I have read many things here where folks appear to think highly of electrical transportation. I don't think much of it because the energy needed is much higher than traditional solutions. On another thread, it was reported that only 15-20% of the input energy at an electrical power plant was used at the final destination (e.g. the fuel content at the electrical plant contained 5 to 6.7 times the energy used in the home). This is because they are unable to capture all the energy in the fuel, there are productiion losses such as friction in the generators and turbines, and there are transmission losses. I do not know what the ratio is for petroleum IC engines, but I am under the impression it is much better than this. Are there any automotive engineers here that can provide some comparisons? Thanks.
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Is electric powered transpo the answer? 2
- Thread starter Dinosaur
- Start date
Assuming electrical powered transpo. is a light rail system with which can hold 40-80 people pure trip from a suburb to a city. I would say that is about 40x-80x more efficient than personal car transpo. from the suburbs to a city... O but I forgot the American way is for every person NEEDS to drive there own extremely inefficient vehicle for their daily commute and most major metro area’s have a neglected public transit system so pubic transpo isn’t even an option…sry I think I miss read the OP
Overhauling the transportation system would probably be the best way to “go green” have support Al Gore, but that would require politicians to actually do something useful to improve infrastructure, as apposed to telling people to drive hybrids while they continue to do nothing and line their pockets with public funds.
Maybe I am having a bad Friday….
Overhauling the transportation system would probably be the best way to “go green” have support Al Gore, but that would require politicians to actually do something useful to improve infrastructure, as apposed to telling people to drive hybrids while they continue to do nothing and line their pockets with public funds.
Maybe I am having a bad Friday….
Once we have fusion, or an overflow of renewable energy sources generating electricity, or at least nukes on the french scale sure.
Until then for personal transport I'm not sure how much sense it makes.
Of course same goes for hydrogen.
KENAT, probably the least qualified checker you'll ever meet...
Until then for personal transport I'm not sure how much sense it makes.
Of course same goes for hydrogen.
KENAT, probably the least qualified checker you'll ever meet...
electricpete
Electrical
For steam cycles, there is a max theoretical limit for efficiency elucidated by someone named Carnot:
Carnt Efficiency = (Th-Tc) / Tc
Where Th and Tc are the heat source and heat sink temperautres respectively.
This does not include any friction... just a thermodynamic fact (Something to do wtih entropy) that you have to reject a lot of heat to your condensor (wasted heat) in order to keep the cycle running. A typical nuke plant puts twice as energy (heat) into the cooling reservoir as it does into the generator (mechanical work into the generator before converted to electrical).
Then there are the traditional more easily understandable losses due to friction in tubine, generator, electrical losses in generator, transformers, lines, etc.
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Carnt Efficiency = (Th-Tc) / Tc
Where Th and Tc are the heat source and heat sink temperautres respectively.
This does not include any friction... just a thermodynamic fact (Something to do wtih entropy) that you have to reject a lot of heat to your condensor (wasted heat) in order to keep the cycle running. A typical nuke plant puts twice as energy (heat) into the cooling reservoir as it does into the generator (mechanical work into the generator before converted to electrical).
Then there are the traditional more easily understandable losses due to friction in tubine, generator, electrical losses in generator, transformers, lines, etc.
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Eng-tips forums: The best place on the web for engineering discussions.
electricpete
Electrical
Although centralized electric plants plants tend to be inefficient for reasons mentioned, motors tend to be tremendously efficient compared to engines. Also you have to consider differences in size/weight of coponents that need to be carried on the vehicle of course.
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electricpete
Electrical
"motors tend to be tremendously efficient compared to engines"
That is just looking at input/output quantities of motors vs engines... doesn't take into account upstream inefficiencies.
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That is just looking at input/output quantities of motors vs engines... doesn't take into account upstream inefficiencies.
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Eng-tips forums: The best place on the web for engineering discussions.
One side issue that is always neglected in these discussions is water usage in central facilities. A 200 MW plant evaporates something on the order of 20 million gallons of water a day in rejecting heat to the heat sink. Water issues in the Western US are often bigger problems than the price of fuel. Sure, the evaporated water will fall as rain somewhere, but most rain falls on the oceans and is lost as an easy water source.
In the end, all of these issues are pretty much moot. With a bunch of assumptions about energy required to transport gasoline to stations, mechanical and thermodynamic effeciencies of electric plants and motor transport; vehicles on the road represent something like a 1,200,000 MW load--does anyone think that we have anything like that much spare generating capacity or the werewithal to build it? According to the EIA, summer electric-generating capacity in the US is 990,000 MW, so this is at least doubling capacity. In 2006 the US added 12,000 MW of capacity.
"Going electric" is kind of like the transition to a hydrogen economy--the practical and engineering hurdles of the real problem far exceed our ability to solve them with today's technology. Will technology evolve to provide as-yet undreamed of solutions? Probably, but when? Linear thinking is just not going to solve the truly horrible energy problems that have been on the horizon for 50 years, but didn't get much attention until the news media got their teeth into the dual story of "Global Warming" and "High fuel prices".
Energy is so cheep in the world today that without these manufactured crises no one would be talking about alternatives. If you don't think that energy is cheep, realize that up until about 1800 a family would expend about 1/2 of their waking life in the acquisition of energy sources (chopping fire wood, transporting it, cleaning out the ashes, etc. and they mostly went to sleep at dark), today it is on the order of 1/8 in the developed countries and still very close to 1/2 in many "developing countries". Cheep energy brings many fair and wonderful things, but take it for granted and waste it at your peril.
David
In the end, all of these issues are pretty much moot. With a bunch of assumptions about energy required to transport gasoline to stations, mechanical and thermodynamic effeciencies of electric plants and motor transport; vehicles on the road represent something like a 1,200,000 MW load--does anyone think that we have anything like that much spare generating capacity or the werewithal to build it? According to the EIA, summer electric-generating capacity in the US is 990,000 MW, so this is at least doubling capacity. In 2006 the US added 12,000 MW of capacity.
"Going electric" is kind of like the transition to a hydrogen economy--the practical and engineering hurdles of the real problem far exceed our ability to solve them with today's technology. Will technology evolve to provide as-yet undreamed of solutions? Probably, but when? Linear thinking is just not going to solve the truly horrible energy problems that have been on the horizon for 50 years, but didn't get much attention until the news media got their teeth into the dual story of "Global Warming" and "High fuel prices".
Energy is so cheep in the world today that without these manufactured crises no one would be talking about alternatives. If you don't think that energy is cheep, realize that up until about 1800 a family would expend about 1/2 of their waking life in the acquisition of energy sources (chopping fire wood, transporting it, cleaning out the ashes, etc. and they mostly went to sleep at dark), today it is on the order of 1/8 in the developed countries and still very close to 1/2 in many "developing countries". Cheep energy brings many fair and wonderful things, but take it for granted and waste it at your peril.
David
SomptingGuy
Automotive
... and the weight of fuel. An electric train carries none.
- Steve
Many good points here, especially Zdas's about the water impact of electrical generation, and Gymmeh's point about electric rail vs personal transportation. Electric light rail is the only long term solution IMO, having ridden such public transit systems for many years. As pointed out, the real primary issues are sprawl and the SOV use that results. So my point is, I don't see ANY potential gov't program that has any chance of moving people closer in, to achieve the population densities needed to make light rail economically viable. Nor do I want the gov't to even try, it will surely be a waste of our money.
What I want is for the very real power of supply and demand, economics, to make this happen. The less the gov't interferes, the quicker the economic reality will start to hit home. People already claim to be choosing between fueling their SUV's and buying food; while I have a hard time believing there is any question which to choose there, maybe the light bulb will come on and these people will change their ways in the near future.
What I want is for the very real power of supply and demand, economics, to make this happen. The less the gov't interferes, the quicker the economic reality will start to hit home. People already claim to be choosing between fueling their SUV's and buying food; while I have a hard time believing there is any question which to choose there, maybe the light bulb will come on and these people will change their ways in the near future.
I think virtual travel may be the key to reducing our need for individual travel. If the quality of communication could be improved to the extent that we don't have to go there physically then we could reduce individual travel. Consider shopping, given the suburbs will be there for quite a while. Thousands of us could each get in our cars or SUVs and go to the mall, make our purchases and drive home. With better communication we could virtually go to the mall, make our purchases, and a few trucks could make the rounds delivering our purchases. This approach can be applied to school, vacations, and work. Maybe we should research in this direction, instead of windmills, ethanol, electric cars fueled by nuclear power, soya beans to diesel, tidal power, and clean coal. Its a tough subject to Google but "virtual travel" is a starting point.
HAZOP at
HAZOP at
There are a gozillian different retail ways to improve overall fuel consumption. Denver has light rail with a Park & Ride concept that is very well utilized (but there are always complaints by RTD that the systems loses money even with full trains during rush hours).
Many tasks can be done very well via telecommuting (in my business I typically don't leave my home 4 days a week on average), collaboration over telephone lines, e-mail, and net meeting are all less effective than face to face, but they are often good enough. I'm chairing the program committee for an SPE Applied Technology Workshop, and I insisted on a face-to-face kick off meeting so everyone would be able to see faces, and the next time we'll see each other is at the ATW--so far it is working fine to hash out the details with virtual meetings.
At the end of the day, all of these things combined will not make a significant dent in what I see as the main problem--the U.S. is importing $1.7 billion/day of hydrocarbon products. No economy can stand that kind of bleed indefinately. The price simply has to increase enough to impact each individual's disposable income enough to make them change--supply and demand is really the only effective tool.
Back to the topic of this thread, electric vehicles (like biomass fuel) will never be more than a side show unless someone comes up with a way to solve the difficult problems.
David.
David Simpson, PE
MuleShoe Engineering
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
Many tasks can be done very well via telecommuting (in my business I typically don't leave my home 4 days a week on average), collaboration over telephone lines, e-mail, and net meeting are all less effective than face to face, but they are often good enough. I'm chairing the program committee for an SPE Applied Technology Workshop, and I insisted on a face-to-face kick off meeting so everyone would be able to see faces, and the next time we'll see each other is at the ATW--so far it is working fine to hash out the details with virtual meetings.
At the end of the day, all of these things combined will not make a significant dent in what I see as the main problem--the U.S. is importing $1.7 billion/day of hydrocarbon products. No economy can stand that kind of bleed indefinately. The price simply has to increase enough to impact each individual's disposable income enough to make them change--supply and demand is really the only effective tool.
Back to the topic of this thread, electric vehicles (like biomass fuel) will never be more than a side show unless someone comes up with a way to solve the difficult problems.
David.
David Simpson, PE
MuleShoe Engineering
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RossABQ - I too have tried a version of Virtual Office on a project with limited success. The technology needs a lot more development before it can make a major impact.
HAZOP at
HAZOP at
- Thread starter
- #17
The point made by Zdas04 is along the lines of what I am concerned about. I hear folks speak of the cost of gasoline and then speak very cavalierly about just switching over to electric cars to avoid buying gas and reduce emisions. I don't think they get the impact to the electric grid and that with all the efficiencies computed they would probably not be any less of an impact for emissions. I also think this a failure of the mass media to ask the right quesitons so folks get a better understanding of the big picture.
Dinosaur, this is the same mass media that tout 'water powered cars' when they mean hydrogen powered, with the hydrogen coming primarily from electrolysis and hence effectively electricity.
While not the only hurdle, until they determine where all this extra, presumably clean, electricity is actually going to come from any variation on electric vehicles, hydrogen power or even large scale plug in hybrids faces a masive hurdle.
I'd guess one of the big advantages of electic & plug in hybrids is the use of regenerative breaking but I don't think it's enough to overcome the above concern.
KENAT, probably the least qualified checker you'll ever meet...
While not the only hurdle, until they determine where all this extra, presumably clean, electricity is actually going to come from any variation on electric vehicles, hydrogen power or even large scale plug in hybrids faces a masive hurdle.
I'd guess one of the big advantages of electic & plug in hybrids is the use of regenerative breaking but I don't think it's enough to overcome the above concern.
KENAT, probably the least qualified checker you'll ever meet...
Good point Ross, in terms of the infrastucture you can get so far/some benefit only recharging off peak, maybe the charging unit can even be turned off by the electric company during high demand.
However, as you start to point out, except on a small scale, with the current infrastructure you'll start to increase emissions from electrical generation.
KENAT, probably the least qualified checker you'll ever meet...
However, as you start to point out, except on a small scale, with the current infrastructure you'll start to increase emissions from electrical generation.
KENAT, probably the least qualified checker you'll ever meet...
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