Fraunhofer Institute for Solar Energy Systems ISE
Optical power transmission with Power-by-Light systems (also known as Power-over-Fiber) is an elegant method for powering sensors or actuators, when a conventional power supply with copper cables is limited or not available. The reasons for this are manifold, for example: the need for galvanic isolation, high voltage or lightning protection, electromagnetic interference, wireless transmission, weight reduction, spark protection, corrosion resistance, high magnet fields or rotating systems. There are a wide variety of applications for Power-by-Light systems such as structural health monitoring of wind turbines, fuel gauges in airplanes, monitoring of high voltage lines, optical power supply of automotive sensors, biosensors in smart implants, or the monitoring of passive optical networks.
At Fraunhofer ISE we develop special photovoltaic cells for Power-by-Light applications. These so-called laser power converters convert monochromatic light into electricity with highest efficiency. Currently our research focuses on developing materials for specific laser wavelengths, optimizing the cell structure for converting monochromatic light and developing advanced cell concepts for increasing the output voltage. Our other research topics consist of characterizing cells under monochromatic light, reliability investigations, as well as packaging and system integration. The latter also includes the combination of power and data transmission and coupling the systems to the electronics or electronic circuitry.
For a laser power converter based on GaAs, which was prepared by thin-film technology with a back-surface mirror, we achieved an opto-electric conversion efficiency of 67.3%, measured with a laser wavelength of 860 nm at an irradiance of 9.6 W/cm².
When one thinks of photovoltaic cells, then it is usually in connection with the conversion of solar radiation into electricity, a main research area at Fraunhofer ISE in line with the energy transformation. However, researchers at Fraunhofer ISE are also working on another application for photovoltaic (PV) cells: Power-by-Light systems (also known as Power-over-Fiber) in which optical power transfer is used to supply electricity to electronics. Energy transmission is carried out in the form of light, and the photovoltaic cell is not used as a “solar cell,” but rather to convert the transmitted laser light into electricity.