On the comparison of energy sources: feasibility of radio frequency and ambient light harvesting

TL;DR

This paper compares radio frequency and ambient light energy harvesting in urban environments, finding solar energy generally dominates except in specific conditions like closed spaces or during a new moon.

Contribution

It provides a theoretical comparison of RF and solar energy sources for microdevices in city environments, highlighting when RF harvesting may be advantageous.

Findings

Solar energy dominates in urban environments during the day and night.

RF harvesting is beneficial in closed compartments or during a new moon.

Ambient light energy is sufficient for most applications except in specific conditions.

Abstract

With growing interest in multi source energy harvesting including integrated microchips we propose a comparison of radio frequency (RF) and solar energy sources in a typical city. Harvesting devices for RF and solar energy will be competing for space of a compact micro or nano device as well as for orientation with respect to the energy source. This is why it is important to investigate importance of every source of energy and make a decision whether it will be worthwhile to include such harvesters. We considered theoretically possible irradiance by RF signal in different situations, typical for the modern urban environment and compared it with ambient solar energy sources available through the night, including moon light. Our estimations show that solar light energy dominates by far margin practically all the time, even during the night, if there is a full moon in the absence of clouds. At the same time, in the closed compartments or at the new moon RF harvesting can be beneficial as a source of "free" energy.