Last season I watched this show called Mean Green Machines on Discovery Channel which compared the performance of two Drag Bikes. One was gas-powered and the other electric-powered, called the KillaCycle.
There were two speed challenges and one efficiency challenge. In the speed challenges the gas-powered bike was only slightly faster than the electric-powered. But in the efficiency test the electric-powered bike was the winner by a long shot. It was estimated that the gas-powered bike uses about $3.70 worth of fuel for one run, whereas the electric-powered bike uses about 6.5 cents worth of electric power for one run. That’s around 50 times less energy cost than the gas-powered bike.
There’s also the fact that the electric bike is much simpler in terms of design and maintenance. The gas-powered bike, although mechanically beautiful, takes a lot of effort to keep it running well. In addition, there’s the noise factor. The electric bike produces much less noise than the gas bike. It’s completely quiet as it pulls up to the starting gate.
The technology of electric vehicles is still relatively new so the next time they face off the electric bike will stand a serious chance of winning the speed challenge.
It got me thinking. How much more efficient would an electric car be than the gas-powered cars we currently use?
Let’s consider my own vehicle.
Right now my car takes about $50 to fill up. Its optimal mileage is about 44 mpg on the highway (US gallons). It’s actually one of the more efficient vehicles. Now let’s compare that to how much it would cost to run on electric power, keeping everything else the same.
The average gas-powered vehicle maximizes its fuel efficiency at around 60 mph. At this constant speed the power required to keep the car moving is approximately 16 hp. This is approximate power usage for average vehicles, resulting from air drag and friction. I don’t know the specific power for my vehicle, but 16 hp will suffice as an average value.
Now, 16 hp = 11.9 kW
The gas tank holds 13.2 gal
The distance traveled on a full tank is 44×13.2 = 581 miles
The time to travel this distance is 581/60 = 9.7 hrs
Currently, the cost of electricity in my area is 15 cents/kWh
The net cost of electricity to power the car for 9.7 hrs on the highway is, 11.9×0.15×9.7 = $17.31
We can assume a minimum efficiency of 80% for electric motors, and roughly 85% battery storage efficiency. This gives a combined conversion efficiency of 68% (0.80×0.85 = 0.68).
Therefore, the actual cost of charging the vehicle is $17.31/0.68 = $25.46 – much cheaper than $50!
In reality, the cost savings is even greater since I was using the maximum highway mileage of the gas-powered car and the minimum efficiency of the electric motor, in the calculations. Due to regenerative braking, the savings are even greater for city driving, but for the gas-powered car, all the starting and stopping reduces its efficiency by quite a margin.
In addition to paying much less to “fill up” there are other advantages of electric-powered vehicles:
• They can be charged at your house overnight. No service stations are necessary
• There is no infrastructure necessary such as for fossil fuels, where you have to retrieve oil, refine it, and ship it across the country. The only infrastructure necessary for electric vehicles is power lines to deliver electricity
• Less maintenance requirements since the powertrain of electric vehicles is simpler in design than in fossil fuel powered vehicles
• No air pollution and almost no noise pollution
Power plants may have to produce more power to accommodate extra demand on the power grid, but they can use clean sources such as hydro, solar, or wind power.
Now, there’s the common perception that battery capacity of electric vehicles is insufficient for long distances. But that too has come a long way. Have a look at the Tesla Roadster.