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Published on June 10th, 2015 | by Tina Casey


Electric Buses Could Beat CNG Buses By A Mile — Or Nearly 6

June 10th, 2015 by  

At one point in time, compressed natural gas was supposed to rescue urban mass transit from the horror of diesel bus fumes but it seems that moment has come and gone. The US company Proterra has been testing out its new high-performance electric buses in Altoona, Pennsylvania, and so far the results indicate that zero-emission electric buses are far more efficient than their gassy cousins.

We’ve been following the development of Proterra’s electric buses along with our sister site Gas2.org, so let’s check out the latest news.

Proterra electric buses beat CNG buses

Electric Buses Vs. Diesel Vs. Compressed Natural Gas

The last time we caught up with Proterra was just a couple of months ago, when we had a chance to chat with the company’s VP of sales and Marketing Matt Horton.

Horton made a good case for the bottom-line benefits of switching over from diesel to electric buses. He also pointed out that as far as Proterra’s experience goes, “the early adopters have already adopted” — meaning that transit agencies looking to get out of diesel can leverage the real-world track record of electric buses.

That’s all well and good when it comes to electric buses vs. diesel, but as the pressure builds for cities to adopt zero-emission vehicles, the real competition is going to come from compressed natural gas (CNG) buses.


Proterra Electric Buses Beat CNG Buses

That brings us to the Altoona tests. The city of Altoona happens to host the Altoona Bus Research and Testing Center, and if you’re looking for third-party testing cred, this is where you’ll find it. The facility is run by Penn State University under a 1987 law that requires transit buses to meet certain standards before they can be purchased with federal funds.

That’s where Proterra took its Catalyst model to show off its stuff, and here’s how the company sums it up:

While conventional diesel buses average 3.86 MPG, the Proterra Catalyst achieved the best efficiency rating ever for a 40’ transit bus at 22 MPGe. Nearly six times more efficient than a diesel or CNG bus…

For the record, according to Proterra, the Catalyst also beat its nearest electric bus competitors for energy efficiency per mile by a comfortable margin, and it is “more energy efficient per mile than most light-duty trucks and SUVs on the road today.”

Proterra electric buses

The Proterra Catalyst electric bus.

That certainly takes care of the bottom line issue for Proterra electric buses. However, performance is an equally big issue for transit buses, especially when it comes to “gradability” — the ability to navigate hilly terrain without struggling to maintain speed. That’s a particular challenge for electric buses, which tend to be on the heavy side due to their battery load.

So, how’d Proterra fare in that regard?

Pretty good, as it turns out:

In addition to energy efficiency, the Proterra Catalyst broke records in gradeability, weight, and acceleration… The Catalyst conquered a 15.5% grade, unprecedented in this test by an electric bus…

[major snip]

As proof of the vehicle’s superior power-to-weight ratio, the Proterra 40’ Catalyst also achieved 0-20 acceleration in just 6.7 seconds.

Proterra’s secret sauce is a body made of carbon fiber and other lightweight material, which helps to offset the battery weight. Durability and resistance to corrosion is another plus for the advanced body materials.

Rapid acceleration is particularly critical for keeping routes running on time, allowing bus operators to move in and out of traffic with greater ease.

Blowing Up The Case for CNG Buses

Throw in solar and wind energy charging options for electric buses, and you can see how CNG buses will get left behind in the dust, in terms of overall environmental impacts.

While CNG is a low-emission technology for buses and their environs, natural gas shoulders a heavy load of environmental impacts linked to fracking, and a growing number of studies indicate that the natural gas lifecycle — including transportation and storage — tends to wipe out its tailpipe advantages.

In that regard, now would be a good time to revisit that recently released fracking report from the US Environmental Protection Agency.

The way we see it, if you read between the lines, it’s obvious that the EPA fracking report is a cry for help. The agency actually does a bang-up job of pointing out that it has no legal mandate to collect the relevant information, much of which is protected by loophole in federal water protection regulations created during the Bush presidency.

One of our colleagues followed up with another take on the EPA fracking report. Take a look and if you have any thoughts, leave us a note in the comment thread.

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Image Credits: Courtesy of Proterra. 

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

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