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Electric Car’s Achilles’ Heel
By Claus Schafhalter | September 7, 2010
Manufacturer are busy developing a new breed of cars, electric cars. There are some examples on the market today, and many more are expected to hit dealer’s showrooms over the next few years.
There are still many challenges to overcome to make electric cars ubiquitous. We need a charging infrastructure preferably based on renewable energy as opposed to electricity generated by fossil fuels. We need to bring the electricity for charging to the spots where cars are recharged, which brings new challenges to the electric grid and to the connections to homes and businesses.
Still, it seems that most of these challenges can be addressed with technology that is available today. However, the weak link today is the energy storage medium, the battery powering the electric car.
Have a look at energy density:
- Wh/kg — Watthours per kilogram as indicator of how much energy is stored per unit of weight
- Wh / L — Watthour per liter as indicator of how much energy is stored per unit of volume.
| Energy Density per | ||
| Weight | Volume | |
| Energy Storage Medium | [ Wh/kg ] | [ Wh/L ] |
| Gasoline | 12200 | 9700 |
| Lithion Polymer battery (available) | 110 | 300 |
| Lithion Polymer battery (lab) | 440 | 970 |
These numbers show that you need much more weight and volume to carry around when you want to drive an all electric car as opposed to a conventional gasoline car if you want to go the same distance without refueling stop.
Now, there are some mitigating factors: Internal combustion engines are inherently inefficient compared to electric motors, and while the energy density of gasoline has turned out to be stable for decades, batteries became much better and technological advancements are expected to continue. Combine this with charging stations at home, at work, at shopping centers, and other places, the Achilles’ heel of poor energy density for batteries might just become manageable.
Claus Schafhalter, Management Consultant @ Sunogos
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