Richard Quinn
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| posted on 7/6/09 at 05:50 AM |
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Why are we arguing over the relative efficiencies of petrol engines v. electric motors here?
I think that we should be promoting electric/hybrid/whatever to all our friends and relatives. The less petrol others use, the more is left for me for
the time being.
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Ivan
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| posted on 7/6/09 at 08:44 AM |
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Sorry to take so long to reply - when I wanted to reply I think I broke the forum because I clicked "Reply" last night and everything
ground to a halt.
Firstly - Battery conversion rate = power input compared to output . Edit - whoops - big error here - I misread the article as they where talking
about solar energy not Li - yes conversion rate seems closer to 90% so you are looking at closer to 20% efficiency overall.
Secondly - I readily concede that I know very little about the accuracy of my calc but there appears to be an awful lot so called experts who seem to
be fudging the truth re the practicalities of purely electric cars, so I put this rough and ready calc out there to see if anyone can correct it and
show the true position.
Thirdly - I strongly believe that Hybrids are the way of the future.
Fourthly - This was prompted by an interview on SA TV done at the Paris (I think) Auto show with a potential producer of an all-electric car who spent
the whole interview skirting around the questions of practicality and could only say that Wind power generated electricity could be used for charging
with little environmental impact. Totally ignoring the fact that in most countries the majority of electricity comes from Coal and the power grids are
already overloaded.
Fifthly - Although I will readily concede that my Calcs may be totally wrong and ignore many factors I believe that they are not far from the truth
(just a gut feel folks) and if so it is time for the relevant engineering community to publicise the truth with real world studies - or is there too
much money to be made in developing unrealistic prototypes?
Sixthly - It is well beyond my abilities to calculate all the cost factors such as crude oil and coal exploration, extraction, transport,
beneficiation etc etc so I just worked to the nearest practical point
Seventh - most electric car studies seem to totally ignore the ability of the electric grid to carry the load if everyone switched to them.
Eighthly - I thought it would lead to interesting discussion and I would learn something from the posting, which I did so thanks to all and keep on
shooting me down. 
Lastly - of course if they eventually succeed in getting electric powered cars to be pervasive I bet that the tax revenues lost to reduced petrol sale
will be recovered from taxes on electricity. 
[Edited on 7/6/09 by Ivan]
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Badger_McLetcher
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| posted on 7/6/09 at 09:05 AM |
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quote:
Originally posted by Richard Quinn
Why are we arguing over the relative efficiencies of petrol engines v. electric motors here?
I think that we should be promoting electric/hybrid/whatever to all our friends and relatives. The less petrol others use, the more is left for me for
the time being.
Actually I agree. When you come down to it, all petrol is anyways is an incredibly energy dense battery (or rather energy carrier to be accurate). So
I'm all for hybrid cars etc, and there adoption as soon as possible.
Firstly it'd help get the tree hugging type off the backs of the personal cars.
Secondly it may even lower petrol prices enough I can afford to run my car without taking out a morgage!
If disfunction is a function, then I must be some kind of genius.
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oldtimer
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| posted on 7/6/09 at 09:59 AM |
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Good post Ivan. As a starting point for discussion it was really very good and drew lots of facts, figures, guesses and comment - so it worked.
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NS Dev
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| posted on 7/6/09 at 10:04 AM |
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quote:
Originally posted by gazza285
You are all looking at the wrong sort of efficiency, when electric cars become more profitable that petrol/diesel is when they will become viable.
quote:
Originally posted by Badger_McLetcher
one day, too many people, too few resources, boom
What we need is a good, old fashioned epidemic, kill off a few billion or so. How about swine flu? As long as I'm immune!
aha, now we're seeing sense
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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nstrug
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| posted on 7/6/09 at 10:48 AM |
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quote:
Originally posted by MautoK
Another aspect of electric cars is the horrendous amount of heavy metals that go into their construction.
And while I'm here, when will people realise that there's no such thing as 'renewable energy'. All our energy comes from
the sun - whether immediate, as direct radiation, or delayed, as captured in the specific energy content of oil or gas, or for example from the
gravitational effects of sun + moon giving tides. I'm all in favour of using the energy encapsulated in tidal flow, but tapping that will have
an effect on the moon's orbit (eventually.........)
The fatuous use of the wind as an energy source is not like a magic bucket where you scoop out a ladleful of energy and it mysteriously remains full -
it gets refilled (i.e. more winds blow) only as a result of more energy from the sun.
All energy ends up as low-grade heat.
It's very simple!
Slightly fatuous argument really. Not all our energy comes from the Sun - geothermal, nuclear and tidal being the obvious exceptions.
Renewable energy is effectively a way of saying 'unlimited energy', because that is exactly what geothermal, tidal, hydro, solar etc are -
they are replenishable by an external heat source that is effectively undiminishing on any human, and indeed planetary, timescale.
Of course a simple calculation can show that the use of tidal energy will cause the Moon's orbit to decrease, but the effect is so infinitesimal
that it's not worth considering.
I really don't think this sort of pedantry brings anything to the argument other than confusion.
I think the environmental cost of many renewable energy sources (in particular large tidal and wind) are unacceptable, however some hydro, geothermal
and solar seems promising - particularly Space-Based Solar Power. Simple things like insisting on the installation of ground-source heat pumps in new
house builds (as done in Switzerland, Sweden and parts of the US) would save a huge amount of energy, and money.
Personally I'm a huge supporter of nuclear power and I'm avidly following the developments in fusion power at ITER and the NIF.
Fusion+H2+fuel cells will power the world.
Nick
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brianthemagical
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| posted on 7/6/09 at 11:04 AM |
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On the subject of renewable energy, this implies energy is lost and created, which isn't true. All the energy put into an engine, and indeed the
logistics network in getting the fuel to the car, is used, and converted, thus everything is 100% effecient in converting energy, just not into the
required or saveable form. If the wasted energy from the whole process could be used, then the lack of direct waste from an electric vehicle would
render them in many ways deficient.
Either way, i like IC power in my cars.
On a side note, it is possible to get IC engines to around 50% useable effeciency, allbeit very big, diesel 2 strokes.
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Ninehigh
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| posted on 7/6/09 at 05:58 PM |
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quote:
Originally posted by smart51
I reckon an electric car to be more efficient than an internal combustion car but I also believe the best solution NOW is an electric car fueled by a
small generator, say 30 BHP or so, optimised to run at 1 speed, generating 1 power at 1 throttle opening. Then your engine will exceed 30%.
For the future, who knows. I'll tell you this though, as soon as a good way of making / storing hydrogen is invented, the petrol engine will
die. I attended a lecture on the development of the fuel cell powered car. There's still a way to go but the smart money will go into
developing electric cars now so that when hydrogen fuel cells are available, they'll slot right in.
Ok paragraph one, I suggested this a few weeks back and got shot down on the basis that the Prius has a 1.5l engine, I think you might have explained
it better though.
Paragraph two, they have. Honda FCX, iirc the website is www.problemplayground.com
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smart51
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| posted on 7/6/09 at 06:22 PM |
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quote:
Originally posted by Ninehigh
quote:
Originally posted by smart51
I reckon an electric car to be more efficient than an internal combustion car but I also believe the best solution NOW is an electric car fueled by a
small generator, say 30 BHP or so, optimised to run at 1 speed, generating 1 power at 1 throttle opening. Then your engine will exceed 30%.
For the future, who knows. I'll tell you this though, as soon as a good way of making / storing hydrogen is invented, the petrol engine will
die. I attended a lecture on the development of the fuel cell powered car. There's still a way to go but the smart money will go into
developing electric cars now so that when hydrogen fuel cells are available, they'll slot right in.
Ok paragraph one, I suggested this a few weeks back and got shot down on the basis that the Prius has a 1.5l engine, I think you might have explained
it better though.
Paragraph two, they have. Honda FCX, iirc the website is www.problemplayground.com
The Prius is a petrol car with a bit of hybridness added. Enough for gentle acceleration and urban speeds only. The problem is that batteries are so
heavy for the power they hold that they use up almost all the benefit the hybrid system gives. The result is that in heavy congestion it all works
well. On the motorway you lose.
I've been talking about my alternative solution to whoever will listen for a couple of years. Hybrids work because engines are only efficient
in a narrow band of operation. My system has, say 100 BHP of electric motors which deliver all the power and performance of the vehicle. You have a
quite small battery pack which can deliver enough power for a few accelerations and a few minutes of constant speed. You have a generator which can
deliver the average power requirements of a vehicle, or perhaps enough to maintain 75 MPH. During acceleration or up steep inclines, the battery
levels drop. During deceleration, periods at idle, down hill or at low and medium speeds, the engine charges the battery. You design the engine like
that of a ship - everything is at its most efficient at 1 speed even if that means the engine is useless at all other speeds. Use it at that one
speed the whole time or switch it off.
You have all the benefit of a hybrid without the weight of the batteries and with a more efficient engine than that of a car. Not only that, when
fuel cells or other power is developed it will bolt on in place of your petrol or diesel generator. You might even get a DIY slot in replacement.
As for where we get all this electricity, infrastructure is just a matter of making more of it. We have giga miles of ocean .Wave power and wind
power farms are starting to become a reality. We just have to make more of them. Have you seen the solar tower power station in Spain?
There's plenty of room for them in sunny but landlocked countries. We don't have to wait for cold fusion before adopting non carbon
energy, we just have to get up and do it.
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Benzine
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| posted on 7/6/09 at 07:36 PM |
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BATTERY!
BAT-TE-RY!
The mental gymnastics a landlord will employ to justify immoral actions is clinically fascinating. Just because something is legal doesn't make
it moral.
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gazza285
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| posted on 7/6/09 at 07:58 PM |
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Get out of the 80s man........
DO NOT PUT ON KNOB OR BOLLOCKS!
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smart51
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| posted on 8/6/09 at 08:29 AM |
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quote:
Originally posted by brianthemagical
On a side note, it is possible to get IC engines to around 50% useable effeciency, allbeit very big, diesel 2 strokes.
Yep. Marine diesel engine are this efficient,
But only at one speed, Which is OK if your journey is 4000 miles in a straight line, turn left a bit then 3000 miles in a straight line. Also a power
band of 100 - 102 RPM might be a bit limiting in a car.
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MikeR
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| posted on 8/6/09 at 11:30 AM |
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If peeps want to make IC engines more efficient look at the stirling engine. Fantastic design and works very well. Their was some research done at
fitting them into cars and it went very well ....... just needed a lot more research but is ideal for this conversation.
Philips did a lot of the pushing / development of the idea in the 40's onwards.
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MikeRJ
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| posted on 8/6/09 at 12:52 PM |
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quote:
Originally posted by MikeR
If peeps want to make IC engines more efficient look at the stirling engine.
The Stirling engine is an external combustion engine, not IC. This is one factor that makes it less useful for propelling cars since regulating power
within a reasonable response time is very difficult. The other is that whilst the theoretical efficiency is very high, practical engines don't
get anywhere near it and are barely better than current internal combustion engines.
BTW, the Prius uses an Atkinson cycle engine that is more efficient than a conventional 4 stroke.
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Bob C
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| posted on 8/6/09 at 11:16 PM |
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Back to post 1 "IC engines are 30% efficient", this is the biggest error. Your petrol engine's maximum efficiency is 30% - but
it's never there, most operation is round the 5 to 10% range. Obviously while idling efficiency is zero. The big efficiency improvement with
diesels is in their off peak efficiency where they slaughter petrol hands down - due to them not being "throttled" they always work with a
higher compression ratio.
All the decent sized BLDC motors are in the 90s % efficient, pretty much all the time even operating down at a few% load.
Basically if you burn the petrol in a power station to make electricity for a battery car, you'll get 30% efficiency from the petrol engine in
the power station. If you burn the petrol in a car you get about 3. So if you lose another 50% in the distribution & the battery you're
still 5 times better off with battery electric car.
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