Now, transit systems are also going green. German carbon credit validation firm TUVNORD has certified that New Delhi's metro railway has prevented 90,000 metric tons of carbon dioxide from being emitted through its regenerative braking system. The Delhi Metro Rail now plans to use the carbon trading earnings to offset the installation cost and additional training required.
The railway's system cuts back on energy use by about 30 percent by powering trains with energy harnessed while braking. As trains' brakes are applied, the force drives three traction-phased motors to produce electricity, which is then sent to the electricity lines to reduce the overall energy requirement.
The Delhi metro became the first railway project to be registered for carbon credits by the United Nations in 2007 for the regenerative braking system installed in 2004. The emissions were prevented during a three-year period, also cutting back on electricity use by 112,500 megawatt-hours. The Delhi Metro Rail says it expects the 2008 tally for carbon emissions prevented to be 39,000 metric tons, growing to 100,000 metric tons per year when the project is fully built out.
Recently, General Electric division GE Locomotive said it was designing a hybrid train for Indian Railways to capture energy dissipated during braking and store it in batteries to be used later The design could reduce fuel consumption by 15 percent and emissions by 50 percent.
The West is also thinking on these lines now. New York's transit system has also explored regenerative braking systems for its fleet. Other companies that are developing regenerative braking systems include UK-based PML Flight Link and Colorado company Proterra.