OT: CO2/Km

The message from "ARWadsworth" contains these words:

Sloppy terminology from the BBC (so what's new) but there is some merit in the underlying idea provided it is wood discards or wood harvested from a sustainable resource that is burnt. What you get is a short term cycle in which CO2 is extracted from the atmosphere and then quickly returned and if the replacement wood is growing at the same rate as the fuel is burnt overall it really doesn't change the CO2 levels in the air.

Large scale destruction of carbon sinks like areas of forest or peat bog are a different ball game. The CO2 that liberates would not be absorbed by natural processes for a very long time and the same goes for burning fossil fuels.

Reply to
Roger
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Well it arises out of the total 'sustainable/renewable' perspective: i.e. try to use what energy is replaceable from current incident sunlight, nit what depends on the stored output of a million years of dinosaur's stored sunlight etc. etc.

I went to Mackay's lecture and book launch last night. One of te salient facts that stuck in my mind, was that biomass is about 0.2% efficient at turning sunlight into energy.

The other was his way of presenting the 'renewables' in terms of watts per square meter. The very best renewable..which was in fact IIRC desert solar furnaces - is around 15W/sq meter.

The rest are somewhere down around 1-5W/sq meter. That's tidal, wave, wind etc etc.

A typical power station of the conventional sort is around 3.5Kw per sq meter land used for something sprawly like coal. Probably even higher for Nasty Nuclear.

Leading to the inescapable conclusion that you need an area the size of Wales COMPLETELY covered with 'renewable stuff' to run the country. Including all the access roads to get to it. And the rest of the country criss crossed with wires to deliver it. From where it happens to be being generated today, to where it happens to be needed, today.

Fascinating book, full of factoids.

Did you know that the *average* fuel consumption of london buses is actually only two times better than the average car with one driver? In terms of energy per passenger mile?

Largely because most of the time the buses are not full.

You might as well use cars with a passenger.

Reply to
The Natural Philosopher
[snip]

I regard that comment as complete and utter bollocks on the part of DfT. I cannot and have not been able to find any requirement for a hybrid vehicle to have the state of charge of the battery recorded at the start and end of the test, nor for the energy consumed to be converted into CO2 equivalent. The fact that they duck actually answering the question is IMO significant.

Reply to
Steve Firth

My brother in laws 2 liter diesel skoda estate delivers 50-60mpg summer and winter.

The newest VW diesel does about 70mpg.

You. Its almost cost effective to drive my 2 liter 22mpg camper versus the 33mpg diesel freelander.

I have to agree with Clarkson though. Prius is an interesting exercise in engineering, but fuel efficient it aint. You can do a lot better with a well engineered small turbodiesel.

Reply to
The Natural Philosopher

A lot of broken links and incomplete documents, but suitable search engine fodder

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Reply to
Andy Burns

I eventually found an available copy of the document

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Reply to
Andy Burns

Andy Burns gurgled happily, sounding much like they were saying:

account...

Reply to
Adrian

Not for the Prius, the current model was introduced two years before the test was devised. And the battery charge isn't taken into account in terms of CO2 equivalent, is it?

Reply to
Steve Firth

There's no question of hybrids being extremely economical in heavy town traffic in comparison to conventional cars. But then if town use is exclusive pure electric cars would make more sense - especially for something like a government agency. It's when they are used in other than heavy town traffic use that the results claimed are more than questionable. As truly independant tests show.

Reply to
Dave Plowman (News)

"Dave Plowman (News)" gurgled happily, sounding much like they were saying:

That's as much a factor of the stop-start as the semi-electric propulsion, of course - and there's a pile of "non-hybrids" which contain that same tech.

Reply to
Adrian

%steve%@malloc.co.uk (Steve Firth) gurgled happily, sounding much like they were saying:

Ah. Good point. I s'pose the preceding version of the regs aren't easily available.

If the battery's charged by on-board power, yes.

Reply to
Adrian

s:

The point is that the cycle of burn-grow-burn-grow is very short, compared to that of buring stuff that grew millions of years ago, so any CO2 released can be re-absorbed.

Unfortunately, log burning can never be more than a token gesture as we would very quickly burn all the available material compared to the time taken to regrow it.

MBQ

Reply to
Man at B&Q

Come off it.

In my book any automatic petrol vehicle that can seat 5 adults (not amputees) and return 50mpg+ year round average in town and non-motorway driving can be said to be pretty fuel efficient.

Looked at in miles per pound the equivalent diesel would need to return

57.5mpg. I know many diesels are much better than that but you have to be objective and compare like with like.

Changing the subject last week I had a ride across Germany on a new Mercedes C Class 320D. Now that was a nice motor. Owner claimed fuel usage about 7 litres per 100km (I think about 40 mp-imperial-g) at German motorway speeds. That was a truly impressive car.

D
Reply to
Vortex2

Only if the test ends up having charged the battery to full and then discharging it to the same state it was in at the start of the test. I can't see that happening TBH, given the test protocol.

Reply to
Steve Firth

In terms of stopping the engine and using a form of regenerative braking, yes. But the average IC engine is much poorer efficiency wise running at very low speeds. With the Prius the engine is designed to run at peak efficiency in town while recharging the batteries or aiding movement. Which is also its major drawback - it's inefficient when called upon to work hard.

Reply to
Dave Plowman (News)

The only fuel consumption advantage the Prius has is in regenerative braking. That does very little at low speeds and even less on long runs. Unless your drive involves lots of braking from 50-ish to 20- ish, you might as well stop lugging those heavy and environmentally unfriendly batteries around and just have an efficient car.

In short: the Prius is an overhyped token gesture.

Ian

Reply to
The Real Doctor

You've totally missed the obvious one - it uses near zero fuel when at a standstill and very little when starting off/ moving slowly. And in all these sort of conditions the IC engine/transmission is at its worst, efficiency wise.

It's designed as a town only car for the US - where it's pretty good at that task. In the UK it's too big and expensive for that task and hopeless for other use.

Reply to
Dave Plowman (News)

I'd be fascinated to know what a Prius Diesel would do. You could put a

*big* turbo on it with no worries about lag too.

Of course, it would be no use for the USA where diesel isn't so widely available.

Andy

Reply to
Andy Champ

There's not really a problem getting diesel as most large trucks use it. There was/is a problem with the quality of it, though - high sulphur. And a hate of it by motorists - rather like here a few years ago.

Reply to
Dave Plowman (News)

I think "was" is the right word. Though a little behind this side of The Pond, standards are now similar and I think the US (I could be wrong - it might be California)is introducing tighter standards in advance of the EU in the immediate future for trucks.

An interesting point in that in EU waters, standards for marine emissions, I gather, are now tighter than on the ocean as a result of which Falmouth is a fuelling place of choice for those coming to these shores.

Reply to
Clot

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