There are several components to the savings to society (and individuals) obtained by a unified vehicle transport system of the kind I've previously outlined.
Just a couple of them for starters:
Since the system doesn't require heavy vehicles, the energy cost of motion of the vehicles is the first and most direct source of savings.
F=ma... force (to move something) equals its mass times it acceleration.... add force to overcome frictional loss or resistances (wind, tire's, bearing friction). So if a vehicle to transport a single person (commuting for example, or shopping mom's to store or mall) weighs only 3x the weight of a normal adult (say 180 lbs/person) or on the order of 600 lbs, then the mass being moved is on the order of 800 lbs. Compared to a standard vehicle today at 3000 lbs transporting that same person the difference is 3200 lbs vs 800 lbs or 25% of the mass of the normal vehicle and single adult being tranported.
Therefore 25% of the energy is required.... all other things equal.
Electrical Energy Power Source
Electric motor energy losses are about 20% relative to internal combustion engine energy losses. Electrical energy transport efficiency (transmisson lines) are more efficient per unit energy transported than for gasoline (from refinery to gas stations). Of course coal mining and burning at power plants vs oil extraction and refining to gasoline could be considered awash, but transport facilities for US tranport of coal to power plants would have to be substantially increased to satisfy the energy demands for an all (or mostly) electrical vehicle fleet, even with only 25% - 30% of the transport energy demand of the vehicle transport concept I'm referring to.
On a relative basis, assuming the difference in gasoline prices and coal power electrical energy prices remain approx. the same in the coming centuries... and I seriously doubt this as oil extraction costs will continue to increase to find more and more oil in less and less easily exraction locations over time. ... but this assumption is therefore a pessamistic one relative to savings. Coal extraction costs are likely to remain constant or even decrease slightly over time as more efficient mining methods are implemented.
Vehicles will achieve (gasoline powered) on the order of 50-75 mpg as time goes forward... this is technically achieved today but not in the interests of engine and oil mfg'ers short term profit motives.
Electrical energy is created by burning fossil fuels in a power plant at 40% efficiency, followed by transmitting it to your house at 93% efficiency, and using it in an electric vehicle at 92% efficiency, providing a total efficiency of around 34% for an electric vehicle.
Crude oil refineries operate at 75% efficiency, and gasoline distribution might cause another 6% energy loss. Since internal combustion engines are only 20% efficient, total efficiency would be around 14%.Gasoline contains ~125k BTU's / US gallon, so energy consumption at the vehicle level is ~3.5k BTU's / US gallon (20% x 125k). Gasolune weighs ~ 6.2 lbs/gallon, so in terms of BTU's/lb, gasoline consumtion at the vehicle use level is ~0.56k BTU's / pound. There are 3413 kW h of electrical energy per BTU so that gasoline consumption at the vehicle tranport level is ~ 1911 kW h / pound of gasoline.Coal contains from 8100 - 13k BTU's / pound. There are 3413 kW h of electrical energy per BTU, therefore a pound of coal contains from 27.6m - 44.4m BTU's / pound. At point of consumption, then coal provides from 10.26m - 16.5m BTU's / lb or in terms of electrical energy, then from 3k - 4.8k kW h / pound of coal.On a pound per pound basis, coal is over twice as efficient in energy production at the automobile transportation consumption level as gasoline... interesting tid-bit.... I didn't know that before.
Coal fired electrical costs of generation are ~ $0.11 / kW h (advanced coal, plants entering service in 2015, including transmission, source DOE). Add local utility cost factors and delivered electricity costs are on the order of $0.14/kW h.
Gasoline costs on a national average level are currently just under $3/gal of regular ($2.94). Since 1990 gasoline prices have increased by ~ 2.3%/year.... which is about the rate of inflation on a gross basis. Therefore, I assume the relative price relation of $0.14/kW h of electricity and $3/gallon of gasoline will remain the same (or actually get worse since gasoline prices would rise with increasing costs of extraction from more and more diffucult sources).
Currently Tesla Roadster reports an energy consumption of 0.21 kW h / mile, of which ~20% is due to battery charging efficiency losses... so that on the order of 0.16 kW h/mile is for transport alone. But this is for the relatively heavy vehicle and battery pack which has a curb weight of 2700. Assuming a 180 lb driver, then on a per mass basis, then Tesla's roadster consumes gets 5.55e-5 kW h/ mile/ lb. This equates to $7.77e-6 / mile/ lb.
The new (yet to be released) Tesla S (sedan) reports 0.26 kWh / mile for a 2 ton (4000 lb) vehicle. This translates to ~0.21 kW h/ mile for transportation alone (omitting battery charging inefficiency). Assuming a single driver, 180 lbs, then the Tesla S consumes ~ gets 5.02e-5 kW h / mile / lb... slightly more efficient than the roadster. This equates to $7.03e-6 / mile/ lb.
I assume gasoline powered vehicles will get to 75 mpg as time progresses. so that relative to current mileage of new vehicles 32.6 mpg, gasoline efficiency for transportation will improve by 2.3x. This means on a relative basis, gasoline will cost $1.28/gal. Thus, transport costs will be (for a 3000 pound vehicle) be $4.025e-4/mile / lb. = $0.04 e-6 / mile / lb.
Assuming average annual vehicle miles of 12k, then the difference in annual costs would be (at ~$7 e-6 / mile / lb delta) $0.084 lb / year less for the electric vehicle. Note importantly that if PEV's and Gasoline powered vehicles weigh approx. the same then the savings for PEV's is virtually nil (this is because of my assumption is that within time competition of gasoline engines with PEV's will give gasoline engines a mileage of 75 mpg). But, if the difference in average vehicle weights is on the order of 2400 lbs (800 lbs vs 3200 lbs), then the average annual energy cost savings is ~$200 / vehicle /year. ... it would be ~2x this (~$400/vehicle/yr) if gasoline engine efficiencies don't improve to 75 mpg over time. In 2006 there were ~ 250 million vehicles registered in US (2 axle, 4 tires)... this number will rise with population growth going forward .. so that on an average annual basis the total savings in fuel energy costs will be no less than $50 Billion (and up to or over $100 Billion until gasoline vehicle mileage reaches 75 mpg). Over any 20 years this amounts to at least $1 Trillion.... possibly approaching $2 Trillion.
These are just two of societal savings... this doesn't yet include initial or amortized costs of vehicle, annual maintenance and insurance costs, or direct costs of accidents & injuries, not to mention indirect costs (loss of productivity &/or income).
Next, think about this for a minute: In any given local area (say 20 or 30 mile radius), at any given point in time what proportion of private vehicles are in actual use vs parked and unattended for 30 minutes or more?. Also think about this ... if the average commute distance is 20 miles each way, with 220 commuter days/year, this amounts to 8.8k miles/year commuting only... that's over 2/3's of the approx. average annual vehicle mileage. In other words, food for thought.... over 2/3's (or possibly only half) the cost of purchase, maintaining, and insuring a vehicle is for the express purpose of having employment... a cost of employment.
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