Solar energy harvesting with light emitting diodes

This work evaluates the concept of employing light-emitting diodes (LEDs) to harvest solar energy. Due to the optical properties of the semiconductor materials employed in the fabrication of LEDs, LEDs can absorb photons and generate electron-holes. Thus, in principle LEDs can behave as small solar cells from which power can be harvested. Unlike solar cells, LEDs are not optimized to absorb light. As a result LEDs have lower light-to-electricity conversion efficiencies. However, there are scenarios such as outdoor displays or billboards where a large amount of LEDs are already installed. These LEDs represent an energy resource whose installation and fabrication costs have already been covered by the primary application of message displaying. With this motivation, an evaluation of the energy-harvesting capability of a number of LEDs has been carried out in this work. In the proposed concept, LEDs become a source and a sink of energy. A bidirectional buck-boost DC-DC converter able to transfer energy to and from the LED has been built and tested. It is found that red LEDs provide the highest power. Up to 2.76 W can be harvested from a 96×216 display.