Hey guys, Trace here for DNews. San Francisco is notoriously hilly and when you're going up and down those hills, you get potential energy and kinetic energy and it gets wasted if you don't harvest it back from your environment which brings us to something called regenerative braking. Before we get to the science of harvesting energy from your brakes, we're on Potrero Hill, one of 43 different hills in San Francisco. Some are so steep, they feel like rollercoasters. Some of the steepest and most beautiful are Pacific Heights, Knob Hill, and Potrero Hill. The reason we're on this hill is energy. When a car drives to the top of the hill, it gains potential energy. As it accelerates down the hill, the potential energy is converted to kinetic energy. Usually the kinetic energy just dissipates unless we can capture it. In a regular car, friction is applied using hydraulics and brake pads in order to slow the vehicle, with heat being the byproduct. Hybrids take that a step further by intelligently making use of a relationship between magnetism and electricity. With regenerative braking, that electric motor that propels the car forward can actually be turned by the kinetic momentum of the car during deceleration and braking. By turning the electric motor, it acts as a generator, so instead of heat, electricity is the byproduct. This electricity is then fed back into the battery, helping to recharge it. This means when you're hitting the brake in a Toyota Prius Prime, like this one Toyota let us use, the car doesn't let all that potential energy go to waste, from the top of the hill to the bottom. Instead, the hill itself plus gravity and the trade-off of potential and kinetic energy are all contributing to recharging the car's batteries. It's not just helpful on these straight hills, but on curvy ones as well. Lombard Street is considered the crookedest street in San Francisco but that's not, strictly speaking, true. It's actually Vermont Street here in Potrero Hill. Regenerative brakes aren't super new. In fact, in 1903, Louis Antoine Krieger built one of the first electric cars by putting an electric motor on a Parisian horse carriage and it had regenerative braking. The idea was incorporated into trolley cars, early electric vehicles and even today, you can even find it in my e-bike, the Stromer ST1X. This bike has regenerative braking too. This bad boy has an electric motor to help me get up these hills, but when I'm heading down, it will recharge the battery. When I'm coasting down a hill, I can generate up to 15 amps of current, more than enough to power even the fanciest vacuum or electric lawnmower. You don't have to be on a hill to harvest electricity from your environment. Even just driving down the highway can do it. If you're traveling 50 miles (80.46 kilometers) per hour and let off the gas, you've still got a lot of potential energy flowing through your vehicle. Braking, even on flat ground, will still gather electricity through the coiled wires around the axles. Who'd have thought technology from around the turn of the last century, would finally hit everywhere in THIS century? Hopefully, with more hybrid, plug-in hybrid, and electric vehicles hitting the road in the coming years, we will keep thinking about how to grab all of those stray energy sources.
