“When it comes to reducing energy consumption and greenhouse gas emissions, we’re increasingly hitting the law of diminishing returns when it comes to cars and other light duty vehicles,” according to Sam Abuelsamid writing for Forbes. “The low hanging fruit that remains in this space is in heavy duty vehicles and that’s where Tesla Motors co-founder New Zealander Ian Wright has focused his efforts in recent years.

“His company, Wrightspeed has just won a US$30 million contract [with Infratil-owned NZ Bus] to convert hundreds of New Zealand transit buses with its turbine-powered plug-in hybrid powertrain.

“Providing enough battery capacity to move [medium and heavy trucks and buses that frequently drive 160km or more per day] would consume half the payload capacity making the vehicle essentially useless.

“Thus Wright devised a series plug-in hybrid system that would provide a balance of efficiency and cost without compromising the capability of these larger vehicles. Wrightspeed developed a geared-traction-drive (GTD) unit that combines a high-power electric motor and reduction gearbox and mounts right on the drive axle of the truck or bus to provide propulsion and regenerative braking.

“In order to meet the total range requirements, Wright also devised a very clever turbine-generator system to act as a range extender. While turbine power for cars was developed extensively in the 1950s and 1960s, most famously by Chrysler, jet engines were not well suited to these applications. Jets are most efficient when they operate at high, constant loads. Road vehicles frequently accelerate and decelerate making them ill-suited to direct turbine propulsion.”

Wright co-founded Tesla Motors in 2003. He has built the fastest street legal electric car in the world – the X1.

Original article by Sam Abuelsamid, Forbes, April 22, 2016.