What if instead of building huge powerplants to power our homes, phones and cars, we would produce electricity ourselves? As sci-fi as it may sound, it’s already possible.

At the Green Microgym in Portland, Oregon, users can generate electricity as they burn calories on some of the exercise machines.

The human engine runs on calories. A bowl of cereal has about 300 calories, which provides enough energy for an hour’s worth of walking.

An average bicyclist pedaling at road speed is producing around 75 watts of power. Lance Armstrong supposedly generated 500 watts while climbing hills in the Tour de France.

Some of that human work could be siphoned off with a special backpack or knee brace to charge a cell phone.


“Since muscles are the powerhouses of the body, my colleagues and I designed our device to generate electricity from the motion of the knee joint. It resembles a knee brace and weighs about 1.5 kilograms [3.3 pounds] including the gearing and generator,” said Max Donelan, director of the Locomotion Laboratory at Simon Fraser University in Canada.

The device captures the energy of a one’s movement through an electrical generator, sensitive to knee motion. When the wearer extends the knee, the device turns and spins the generator, which builds up energy. And when the knee is flexed, the device turns off. Also, it senses motion and activates by itself.

“People are an excellent source of portable power. An average-sized person stores as much energy in fat as a 1,000-kilogram battery. People recharge their body batteries with food and, lucky for us, there is about as much useful energy in a 35-gram granola bar as in a 3.5-kilogram lithium-ion battery,” Donelan said.


Researchers have built a backpack that turns your movement into electricity to power your cellphone. It uses natural up-and-down motion to generate power. It can be used immediately or stored in a power bank.

“As humans walk, they vault over their extended leg, causing the hip to rise five to seven centimeters on each step. Since the backpack is connected to the hip, it must be lifted five to seven centimeters. It is this vertical movement of the backpack that ultimately powers the electricity generation,” said Lawrence Rome of the University of Pennsylvania.

The wonder backpack has two parts. First, there is the rigid frame that’s strapped to the back of the wearer. Then, a load plate is suspended from this frame, and as you walk, this slides up and down.

“We are working on parallel development of ergonomic backpacks for everyone – from school children carrying heavy bags of books, a worldwide public health problem, to the normal backpack used to carry laptops, to hikers’ backpacks to military and explorers,” Rome said. “Everyone can benefit from a more ergonomic backpack.”