Free energy is the idea that a low-cost power source can be found that requires little to no input to generate a significant amount of electricity. Such devices can be divided into two basic categories: “over-unity” devices that generate more energy than is provided in fuel to the device, and ambient energy devices that try to extract energy from the environment, such as quantum foam in the case of zero-point energy devices.
Not all “free energy” claims are necessarily bunk, and not to be confused with Renewable Energy. There certainly is cheap-ass energy to be had in the environment that may be harvested at either zero cost or sustain us for long amounts of time. Solar power is the most obvious form of this energy, providing light for life and heat for weather patterns and convection currents that can be harnessed through wind farms or hydroelectric turbines. In 2009 Nokia announced they expect to be able to gather up to 20 milliwatts of power from ambient radio sources such as broadcast TV and cellular networks, enough to slowly recharge a typical mobile phone in standby mode.This may be viewed not so much as free energy, but energy that someone else paid for.