As every high school student knows, kinetic energy is energy an object has because of its motion. Every moving object has kinetic energy. Hydroelectric plants and windmills already make use of this fact to generate electricity. Now, researchers are looking for additional sources of kinetic energy to convert to power—and people and cars jump to the forefront simply because there are so many of them.
As of 2022, there are about 1.446 billion cars in the world. (PD.com)
The overall efficiency of the conversion from kinetic to electric power has been shown to range between 0.25 and 0.5. (European Commission)
A person dancing on an energy-harvesting floor can generate 5–10 watts; in a packed dance club, the production can meet up to 60% of the total energy required for the club. (Medium.com)
When you look at the mobs of people surging out of transport hubs in any of the world’s major cities or in and out of sports stadiums, you are witnessing the creation of a massive amount of kinetic energy. One of the latest civil engineering technologies under development involves harnessing this energy and using it to feed the power grid.
For example, a company in London has developed floor tiles that use an electromagnetic induction process and flywheel energy storage to generate electricity from pedestrian footfall in indoor and outdoor high traffic areas. The tiles have been installed in almost 40 countries and can generate up to five joules of renewable energy per footstep. This is enough energy to power low-energy applications, such as LED lighting and display screens.
The largest deployment the company has done so far is in a football pitch in Rio de Janeiro to help power the floodlights around the pitch. It also currently has an installation outside London’s Canary Wharf station powering street lights.
Other installations include Heathrow—which used the energy generated by the kinetic tiles to turn a traditionally passive, dull terminal into a uniquely interactive infrastructure resulting in overall more engaging travelling experiences—and the train station in Bedfordshire, UK, which has installed two kinetic walkways that help to power a data screen and display monitor, as well as two USB charging benches for commuters by the station entrance.
Cars are another focus of kinetic-to-electrical energy research. An Italian company is exploring the potential of using the kinetic energy generated on roadways. It has developed a technology that uses a rubber-like paving material that converts the kinetic energy produced by moving vehicles into electrical energy. The technology is based on the principle that a braking car dissipates kinetic energy by turning that energy into heat. By coating the road in areas requiring a mandatory slowdown—entering a roundabout, before a pedestrian crossing, before an intersection or toll booth, etc.—the energy-absorbing surface is able to collect and convert the auto’s kinetic energy into electricity, which can be used immediately or passed on to the electricity grid.
Exactly how much kinetic energy is dissipated, and thus how much electrical power is generated, depends on the speed and size of the car. But we can get a rough idea by assuming a 2200 lb car is moving at 70 mph when it needs to brake to a stop. The car’s kinetic energy while moving at that speed is 488 kj. As the car comes to a stop, the kinetic energy that was created while driving needs to dissipate. In the case of a braking car, it is changed into heat. This dissipated energy converts to about 135 watt hours of power. (For comparison, an LED light bulb consumes about 34 watt hours of electricity.)
Formula I race cars already use a kinetic energy recovery system (KERS) to increase the power to the battery and wheels. A KERS harnesses the energy produced by braking and saves it to be deployed later when it's beneficial to the driver. When required, the driver can press a button on the steering wheel to merge the converted energy, which is stored in a special battery, with the engine's output. This is similar to the regenerative braking system used on most electric vehicles, though more complicate, as would be expected given a race car’s unique energy requirements vs. those of a family car.
In addition to kinetic roadways, research is progressing on developing shock absorbers that can use the car’s kinetic energy to charge the battery. The bumpier the road, the more energy produced. This research does not require any additional infrastructure or public works installation, and could easily become a standard feature on every car.
The challenge now isn’t to find ways to convert kinetic energy to electricity. It’s to scale the systems for efficiency and cost. But we’re on the way. We have self-driving cars. Next is self-fueling cars.