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kkersey
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re: Chevy Volt flap: What's the big deal?
kkersey   10/29/2010 8:48:10 PM
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Etmax - thanks for the update with eff.numbers. It basically validates what I was saying...but a few numbers may be misleading. Here are my tweaks. *A coal plant is ~33% efficient* yes. *A gas plant is ~50% efficient* yes - but most are less.(60% is the newest high-tech GE natural-gas fired plant, not deployed in great qty yet.) *Transmission losses are 6.5%* yes. or more. *A diesel ICE is 50%(2 cylinder Large)* Only HUGE ship engines reach this level. Advanced auto diesels (VW / Audi TDI) are up to about 40% thermal eff. *A Gasoline ICE is 43% efficient* A bit optimistic, usually low 30's%, mid 30's% for advanced ICE like the Prius Atkinson engine. Old V-8's were mid-20's% efficient. *An electric brush-less motor is 90% efficient. An electric brush motor is 80% efficient.* yes *Battery storage is ~90% efficient* Less when considering full charge / discharge cycle. Regenerative braking helps city cycle efficiency a lot, but doesn't help highway cruising at all. It all depends on driving cycle. Net-Net, pure electric vehicles do NOT save energy, do NOT reduce CO2, have serious practical problems and cost a mint. Hybrids solve most practical problems, but also have high cost. Once a high percentage of the grid is powered by renewables - THEN (and only then) will EV's make sense. For those that don't care about the cost - hybrids (or plug-in hybrids) are an OK mid-term solution.

Etmax
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re: Chevy Volt flap: What's the big deal?
Etmax   10/29/2010 1:24:47 PM
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Thank you for your insight, it will be indeed be interesting to see the Auris to Auris comparison. I hope they give the cradle to grave CO2 figures too. It will be interesting. FYI, I don't disagree that regenerative braking works and is a significant aspect of electric vehicles hybrid or otherwise, only that it is not as efficient as one would hope. :-(

markogts
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re: Chevy Volt flap: What's the big deal?
markogts   10/29/2010 8:31:07 AM
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To compare a Fiesta with a Prius is not fair. A Prius has almost twice the boot and has better seating. On the Italian market, I read as follows: VW Polo 1.2 TDI avg. 3.3 l/100 km, 87 g/km CO2, 0-100 km/h 13,9 s, wheelbase 247 cm, 16 k€ Toyota Prius avg. 3.8 l/100 km, 89 g/km CO2, 0-100 km/h 10,4 s, wheelbase 270 cm, 26 k€ A good comparison will be done with the Auris Hybrid, which has a direct concurrent model, the Auris diesel. That will be interesting. About the fact that batteries dump energy, your statement would imply that batteries heat up like brakes do, but that is not the case. Try driving a hybrid (even a mild one, like the Insight) and you'll see how the charge indicator jumps when braking gently (with empty batteries).

Etmax
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re: Chevy Volt flap: What's the big deal?
Etmax   10/29/2010 7:12:02 AM
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To some extent hat is an issue, but Regenerative braking is more beneficial to saving brake pads than restoring power as batteries dump energy a lot better than they accept it. Because of this the CSIRO has worked on capacitor/battery combos but until they have a commercial example I will sit on the fence. What I do know is that small diesel non-hybrids currently have better economy than hybrids (perhaps due to weight advantages) and because they are a lot less carbon intensive to make may well be better (for the moment) for the environment. Diesels have good low end torque, not as good as electric motors, but over all performance is comparable. This link http://rac.com.au/About-Us/RAC-eNews/March-2010/Top-20-most-fuel-efficient-cars.aspx shows the top 20 cars tested and the Ford Fiesta is better (No 1) than the Prius (No. 2). I believe the VW Polo is also better. though not listed. There are 3 other Diesels that are on par with the Prius, and given the cost and lifetime CO2 difference they make the diesels environmentally friendlier.

markogts
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re: Chevy Volt flap: What's the big deal?
markogts   10/29/2010 6:52:02 AM
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@Etmax: one important point that IMO you are missing is the *mean* efficiency of an ICE during *all* possible load conditions. I agree with you that a properly sized diesel engine can be the best solution for highway cruising but no matter how efficient, it will still waste energy while braking, idling or when simply throttled down. Here comes the great efficiency of electrical motors, which are reversible and have good efficiency on a wide range of load-speed combinations (way higher/wider than an ICE). So, for urban driving, EV (and hybrids) have big advantages. I still think that the best solution will be a hybrid with a good ICE. BTW, I think the weak point of the Chevy Volt is the ICE: four cylinders are too many for such a small power output: a new design is needed, something like one or two cylinders, with staged and intercooled compression and turbocompound or miller/atkinson recovery, everything calibrated for a narrow working band.

Etmax
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re: Chevy Volt flap: What's the big deal?
Etmax   10/29/2010 3:01:19 AM
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I did a few checks on Google and most of the results pointed to Wikipedia: A coal plant is ~33% efficient A gas plant is ~50% efficient Transmission losses are 6.5% A diesel ICE is 50% (2 cylinder Large) A Gasoline ICE is 43% efficient freight losses for fuel? but a lot less than 6%. An electric brush-less motor is 90% efficient An electric brush motor is 80% efficient Battery storage is ~90% efficient Both of these are taken at full speed, ie partial load speed control losses not included, but I would 10-15% wouldn't be unreasonable. This suggests to me that if you look at CO2 emissions over the life of the vehicle a small diesel may just be the best (current) solution due to the lowest effort to produce and one of the highest efficiencies.

selinz
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CEO
re: Chevy Volt flap: What's the big deal?
selinz   10/27/2010 5:06:03 PM
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The biggest question is does it work? And does it avoid a great deal of inconvenience for the driver? Since it has a gas engine and an electric engine, it is a hybrid, period... The government categories should be based on effectiveness. If a gas or diesel engine gets 60mpg, it should recieve more tax benefits than a hybrid that gets 20mpg. That gets rid of all the silly positioning...

kkersey
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re: Chevy Volt flap: What's the big deal?
kkersey   10/25/2010 5:52:33 PM
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I checked the difference between the VOLT and Toyota hybrid transmissions...and it confirmed my suspicions. Toyotas "synergy" drive connect 2 electric motors and the gas engine to the wheels without mechancial clutches (except for normal gear-changes). They do "mode changes" electronically by how the electric motors are energized. The VOLT's clutches do the same thing...with higher complexity. GM must be doing "patent avoidance". Re being "mistaken" about using EV's+Power Plants vs. ICE cars - no, I don't think I'm mistaken, I'm pretty informed. The facts are surprising, but are counter to most of the hype we hear from the government, car companies, even well-intentioned green folks. Don't get me wrong - I'm 100% in favor of changing our power grid to renewables ASAP. My point is that if you look at fuel-to-wheel (with TODAY'S grid) you'll see that pure EV's make no sense, don't reduce CO2 or energy usage. It's the coal and lithium lobbies, the govt (and misinformed green consortiums) that are pushing for EV's before their time. I'm not saying EV's are BAD, I'm saying that they don't do much good today, and are a distraction from the more pressing need to green the power grid. However, EV's CAN make sense once most of the grid is green. HYBRIDS do have efficiency advantages today in some usage profiles due to regenerative braking and optimizing ICE efficiency...so that is a different conversation than pure EV's. Lastly, we need to start doing more forward-thinking on how to convert the grid to renewables. PV's and Wind are OK for now...but can't be the MAIN power sources without energy storage for 365/24/7 power. Therefore, energy storage on a mass scale is needed. I think this is best done by solar thermal power plants, and biofuels (algae based being my favorite). Electric batteries (in battery farms or in vehicles) are too expensive and limited cycle-life to function as the grid's energy storage medium...at least today's battery technology.

Etmax
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re: Chevy Volt flap: What's the big deal?
Etmax   10/23/2010 2:11:15 PM
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Slightly off the Chevy Volt topic, another badly thought out government regulation is lead free soldering in electronics. I actually increases land fill and dramatically increases CO2 emissions due to higher soldering temperatures. As you say, no system thinking.

SteveHamilton
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re: Chevy Volt flap: What's the big deal?
SteveHamilton   10/21/2010 9:50:47 PM
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Its only been about 15 years since i ran the numbers, but i think your starting point is incorrect. At HW speeds (say 70 MPH) wheel and air resistance costs about 5 HP. That is 3.5 KW, not tens. Where 10s of KW are needed is for acceleration, not for high speed.

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