Fuel Efficiency and Hybrid Cars
Posted by: DAVOhorn on 28 June 2008
Dear All,
in today's Daily Telegraph Australia is an article on Hybrids and fuel efficiency.
The title:
Hybrid Future's Perfect But Show Us The Money.
Now reading this article it states that Hybrids use less fuel than normal cars.
Now unless they invented perpetual motion this is a falacy. How so.
You need fuel to move the car. Remember the battery needs to be dragged along and it weighs about 200kg.
You need fuel to charge the Battery, The engine runs a generator which charges the battery.
So how is it possible when looking at all the losses in converting fuel into heat and energy then turning that into electrical energy to then store in a chemical battery. Which is then used to turn this stored energy back into electrical energy to move the car. Which is now dragging its petrol engine along and this weighs about 300kg.
The losses inherent in this scenario surely render this technology a blind alley.
Using the energy content of 50L of fuel.
How much energy is given up by the the electrical motor after all the exchanges ans losses due to inefficiencies of this energy exchange.
Surely taking a hybrid car throw away the battery electric motor control systems etc and just run what is left as a standard car is this resultant in a lighter more fuel efficient car or not?
A level physics is not good enough to do all the maths.
But i bet energy released by just burning the fuel will be of a higher efficiency than changing it to electrical energy.
The article said that it would take 10 years of use to recoup the purchase price of a hybrid compared to a normal car as their is a price premium for hybrids.
In March this year the SUNDAY TIMES news paper compared a Toyota Prius to a BMW Diesel.
The journey was 900km.
The BMW used 49L
The Prius used 51L
The journey was London to Geneva.
So i would consider this a good test as it would have taken in large range of roads and environments.
I still hate Hybrids.
Now here FORD have just released the FORD FALCON XR6 Turbo.
This high performance sports saloon has 270kw and 560nm. On a run at 100kmh it used 7.9L per 100km which is shopping trolley teritory. Problem is if you lead foot it it gets a bit ERM Ahhhh Thirsty about 13L per 100km.
It costs $46,000.00 Aussie now for those in UK divide by 2.2 to give you pounds.
Now lets see a crappy Prius or a XR6 Turbo, i believe i will be visiting my local FORD dealer in August for a test drive .
Any one with better maths than me can they postulate the efiiciency losses i have outlined.
regards David
Posted on: 28 June 2008 by u5227470736789439
Definitely a car that hangs its green colours on the mast should be assessed in terms of its relative total carbon footprint in the making and the disposal/recycling as well as fuel economy in use.
There are some cars now that are entirely conventional IC type designs, like the new Fiat 500 and the Audi A2, which would floor the Prius on fuel economy, and it seems there are other less small vehicles that may well do the same.
For a long time I have had the idea of a ultra-lightweight town car of perhaps two seat design that would have a small electric motor, a top speed of thirty miles per hour, and range on a charge of perhaps forty miles on charge.
On the top surfaces would be mounted solar cells for recharging, and I can imagine that in some circumstances that might be enough for all the miles travelled.
Naturally it would have to be chargeable from the mains as well. But I suspect that with perhaps two or four conventional van sized lead acid batteries, it would be a very useful vehicle for many people with a five or eight-mile town commute ...
George
Posted on: 28 June 2008 by Don Atkinson
As I said elsewhere....
the maths isn't up to speed yet and the politicians and big business don't want facts to spoil a good story.
however, USING oil or other fossil fuels is only part of the story, and so are the EMMISSIONS. naturally the "whole-life" use of resources is important, especially limited resources that can't be sensibly recycled.
An internal reciprocating piston engine probably uses only 10% of the heat content of the fuel it burns. An oil-fired power station probably extracts 30% of the heat from the oil it burns AND can be linked to a carbon capture system (if we want). A few lossess in transmission, plus the energy-use in producing a battery and dragging it around, might still work out more energy efficient and CO2 friendly than a conventional piston engined car.
The French generate most of their electricity from nuclear sources and their use of scarce resources and CO2 emmissions are exemplary in this respect. In otherwords, in France it would make oil/CO2 sense to have hybrid cars.
Given that we import large chunks of elecricity from France (via the Sellindge Cables), it might already make sense here in the UK as well.
Cheers
Don
Posted on: 28 June 2008 by u5227470736789439
quote:
The French generate most of their electricity from nuclear sources and their use of scarce resources and CO2 emmissions are exemplary in this respect. In otherwords, in France it would make oil/CO2 sense to have hybrid cars.
Dear Don,
Do you [or anyone else here] know how much nuclear fuel there is in the ground for use in Nuclear Power Stations? Whatever else it is, it is certainly also a finite resource ...
Another unknown which needs pondering, perhaps?
ATB from George
Posted on: 28 June 2008 by Don Atkinson
Fredrik
To all intent and purpose, I believe that the supply of nuclear power can be considered infinite.
The safe disposal of "spent" fuel might be a bit of a problem, unless Sellafield improves its re-processing capability.
Before long, when a child is born, it might be allocated its own, personal, life-long nuclear power supply.
Goodbye Iran/Saudi/Iraq..........OTOH how would you all like to move into the safe storage of spent nuclear fuel....OMG, let me think this one through a bit more....
cheers
Don
Posted on: 28 June 2008 by Don Atkinson
quote:
Do you [or anyone else here] know how much nuclear fuel there is in the ground for use in Nuclear Power Stations?
quite a bit of uranium up in the Yukon. near a place called, errrr uranium city IIRC. But exactly hhow much? not sure.
Cheers
Don
Posted on: 28 June 2008 by u5227470736789439
There will be a fortune to be made for the right [clever] people safely storing spent nuclear fuel!
Did you see my idea for a simple short range low speed car? I reckon that would be a goer, if I had the backing.
ATB from George
Posted on: 28 June 2008 by Don Atkinson
quote:
Did you see my idea for a simple short range low speed car?
Nope, missed that one. How short and how slow?
quote:
I reckon that would be a goer,
I hope the pun was intended....
Cheers
Don
Posted on: 28 June 2008 by Don Atkinson
quote:
if I had the backing
So I look forward to seeing you in the next episode of The Dragons' Den
Cheers
Don
Posted on: 28 June 2008 by u5227470736789439
quote:
For a long time I have had the idea of a ultra-lightweight town car of perhaps two seat design that would have a small electric motor, a top speed of thirty miles per hour, and range on a charge of perhaps forty miles.
On the top surfaces would be mounted solar cells for recharging, and I can imagine that in some circumstances that might be enough for all the miles travelled.
Naturally it would have to be chargeable from the mains as well. But I suspect that with perhaps two or four conventional van sized lead acid batteries, it would be a very useful vehicle for many people with a five or eight-mile town commute ...
A little earlier in this thread. ATB from George
Posted on: 28 June 2008 by av in bc
quote:
Originally posted by DAVOhorn:
Dear All,
The article said that it would take 10 years of use to recoup the purchase price of a hybrid compared to a normal car as their is a price premium for hybrids.
regards David
well i bought my prius 4 years ago, and not only have i recouped
the "premium" i paid for it (whatever that means, nothing really. you get what you pay for)
but the car has paid for itself in fuel savings, maintenance savings and repair savings (yes, documented)
and with the price of gas now 1.5 a liter i'm making money now.
as far as "
The losses inherent in this scenario surely render this technology a blind alley. "
very little energy is "wasted" recharging the batteries while driving most of that is done
while braking or coasting downhill. it takes very little to get a good charge.
it creates fuel as it drives, it uses the energy that is normally wasted and stores it in batteries for later use!
what do you think an alternator does? the hybrid system is the same thing except smarter and bigger.
while i was waiting in bumper to bumper traffic at the u.s.a. border crossing this morning for 45 minutes
my car that you "hate" produced not a single once of pollution or carbon or noise
and didn't cost me a dime for the entire 45 minutes of crawling along to travel less than a mile.
same goes while i wait for red lights or drive in mall parking lots
and stop for a quick errand and continue on my way without having to restart my engine.
the prius is not the most economical car if all you do is drive on freeways, a lot of the economy comes when you're not moving at all actually.
you also have to want to save gas and drive accordingly (normally but a few minor adjustments are necessary)
some who can't be bothered get 40-45 mpgs others get 60. it's not hard and you definitely don't have to "granny drive" either.
i get 52mpgs with my old 2001 prius, i only need oil changes every 15000 kms
i also get about 258 lb-ft of torque @ 0 rpm (that's just from the electric motor)
and have all original brake parts @ 275000 kms (pads,rotors,drums)
and i have no starters or alternators to fix and replace.
you and your FORD FALCON XR6 Turbo will get maybe 12L per 100 (if you're lucky those estimates are always optimistic and misleading)
i get 4.6 calculated at the pump over years of tracking. that's close to 3 times less and the new prius is about 15% better than that.
Posted on: 28 June 2008 by northpole
av
You must be very lucky or perhaps the Canadian climate works particularly well with hybrids.
Here in UK, we were all treated last Sunday to an entirely impartial test carried out by the BBC Top Gear team to establish the truth.
The test involved a Prius being driven vigorously around a test track, followed by a new BMW 3 series with V8 engine. The Prius averaged 17 mpg whilst the BMW achieved over 19.
Pretty conclusive then - all people concerned about the environment and fuel economy should visit their local BMW dealer soonest!!
Peter
Posted on: 29 June 2008 by Don Atkinson
Mrs D has a nice little (relatively) new car that I bought for her 2 years ago. It was four or five years old when we bought it.
She travels to school in it each day, about 6 miles each way including a 400 foot hill to cross over and a level crossing that is often closed to road traffic for up to 20 minutes.
she averages over 55 mpg.
when I drive it "normally", ie like the Top Gear BMW, I get about 60 mpg. On a steady run with cruise control on and taking care to avoid situations that require braking, at 60 mph I get 72 mpg.
the car goes 16,000 miles plus between service intervals and doesn't need any oil or other top up between services. She has done about 10,000 a year in it.
depreciation is about as low as you get on any sort of car. it will probably last at least 30 years before looking "tired"
it carries four people comfortably and five at a push.
It has a diesiel engine and a range of almost 1,000 miles on a tankfull.
It isn't a Smart car or a Prius or any other sort of "compromise" buggy. from a financial point of view, its as cheap as chips, in car terms, so it is probably as environmentally friendly as any other "normal" car.
Cheers
Don
Posted on: 29 June 2008 by djftw
My father evaluates things like this for a living. When he last bought new cars it was relatively obvious even with the limited data that is available that modern diesels are not only cheaper to buy and run, but over their lifetime significantly less harmful to the environment. If you want to make a purely "green" decision the best thing to do is probably not to buy a new car at all.
Posted on: 29 June 2008 by u5227470736789439
I was given a good suggestion of a way forward with my old car. eBay! When the time comes. After all, the fixed polution cost of building the thing in the first place deserves to be stretched out over the five or ten years she might still be in a serviceable condition, even if it the sale only nets me a few tenners!
It will not be replaced with another conventional car, though I may build an ultra-lightweight electric car for the fun of it!
George
Posted on: 29 June 2008 by djftw
I will be very impressed if you can George! Where will you find a DC motor with sufficient torque?
Posted on: 29 June 2008 by u5227470736789439
The motors already exist.
In India, they have electric rickshaws coming along nicely. Slightly different bodywork and the appliance would be well suited to short haul commutes in Britain.
ATB from George
Googling showed me this, but a suitable British variant should definitely be made:
http://www.bluebird-electric.net/bluebird_solar_powered_rickshaw.htmPosted on: 29 June 2008 by Don Atkinson
Fredrik
I have spent a lot of time working and on holiday in India, mainly in 1972 (holiday) and 1980(approx)-working.
India is trying (quite succesfully) to improve on what we had in 1980 and what we have today. I can see no reason for us to try to emulate what they are trying to leave behind them.
An auto-rickshaw (Petrol/diesel/electric) is the last place you want to be if you attach any value to your life.
Alan Sugar in his Roller wouldn't even bother to stop to complain that your rickshaw, which has just been squashed (with you in it) had slowed him down. He would just get one of his lackeys to wash your blood-splatted remains off the front and sides of his car before he needed to drive to the Ritz for afternoon tea.
You could do better with one of Sinclair's C5s or whatever they were called, at least you KNOW you're vulnerable in one of those.
Life-threatening economy isn't worthwhile.
cheers
Don
Posted on: 29 June 2008 by u5227470736789439
Dear Don,
Try a bicycle and you would soon see the value in some width to the vehicle on terms of being seen and not simply ignored! Some car, van, and lorry drivers pass without shifting their position in the lane at all. The other day a woman passed me and came back in before finishing the manoeuvre. I was able to warn her by belting the passenger window [quite hard actually, but the adrenalin was working I suspect!] and she adjusted course and was rather embarrassed at the next lights where she met my eyes in the mirror!
What I am thinking of is the electric version of the "auto rickshaw" with an enclosed cabin, two seats wide, sitting on four wheels and the obvious advantage over the Sinclair C5 of being conventionally tall like a normal car. The problem for bikes and the C5s was visibility to other road users. You do not see tricycles being hit, because they are wide enough to see, even though they are slower than normal bicycles.
If I can afford to do it I shall build this ultra-light vehicle on the Indian electric power-train but with four wheels and fully glazed cabin.
It might catch on!
George
Posted on: 30 June 2008 by Staedtler
quote:
Originally posted by GFFJ:
Did you see my idea for a simple short range low speed car? I reckon that would be a goer, if I had the backing.
ATB from George
George, Gordon Murray (ex McLaren F1 designer) is currently developing something similar to your idea at the moment, but the exact details are not available at the moment.
On the Prius debate, it does recover energy normally wasted as heat in braking by charging it's batteries then (which can then be used later), but when it is crusing it is carrying around the excess weight of the batteries thus reducing it's mpg.
Sure, it can run on purely electric power, but if they get too low the petrol motor is started to not only power the vehicle, but charge the batteries increasing the load on the engine during this cycle!
BMW have a very clever, but simply executed solution, where they have an intelligent alternator that only charges the battery when it's needed, stop start technology to cut the engine when the vehicle is stationay and active control of the air flow around the engine to reduce drag. All seemingly minor and not "Hybrid" headline grabbing, but effective and can be installed on most vehicles.
An altogether more simplistic approach....
Posted on: 30 June 2008 by DAVOhorn
Dear All,
Regenerative braking.
You have travelled for 25miles and you finally have to stop at traffic lights.
So slowing from 50mph is done in 50 mts what amount of energy is put into the batteries by this.
Of course this would be lost as you accelerate back up to your previous cruising speed.
regards David
Posted on: 30 June 2008 by Staedtler
1500kg car has KE of 370kJ when travelling at 50mph. This would be the maximum that could be put into the batteries assuming 100% efficiency of transfer and all of the energy is removed by the generator i.e. no brakes.
This energy is then used to supplement the engine in accelerating the car back up to speed (lowering the engine's demand for a give rate of accel), so yes it is lost, but that's the point.
Posted on: 30 June 2008 by Staedtler
*
Posted on: 30 June 2008 by Ewan Aye
I use my mountain bike sometimes, but it runs on fuel as much as anything. To do a long run I need carbohydrates and water, but manufactured pasta has to be milled, processed, dried, packaged and transported to the shops, and I have to boil it in water that is metered and heated by gas which is ridiculously expensive.
Cycling isn't as fuel efficient as many would like to make out.
(Just expanding David's opening point really)
Toyota's Prius is sleight of hand
Posted on: 30 June 2008 by BigH47
quote:
By the way many are made by Ligier of Le Mans fame!!
Some of the Simcas were made by Matra (rockets and planes) it didn't make them any quicker though.
Posted on: 30 June 2008 by BigH47
quote:
Regenerative braking.
Going to be on F1 cars next I believe.
