Wearable flexible lightweight modular RFID tag with integrated energy harvester

A novel wearable radio frequency identification (RFID) tag with sensing, processing, and decision-taking capability is presented for operation in the 2.45-GHz RFID superhigh frequency (SHF) band. The tag is powered by an integrated light harvester, with a flexible battery serving as an energy buffer. The proposed active tag features excellent wearability, very high read range, enhanced functionality, flexible interfacing with diverse low-power sensors, and extended system autonomy through an innovative holistic microwave system design paradigm that takes antenna design into consideration from the very early stages. Specifically, a dedicated textile shorted circular patch antenna with monopolar radiation pattern is designed and optimized for highly efficient and stable operation within the frequency band of operation. In this process, the textile antenna's functionality is augmented by reusing its surface as an integration platform for light-energy-harvesting, sensing, processing, and transceiver hardware, without sacrificing antenna performance or the wearer's comfort. The RFID tag is validated by measuring its stand-alone and on-body characteristics in free-space conditions. Moreover, measurements in a real-world scenario demonstrate an indoor read range up to 23 m in nonline-of-sight indoor propagation conditions, enabling interrogation by a reader situated in another room. In addition, the RFID platform only consumes 168.3 mu W, when sensing and processing are performed every 60 s

Robust optimization for energy transactions in multi-microgrids under uncertainty

Independent operation of single microgrids (MGs) faces problems such as low self-consumption of local renewable energy, high operation cost and frequent power exchange with the grid. Interconnecting multiple MGs as a multi-microgrid (MMG) is an effective way to improve operational and economic performance. However, ensuring the optimal collaborative operation of a MMG is a challenging problem, especially under disturbances of intermittent renewable energy. In this paper, the economic and collaborative operation of MMGs is formulated as a unit commitment problem to describe the discrete characteristics of energy transaction combinations among MGs. A two-stage adaptive robust optimization based collaborative operation approach for a residential MMG is constructed to derive the scheduling scheme which minimizes the MMG operating cost under the worst realization of uncertain PV output. Transformed by its KKT optimality conditions, the reformulated model is efficiently solved by a column-and-constraint generation (C&CG) method. Case studies verify the effectiveness of the proposed model and evaluate the benefits of energy transactions in MMGs. The results show that the developed MMG operation approach is able to minimize the daily MMG operating cost while mitigating the disturbances of uncertainty in renewable energy sources. Compared to the non-interactive model, the proposed model can not only reduce the MMG operating cost but also mitigate the frequent energy interaction between the MMG and the grid

Space station power system

The major requirements and guidelines that affect the space station configuration and power system are explained. The evolution of the space station power system from the NASA program development-feasibility phase through the current preliminary design phase is described. Several early station concepts are described and linked to the present concept. Trade study selections of photovoltaic system technologies are described in detail. A summary of present solar dynamic and power management and distribution systems is also given

Experimental tests to recover the photovoltaic power by battery system

The uncertainty and variability of the Renewable Energy Sources (RES) power plants within the power grid is an open issue. The present study focuses on the use of batteries to overcome the limitations associated with the photovoltaic inverter operation, trying to maximize the global energy produced. A set of switches, was placed between a few photovoltaic modules and a commercial inverter, capable to change configuration of the plant dynamically. Such system stores the power that the inverter is not able to let into the grid inside batteries. At the base of this optimization, there is the achievement of two main configurations in which the batteries and the photovoltaic modules are electrically connected in an appropriate manner as a function of inverter efficiency and thus solar radiation. A control board and the relative program, to change the configuration, was designed and implemented, based on the value of the measured radiation, current, batteries voltage, and calculated inverter efficiency. Finally from the cost and impact analysis we can say that, today the technology of lithium batteries, for this application, is still too expensive in comparison with lead-acid batteries

Coordinated Control of Energy Storage in Networked Microgrids under Unpredicted Load Demands

In this paper a nonlinear control design for power balancing in networked microgrids using energy storage devices is presented. Each microgrid is considered to be interfaced to the distribution feeder though a solid-state transformer (SST). The internal duty cycle based controllers of each SST ensures stable regulation of power commands during normal operation. But problem arises when a sudden change in load or generation occurs in any microgrid in a completely unpredicted way in between the time instants at which the SSTs receive their power setpoints. In such a case, the energy storage unit in that microgrid must produce or absorb the deficit power. The challenge lies in designing a suitable regulator for this purpose owing to the nonlinearity of the battery model and its coupling with the nonlinear SST dynamics. We design an input-output linearization based controller, and show that it guarantees closed-loop stability via a cascade connection with the SST model. The design is also extended to the case when multiple SSTs must coordinate their individual storage controllers to assist a given SST whose storage capacity is insufficient to serve the unpredicted load. The design is verified using the IEEE 34-bus distribution system with nine SST-driven microgrids.Comment: 8 pages, 10 figure

Reliability constrained planning and sensitivity analysis for Solar-Wind-Battery based Isolated Power System

Isolated power systems have emerged as a practical substitute to grid extension for electrification of remote areas. The environmental hazards associated with conventional sources of energy like diesel and coal has forced system planners to resort to renewable energy sources(RES) based technologies such as solar and wind. Increased penetration of RES can effectively cut down system operating costs but can create reliability issues owing to their unpredictable nature. The risk of lower reliability standards can significantly hamper utilization of these sources on large scale. Thus an effective backup system is needed in order to ensure reliability standards. The backup is provided either by diesel generators or energy storage systems. The intermittent nature and cost intensive structure of RES based DGs makes it essential to perform sensitivity analyses for optimal system planning. In this paper, reliability and cost based sizing of solar-wind-battery storage system has been carried out for an Isolated hybrid power system(IHPS). Sensitivity analyses are performed by studying the effect of addition/removal of RES based DGs and storage units on system reliability. Considering variable nature of solar and wind sources, modelling of solar irradiance, wind speed and generator availability has been done using appropriate probability density functions. Dual reliability indices have been used for determining system reliability. For solving optimal sizing problem, a stochastic optimization technique Particle Swarm Optimization(PSO) has been employed. A new index termed as Incremental cost of reliability has been utilized in order to assess the additional investment required to improve reliability standards. Optimal sizing study in conjunction with sensitivity analyses facilitates a deeper insight into system planning

Dual Output Power Management Unit for PV-Battery Hybrid Energy System

The tremendous evolution in the electronics industry has provided high performance portable devices. However, the high power demand and the limited capacity of batteries, prevent the devices from operating for a long time without the need of a power outlet. The ease of deploying Photovoltaic (PV) cells close to the device enables the user to harvest energy on the go, and get rid of the conventional power outlets. However, applying the PV power to the electronic devices is not as easy as the plug and play model, due to the unstable output voltage and power of the PV cells. In this thesis, a power management unit is proposed to provide dual regulated outputs using a PV module and a rechargeable battery. The main components of the unit are a Dual Input Multiple Output (DIMO) DC-DC converter and a digital controller. The converter is used to interface the battery and the PV module with the loads. Moreover, the proposed converter has the ability to step up or step down the input voltage. The controller maximizes the PV power using the fractional open circuit voltage Maximum Power Point Tracking (MPPT) method. Furthermore, the controller manages the amount of power supplied to or from the battery in order to satisfy the load demand and regulate the outputs at the required levels. The controller has been implemented and synthesized using VHDL. A prototype has been implemented using an FPGA and off the shelf components. The functionality of the system has been tested and verified under varying environmental conditions

Implement Using KY Converter for Hybrid Renewable Energy Applications: Design, Analysis, and Implementation

This chapter mainly focuses on meeting the energy demand and methodologies of renewable energy. Nowadays, researchers are mainly focusing on renewable energy from the sun, wind, biomass, etc. due to energy crises and the lack of non-renewable energy. The potential for solar energy is high and this demand can best be met with hybrid systems, which can provide an uninterruptible power supply. This chapter looks at the performance metrics of hybrid energy as well as the methodologies and various control techniques connected with power management. The chapter also defines the photovoltaic (PV)-based, novel, dual KY boost converter. Dual PV sources act as input for the dual KY boost converter to generate as much energy as possible from the dual PV system, using the inverter module to produce single-phase alternating current output. A dual KY boost converter can provide higher maximum power, a faster response, and smaller voltage ripple. KY boost converters are designed to generate stable output values according to various conditions because of various control techniques and the maximum power point tracking control algorithm