by Quinny » Sat 09 Aug 2008, 04:44:41
Fairly new here, but this seems to break the second law. Losses at each conversion need to be taken into account.
Standard vehicles Fossil Fuel -> Motion (some heat and other Loss)
EV Fossil Fuel -> Electric (losses) -> Distribution (losses) -> Motion (losses)
I cannot see how its possible for an EV to be more Energy Efficient taking into account whole system.
Please correct me if I'm wrong.
$this->bbcode_second_pass_quote('lper100km', '')$this->bbcode_second_pass_quote('lper100km', '
')So, at a superficial level, an EV is approx 67% more energy efficient than an equivalent gasoline powered vehicle. What should be added in each case, is the energy needed to produce a 36,000kW energy by the extraction, refining and delivery process for gasoline and to produce 21,500kW by the generation process for electrical power. This would give a more complete statement of the overall power consumed to drive one mile down the hiway. I do not have access to those numbers unfortunately.
The underlying assumption is that 'normal' driving speeds are being achieved. 100kWh per mile will get you there, just at 15mph, not 65mph.
I was just being lazy. A few minutes search found these two references which I think can be taken to summarize both the gasoline and electrical energy production overhead.
www.vihrealiitto.fi/yleviarkisto/11...
It's in Finnish! Here's a summary:
This was meant to account for the fossil energy used to extract, transport and manufacture the raw material (crude oil) into the final energy product (gasoline).. According to the study, gasoline has an energy ratio of 0.805. In other words, for every unit of energy dedicated to the production of gasoline there is a 19.5 percent energy loss.
http://www.aph.gov.au/library/Pubs/rn/1 ... 99rn21.htmThis is a comprehensive Australian study, showing that with the proper design, efficiencies of up to 80% can be achieved in the conversion of fossil fuel to electrical energy.
Hydro and nuclear generation plants would show significantly higher efficiencies. I’m estimating at say 95%.
For the purposes of my posts, I will ignore hydro and nuclear, and say that the energy overhead for the production of both gasoline and electrical power is 20%.
Thus the total energy required for one US gall of gasoline is 45,000kW
The total energy consumed for an equivalent battery charge to operate an equivalent auto at 50mpg is 27,000kW
The gross energy per mile for gasoline is 900kW and could well be higher
The gross energy per mile for electrical is 538kW and could go lower.
Electrical power turns out to be 67% more energy efficient overall than gasoline and could go higher on average. All in rounded numbers and generalized assumptions.