San Francisco And Their Ambitious Plans for Reduced Emissions

                                                                                         

San Francisco has long been an environmentally conscious city. And recently it has unveiled plans to make the city even more biofriendly by investing in hybrid buses. The goal of the San Francisco Municipal Transportation Agency (SFMTA) is to reduce greenhouse gas emissions to 30% below 1990 levels by 2012 and to become 100% emission-free by 2020.

In a bold move towards that goal, SFMTA purchased 86 Orion VII diesel-electric hybrid buses, the first of which was unveiled on April 11, 2007. These buses operate in a similar manner to San Francisco's famous trolley buses, in that they are powered by electric motors. The difference lies in that these buses have a small diesel engine that turns a generator to supply the electricity, rather than having the overhead wires that power the trolleys.

These buses are called serial hybrids, which means that there is no mechanical link between the diesel engine and the wheels of the bus. The diesel engine drives the generator, which then supplies electrical power for the electric motors that drive the wheels. This is in contrast to the "parallel" system, as in a Toyota Prius, where the vehicle is powered by a combination of its engine and its electric motors. The diesel engine of the Orion bus is tuned to run at its most fuel-efficient and least emission-producing speed. When the bus uses less electrical energy than it needs to move, the surplus is stored in highly efficient batteries, for later use when extra energy is needed, as in climbing hills or acceleration. When the bus has to slow down, the electric motors are used as generators and feed power back into the batteries. This further improves fuel economy and reduces wear and tear on the brakes.

For SFMTA, the hybrid buses are a stepping stone towards the 100% emission-free vehicles. Plans are underway to upgrade to hydrogen fuel cell buses when they become commercially available for large fleets. Meanwhile, the diesel engines are powered with a bio-fuel mixture.

The improvements obtained with the switch to hybrids are considerable. The new hybrid buses emit 95% less soot than the old diesel buses, 40% less nitrous oxide and 30% less greenhouse gases. And of course there will be fuel savings too, as a result of the improved efficiency, estimated at 30%, or 20,000 gallons of diesel oil over 12 years.

There are advantages for the passengers as well. The floor of the bus is low enough that it does not require steps, which makes it easier and more comfortable to get in and out of. The hybrids also provide smoother and faster acceleration and less engine noise.

San Francisco's example is most encouraging. And, with the rapidly rising cost of fuel, many other cities are likely to follow suit. Another path to a cleaner environment is to improve the efficiency of existing internal combustion engines. Biofriendly Corporation has developed a liquid fuel catalyst, called Green Plus®, which causes a cleaner, more linear burn that results in improved fuel economy, higher torque and reduced emissions.

For more information about Green Plus visit the Biofriendly Corporation website at www.biofriendly.com.

References:
(1) http://www.sfmta.com/cms/mfleet/hybrids.htm

About the author:
Author, Peter Verhoeff, contributes articles on environmental issues for Biofriendly Corporation. More information on these and other topics can be found on the Biofriendly site.

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