Naked Science Forum
Non Life Sciences => Technology => Topic started by: stewgreen on 26/10/2011 12:31:40
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- Which produces the least CO2 a natural gas car or an electric car when the original electricity is generated at a gas power station ? bearing in mind the new Blackpool gas field
- I see there are 2 old threads on electric cars, but maybe there are some new ideas especially for gas and LNG
http://www.thenakedscientists.com/forum/index.php?topic=15772.0
http://www.thenakedscientists.com/forum/index.php?topic=27098.msg286741#msg286741
please think about total CO2 : from manufacture, use and disposal
- an issue seems to be heavy batteries
- I guess LNG is as safe as petrol
- I note gas powered buses are much more common than electric
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bearing in mind the new Blackpool gas field
I never heard of that. Perhaps they had been eating too many winkles?
(Welcome, and sorry for the comment, but it's typical of the sort of abuse you are likely to receive on this forum [;D])
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The work on the blackpool field is in abeyance at present, I believe. There was a problem with a link between a few earth tremors and the fracking (http://www.bbc.co.uk/news/uk-14432401) process that was being used. I think there is an investigation on going at present.
the beeb http://www.bbc.co.uk/news/uk-england-lancashire-13700575
the green view http://www.guardian.co.uk/environment/2011/sep/22/shale-gas-exploration-halted
industry view http://www.eaem.co.uk/news/shale-gas-find-lancashire-may-never-be-exploited
PS please try to ignore geezer - he is here as part of our community outreach programme
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I'm going to assume your comparison would be between a conventional IC engine and a BEV.
My gut reaction would be that a Natural-gas powered IC would be the more efficient (plus lower CO2) of the two overall if the vehicle was a hybrid. If not, then a reversed result.
Back of envelope...
Electric (BEV) from natural-gas:
NG fired power station(65%) + transmission losses ~ 55% of fuel energy recovered.
+ Charger conversion losses ~ 48%
+ Pwr controller/motor losses ~ 40%
On-board natural-gas:
A purpose-built engine using NG can achieve higher compression-ratios than petrol, so a hybrid NG-powered vehicle could conceivably reach high forties overall (might be a little lower with drivetrain losses) - Say ~46%.
Can ignore energy cost of well-to-pipeline as common to both.
If an onboard catalyst allowed H2 generation instead - to be used for a fuel-cell then it would seem an easy win.
Adsorbed Natural Gas would be a better alternative to LNG and the technology is coming to market now (or very soon!).
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I'm not sure how much difference it will make in the end, but don't you also need to include a piece of the the CO2 released in constructing the power generation and distribution systems, or would that depend on whether one was biased for or against EVs? [;D]
BTW, I see Tesla has reported to the SEC (Securities Exchange Commission) that they don't plan to make a profit in the foreseeable future! Sounds like a pretty safe investment to me.
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BTW, I see Tesla has reported to the SEC (Securities Exchange Commission) that they don't plan to make a profit in the foreseeable future! Sounds like a pretty safe investment to me.
Very O/T - no company with an accountant worthy of the name makes any profit more than they can get away with in a corporation tax zone. is there a chance that tesla are exporting the profits so that they might hold on to more of the cash? this is one of the valid points the ows guys have!
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Electric (BEV) from natural-gas:
NG fired power station(65%) + transmission losses ~ 55% of fuel energy recovered.
+ Charger conversion losses ~ 48%
+ Pwr controller/motor losses ~ 40%
On-board natural-gas:
A purpose-built engine using NG can achieve higher compression-ratios than petrol, so a hybrid NG-powered vehicle could conceivably reach high forties overall (might be a little lower with drivetrain losses) - Say ~46%.
Earlier, we discussed gasoline engine energy losses here (http://www.thenakedscientists.com/forum/index.php?topic=41263.25)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.fueleconomy.gov%2Ffeg%2Fimages%2Fenergy_requirements_combined.jpg&hash=8a005d843d3669173c1ba88b5daa1873)
The gasoline engine was only about 30% efficient, plus some other related engine losses including the water pump dropping it down to about 25% efficiency.
I would assume LNG or CNG would be similar.
Assuming distribution in pipes to either a central generator, or to fill-up location, the NG distribution would be similar, but as mentioned, the BEV has the additional line distribution loss. What about the compressor if using LNG, and possibly also CNG?
The Electric Motor efficiency is higher with the BEV, but there still are some drivetrain losses.
A Lead-Acid BEV is HEAVY. Lithium or NiMH BEVs might be closer in weight to the gasoline/NG versions.
Anyway, assuming the same primary fuel source, the two would be similar. The BEV is easier to augment with alternative fuels such as wind, hydro, or solar.
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The gasoline engine was only about 30% efficient, plus some other related engine losses including the water pump dropping it down to about 25% efficiency.
Indeed. And that's why I said as much - for a non-hybrid car.
My quick breakdown of losses was for the hybrid vehicle energy route.
... admittedly it may have been a bit optimistic even then!
Technically, a mass produced petrol car could approach 1L/100km in hybrid format (even without plugging-in capability)... I'm not what that equates to in percentage-fuel-efficiency or how it would stack up against NG.
More importantly it's highly questionable whether anyone would buy it, as it is likely to seem woefully underpowered (esp. in North America!) and would be a long way from the conventional idea of a 'compact' car (probably 2 tandem seats & no boot/trunk).
It would however be likely to go a fair bit further than its electric competitor on one 'tank' and take far less time to 'recharge' [:D]
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I'm not sure how much difference it will make in the end, but don't you also need to include a piece of the the CO2 released in constructing the power generation and distribution systems, or would that depend on whether one was biased for or against EVs? [;D]
Good point! I will include that then [since it suits my bias! ;) ]
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There is also a CO2 cost to liquify gas for fuel & an additional cost for distribution.
If I recall correctly there is also an issue with CH4 in 2 & 4 stroke engines - CH4 is harder to compress than more complex (liquid) hydrocarbon fuels - thus reducing engine efficeincy This could be overcome by using turbines...
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There is also a CO2 cost to liquify gas for fuel & an additional cost for distribution.
If I recall correctly there is also an issue with CH4 in 2 & 4 stroke engines - CH4 is harder to compress than more complex (liquid) hydrocarbon fuels - thus reducing engine efficeincy This could be overcome by using turbines...
Yes - that should be taken into consideration too. Hard cheese Peppercorn.
The compression issue with CH4 is a new one on me. Most of the stuff being compressed is nitrogen and oxygen, so I don't understand what difference it would make.
Perhaps it's because the engine has to do work to compress it because it's a gas?
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The compression issue with CH4 is a new one on me. Most of the stuff being compressed is nitrogen and oxygen, so I don't understand what difference it would make.
Unless you wish to tether your car to your stove outlet with a long hose, you will have to transport Natural Gas as either CNG (compressed Natural Gas) or LNG (Liquid Natural Gas). Which means at some point the fuel needs to be compressed.
Gasoline, on the other hand, doesn't need to be compressed for transport.
Ocean Tankers, and presumably railcars and tanker trucks all carry LNG.
I have no idea what central distribution pipelines carry.
Your home delivery lines are all at low pressure.
Anyway, so the repressurizing of the Natural Gas may or may not be an issue (with the original distribution mode being equal for electricity generation or vehicle use).
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The compression issue with CH4 is a new one on me. Most of the stuff being compressed is nitrogen and oxygen, so I don't understand what difference it would make.
Unless you wish to tether your car to your stove outlet with a long hose, you will have to transport Natural Gas as either CNG (compressed Natural Gas) or LNG (Liquid Natural Gas). Which means at some point the fuel needs to be compressed.
Gasoline, on the other hand, doesn't need to be compressed for transport.
Ocean Tankers, and presumably railcars and tanker trucks all carry LNG.
I have no idea what central distribution pipelines carry.
Your home delivery lines are all at low pressure.
Anyway, so the repressurizing of the Natural Gas may or may not be an issue (with the original distribution mode being equal for electricity generation or vehicle use).
True. If it's already liquefied, why not inject it into the engine in liquid form?
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True. If it's already liquefied, why not inject it into the engine in liquid form?
I was talking about transport (in vehicles).
However, you could run something like common-rail injection without requiring an injection pump.
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True. If it's already liquefied, why not inject it into the engine in liquid form?
I was talking about transport (in vehicles).
However, you could run something like common-rail injection without requiring an injection pump.
This could cool the charge quite considerably couldn't it?
This has both potentially good and bad effects.
It would indeed be naturally suited to a late-in-the-compression-stroke injection strategy though.
As Geezer says I can't see how the gaseous-fuel content (what: 5% by mass?) of the charge would make any noticable difference in the compressive work needed (in the cylider that is), even if the CH4 was pre-injected at ambient P & T.
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True. If it's already liquefied, why not inject it into the engine in liquid form?
I was talking about transport (in vehicles).
However, you could run something like common-rail injection without requiring an injection pump.
This could cool the charge quite considerably couldn't it?
This has both potentially good and bad effects.
It would indeed be naturally suited to a late-in-the-compression-stroke injection strategy though.
As Geezer says I can't see how the gaseous-fuel content (what: 5% by mass?) of the charge would make any noticable difference in the compressive work needed (in the cylider that is), even if the CH4 was pre-injected at ambient P & T.
....and, even if it did expand a bit and take in some heat, it's going to get compressed and give it back PDQ!
Petrol is usually in liquid form too, which means it's a bit tricky to compress (much).
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- I'll put this one down as a "we don't know so far"
- My qualification is as an electrical & electronic engineer but electric vehicles are not my speciality. My gut instinct was for LNG gas :
- 1. it's a lot more convenient to transport than heavy batteries.
- 2. this is backed up by the predominance of LNG buses
- but there must be some proper peer reviewed scientific data out there somewhere
(Politics is a Russian doll inside a Russian doll, so maybe not long to fusion power now, but cheap fuel has complicated ecological implications)
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I'm pretty sure most of us find electric cars very interesting.:) Anyway, just a little trivia regarding electric cars, I read from an article recently that the Hiroko, an electric city car depending on MIT designs, will be constructed starting next year in Spain. The car is the product of MIT, and a consortium of companies from the Spanish Basque regions. Resource for this article: MIT designed Hiriko city car to be built in Spain < url of questionable value/backing (removed cause better safe than sorry!)
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AFAIK the two are about the same, there's transmission and battery storage losses that wipe out the extra efficiency you normally get at a power station, although very high efficiency power stations might improve the electric car over that of LNG.
The other answer is that in the UK you can pay for your electricity to be produced (on average) entirely using wind, so an electric car has zero carbon footprint.
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The other answer is that in the UK you can pay for your electricity to be produced (on average) entirely using wind, so an electric car has zero carbon footprint.
That's a bit of an over-statement. It would be true if the production of the vehicle, the power generation method, and the power transmission method all had zero carbon footprints.
Wind power generation systems do not have a zero carbon footprint. It's not obvious that the energy they produce during their useful life is sufficient to compensate for the carbon released in their manufacture.
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Since there is a positive return on the investment... I'm going to interpret that as indicating that the windmills produce more energy than they consume. Of course there may be government subsidies, but it appears to be a profitable business.
Apparently there is some competition of selling the electricity though, as the government who has been running several local dams for 3/4 century or so is reluctant to dump more water over the spillways so that they can buy more private wind power.
I'm still not convinced about the benefits of paying a premium for "wind energy". At the substation, there is really no difference between wind, water, or coal power.
If, say 5% of the power is generated by wind, and 95% by other sources.
Then, if 4% of the people pay for "pure wind power"...
Then they get 100% "wind power".
Everyone else gets 1% Wind power, and 99% Other.
It really doesn't change anything.
And, on a calm, windless day... are those people buying the wind power accepting a brown-out?
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"I guess LNG is as safe as petrol"
Not if you want to take your car on the Euro tunnel train to the mainland they won't let you on.
I buy my electric from France as I am enthusiast for nuclear power.
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If, say 5% of the power is generated by wind, and 95% by other sources.
Then, if 4% of the people pay for "pure wind power"...
Then they get 100% "wind power".
Everyone else gets 1% Wind power, and 99% Other.
Yeah, but what happens when 6% demand wind power? The price of wind power goes up, and it becomes more cost-effective to build new wind turbines and then the energy market responds and the price goes back down again. It looks like we're going to be getting 20% wind penetration in the next decade or so anyway; wind power is growing 20+% per annum.
The reason it's growing like that is that the cost of new wind installations is about the same as new natural gas installations per kWh delivered to the end-user, but it's carbon negative and you don't have to rely on foreigners who may push up their prices.
And, on a calm, windless day... are those people buying the wind power accepting a brown-out?
No, they're buying energy produced by other sources, which lend them the energy. On a very windy day, those sources shut down, and wind power pays it back- with interest. The net effect is strongly carbon negative; that's fuel you didn't have to burn. It's called 'grid storage' and solar panels do the same thing.
Also, if there's a lot of electric cars attached to the grid you can use them as storage; so the wind/electric car combo is particularly attractive.
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How do you rapidly shut down a nuclear plant when the wind picks up ? or will it be easy when all the power plants are fusion (hot or cold).
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Nuclear power is base load power, and very expensive; it's left running at constant power, and doesn't work well with variable loads or variable sources.
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It is even hard to vary the output of a coal or NG plant, at least with short-term variability. Presumably one could program it to have peak output at the same time of a predicted peak demand on a diurnal basis.
The government likes to also run the big hydro-electric plants at a constant rate (base load power), but it would seem that hydro would be perfect for variable load power. Perhaps coupling a large base-load generator with a smaller variable load generator, with the goal of maintaining an average river flow over a 24 hr period.
Obviously average flow rates vary by the season in places like the Northwest USA, but fortunately, in the winter when heating demands are the highest, flows are also generally the highest.
I certainly don't want the government to start discharging my EV car without my permission. And, my charger is designed as a 1-way device.
The local power company is discussing variable power rates, with cheaper rates at night, and higher rates during the day. In that case, I would certainly put a timer on my charger to kick it in at midnight, for example to capture the cheapest power rates. I may do that anyway. If they had a buyback, I might consider uploading power at noon (on days I wasn't using the car) and downloading power at midnight. What would the efficiency be? 80% max? However, the life of batteries is in part dependent on depth of discharge and cycles. If my net savings per cycle would be on the order of 1 dollar, I don't think I would choose to allow diurnal cycles as wear on my battery packs would likely be greater than the diurnal cycling. And, of course, if something came up in the afternoon and my vehicle was discharged, I'd be out of luck. Rapid 1hr charging might help some, but I don't have that capability.
Anyway, I'm still convinced that the best place to intentionally vary the power generation is to install a small variable power module in the dams. Would it cause more silting?
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You mean Dinorwig, it's a 1.8GW hydro peaker plant in Wales.
http://en.wikipedia.org/wiki/Dinorwig_Power_Station
Also peaker plants in general, are specifically designed to be fast start power generation:
http://en.wikipedia.org/wiki/Peaker_plant
And the idea of the car thing, is that you can CHOOSE to sell (some of) your car's electricity that you bought at base-load cost, back to the grid and make a profit. You don't have to though. Peaking electricity is usually priced at several times higher price.
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I certainly don't want the government to start discharging my EV car without my permission.
It would not be without your permission. There would have to be a system that allowed you to set a price for the energy you supplied. At a certain price, you would be happy to sell it!
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I certainly don't want the government to start discharging my EV car without my permission.
It would not be without your permission. There would have to be a system that allowed you to set a price for the energy you supplied. At a certain price, you would be happy to sell it!
Like I said, I would be more willing to charge during off-peak hours than to resell the electricity.
However, if the power company offers $1 per discharge cycle on my batteries.
And the battery pack is valued between $3,000 and $20,000.
And, the power company wants to discharge my car at the time I'm most likely to want to use it.
I might choose not to add the extra unnecessary discharge cycles.
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However, if the power company offers $1 per discharge cycle on my batteries.
And the battery pack is valued between $3,000 and $20,000.
I don't think you're quite getting it. At peak load, the power company probably offers more like $0.6-$0.8 or more per kWh, not per discharge cycle. So if it's 50kWh battery, then your battery charge is worth $30+.
The situation is that the power company is desperate for electricity, if they paid $0.2 per kWh nobody would build peaker plants, and nobody would give them any juice!
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The situation is that the power company is desperate for electricity, if they paid $0.2 per kWh nobody would build peaker plants, and nobody would give them any juice!
That's true. The "spot price" for electricity (in the US anyway) can be incredibly high, and it explains why some utility companies have invested heavily in energy storage systems.