Plug-in hybrids: 100 miles per gallon or 59?
Plug-in hybrids have emerged as the favorite form of transportation for reducing greenhouse gases in the near term, but calculating their energy efficiency can be a little complicated.
Plug-ins won't conk out after 130 to 200 miles, like electric cars, and they don't require major technological breakthroughs, like hydrogen cars. Converting a Prius to a plug-in hybrid costs about $10,000 to $15,000 now--that's part of the reason only about 50 exist--but if car manufacturers decide to make these at the factory, the additional cost may only run $6,000 or so, say proponents. That's a lower premium than what electric cars will run, by the way.
Plug-ins have more batteries than regular hybrids and can get charged from a wall socket.
A plug-in hybrid
(Credit: Tom Krazit/CNET News.com)But there's some disagreement over how much energy these cars actually consume. Owners report their cars going 70 to over 100 miles on a gallon of gas. But that doesn't include the electricity used the charge the batteries. The cars do get 100 MPG, but what is the total energy consumption?
When you add in the electricity, plug-ins get the equivalent of 59 miles per gallon, according to John Shore, who is organizing the X Prize for automobiles. He gets this number by examining data from Google's experiments with plug-ins.
"The most reliable information available today about PHEVs is from the Google project RechargeIT, in which they report actual data from real driving conditions for a Prius modified to be a PHEV. Google currently reports that, on average, the vehicle gets 73.6 MPG (gasoline) and uses 118.1 watt-hours/mile of electrical energy--these equate to 59 MPGe, considerably less than the AXP goal of 100 MPGe," he wrote in an e-mail.
Shore, by the way, is a big fan of plug-ins. However, those numbers mean that current plug-ins won't be able to waltz away with the automotive X Prize, which will likely give more than $10 million to inventors who can come up with a car that can get 100 miles a gallon and win a cross-country race.
Not so fast, say Felix Kramer and Ron Gremban of CalCars, one of the chief organizations promoting plug-ins. Argonne National Labs has a plug-in that reportedly gets 150 miles a gallon. If you go through the equivalency calculations, you end up with 103 miles per gallon equivalent.
Regardless of the actual mileage, Gremban points out that the important thing is that plug-ins reduce greenhouse gas emissions and dependence on foreign oil, and there is not a lot of debate about that.
If you live in a state where coal is the main source of electricity, like Ohio, the emissions from a plug-in are about the same as a regular hybrid. But in California, the emissions are much lower because of hydroelectric power, wind and other renewables. (Coal accounts for approximately 52 percent of U.S. electricity, according to the Department of Energy.)
Using the power from them would cut the excess fossil fuels used to generate electricity needed for their car.
Thinking green isn't hard. :)
about 100 percent of the sunlight that falls on them and turn
about 10 to 15 percent of that energy into electricity (or
whatever the electrical conversion efficiency is for the cells
used). The rest becomes infrared, which is to say, heat. So, 85 to
90 percent of the sunlight that falls on the solar cells goes to
directly warm the atmosphere. Before the cells were installed,
whatever they were installed over probably converted less than
that to heat. For the earth as a whole, the average is 70 percent.
Light backgrounds might convert a lot less than that.
Not saying don't use solar cells, by any means, but if you're
going to cover something reflective with them, just realize you're
not getting quite the contribution to reducing global warming
that you otherwise might.
The problem with putting solar panels on your roof is that unless you disconnect from the grid completely you are just making matters worse. Solar PV output peaks around local noon when the sun is as close to vertical as it gets. Unfortunately electricity demand usually peaks several hours later when people get home turn on lights, heat / cool and cook
If you don't demand the baseload from the utility because you have solar -- the utility will have less baseload and then when you do demand the peak will be steeper. Peak power is usually produced by combustion turbines that produce very expensive electricity.
The same applies to wind except it is even more unpredictable and hence can't be counted on to produce more than a small fraction of total demand.
All of the above doesn't apply if there is local, distributed throughout the grid or central energy storage that is efficient and low cost.
Unfortunately, at the present the only storage that is reliable and cost efficient is pumped-hydro.
Moral of the story -0- it really is not easy to be green
westy
http://www.chevrolet.com/electriccar/
I think it would be better to quantify efficiency in terms of energy cost per mile, assuming average baseline prices for gasoline and electricity.
Measured that way, a plugin like the Chevy Volt could be twice as efficient as today's Prius. Too bad it's still just a concept.
I heard too much of solar, wind, shoe, ...
energies these days. Just started getting bored.
1/MPGe = 1/124 gal/mi + 123/33,000 kWh/mi / kWh/gal = 0.00807 + 0.00373 = 0.0118 gal-equiv/mi.
1/0.0118 = 84.7 MPGe
Felix, who just left today on vacation, says, "On Google, we are hoping to be able to give them some pointers soon to enable their drivers to take a few easy steps to improve those numbers. As you can see if you look at the Google data, often their cars are going on short trips with significant cold-engine use, which is another reason their #s are low." To which I also add that, though I don't know because I've never driven a Hymotion conversion, Felix's EnergyCS conversion may be more aggressive at displacing gasoline with more-efficient electricity than are Google's Hymotion conversions.
- Totally deceptive reporting on Plug-in-hybrids"
- by tedpk August 9, 2007 6:54 PM PDT
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(19 Comments)1) Gasoline internal combustion engines are at least as efficient as any thermal source of motive power for generating electricity
2) then you must incorporate the inefficiency of generation, transmission, distribution toi get the electricity to the plug
3) then you must consider charger and battery charging and discharging to get the electricity to the motor
4) finally once you are converting the electrical energy to motive power
None of the above is 100% efficient -- so the only gains that you can have from a hybrid comes from the regenerative braking
Even the city benefit from not idling at a stoplight can be equaled by turning off the engine and using some sort of stored energy start {e.g. compressed air}
So then we come to the presumed benefit of the plug-in-hybrid ore even pure-electrics and even hypothetical hydrogen-economy vehicles with respect to "Greenhouse Gas" emission
This too is bogus as mostly you are simply shifting the location of the emission from the highway to the fossil fuel power plant -- although in the case of the hydrogen vehicle -- you aren't really even doing that {see the PS}
The comments about wind and solar are totally specious as they represent an insignificant amount of useful deliverable energy
There are only two currently non fossil fuel sources of electricity -- hydroelectric and nuclear
Hydroelectric is limited to the seasonal hydrological cycle and geographic locations and in the continental US is close to being fully utilized
Therefore the only benefit from the plug-in-hybrid is derived from the use of nuclear power to generate electricity
The rest is "pardon the pun" just hot air
Westy
PS: of course H20 vapor is a more potent "Green House Gas" per unit volume than CO2 and of course far more prevalent in the atmosphere