Hybrid Drives Make City Buses Cleaner

Rather than powering the rear axle via an automatic transmission, as usually, the diesel engine in the Elfa system drives a generator that uses power electronics to supply electricity to one or more drive motors.

Around half of all local public transit trips in Germany are by bus. Like other heavy vehicles, however, buses are loud and produce emissions that are harmful to humans and the climate. The long-term solution is to use an all-electric drive. The problem is that today’s battery technology is relatively expensive.

Although in China, for example, there are already several buses powered by innovative lithium ion batteries. City buses make frequent stops for traffic lights and passengers, so they are well suited for use with a hybrid drive. This system marks an intermediate step on the road toward zero-emission buses powered either by batteries alone or a combination of batteries and a fuel cell system.

In the Elfa system from Siemens, the electric motors act as generators during braking and thus feed electricity back into the batteries. This power can then be subsequently used to drive the vehicle, which means at times the bus can run fully electrically and without producing any emissions. The vehicle range depends on battery capacity and can vary between a few hundred meters and several kilometers.

In combination with a clever power management system, Elfa not only reduces fuel consumption but also noise, since the diesel engine doesn’t provide acceleration and therefore operates only at quiet and economical engine speeds. As a result, fuel consumption falls by around one-third. On the basis of 60,000 kilometers a year, that corresponds to savings of around 10,000 liters of diesel, depending on the type of route driven.

Buses with Elfa drives are now being used in a number of cities worldwide, including a test fleet of double-deckers in London. Hamburg, meanwhile, is planning to introduce buses with an Elfa hybrid drive equipped with a fuel cell system rather than a diesel engine. This new drive technology is also ideal for other commercial vehicles that make frequent stops, such as garbage trucks or light delivery trucks. The Elfa system forms part of the Siemens environmental portfolio, which generated around €28 billion in sales for the company in fiscal year 2010.

Media Contact

Dr. Norbert Aschenbrenner Siemens InnovationNews

All latest news from the category: Power and Electrical Engineering

This topic covers issues related to energy generation, conversion, transportation and consumption and how the industry is addressing the challenge of energy efficiency in general.

innovations-report provides in-depth and informative reports and articles on subjects ranging from wind energy, fuel cell technology, solar energy, geothermal energy, petroleum, gas, nuclear engineering, alternative energy and energy efficiency to fusion, hydrogen and superconductor technologies.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors