I'm the gent who posted "Questions on electrical distribution system and motor efficiency" last weekend. Thanks for the responses.
The reason I posed my questions was to be able to better contest assertions made by a guest on N.P.R.'s "Science Friday" on June 30. The host was interviewing someone who's put together a movie, now showing in a few cities, which supposedly documents how politicians, acting on behest of the oil and automotive industries, quashed efforts to develop electric cars in the mid and late 1990s. That is, these cars had batteries charged by household power, and a battery-powered motor.
The guest said these cars were sought in California, for their supposed advantage of eliminating tailpipe exhaust (for cleaner air). Some advantages he cited are ones I concede, such as the car can be lighter, as a heavy engine and transmission are not required. He said G.M. made these cars for a while and leased them, and they were quite popular, but ultimately, G.M. stopped leasing them, and destroyed them.
My reaction was that he was a non-technical person who didn't understand what he was asserting, and had overstated the case for electric cars, also convincing a lot of others who also aren't energy-savvy. He didn't seem to be aware of the drawbacks of using electrically driven cars; nor did he mention any.
Someone who knew about these electric cars called in, said they had very limited range for driving - about 30 miles - between recharging, and that was the main reason they fell out of favor.
I tried to reach Science Friday to challenge the guest, but the line was busy.
Anyway, my reasons for skepticism about the guest's arguements include the following:
-- Use of electric cars shifts the source of air pollution and CO2 to the atmosphere from tailpipe exhaust to power plant exhaust (assuming a fossil fuel is used for power generation, a safe assumption in the U.S.) Coal and fuel oil produce lots of pollution and CO2.
-- A widespread switch from gasoline to electric powered cars would require a huge investment in more generation capacity by electric utilities.
-- Although cars are known to have poor thermal efficiency (to my knowledge about 20% of the useful energy in gasoline is converted to mechanical power), similar inefficiencies abound in use of electric cars. Here is a list of inefficiencies that apply, and I'm sure others in this group could expand the list, or expound upon it:
- Fossil fuel plants have limited thermal efficiencies. I used to work at a power company, and about 1990 its best coal-fired plant had a thermal efficiency of about 35% (thermal efficiency compares the thermal equivalent of kilowatt-hours to the energy content of the fuel burned);
- Impedance of power lines, and related factors result in energy lost in electric power distribution;
- There are losses in each stage of each transformer to the homeowner's
120/240 VAC 3-wire connection to utility lines;- The converter used to charge a car battery will have losses; it has to be stepped down in voltage and rectified.
- In the car itself, not all of the energy the battery applies to the motor will result in mechanical power (hence my previous question about the efficiency of DC motors.)
I'm very interested in responses from other posters. I intend to contact "Science Friday" about this. I suspect this guy was spouting a lot of nonsense.
M.H.