Inductively Coupled CMOS Power Receiver For Embedded Microsensors

Inductively coupled power transfer can extend the lifetime of embedded microsensors that save costs, energy, and lives. To expand the microsensors' functionality, the transferred power needs to be maximized. Plus, the power receiver needs to handle wide coupling variations in real applications. Therefore, the objective of this research is to design a power receiver that outputs the highest power for the widest coupling range. This research proposes a switched resonant half-bridge power stage that adjusts both energy transfer frequency and duration so the output power is maximally high. A maximum power point (MPP) theory is also developed to predict the optimal settings of the power stage with 98.6% accuracy. Finally, this research addresses the system integration challenges such as synchronization and over-voltage protection. The fabricated self-synchronized prototype outputs up to 89% of the available power across 0.067%~7.9% coupling range. The output power (in percentage of available power) and coupling range are 1.3× and 13× higher than the comparable state of the arts.Ph.D

Engineering of Photo-Rechargeable Energy Storage

Solar photovoltaics (PV) is a very promising renewable energy technologies as it is abundant and pollution-free. However, the major drawback of PV power is its intermittency. Integration of batteries with solar modules can reduce overall PV system costs and increase the practicality of PV power. Integration of the photovoltaic cells with supercapacitor storage proved feasibility of combined photovoltaic energy generation and storage but the supercapacitors had low energy storage capacity. Photovoltaic cells with integrated Li-ion batteries as energy storage were demonstrated but had a complex structure due to multiple PV cells; low efficiency due to a mismatch between the PV cell and battery; and low storage capacity due to TiO2 nanotube structure as battery electrode material which possesses high power density but low energy density. There is a need for an efficient integrated photovoltaic rechargeable energy storage system that is cost effective. The objective of this research was to develop an integrated photovoltaic/energy storage device that uses a single solar cell to simply manufacturing (roll to roll); is more efficient by using MPPT with boost converter; and has higher energy storage using a suitable battery electrode material. The performance of DSCs, PSCs with a MPPT boost converter using discrete single solar cells to charge batteries were investigated to determine if the MPPT boost converter can provide the boost function with maximum PV power. Integrated PV/energy storage devices using DSCs, PSCs and Li-ion batteries were fabricated and characterized with MPPT. Li4Ti5O12 battery material had greater than 10% higher specific capacity and better cycling stability with 10% higher energy storage efficiency in both half and full cells than TiO2 tested. The efficiency of PSCs were 14.2% vs 7.8% for DSCs. MPPT led to 9% overall efficiency for PSC-charging vs 5% for the DSC. This was attributed to the higher efficiency of PSC. The PSC efficiency decreased by 2.2% while DSC was more stable with a decrease of 0.4% for 10 cycles studied. The overall efficiency was 4.2% for PSC integrated cell. The overall efficiency of the PSC integrated cell was lower than the discrete PSC charging of a Li-ion coin cell. This was attributed to the lower efficiency of the rear illuminated solar cell in the integrated cell. The storage efficiency of the integrated cell was comparable to that of discrete DSC charging of Li-ion coin batteries. A decrease in discharge capacity of the integrated cell was observed similar to that of the thin film battery studied separately. This integrated device had less complex fabrication, higher storage capacity and was more efficient in comparison to previous reports on third generation solar cells such as dye sensitized solar cells. A simple analysis demonstrating the use of the integrated cell for PV ramp rate application showed that the PSC/Li4Ti5O12-LiCoO2 integrated cell had storage time \u3e 150 secs to satisfy the desired 10%/min ramp rate and also could satisfy even lower ramp rate of 5%/min which required 424 secs. PSCs are at an early development stage and have achieved high efficiency, but stability is a major concern. If this problem is solved then, use of PSC for PV-battery integration will be promising

Applications

Volume 3 describes how resource-aware machine learning methods and techniques are used to successfully solve real-world problems. The book provides numerous specific application examples: in health and medicine for risk modelling, diagnosis, and treatment selection for diseases in electronics, steel production and milling for quality control during manufacturing processes in traffic, logistics for smart cities and for mobile communications

Fast-waking and low-voltage thermoelectric and photovoltaic CMOS chargers for energy-harvesting wireless microsensors

The small size of wireless microsystems allows them to be deployed within larger systems to sense and monitor various indicators throughout many applications. However, their small size restricts the amount of energy that can be stored in the system. Current microscale battery technologies do not store enough energy to power the microsystems for more than a few months without recharging. Harvesting ambient energy to replenish the on-board battery extend the lifetime of the microsystem. Although light and thermal energy are more practical in some applications than other forms of ambient energy, they nevertheless suffer from long energy droughts. Additionally, due to the very limited space available in the microsystem, the system cannot store enough energy to continue operation throughout these energy droughts. Therefore, the microsystem must reliably wake from these energy droughts, even if the on-board battery has been depleted. The challenge here is waking a microsystem directly from an ambient source transducer whose voltage and power levels are limited due to their small size. Starter circuits must be used to ensure the system wakes regardless of the state of charge of the energy storage device. The purpose of the presented research is to develop, design, simulate, fabricate, test and evaluate CMOS integrated circuits that can reliably wake from no energy conditions and quickly recharge a depleted battery. Since the battery is depleted during startup, the system must use the low voltage produced by the energy harvesting transducer to transfer energy. The presented system has the fastest normalized wake time while reusing the inductor already present in the battery charger for startup, therefore, minimizing the overall footprint of the system.Ph.D

Applications

Volume 3 describes how resource-aware machine learning methods and techniques are used to successfully solve real-world problems. The book provides numerous specific application examples: in health and medicine for risk modelling, diagnosis, and treatment selection for diseases in electronics, steel production and milling for quality control during manufacturing processes in traffic, logistics for smart cities and for mobile communications

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen