Mitsubishi Electric Corporation has developed technology that reduces total railway energy consumption by up to five percent through efficient use of regenerative power from trains and optimized voltage control at multiple railway substations.
The technology enables full use of regenerative power in trains through real-time control of voltages at nearby substations. Mitsubishi achieved the five percent energy reduction in numerical simulations using a high-density urban railway model.
Railway systems consume a high volume of electricity and need to find ways to save energy. Currently, electricity generated when trains decelerate using regenerative brakes is reused by other trains that need to accelerate. Such regenerative systems, however, limit the amount of reused power when there is excess regenerative electricity or when there are few accelerating trains, because voltage distributed from substations is maintained at a high, fixed level to provide enough power to all trains even if they accelerate at the same time. As a result, a large amount of regenerative power is wasted as heat, Mitsubishi says.
Mitsubishi’s new system controls the voltage distributed from substations based on train locations as well as acceleration and deceleration data collected from each train’s integrated management system. The company’s simulation shows that the new system reduces regenerative power wasted as heat in current systems by as much as 80 percent, and prevents voltage in feeding lines from becoming too high. Even if the amount of regenerative power becomes excessive, it can be fully utilized with power storage systems, such as batteries or regenerative inverters installed at stations.
The company is aiming to have the product ready for the commercial market in the fiscal year beginning April 2014.
In April last year, Philadelphia-based demand-side energy startup Veridity Energy announced that Southeastern Pennsylvania Transportation Authority trains would supply energy recovered from braking back to the grid. At the tine, Viridity said it had reached a “significant milestone” in enabling SEPTA to capture the kinetic energy created from the regenerative braking ability of trains and trolleys at a high-use propulsion substation in Philadelphia.