Possibilities and Challenges of Radio Frequency Energy Harvesting in Dar es Salaam, Tanzania

This paper presents investigation on the possibilities and challenges of harvesting ambient Radio Frequency Energy (RFE) at Dar es Salaam region in Tanzania. The Radio Frequency (RF) signals were measured using a Rohde and Schwarz FSC 3 spectrum analyzer observing available frequencies with their respective power. Among several RF signals received, the most powerful signals observed were; 800 MHz, 950 MHz, 2100 MHz and 2400 MHz, having average signal strengths of about -30.29 dBm, -35.94 dBm, -42.90 dBm and -30.42 dBm respectively. The power possessed within these frequencies were suitable to be harvested due to their signal strengths, an overall power average of -34.89dBm was obtained and a multi narrowband harvester was designed and simulated using real-time values on Keysight’s Advanced Design System (ADS) 2019. The simulation results confirm a promising possibility of harvesting RF energy to power ultra-low-power devices in the Internet of Things (IoT) and beyond.

Power Generation from Salinity Gradient by Reverse Electrodialysis in Silicon Nitride Nanopores

Solid-state nanopores have shown great potential in investigating salinity gradient energy generation as a renewable power generator. In this work, various diameter silicon nitride (Si3N[Formula: see text] nanopores were fabricated to investigate the power generation between two potassium chloride solutions with different concentration gradient ratios by reverse electrodialysis. The maximal estimated power density of a Si3N4 nanopore measured experimentally can be high to 16[Formula: see text]649Wm[Formula: see text]. To compare with the single Si3N4 nanopore, multiple nanopores array has also been investigated. The equivalent circuit model of multiple Si3N4 nanopores array generator is quantitatively constructed by massive reproducible experimental data and theoretical derivation. For nanopore array, the osmotic current basically keep a linear growth with the number of the nanopores at every concentration ratio. While, the osmotic voltage is basically independent on the number of nanopore. The power generation circuit of the nanopore array can be regarded as a parallel circuit of multiple nanopores. Power generation from concentration gradients in Si3N4 nanopores could be widely used in a variety of applications like ultra-low power devices and micro-nano electromechanical systems.

Crack Protective Layered Architecture of Lead-Free Piezoelectric Energy Harvester in Bistable Configuration

Kinetic piezoelectric energy harvesters are used to power up ultra-low power devices without batteries as an alternative and eco-friendly source of energy. This paper deals with a novel design of a lead-free multilayer energy harvester based on BaTiO3 ceramics. This material is very brittle and might be cracked in small amplitudes of oscillations. However, the main aim of our development is the design of a crack protective layered architecture that protects an energy harvesting device in very high amplitudes of oscillations. This architecture is described and optimized for chosen geometry and the resulted one degree of freedom coupled electromechanical model is derived. This model could be used in bistable configuration and the model is extended about the nonlinear stiffness produced by auxiliary magnets. The complex bistable vibration energy harvester is simulated to predict operation in a wide range of frequency excitation. It should demonstrate typical operation of designed beam and a stress intensity factor was calculated for layers. The whole system, without presence of cracks, was simulated with an excitation acceleration of amplitude up to 1g. The maximal obtained power was around 2 mW at the frequency around 40 Hz with a maximal tip displacement 7.5 mm. The maximal operating amplitude of this novel design was calculated around 10 mm which is 10-times higher than without protective layers.