Energy a device, extending the battery life would

Energy harvesting is exchanging the captured little dosage of
useful energy that is cultivated from the space around us and turned to
electrical energy that can be put to use. 
Capturing the usable energy in the electrical form can either be accumulated
in storage for later use or put to use in the moment. Where no power grid is present
or the option to install solar panels or wind turbines these can now be used as
the primary power source alternatives. 

Outside of solar energy outdoor specifically, no small sources
of energy produce large amounts of energy. Even though, the energy harnessed is
enough for some Implants inside the body sensing by remote and wireless type
applications RFID, and lower segment of the power spectrum type applications. Even
if there were low amounts of energy harvested and not able to power a device, extending
the battery life would still be an option.

Energy harvesting is also known as energy scavenging or micro
energy harvesting.
Modern electronic systems solve so many difficult problems that they often seem
like magic. Nonetheless, these systems all have the same basic limitation: they
need a source of electrical power! Most of the time this is a straightforward
challenge for the electronic designer, because there are many power-delivery
solutions. Yet sometimes a device has no direct power source, and running wires
or replacing batteries is impractical. Even when long-life batteries are
usable, they eventually need to be replaced, which requires a service call.

Enter energy harvesting. Energy harvesting (also known as power
harvesting or energy scavenging) allows electronics to operate where there is
no conventional power source. It eliminates the need for wires or replacement
batteries.

This article discusses energy harvesting and its applications.
It explains how the process works and the challenges that designers must
address to implement a fully functional solution.