Photo: Flickr, CC
It's all about low-pressure areas...Most long-haul freight should be transported on trains rather than trucks, since rail shipping is more fuel-efficient, doesn't add to road congestion, and reduces infrastructure maintenance costs (70,000lbs trucks can be very damaging to roads). But sadly, the reality in the U.S. is that over the past few decades, the number of long-haul trucks has only gone up. There is now about 1.3 million semi trucks transporting goods over long distances, each traveling around 150,000 miles per year, burning billions of gallons of diesel fuel. Is there anything that can be done - except pushing for more rail - to make things better?
Photo: Flickr, CCInspired by research done by the aerospace industry and the fact that "in the aerospace industry, new aircraft are generally 20% more fuel efficient than the units they replace. So why not try to accomplish the same concept in trucking and challenge the status quo?", the company BMI from South-Carolina has decided to crack some of the fluid dynamics challenges that keep trucks from being as fuel efficient as they could be. They found that by installing a few deflectors on trucks, they could reduce the low pressure area that forms behind the trucks and that 'sucks' it backwards, making it burn more fuel to move forward.
Here's what BMI's solution look like (they removed the wheels from this rendering, but this is the back of the truck):
Here's another view but with the wheels:
They estimate that over time, as they refine their products, they could bring trucks from a drag coefficient (CD) of around 0.6 for the best current trucks to one of about 0.45 at first, then 0.35, and even 0.25 would be possible (that's Prius territory!).
According to the Economist:
The company claims its UnderTray can improve fuel efficiency in a semi-trailer by as much as 12%. The Department of Energy estimates if all the semis in America had such devices installed it would produce fuel savings of 1.5 billion gallons of diesel a year. At current prices that would add up to about $5 billion a year. A typical semi-trailer travels about 240,000km (150,000 miles) a year, and at $3 a gallon for diesel BMI estimates that its system would pay for itself in 12 to 18 months.
This is a particularly elegant solution because it can be retrofitted on almost any truck, without the need to change the engine or add expensive electronics. And since the payback is so quick, there's very little reason not to do it.
It's still better to increase rail shipping, but if this simple tweak could reduce fuel consumption by the equivalent of removing around 12% of all the truck on the road, why not do it ASAP?
Photo: Flickr, CC
Via BMI, The Economist
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