>>even if you went home and ran a diesel generator to recharge your cars batteries you would come out ahead. <<

sorry no... if that was the case you would break the fundemental laws of physics... everytime one converts energy one loses some

electricity generation is relatively inefficient with only 40% of the energy being captured. 60% is lost in heat generation...

regards

gm23

Oh…… so much to reply too…

>>Begin with braking, as this is the best-understood principle. Cars reject a lot of energy as heat from the brakes.<<

This is true regardless of propulsion source… it takes energy to stop anything and the energy required is as a consequence of the mass and momentum, not the source of propulsion…

>> Electric and hybrid cars have the ability to recover a substantial portion of that energy and re-use it to bring the car back up to speed afterwards. There is no equivalent vector to turn that energy back into gasoline. <<

In most cases and the only commercial mechanism I have seen for this is with the use of a large and heavy flywheel to transfer the energy… its use is limited to vehicles that regularly stop and start.. i.e. buses; largely due to the additional energy required to carry the heavy load around.. this is also true to some extent with electric cars which still rely on battery technology that is similarly very heavy and hence costly to carry around. The efficiency of such recapture devices is dependent on the stop start frequency and are similarly more likely to lead to a benefit in a heavy (i.e electric) than a light (internal combustion) vehicle because the relative mass of the recapture device is less in a heavy vehicle than a light..thus adding it to a light vehicle negates the gain due to the greater relative increase in the overall mass and the increase in energy requirements to move it… in short it costs more to carry than it recaptures…


>>No gasoline/diesel engine can start from a standstill. Mechanical constructs have to be put in place (clutch/transmission) in order to make it possible to move a vehicle at all. Substantial amounts of energy will be rejected from the transmission in the effort to load the engine gently enough as not to make it stall.>>

Not totally sure what you mean by ‘standstill’… but assume you mean whilst ‘loaded’ i.e the drive mechanism engaged… if that is what you mean then you are incorrect.. whilst requiring more input a engine can be made to start whilst loaded… in fact most small plant (potable generators, cement mixers, etc) are direct drive and without a clutch, they can only be started loaded.. in the case of a vehicle the clutch facilitates reducing the load thus needing a smaller amount of energy to turn it over.. it also facilitates changing gear and allows one to stop the vehicle without having to also stop the engine.. whilst an electric car doesn’t need a clutch, the same effect being achieved by reducing the current, it still has an optimum rpm.

>>This is why railroad locomotives are designed this way. <<
not all trains are electric, many run on diesel or bio-diesel. Generally you will find electrified tracks in built up/urban areas and diesel locomotion where more remote routes are taken… this is largely down to the economics of transporting electricity and the power loss over long distances (resistance of the wires) But lets not knock trains here… I AM A BIG FAN OF THE RAILWAYS.. trains by a long margin are the most efficient means of transporting people and goods regardless of the means of propulsion… a transport of the future, born in the past…

>>Taking this a step further, energy produced at a power plant will be produced at optimal conditions for the engines/generators used. They will be purpose-tuned to run most efficiently at that particular speed, and efficiencies of up to 55% can be realized with some engine classes (look up combined-cycle turbine)<<

I beg to differ here.. power plants need to cope with daily and seasonal fluxes to cope with surges (half time kettles boiling, sudden cold snaps, heat waves, etc). In order to do so they generally run at below optimum..but they still then overproduce, hence they sell off cheap energy at night both to industrial and domestic uses (night storage heaters).. the problem is complex (as I’m sure you know) and very politically charged (i.e. public verses private ownership)…

Similarly whilst efficiencies of up to 55% can be achieved with modern technology most power plants are far from modern and the mean efficiency is as I posted earlier nearer 40%... by the same token a modern diesel engine has an optimum efficiency rating of 56% (For an air standard engine with  = 1.4 , compression ratio rC = 15 and expansion ratio rE = 5, this gives an ideal diesel efficiency of 56%. Source hyperphysics.phy-astr.gsu.edu/Hba...html )

>>Finally, electric cars are source-agnostic. Gas/Diesel cars require oil, of a particular grade, and can't run on much else (noted exception for biodiesel). An electric car can run on any electricity, regardless of how it is generated, hence, it can bring us to cars powered by wind, solar, hydro, etc.<<

True, but that doesn’t negate responsibility for CO2 generation. At present I believe that in the US Texas has the highest amount of electricity production from renewables… a miserable 2%.. thus without addressing this issue first and 2% is pretty insignificant…. Then all electric cars will likely source there power from non-renewable and out dated power plants…

I’m afraid the source of the electricity is perhaps the most critical component.. if it is from wind/solar or magic perpetual energy machine then, as you have a free and benign source, efficiency becomes irrelevant.. for efficiency is only an issue where it impacts on the economics and the availability of supply…. As with fossil fuels.

Don’t get me wrong… electric transport has a future but it’s not a solution to the energy crisis… private transport is one of the largest uses of fossil fuels and if every car went electric tomorrow the figures would remain largely the same… the same oil, the same coal, the same CO2 problem only the air in cities would be cleaner, our cars wouldn’t fart (no Cat) but our power stations would ensure that the net difference to global atmospheric concentrations would remain the same….. in my book a lot of energy wasted in shifting a problem rather than tackling and solving it….. the problem being the belief that we need personal transport and that having it is a right…

Regards

GM23