Battery Charger for Electric Vehicles based on a Wireless Power Transmission

In this paper,the case of a battery charger for electric vehicles based on a wireless power transmission is addressed.The specificity of every stage of the overall system is presented.Based on calculated and measured results,relevant capacitive compensations of the transformer and models are suggested and discussed in order to best match the operating mode and aiming at simplifying as much as possible the control and the electronics of the charger.

Theoretical Design of Energy Harvesting Module or Wireless Power Transmission Receiver Using Magnetic Field of 0.2 mT at 60 Hz

This paper presents a theoretical design method for a magnetic energy harvesting module. This module consists of an air-core coil and resonant capacitor. With a simple RLC circuit model, it can derive an equation of harvesting energy as a function of coil size. In order to demonstrate the magnetic field, a uniform magnetic field is generated by the developed coil system. From the experimented results, it is successfully demonstrated 100 mW of energy harvesting from a magnetic field of 0.09 mT at 60 Hz. This value is in good agreement with the estimated results. Harvested energy is proportional to the square of the magnetic flux density. However, ICNIRP2010 provides a guideline that an acceptable level for human health in a public space is 0.2 mT at power-line frequency. This paper also discuss the possibilities of several applications related with both magnetic energy harvesting and wireless power transmission.

On Differentiation Among Pilot Signals of Multiple Mobile Targets in Retro-Reflective Beamforming for Wireless Power Transmission

An experimental study is conducted on several retro-reflective beamforming schemes for wireless power transmission to multiple wireless power receivers(referred to herein as“targets”).The experimental results demonstrate that,when multiple targets broadcast continuous-wave pilot signals at respective frequencies,a retro-reflective wireless power transmitter is capable of generating multiple wireless power beams aiming at the respective targets as long as the multiple pilot signals are explicitly separated from one another by the wireless power transmitter.However,various practical complications are identified when the pilot signals of multiple targets are not appropriately differentiated from each other by the wireless power transmitter.Specifically,when multiple pilot signals are considered to be carried by the same frequency,the wireless power transmission performance becomes heavily dependent on the interaction among the pilot signals,which is highly undesirable in practice.In conclusion,it is essential for a retro-reflective wireless power transmitter to explicitly discriminate multiple targets’pilot signals among each other.

Retro-reflective Beamforming Technique with Applications in Wireless Power Transmission

Retro reflective beamforming technique has the potential of enabling efficient wireless power transmission over long distance(on the order of meters and even kilometers).In retro reflective beamforming,wireless power transmission is guided by pilot signal:Based upon pilot signal broadcasted by a wireless power receiver,a wireless power transmitter delivers focused microwave power beam(s)onto the location of wireless power receiver.When the wireless power receiver’s location is not fixed or when the wireless power receiver’s location is unknown to the wireless power transmitter,the microwave power beam would follow the wireless power receiver’s location dynamically as long as the wireless power receiver broadcasts pilot signal periodically.This paper reviews our research endeavors in recent years on retro reflective beamforming technique targeting three applications:(1)wireless charging for low power mobile/portable electronic devices,(2)space solar power satellites(SSPS)application,and(3)wireless charging in fully enclosed space.The feasibility and potential of retro reflective beamforming technique with applications in wireless power transmission are demonstrated by some preliminary experimental results.

Optimal Design of Wireless Power Transmission Systems Using Antenna Arrays

Three design methods for wireless power transmission(WPT)systems using antenna arrays have been investigated.The three methods,corresponding to three common application scenarios of WPT systems,are based on the method of maximum power transmission efficiency(MMPTE)between two antenna arrays.They are unconstrained MMPTE,weighted MMPTE,and constrained MMPTE.To demonstrate the optimal design process with the three methods,a WPT system operating at 2.45 GHz is designed,simulated,and fabricated,in which the transmitting(Tx)array,consisting of 36 microstrip patch elements,is configured as a square and the receiving(Rx)array,consisting of 5 patch elements,is configured as an L shape.The power transmission efficiency(PTE)is then maximized for the three application scenarios,which yields the maximum possible PTEs and the optimized distributions of excitations for both Tx and Rx arrays.The feeding networks are then built based on the optimized distributions of excitations.Simulations and experiments reveal that the unconstrained MMPTE,which corresponds to the application scenario where no radiation pattern shaping is involved,yields the highest PTE.The next highest PTE belongs to the weighted MMPTE,where the power levels at all the receiving elements are imposed to be equal.The constrained MMPTE has the lowest PTE,corresponding to the scenario in which the radiated power pattern is assumed to be flat along with the Rx array.

A Radio⁃Frequency Loop Resonator for Short⁃Range Wireless Power Transmission

A microstrip loop resonator loaded with a lumped capacitor is proposed for short-range wireless power transmission applications.The overall physical dimensions of the proposed loop resonator configuration are as small as 3 cm by 3 cm.Power transmission efficiency of greater than 80%is achieved with a power transmission distance smaller than 5 mm via the strong coupling between two loop resonators around 1 GHz,as demonstrated by simulations and measurements.Experimental results also show that the power transmission performance is insensitive to various geometrical misalignments.The numerical and experimental results of this paper reveal a bandwidth of more than 50 MHz within which the power transmission efficiency is above 80%.As a result,the proposed microstrip loop resonator has the potential to accomplish efficient wireless power transmission and high-speed(higher than 10 Mbit/s)wireless communication simultaneously.

Wireless power transmission based on retro-reflective beamforming technique

This review paper is on the retro-reflective beamforming technique for wireless power applications.The primary merit of retro-reflective beamforming technique is that wireless power transmission is augmented by radar tracking.Specifically,wireless power transmission is initiated by pilot signals broadcasted from wireless power receiver(s);and in response to the pilot signals,a wireless power transmitter delivers directional microwave power beams to the receiver(s).The microwave power beams follow the wireless power receivers’location dynamically as long as pilot signals are broadcasted periodically.The retro-reflective beamforming technique therefore has excellent potential to accomplish efficient wireless power transmission to non-stationary wireless power receivers.This paper reviews the basic principles and potential applications of wireless power transmission based on retro-reflective beamforming technique.

Wireless Laser Power Transmission System for Dynamic Target Using Rotation of Single Component

We design a novel wireless laser power transmission system in which the process of wireless power transmission to a dynamic target was completed based on the rotation of just one component.The design of this system not only reduces the loadbearing of the gimbal,but also avoids the degradation of beam quality caused by lens vibration when tracking dynamic targets.As a result,this WLPT system has been verified by tracking an unmanned aerial vehicle at 122 m away with an offset distance of±26.7 mm.We believe this system offers great potential in highpower,longdistance dynamic laser power transmission.

A comprehensive review of optical wireless power transfer technology

Ground-breaking optical wireless power transfer(OWPT)techniques have gained significant attention from both academia and industry in recent decades.Powering remote systems through laser diodes(LDs)to either operate devices or recharge batteries offers several benefits.Remote LDs can remove the burden of carrying extra batteries and can reduce mission time by removing battery swap-time and charging.Apart from its appealing benefits,laser power transfer(LPT)is still a challenging task due to its low transfer efficiency.In this paper,we discuss the necessity and feasibility of OWPT and discuss several projects,working principle,system design,and components.In addition,we show that OWPT is an essential element to supply power to Internet-of-Things(IoT)terminals.We also highlight the impacts of dynamic OWPT.We outline several OWPT techniques including optical beamforming,distributed laser charging(DLC),adaptive-DLC(ADLC),simultaneous lightwave information and power transfer(SLIPT),Thing-to-Thing(T2T)OWPT,and high intensity laser power beaming(HILPB).We also deal with laser selection,hazard analysis,and received photovoltaic(PV)cell selection for OWPT systems.Finally,we discuss a range of open challenges and counter measures.We believe that this review will be helpful in integrating research and eliminating technical uncertainties,thereby promoting progress and innovation in the development of OWPT technologies.

Full-wave analysis and design of microstrip antenna in-pipe for rectenna using FDTD method

The circular polarized microstrip antenna in the stainless pipe is analyzed by the finite-difference time-domain （FDTD） method with PML absorbing boundary condition. The microstrip antenna is used as a microwave energy supply element for the in-pipe micromachine inspecting. The numerical results agree well with the measured ones.

Optimization of optical wireless power transfer using near-infrared laser diodes

We experimentally demonstrated optical wireless power transfer(OWPT)using a near-infrared laser diode(LD)as the optical power transmitter.We considered a photovoltaic(PV)cell and a photodiode(PD)as the optical power receivers.We investigated the characteristics of the LD,PD,and PV cell in order to determine the optimum operating condition from the viewpoint of transfer efficiency.We also experimentally demonstrated a whole system optimization process to maximize the DC-to-DC transfer efficiency of the OWPT.Our experimental results showed that the optimization process can improve the OWPT efficiency by up to 48%.

An Overview of SWIPT Circuits and Systems

From a circuit implementation perspective,this paper presents a brief overview of simultaneous wireless information and power transmission(SWIPT).By using zero-power batteryless wireless sensors,SWIPT mixes wireless power transmission with wireless communications to allow the truly practical implementation of the Internet of Things as well as many other applications.In this paper,technical backgrounds,problem formation,state-of-the-art solutions,circuit implementation examples,and system integrations of SWIPT are presented.

Self-discharge mitigated supercapacitors via hybrid CuO-nickel sulfide heterostructure for energy efficient, wireless data storage application

With the surge of demand for instant high power in miniaturized electronic and mechanical systems,supercapacitors(SCs)are considered as one of the viable candidates to fulfill the requirements.Thus,long-term resilience and superior energy density associated with self-discharge in SCs are obviously critical,but securing electrode materials,which can meet both benefits of SCs and persist charged potential for a comparatively prolonged duration,are still elusive.Herein,hierarchically refined nickel-sulfide heterostructure(CuO-NS)on CuO(CO)scaffold is achieved through optimized film formation,exhibiting a threefold improvement in the essential electrochemical characteristics and outstanding capacitance retention(∼5%loss).Self-discharge behavior and its mechanism are systematically investigated via morphological control and nanostructural evolution.Furthermore,significant mitigation of self-discharge owing to an increase in surface area and refined nanostructure is displayed.Remarkably,CuO-NS2(20 cycle overcoating)based SC can retain over 60%of the charged potential for a complete voltage holding and a self-discharge test for 16 h.An appealing demonstration of wireless power transmission in burst mode is demonstrated for secure digital(SD)card data writing,powered by SCs,which substantiates that it can be readily leveraged in power management systems.This enables us to realize one of the envisioned applications soon.

Theoretical and experimental studies of retro-reflective antenna array for microwave power transmission from space solar power satellite to earth

The development of space solar power satellites aims to harvest solar power by artificial satellites over the earth’s geostationary orbit and then deliver the harvested power to the earth wirelessly.The retro-reflective antenna array technique is believed to be a close-to-optimal technical approach to achieve efficient wireless power transmission from a geostationary satellite to the earth,as it is capable of generating a microwave power beam aiming at a ground station on the earth via analyzing a pilot signal broadcasted by the ground station.In this paper,some of our preliminary research outcomes on retro-reflective antenna array for space solar power applications are reported.In the theoretical part of this paper,closed-form formulations with precision better than the classic theory of phased array are derived to analyze the performance of retro-reflective antenna array when the far zone condition is not satisfied between the space solar power satellite and the ground station.In the experimental part of this paper,a bench-scale retro-reflective antenna array with physical dimensions of about 0.6 m by 0.6 m is fabricated and tested.The theoretical and experimental results demonstrate that the microwave beam generated by a satellite-borne retro-reflective antenna array could be adjusted in real time to aim at the location from which the pilot signal stems.Based on the theoretical and experimental studies of this paper,systematic research endeavors are being conducted on the retro-reflective antenna array for space solar power applications.

Terrestrial transparent green energy receiving system designed for Space Solar Power Station

In this manuscript,we proposed the concept of a terrestrial transparent energy receiving system for a Space Solar Power Station(SSPS),aiming at solving the problems of environmental destruction and the waste of land resources caused by the construction of large area rectenna arrays at the traditional terrestrial receiving system.We also fabricated a demonstration model of the new system.The system’s energy receiving and converting device consists of many rectenna arrays that are flexible,transparent,and matching network eliminated to harvest the microwave energy averaging about 80 mW/m^(2) on the ground from the Solar Power Satellite(SPS).The rectenna unit of the system operates at 2.45 GHz,and the measured RF to DC conversion efficiency reaches 20%at−10 dBm and up to 64.65%at 6.8 dBm.As the rectenna array of the system has the advantages of both microwave energy harvesting and light transmittance,conventional solar panels can be placed underneath to collect sunlight and convert it into electricity.It is also feasible to build“self-powered”smart agricultural greenhouses for vegetable cultivation underneath so that the collected energy can be utilized locally to avoid the waste caused by long-distance transmission.The proposed system is of great significance to the research on environmental protection and efficient utilization of land resources at the terrestrial energy receiving system of the Space Solar Power Station.

Output Characteristics of GaAs Cell Irradiated by Laser

The output characteristics of GaAs cell are keys for the laser wireless power transmission system design. The measurement platform for the output characteristics of GaAs cell is established by single-junction GaAs cell and 1064 nm fiber laser. The influence rules of laser power and temperature on the short-circuit current, open-circuit voltage, peak power, fill factor, and conversion efficiency are measured. The measurement results show that the conversion efficiency firstly increases and then decreases with an increase in laser power, and reaches a maximum of 54.5% at the laser power of 0.405 W, whereas the conversion efficiency decreases with an increase in temperature, and decreases slowly with an increase in laser power.