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New Energy Harvesting Method for Small Systems

There are several methods to generate power, even if there are no external power sources available. This is particularly useful if you want to make energy systems work independently and not susceptible to power shortages or blackouts. One such method is to use small vibrations, temperature differences in electronic systems and also light and translate them into power through sensors. Sensors are the key elements of the Internet of Things (IoT), as they can collect information about a machine or an infrastructure, process and transmit it. The IoT is a low-power wide-area network radio technology standard which was originally developed for cellular devices and services. The main focus was to achieve low cost, long battery life, and high connection density, especially indoors.

Now (2022), Fraunhofer researchers have taken this technology and improved it so that it can power small electric devices autonomously through energy harvesting without using any batteries or cables. They operated these sensors through vibrations from machines, equipment or buildings, as well as by converting temperature differences between pipes, lines or valves, and the environment into energy.

The scientists at Fraunhofer had already carried out research before into how energy harvesting technologies could be optimised and where they might be deployed. Drawing on the gained knowledge they improved existing systems. One of the most recent developments is the NarrowBand IoT module. This device is capable of collecting and transmitting utility data in a 5G network. In order for the modules and sensors to be operated energy-independently, they were specially measured and optimised for energy consumption. The aim was to create systems that can autonomously power not only LPWANs (low-power wide-area networks) but also other radio systems with higher energy consumption and more advanced functionalities, such as bidirectional communication. The systems could then also be operated in a public network.

The module is combined with a mioty® system, a standardized software-based connectivity solution intended for installing large, secure and powerful Low Power Wide Area Networks (LPWAN), for industrial and commercial IoT applications. The core invention behind mioty® is „Telegram Splitting“. This technology breaks a data packet into numerous subpackets and distributes them over time and frequency. This technology makes the network robust against large interferers in a crowded license-free spectrum and secures a reliable data connection from mioty® end nodes to the base station.

Research into autonomous energy systems are one of the chief interests of modern energy systems research. In 2022, scientists concentrated their efforts on improving the previous design of the energy floor—called Genpath. There, rotational electromagnetic (EM) technique was used to generate electricity from human footsteps. The design consisted of two main parts: the EM generator, including the lead-screw mechanism for translation-to-rotation conversion, and the Power Management and Storage (PMS) circuit. The improvement focused on the EM generator. The scientists found that the EM generator shaft in the previous Genpath design was not able to rotate continuously when the floor-tile reached the bottom end, which, in turn, resulted in no energy generation. Therefore, they implemented a one-way clutch to the system to decouple the generator shaft from the lead-screw motion once the floor-tile reached the allowable displacement. This enabled the EM generator shaft to continue with a free rotation and produce more power. Also, a dynamic model of the electro-mechanical systems with the one-way clutch was developed and used to predict the energy performances of the VEH floors and fine-tune the design parameters. The analytical results showed that the spring stiffness mainly influenced the force passed on to the EM generator, and then the induced voltage and power of the generator. Therefore, the value of the stiffness was one of the critical design parameters to scientists undertook to optimise. Having performed theses analyses, the scientists built and tested the new prototype comprising a 12-V-DC generator, mechanisms of lead-screw and clutch, as well as coil springs with the a stiffness of 1700 N/m. The average energy produced by the new prototype amounted to 3637 mJ (or average power of 3219 mW), per footstep which was 2935 mJ greater than that of the previous design.

Image: Contour plot of the averaged power when generator constant and resistance of generator are varied.

Source: Thitima Jintanawan, Gridsada Phanomchoeng, Surapong Suwankawin, Weeraphat Thamwiphat/ Design of a More Efficient Rotating-EM Energy Floor with Lead-Screw and Clutch Mechanism/ Energies 15(18):6539, September 2022/ DOI:10.3390/en15186539/ Open Source This is an Open Access article is distributed under the terms of the
Creative Commons Attribution 4.0 International (CC BY 4.0)

Also in 2022, scientists performed ferrorestorable polarisation engineering capable of more than doubling the effective permittivity. The research and ab initio calculations showed that a defect dipole composed of Cu³⁺ and oxygen vacancy in a prototypical ferroelectric barium titanate ceramic went hand in hand with spontaneous polarisation. The resultant ferrorestorable polarisation exhibited a high effective relative permittivity, with high energy efficiency up to 89%. This study might make an important contribution towards realising efficient ceramic capacitors for self-powered applications.

Image: Interaction between Cu and VO•• a Total energy (Etotal) of VOn••-Cu⁺, VOn••-Cu²⁺, VOn••-Cu³⁺ and VOn••-V²⁺. In our DFT calculations, low-spin (LS) and high-spin (HS) states were adopted for VOn••-Cu³⁺ with n = 1–3 and n ≥ 4, respectively, according to the ground-state arrangements (Supplementary Fig. 1a, b). b–d Schematics of possible configurations of Ps with μdef in Cu³⁺. μdef, 1 is the most stable for Cu³⁺ because its Etotal is 0.15–0.36 eV lower than those of μdef, 2 and μdef, 3. For Cu²⁺, μdef, 2 is the majority configuration because μdef, 1 and μdef, 2 have almost the same Etotal. For Cu⁺, μdef 1 and μdef, 3 coexist because the difference in Etotal is quite small. e–g Total and partial density of states of VO1••-Cu³⁺ (LS), VO3••-Cu³⁺ (LS), and VO4••-Cu³⁺ (HS). The valence band (VB) and the conduction band (CB) are mainly composed of O-2p orbitals and Ti-3d orbitals, respectively. Red upward and blue downward arrows indicate the majority and minority spin bands, respectively. h Unoccupied antibonding dx2−y2* orbital in VO1••-Cu³⁺. i Partially occupied antibonding dz2* orbital in VO4••-Cu³⁺.

Source: Hiroki Matsuo, Masashi Utsunomiya, Yuji Noguchi/ Utilizing ferrorestorable polarization in energy-storage ceramic capacitors/ NPG Asia Materials 14(1), October 2022/ DOI:10.1038/s41427-022-00426-z/ Open Source This is an Open Access article is distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0)

The new findings may lead to great advances in how we power energy devices: First and foremost, providing a sensor node with energy through energy harvesting technology makes it independent from external energy supplies and possible energy shortages. This can save costs arising from energy-storage devices, such as batteries, and eliminates the maintenance effort required for battery replacement. Cable installations will also no longer be needed. The autonomous sensors can be used for data collection and transmission, e.g., for the condition monitoring of machines, buildings or bridges, as well as for smart metering systems.

Fraunhofer IIS will demonstrate the NarrowBand IoT module and a mioty® radio sensor at the electronica 2022 trade show, held from November 15-18 in Munich, to show how these sensors can be operated entirely without cables or batteries through a thermo-electric generator or a vibration converter. Also, a smart screw connection will be displayed whose preload force can be monitored remotely thanks to energy-autonomous sensor technology. This invention will make sure that loose screws will no longer pose a safety risk to bridges, machines or buildings in the future.