A. turbine powered generator B. battery C. plug in charging D. electric traction motors E. fuel tank
Credit: Wrightspeed/Hybrid Cars
Internal combustion piston engines have many disadvantages:
● inefficient — in lab conditions, perhaps a little more than 30% for a diesel — driving a vehicle, very much less
● not very durable — around 5,000 hours operating life — at peak efficiency (full load) closer to 500 hours
● high maintenance costs
● dirty exhaust
Gas or diesel turbines, are less efficient, but at peak load have an operating life of 40,000 hours & have much lower maintenance costs. Very clean exhaust.
Electric motors are 80 to 90% efficient — largely independent of load — durable too — only one moving part — & much lower operating costs.
Many medium duty trucks, such as delivery vehicles, have many start/stop cycles in daily operation & rarely reach peak efficiency. Add to this, heavy traffic with slow driving in a low gear + idling, to create a recipe for inefficient operation, high fuel cost & short operating life.
Even less efficient are garbage trucks. Much of their operation is: accelerate for a few meters, brake hard (throwing away the energy just consumed to get the truck moving), load the garbage, & repeat.
Wrightspeed had a better idea:
● replace the piston engine with an efficient electric motor
● batteries are expensive, so restrict battery range to reduce cost &
● add a turbine-powered generator to periodically recharge the battery
This improves efficiency because:
● 80-90% efficient electric motor drives the vehicle
● an electric motor brings with it regenerative braking, which further improves the efficiency of the vehicle by returning energy to the battery at each stop
● electric motors don't need to idle, further adding to efficiency
● although peak efficiency of a turbine is less than that of a piston engine, when it is operating, it is always driving the generator at peak efficiency
Wrightspeed claim their powertrain can improve efficiency from eight or ten miles per (US) gallon, to 25 or 30 or more. In operation, this is a saving of $35,000 fuel & $8,000 in maintenance per vehicle per year.
FedEx is trialing delivery trucks with Wrightspeed drivetrains:
http://www.greencarreports.com/news/1094920_fedex-tests-wrightspeed-electric-trucks-with-diesel-turbine-range-extender
Extended interview with Wrightspeed CEO, Ian Wright:
http://chargedevs.com/features/qa-with-ian-wright-the-ceo-of-wrightspeed-on-tesla-gas-turbines-and-electric-trucks/ / EV electric passenger vehicles commercial trucks electric drive huge global fleet reduce emissions fuel costs improving efficiency alternative powertrain power train drivetrain drive train range extender electric delivery trucks diesel turbine generator WrightSpeed turbine range extended electric delivery van conversion FedEx electric powertrain Silicon Valley WrightSpeed turbine takes gasoline combustion engine Chevy Volt BMW i3 REx range extended electric cars tested 39 kilowatt hour lithium ion battery pack range urban delivery constant speed buffered battery pack power train propulsion systems /
