A Class-E Amplifier for a Loosely Coupled Inductive Power Transfer System with Multiple Receivers

Alexander Sutor,Rainer Buchholz,Martin Heining

doi:10.3390/en12061165

Abstract

We present a method for optimizing the electronic power system for a new type of photobioreactor or photoreactor in general. In the case of photobioreactors, photosynthetic active microorganisms or cells are grown. A novel concept for the illumination of photobioreactors was necessary, as the external illumination of those reactors leads to a limited penetration depth of light. Due to the limited penetration depth, no standard reactors can be use for cultivation, but custom made reactors with very small volume to surface ratio have to be used. This still prevents the technology from a large scale industrial impact. The solution we propose in this paper is an internal illumination via Wireless Light Emitters. This increases the manageable culture volume of photosynthetic active microorganisms or cells. The illumination system is based on floating light emitters, which are powered wirelessly by near field resonant inductive coupling. The floating light emitters are able to illuminate a photobioreactor more homogeneously than external illumination systems do. We designed a class-E amplifier and field coils to produce an intermediate frequency electromagnetic field inside the reactor. An appropriate magnetic flux density was found to be approx. B = 1 mT and the driving frequency is f = 176 kHz. We conducted experiments with a laboratory size photoreactor. The cultivation volume was 30 L containing up to 3000 WLEs. The maximum electric power input was more than 300 W and we calculated an efficiency of up to 76%.

Highlights

Wireless power transfer is a classic engineering field currently gaining increasing attention.One reason is the wide variety of applications
The dominant growth affecting parameter for photoautotrophic microalgae cultures is light, which is absorbed by the microalgae and drives photosynthesis
This absorption leads to an exponential attenuation of the light intensity for increasing culture depths and cell densities according to Lambert-Beer’s law of extinction. This fact limits the photobioreactors to small diameter systems and hinders the development of industrial relevant scale ups

Summary

Introduction

One reason is the wide variety of applications It ranges from consumer products like electric tooth brushes and charging of mobile phones to high end medical applications [1,2,3,4,5] like cochlear implants [6], wireless endoscopic capsules [7,8], and cardiac pacemakers [9]. The authors of [10] presented a loosely coupled transformer system for charging an electric vehicle with up to 4 kW power. They used a full-bridge inverter on the primary side and realized zero-voltage switching (ZVS).

Results

Discussion

Conclusion