https://onlinelibrary.wiley.com/doi/pdf/10.1002/pssr.202100113

68.9% Efficient GaAs-Based Photonic Power Conversion Enabled by Photon Recycling and Optical Resonance

This article demonstrates a fiber-based power-by-light system that is capable of delivering up to 6.2 W of continuous electrical power at common voltages of 3.3 and 5 V. This optical link includes bidirectional optical communication, for which the data stream from the base to the remote unit is realized by amplitude modulation of the laser beam over the same fiber. At the remote unit, a gallium arsenide-based photovoltaic (PV) laser power converter receives and converts the light. The data are demodulated with a dedicated electric circuit, while the power is forwarded to a dc–dc boost converter. The optical data uplink is realized over a separate optical fiber. In operation, a PV conversion efficiency of above 50% has been measured. For downlink data rates up to 115.2 kb/s, unperturbed signal integrities are demonstrated, at higher data rates, the signal integrity deteriorates. An assessment of power budget and power losses in the overall system is presented. Finally, a smart power management concept is introduced, which controls the laser output power with respect to changing electrical load, optimizes the operating point of the PV cell, and, thus, increases system efficiency for varying load operation. Thereby, it also minimizes laser and PV cell operating temperatures, and eventually prolongs the lifetime of the system.

/pdf/6-w-optical-power-link-with-integrated-optical-data-m7xdt03z4g.pdf

6-W Optical Power Link With Integrated Optical Data Transmission

This chapter discusses solar cells made of III–V semiconductors, and how they have reached efficiencies of over 46% in 2016, the highest of any photovoltaic technology to date. These high efficiencies are possible due to the ability of stacking solar cells made of different III–V semiconductors. The main focus of current research is on III–V multijunction solar cells with three or more junctions. III–V Solar cells are widely used in space applications, terrestrial concentrators as well as niche markets such as power-by-light or thermophotovoltaics. Today III–V devices find terrestrial applications only under high concentration. But III–V on silicon may be an attractive path to reduce cost and eventually penetrate this high-performance technology into conventional applications of flat-plate photovoltaics.

High-Efficiency III–V Multijunction Solar Cells

Dual-junction GaAs laser power converters optimized for one monochromatic wavelength are presented, and their temperature dependence is experimentally evaluated. External quantum efficiency and irradiance-dependent current–voltage measurements (10 to 104 W/cm2) under monochromatic laser light (809 nm) have been undertaken to quantify temperature- and irradiance-dependent effects on the performance. The temperature dependence of the current matching of the two subcells, caused by the temperature-dependent absorbance, is quantified. Losses in performance due to variations in operating temperature for different power-by-light applications are calculated to be between 16.2% and 21.0%. Future potential enhancements in cell performance are discussed. For elevated temperatures, super-linear behavior of the spectral response with increasing irradiance is observed, which is attributed to effective luminescent coupling from the top to the bottom subcell as the device becomes more radiative limited. For low temperatures, where the bottom cell is overproducing, no dependence on irradiance is found, which shows the influence of photon transport losses to the substrate. © 2016 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pip.2814

On the temperature dependence of dual‐junction laser power converters

Power-over-fiber is a power transmission technology using optical fibers that offers various features not available in conventional power lines, such as copper wires. The basic configuration of power-over-fiber comprises three key components: light sources, optical fibers, and photovoltaic power converters. This review article presents the features of power-over-fiber and its key components. Moreover, recent advancement in power-over-fiber technologies based on their latest results is introduced, focusing primarily on papers presented at the Optical Wireless and Fiber Transmission Conferences (OWPT) from 2019 to 2021.

Recent Advancement in Power-over-Fiber Technologies

Blade condition monitoring systems with fiber-optic sensors attract much attention because they are resistant to lightning strikes, a major issue with increasing blade lengths. However, fiber-optic sensor systems are more complex and more expensive than their electronic counterparts. We describe a new blade condition monitoring system, which combines the lightning safety of optical fibers with the reliability and cost-effectiveness of electronic sensors. The optical fibers transport data from the blades to the hub, and in addition, they provide the electrical power for operating the sensor units in the blades. To achieve full protection against lightning-induced electromagnetic fields, an appropriate shielding of the sensor units is required. We present results on the reliability of a newly developed prototype based on optically powered sensors. In a field trial, the unit monitored successfully the blade vibrations of a 1.5 MW wind turbine for a period of 23 months. Copyright © 2016 John Wiley & Sons, Ltd.

Reliable and lightning‐safe monitoring of wind turbine rotor blades using optically powered sensors

We demonstrate a prototype of a lightning-safe system for condition monitoring of wind turbine rotor blades The system uses non-conductive optical fibers instead of copper cables for powering remote electrical sensor units and for exchanging data with them Thus, complete electrical isolation between the sensor units inside the rotor blades and a base station in the hub of the wind turbine is provided Optical power delivered by fiber-coupled laser diodes is converted at each sensor unit into electrical power by a miniature photovoltaic cell, making 177 mW available to continuously operate a two-axes MEMS acceleration sensor as well as a low-power microcontroller (muC) for data processing Sensor data are sent back to the base station through a fiber-optic transmitter We successfully tested the prototype for an extended 4-month field trial inside a 15 MW wind turbine This work has been realized in the framework of the project OPTOWIND supported by the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB)

J. Vourvoulakis

Papers

Reliable and lightning‐safe monitoring of wind turbine rotor blades using optically powered sensors

Lightning-safe Monitoring of Wind Turbine Rotor Blades Using Optically Powered Sensors