Three university students in Santiago, Chile, have come up with a "green" way to produce power. They developed a device that uses soil to charge mobile phone batteries. The device can also power other small electronics.

The engineering students got the idea while relaxing outside, taking a break from their exams. The batteries on their mobile phones were empty. One of the student-inventors, Evelyn Aravena noted that plants are living things and able to produce energy.

Their invention is a small circuit board they call E-Kaia. The E-Kaia solved two problems for the engineering students. They needed to come up with a class project. They also needed an outlet to plug in their phones.

The E-Kaia captures the energy plants produce during a process called photosynthesis. That occurs when a green plant turns water and gas into food or energy as the plant is exposed to light.

A plant uses only a small part of that energy to grow. The rest stays in the soil. One of the student inventors says the device changes the energy released from the plant into low-level power to charge phones.

The E-Kaia device collects the extra energy from the plant without harming it. It plugs into the soil and then into a mobile phone. The E-Kaia is able to fully recharge a mobile phone battery in less than two hours.

The inventors hope that the technology can one day be used for much bigger projects like public parks. They imagine the power for the park's street lamps coming from its own trees and plants.