Regenerative braking: saving electricity while reducing emissions

What's big, a mode of transportation, and uses regenerative braking? The answer could surprise you.

An easy answer would be hybrid or electric vehicles. A smarter answer would be trains. Energy management solutions can offer up to 30% energy savings for direct current rail transportation. Below are answers to three common questions in regards to energy recovery.

1.  What is the purpose for investing in regenerative braking for trains? 

Transit authorities are among the largest consumers of electricity. They also have renewable energy credit objectives and sustainability commitments to meet. One solution to mitigate the amount of electricity consumed is to use a braking energy recovery system. Kinetic (movement) energy of a train can represent up to 80% of the total energy consumption of a rail transportation system.  This means a lot of energy can be saved. Just using one system can recover the energy equivalent of 30 to 50 homes, and a large transit authority can easily install between 10 to 20 systems. In addition, an energy recovery system reduces power peaks, avoiding the need to invest further capital to meet the power needs from increased ridership.

2. How mature is the technology?

The fundamental technology of regenerative braking is insulated-gate bipolar transistor (IGBT). This technology is quite mature, as it is found in applications such as cars, new airplanes, and other modes of transportation. The new application of the technology is the recovery of braking energy in trains. One great advantage of the technology is the simplicity of deployment. The system is easily connected to the existing power network. There is no need to modify or adjust the trains and substation power equipment. The system is also fault tolerant such that any fault or maintenance downtime does not affect the operation of the train service.

 3. How does energy recovery affect the surrounding grid?

An energy recovery system actually improves the voltage stability of the surroundings. Traction power is extremely “peaky.” Trains consume megawatts of instantaneous power during acceleration and then almost nothing while coasting. This pattern of demand is inefficient and often produces voltage fluctuations in the surrounding distribution network. The energy storage system returns the recovered braking energy during the subsequent acceleration, substantially reducing the peak demand from the grid. The result is stabilized voltage on the grid as well as on the train.

Speak with me and other technology experts at APTA on October 13-15 in Houston, Texas, USA during special “tip of the hour” presentations hosted by ABB. These solution-based trainings will cover other topics including electrification of transport, traction conversion, service and more.