further attempts at efficiency would be impossible for a given type of primary fuel. Does anybody know what that theoretical bottom line would be for average driving conditions? It would be interesting to know as that figure would set the theoretical bottom line for MPG. Incidentally, I am sceptical of some of the claims for electric transportation because they rarely factor in the huge efficiency losses in generating the electricity, or what the source fuels are. For example, Eurostar claim an astonishing 18g of C02 per passenger kilometre. But they buy a lot of their energy from France, which means nuclear. Again, does anybody consider my scepticism on this unjustified? Cheers, Alastair. ************************************************************** * Website: www.AlastairMcIntosh.com * * Email: [log in to unmask] * * Alastair McIntosh * 26 Luss Road * Drumoyne * Glasgow G51 3YD * Scotland * Tel: +44 (0)141 445 8750 * * Hell and High Water: Climate Change, Hope and the Human Condition, now * published by Birlinn, £8.99 - www.alastairmcintosh.com/hellandhighwater.htm * * Soil and Soul: People versus Corporate Power is now in paperback and * in French translation - www.AlastairMcIntosh.com/soilandsoul.htm * * Love and Revolution, collected poetry, is from Luath Press * - www.AlastairMcIntosh.com/loveandrevolution.htm * * Rekindling Community: Connecting People, Environment and Spirituality * is Schumacher Briefing No. 15 from Green Books, * www.alastairmcintosh.com/rekindlingcommunity.htm *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Alastair. To view the terms under which this email is distributed, please go to http://disclaimer.leedsmet.ac.uk/email.htm