Utter the phrase "electric vehicle" and most people will picture a small car with low power and limited range. There's a modicum of truth to the range issue, although it's not nearly as dire as some make it seem, but the "small" and "low power" adjectives are unwarranted. Let's look at a couple of EVs that, shall we say, tip the scales a bit more than your neighbor's Chevy Volt, and we'll see why their applications make these EVs superior to their fossil fuel forerunners.
Range Isn't Always an Issue
Fleet vehicles such as buses, delivery trucks, and construction machines are the perfect candidates for electrification. They make frequent stops, which wastes fuel but not electricity. (In fact, because of regenerative braking, stopping an EV actually produces electricity.) EVs don't travel far from the charging station, so the range isn't an issue. And unlike their gasoline or diesel counterparts, they don't emit unpleasant, toxic fumes.
California Gets on the Bus
It's no surprise that California schools are replacing their "dinosaur" fleet with clean, electric vehicles. The latest school district to hop on the EV bus is the Colton Joint Unified School District (CJUSD) in San Bernardino County, which just purchased a pair of American-made, Type C Starcraft eQuest XL school buses, featuring electric powertrains from Motiv Power Systems.
Electro Motiv Force
The buses feature Motiv's proprietary electric Powertrain Control System (ePCS), a technology-agnostic module that works with a variety of battery and motor technologies.
Adaptive Power Controllers (APCs) - bidirectional 30 kW DC-DC converters - serve as buffers between the batteries and the motor inverters. The APCs are programmable, so they can match a multitude of motors with a bevy of batteries. APC modularity provides scalability, allowing the powertrains to work with vehicles of nearly any size. Rather than relying on off-the-shelf electronics, Motiv designed its own charge controller, which works with standard J1772 chargers, 208V three-phase lines, and 480V three-phase lines, at 98% charging efficiency.
Motiv published a case study showing that switching to an electrified delivery van saved a company $7000 each year in fuel (per van) and provided a 70% reduction in maintenance costs. (I'll discuss EV total cost of ownership in a future article.) If they share a similar case study on these school buses, I'll report it.
World's Biggest EV
An electric school bus isn't big enough for you? How about an electrified 45-ton dump truck with a 65-ton payload capacity? When completed, this Swiss-designed monster truck will be the world's largest electric vehicle, carrying a colossal 4.5-ton battery bank. Almost 1500 Nickel Manganese Cobalt cells (a popular variation of Li-ion) will store a sizable 700 kWh of energy.
Gravitational Energy: It's Not Just for Spacecraft
If you follow the space program, you know that rocket scientists often use the gravity of a planet to help slingshot a spacecraft into a new orbit with a higher velocity. The gravity assist maneuver conserves fuel by accelerating the interplanetary vehicle using gravitational energy. While that technique was created for celestial sojourns, the Newtonian physics that make it possible are quite down-to-Earth.
This truck is designed to work in a quarry, ascending large hills while empty, and returning with a full load. Because the truck weighs more than twice as much coming down as it did going up, it gets an extra-strong gravitational assist from Planet Earth on the descent. Like all EVs, the dump truck will employ regenerative braking, allowing it to convert the energy of its motion into electricity while simultaneously decelerating the vehicle. Since gravitational energy is directly proportional to weight and the return weight is more than twice the ascending weight, the descent could theoretically produce twice as much energy as it took to get the vehicle up the hill in the first place. In practice, of course, there are losses, but the design engineers realistically expect this to be a net-zero energy vehicle that never needs refueling.
Tesla Motors has already proven that EVs can be muscle cars; make way for the electrified muscle truck.
_______________________________________________________________