The previous post detailed how the Benton County Public Utility Department had concluded the intermittent nature of wind power precluded it being a reliable source of power. This post details the need to charge most EV batteries overnight means very little power will come from solar panels. That CO2 emissions from natural gas power plants to charge EV batteries offsets the benefits of reduced CO2 with EVs. That CO2 emissions from coal power plants to power EV batteries will exceed the CO2 reduction with EVs.
Governor Newsom recently announced California will prohibit the sale of new gasoline- or diesel-powered cars in 15 years. His rationale presumably being electric vehicle efficiency, 70%, is 3.2 times the 22% efficiency for gasoline vehicles.
EV mileage commonly refers to how many miles they'll get from the 33.7 kW of electrical power in a gallon of gasoline. At 65 mph an EV typically takes .375 kWh per mile. Thus the EV effective miles per gallon is ~90 empg, a significant improvement over the 28 mpg for gasoline powered vehicles.
The question becomes where do they get the .375 kWh supplied to the EV. A hybrid car gets the power from its gasoline engine. The efficiency of using electric power to drive the wheels rather than the engine typically increases mileage to ~ 55 mpg. However the power for a "plug-in" EV has to come from other sources.
The problem is, even in California, the vast majority of EV batteries will be charged over night when solar power is no longer generated. Unless EV owners have some way of storing the electricity during the day, the electricity used will likely come from fossil fuel powered generators. Clearly EV car use will not be CO2 free.
A gas turbine converts about 38% of its energy into electrical power. That loss along with loss during transmission results in it taking 2.8776 kWh of energy at the source to supply a kW to the car, reducing EV mileage to 31.2 empg. A/C and heat under "ideal driving conditions" at 65 mph would reportedly drop EV empg ~10% on a new car and 18% on a 4.5 year old battery to 27.5 empg. More severe conditions could drop empg by 25% on a new car and 30% on a 4.5-yer old car reducing mileage to 21.8 empg. By comparison the 3% loss in a gasoline powered car from A/C and heat is presumable reflected in the 28 mpg rating. Clearly there is very little mileage gain from EV power.
An EV battery currently costs about $100 for every kWh stored. At .375 kWh per mile, an EV would require a battery costing $10,000 to travel 250 miles between charges. Charging the battery coud take several hours. The cost associated with storing gasoline in either a conventional or hybrid is minimal as is the time to "recharge"it. It's a question of whether the cost of adding electric motors to drive the wheel rather than the engine outweighs the fuel savings.
The EV's principle benefit is their reduction in CO2 emissions. Burning a gallon of gasoline produces 20 lbs of CO2, so a car averaging 28 mpg will emit .71 lbs of CO2 a mile. Natural gas combustion produces 117 lbs of CO2 per million BTU or 289.3 kW or .40 lbs per kW Assuming .375 kW per mile at the meter and 1.08 kW at the source, .43 lbs of CO2 will be emitted at the power station per EV mile, 40% less than a gasoline powered car. (However a hybrid vehicle getting 55 miles from 20 lbs of CO2 would emit only .36 lbs of CO2 a mile.)
Again, A/C, heat, normal driving conditions, and age would increase EV power generated CO2 emissions . Their effects on gasoline engine and hybrid vehicles are presumably reflected in their 28 mpg and 55 mpg ratings.
Meanwhile in states using coal, 228 lbs of CO2 are emitted to generate the 289.3kW. That equates to .79 lbs of CO2 per kW. Again assuming the .375 kW per mile at the meter and the1.08 kW at the source, .85 lbs of CO2 will be emitted to power the EV a mile, 20% more than a gasoline powered car averaging 28 mpg. (Again real life operation would increase that penalty)
That should give pause to those advocating EVs.
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