Small Battery Capacity Research Articles

Regenerative braking kinematic analysis and optimisation strategies

Most of electric and hybrid cars are city oriented due to their reduced pollution and small range. In this paper we intend to analyse kinematics and energy distribution during braking in the scope of city use cases. The purpose is to identify optimization criteria based on system limitations. Our proposal is to describe each case from point of view of kinematics (velocity, acceleration), energy (kinematic energy, instantaneous power). Having relations between data and the results helps us to form optimization strategies: a strategy oriented on driver comfort and two resulted from regenerative braking system component limits. Based on results, maximizing acceleration until its comfort value, in city conditions, does not generate unsupported instantaneous power for generator or energy storage system for an average electric car. Power limitation became more important when keeping same strategy for speed higher than 50 kph. In this case electric vehicles with small battery capacity and hybrid vehicles could show lower efficiency, as more kinetic energy will be dissipated by friction brakes. Presented strategies can be used to implement braking system controlling algorithm for regenerative brakes/friction brakes ratio on-the-fly optimization.

A real-world investigation into usage patterns of electric vehicles in Shanghai

Abstract The usage patterns of EVs is a great concern in Shanghai as the city with the largest number of EVs. Their usage patterns are investigated based on time series association and segmentation of historical static EV data from the real world. The results show that both BEV and PHEV are mostly used as commuting vehicles with an average speed of EVs of less than 25 km/h and about 80% of EVs travel within 60 km per day. Although there is no big difference between the speed of EVs and other models during the morning and evening rush hours, low-speed EVs have a significant environmental advantage over fuel vehicles. About 30% EVs have a relatively concentrated charging time between 21:00–24:00 while PHEVs with small battery capacity still present a small charging peak at about 9:00 in the morning in order to continue to travel with electricity on the way home. The charging locations in urban center are more intensive than those in suburban areas and EVs are charged more frequently in summer than in winter. It is necessary to optimize the layout of charging piles and orderly charging of EVs in the case of no capacity expansion of power transmission and distribution lines. The actual electricity consumption per 100 km of BEV or PHEV is greater than that provided by the manufacturer due to air conditioning energy consumption and complex driving conditions. The results are helpful to promote the development of EVs and layout of charging piles.

Multi-Objective Sizing Optimization of a Grid-Connected Solar–Wind Hybrid System Using Climate Classification: A Case Study of Four Locations in Southern Taiwan

Increased concerns over global warming and air pollution has pushed governments to consider renewable energy as an alternative to meet the required energy demands of countries. Many government policies are deployed in Taiwan to promote solar and wind energy to cope with air pollution and self-dependency for energy generation. However, the residential sector contribution is not significant despite higher feed-in tariff rates set by government. This study analyzes wind and solar power availability of four different locations of southern Taiwan, based on the Köppen–Geiger climate classification system. The solar–wind hybrid system (SWHS) considered in this study consists of multi-crystalline photovoltaic (PV) modules, vertical wind turbines, inverters and batteries. Global reanalysis weather data and a climate-based electricity load profile at a 1-h resolution was used for the simulation. A general framework for multi-objective optimization using this simulation technique is proposed for solar–wind hybrid system, considering the feed-in tariff regulations, environmental regulations and installation area constraints of Taiwan. The hourly load profile is selected using a climate classification system. A decomposition-based differential evolutionary algorithm is used for finding the optimal Pareto set of two economic objectives and one environmental objective with maximum installation area and maximum PV capacity constraints. Two types of buildings are chosen for analysis at four climate locations. Analysis of Pareto sets revealed that the photovoltaic modules are economic options for a grid-connected mode at all four locations, whereas solar–wind hybrid systems are more environmentally friendly. A method of finding the fitness index for the Pareto front sets and a balanced strategy for choosing the optimal configuration is proposed. The proposed balanced strategy provides savings to users—up to 49% for urban residential buildings and up to 32% for rural residential buildings with respect to buildings without a hybrid energy system (HES)—while keeping carbon dioxide (CO2) emissions lower than 50% for the total project lifecycle time of 20 years. The case study reveals that for all four locations and two building types an HES system comprising a 15 kW photovoltaic system and a small capacity battery bank provides the optimal balance between economic and environmental objectives.

A receding horizon control approach for re-dispatching stochastic heterogeneous resources accounting for grid and battery losses

In this paper, we propose a re-dispatch scheme for radial distribution grids hosting stochastic Distributed Energy Resources (DERs) and controllable batteries. At each re-dispatch round, the proposed scheme computes a new dispatch plan that modifies and extends the existing one. To do so, it uses the CoDistFlow algorithm and applies a receding horizon control principle, while accounting for hard time computation constraints that impact on the instantaneous update of a dispatch plan. CoDistFlow handles stochastic DERs and prosumers uncertainties via scenario-based optimization and the non-convexity of the AC Optimal Power Flow by iteratively solving suitably defined convex problems until convergence. We perform numerical evaluations based on real-data, obtained from a real Swiss grid. We show that, with our proposed re-dispatch scheme, the daily dispatch tracking error can decrease more than 80%, even for small battery capacities, and if re-dispatch is frequent enough, it can be eliminated. Finally, we show that re-dispatch should be performed as often as the market allows and the performance continues to improve.

Optimal technical and economic configuration of photovoltaic powered reverse osmosis desalination systems operating in autonomous mode

Renewable energy driven desalination has been proven to be a sustainable, economic and environmental friendly solution for the water deficiency problems in remote areas. However, one of the most important issues is the determination of the optimal configuration so that the system meets the water load at the minimum cost. In this paper, five different configurations of a sea water desalination system powered by photovoltaics were examined at autonomous mode. Αn island in Cyclades, Aegean sea, Greece, was used as a typical case study for the installation of such systems. Then, a comparison among the different configurations was realized in order to determine the optimum technical and economic system, by minimizing the total system installation and operation cost for 20 years lifetime, which then compared in economic terms with the water transportation practice. The present study shows that the application of a photovoltaic powered seawater reverse osmosis desalination unit that incorporates water storage, a small capacity battery bank and an energy management system, is technically feasible to produce fresh water. According to the optimal sizing results, the implementation of an energy management system designed on the basis of Fuzzy Cognitive Maps presents the lowest cost and lowest power losses.

Optimal Energy Trading for Plug-In Hybrid Electric Vehicles Based on Fog Computing

A large number of plug-in hybrid electric vehicles (PHEVs) have high mobility but a small battery capacity; thus, these vehicles urgently need to make charging and discharging decisions in real time. This paper proposes a new architecture based on fog computing for an Internet of Vehicles energy trading system, which we call a vehicle-mounted energy fog. This architecture includes a fog computing energy center (FCEC), which manages local energy trading and reduces the peak load energy trading for an external public energy company. We model the optimization problems for energy trading under two different types of FCECs: 1) a nonprofit-driven FCEC whose goal is solely to benefit the PHEV charging and discharging operations and 2) a profit-driven FCEC whose goal is to maximize its own profits while still guaranteeing that each PHEV achieves a non-negative utility. We also propose efficient algorithms for these two types of FCECs to seek optimal pricing and make supply demand decisions. Simulation results show that our proposed algorithms are superior to existing algorithms in terms of the convergence rate, the final objective value and the evenness of the Pareto solution set. Specifically, the evenness of the Pareto solution set is improved by 23% compared to the results of the existing algorithm.

Distributed primary frequency regulation of grid-connected photovoltaic power station with battery storage

Large-scale renewable energy connects with power system has posed great challenges to the safe and stable operation of power system, in order to solve the problem of frequency stability caused by large-scale photovoltaic connects with grid, a method of distributed frequency regulation by meanings of distributed battery energy storage system (DBESS) in grid-connected photovoltaic power station is proposed. By the way of paralleling a small capacity battery pack into the inverter DC side, fast active support is provided by battery pack when the system frequency is disturbed. Meanwhile, the inverter can adaptively determine the inverter permanent speed droop of itself according to the state of charge (SOC) of the battery pack during primary frequency regulation, to meet the system needs in different situations. Simulation result shows that the distributed frequency regulation proposed in this paper increases rapidity, accuracy and controllability of active control in the photovoltaic power station when system frequency disturbs, and it can meet the demand of the power system primary frequency regulation.

Decarbonizing passenger cars using different powertrain technologies: Optimal fleet composition under evolving electricity supply

Alternative powertrain technologies are seen as key elements to meet decarbonization targets for road-based motorized passenger transportation. But which technology can result in the largest avoidance in CO2, if the electricity sector is evolving in parallel? In this paper we investigate the maximum CO2 reduction potential supply side interventions can have on a national fleet under the best imaginable circumstances, considering the emissions from supply of fuels and electricity. The optimal fleet may contain battery-electric, fuel-cell electric and hybrid-electric propulsion systems, as well as their plug-in variants. Contrary to typical well-to-wheel analyses, we use disaggregated mobility data from a representative national household travel survey to represent individual vehicle usage behavior – some technologies may not be able to cover the demands of certain individuals. Also, we describe the energy conversion efficiency of all powertrain technologies using empirical data from a chassis dynamometer measurement campaign on actual, current vehicles. Using this information, we compute the CO2 optimal fleet compositions, i.e the fleet with largest CO2 avoidance under different CO2 intensities of the electricity. The latter serves as a proxy for the evolution of the electricity supply sector. The study is a potential analysis based on Swiss data.We identified three domains: (1) above 600gCO2/kWh the optimal passenger car fleet only operates on fossil fuels in the from of compressed natural gas, but could avoid about 35% in CO2 emissions, (2) between 600 and 235gCO2/kWh electricity is used as energy carrier, but the long daily distances still utilize natural gas, (3) below 235gCO2/kWh the entire fleet is powered through electricity, directly or by hydrogen electrolysis.Plug-in vehicles have the highest fleet share of around 80%. They are mainly operated as small capacity battery electric vehicles, since the majority of daily trips are rather short. A significant decarbonization requires a large amount of additional electricity, in the optimal case about 34% of the current chemical fuel energy.The potential CO2 avoidance is large even with todays technologies. Hydrogen is not crucial to substantially decarbonize passenger cars.

Joint Charging Tour Planning and Depot Positioning for Wireless Sensor Networks Using Mobile Chargers

Recent breakthrough in wireless energy transfer technology has enabled wireless sensor networks (WSNs) to operate with zero-downtime through the use of mobile energy chargers (MCs), that periodically replenish the energy supply of the sensor nodes. Due to the limited battery capacity of the MCs, a significant number of MCs and charging depots are required to guarantee perpetual operations in large scale networks. Existing methods for reducing the number of MCs and charging depots treat the charging tour planning and depot positioning problems separately even though they are inter-dependent. This paper is the first to jointly consider charging tour planning and MC depot positioning for large-scale WSNs. The proposed method solves the problem through the following three stages: charging tour planning, candidate depot identification and reduction, and depot deployment and charging tour assignment. The proposed charging scheme also considers the association between the MC charging cycle and the operational lifetime of the sensor nodes, in order to maximize the energy efficiency of the MCs. This overcomes the limitations of existing approaches, wherein MCs with small battery capacity ends up charging sensor nodes more frequently than necessary, while MCs with large battery capacity return to the depots to replenish themselves before they have fully transferred their energy to the sensor nodes. Compared with existing approaches, the proposed method leads to an average reduction in the number of MCs by 64%, and an average increase of 19.7 times on the ratio of total charging time over total traveling time.

Enabling IoT interoperability through opportunistic smartphone-based mobile gateways

In the near future, all our everyday things and objects will be both connected to the Internet and equipped with enough sensing, acting and processing capabilities to exploit the full potential benefits of the so called Internet of Things (IoT) paradigm. Even the simplest objects will become “smart” because they will be interconnected to other objects to share and collect data from the environments in which they are placed thus paving the way to novel application services, computing and communication scenarios.In this context, interoperability among different standards and communication technologies is still a significant challenge that we have started to address by proposing a smartphone-based mobile gateway acting as a flexible and transparent interface between different IoT devices and the Internet. The presented unified, high-level and extendible software architecture supports opportunistic IoT devices discovery, control and management coupled with data processing, collection and diffusion functionalities.A specific testbed on common smartphones with different hardware and software capabilities was deployed to evaluate the real feasibility of the designed solution measuring the system performance in terms of energy consumption, memory and CPU usage in high and low load scenarios. According to the obtained results, the implemented software architecture for multi-standard and multi-technology interoperation presents a reduced use of hardware resources in front of a relatively high energy consumption value, mostly due to the simultaneously active radio interfaces combined with a small battery capacity, that limits the smartphone lifetime. Nevertheless, the presented general approach is still remarkable because this latter aspect will most likely be exceeded, in a short time, thanks to daily technological advancements in both batteries and radio interfaces.

Providing primary frequency control with residential scale photovoltaic-battery systems

Decentralized photovoltaic (PV) battery systems have recently received great attention from consumers around the world. PV battery systems allow consumers to reduce their dependence on the local electricity supplier at lower or equivalent costs. However, the profitability of PV battery systems depends greatly on the local meteorological conditions and the local electricity retail tariff. In central European countries, PV battery systems generate and store less electricity in winter months due to lower irradiation. The battery, in particular, can be reserved to provide ancillary services during winter months and thereby improves the overall systems economics. In this study, a large dataset consisting of individual load profiles is used to simulate a virtual power plant which provides ancillary services during battery idle times. The results show that participants with large batteries can greatly increase their overall systems economics by participating in reserve markets. However, participants with small battery capacities may not be able to recover the additional costs for communication with the virtual power plant and are thus not suitable candidates to provide grid stabilizing services (ancillary services).

Usage of the Fuel Cell-Powered Electric Drive in Aviation

Weight and consumed space of the fuel cell systems are one of the most important factors limiting its utilization in electric airplanes. Possibilities of its implementation in electric airplane are frequently discussed issues. Power – mass relationship depending on installed power of the fuel cell shows, that the power/mass ratio is unsatisfactory, when powering electric motor directly from fuel cell. Configuration with high-power small-capacity battery and relatively small fuel cell is more profitable. Some calculations were done for functional prototype of the small airplane VUT 051 RAY, its take-off weight is about 600 kg and its max. power is 55 kW. There are some practical measurements on the Ballard fuel cell system presented in this paper, which can documents disputableness of its usage in airplane. Hydrogen management (hydrogen tank, cooling system, armatures etc.) still represents outstanding issue due to high volumes and weight of the whole fuel cell system. Current progress in the field of the Li-Ion accumulators, generally decreases importance of hydrogen-drive systems and focuses more attention to simply accumulator powered airplane.

주파수 제어에 의한 무선 충전 최적화 기법

본 논문은 무선 충전 시스템의 최적화 기법에 대한 것으로서, 특히 캡슐형 내시경 응용을 위한 회로를 기반으로 한다. 이 논문에서는 저용량 배터리를 내장하는 무선 충전 시스템에서 전자기 유도 원리를 이용한 방식을 적용하여 배터리 용량을 필요 이상으로 증가시키지 않는 상태에서 여러 가지 상황에 대응하여 무선 전력 전송의 효율을 최적화하는 것을 목표로 하였다. 전자기 공진 코일의 무선 전력 전송의 효율을 증가시키기 위하여 전력 전송의 주요 결정 요소를 분석하고 주파수 제어에 의한 효율 최적화를 시도하였다. 모의실험 결과 제안된 최적화 기법은 무선 충전 효율을 안정화시키고 현재 문제가 되고 있는 거리 및 기생 성분에 의한 전송 효율 변이를 효과적으로 개선하는 것을 확인하였다.

An Ultra-Low-Power Long Range Battery/Passive RFID Tag for UHF and Microwave Bands With a Current Consumption of 700 nA at 1.5 V

We present for the first time, a fully integrated battery powered RFID integrated circuit (IC) for operation at ultrahigh frequency (UHF) and microwave bands. The battery powered RFID IC can also work as a passive RFID tag without a battery or when the battery has died (i.e., voltage has dropped below 1.3 V); this novel dual passive and battery operation allays one of the major drawbacks of currently available active tags, namely that the tag cannot be used once the battery has died. When powered by a battery, the current consumption is 700 nA at 1.5 V (400 nA if internal signals are not brought out on test pads). This ultra-low-power consumption permits the use of a very small capacity battery of 100 mA-hr for lifetimes exceeding ten years; as a result a battery tag that is very close to a passive tag both in form factor and cost is made possible. The chip is built on a 1-mum digital CMOS process with dual poly layers, EEPROM and Schottky diodes. The RF threshold power at 2.45 GHz is -19 dBm which is the lowest ever reported threshold power for RFID tags and has a range exceeding 3.5 m under FCC unlicensed operation at the 2.4-GHz microwave band. The low threshold is achieved with architectural choices and low-power circuit design techniques. At 915 MHz, based on the experimentally measured tag impedance (92-j837) and the threshold spec of the tag (200 mV), the theoretical minimum range is 24 m. The tag initially is in a "low-power" mode to conserve power and when issued the appropriate command, it operates in "full-power" mode. The chip has on-chip voltage regulators, clock and data recovery circuits, EEPROM and a digital state machine that implements the ISO 18000-4 B protocol in the "full-power" mode. We provide detailed explanation of the clock recovery circuits and the implementation of the binary sort algorithm, which includes a pseudorandom number generator. Other than the antenna board and a battery, no external components are used.

Ionic Conduction in Zn3(PO4)2·4H2O Enables Efficient Discharge of the Zinc Anode in Serum

Batteries contain corrosive or reactive components necessitating containment in a case, setting a limit to their miniaturization. Miniature, small-capacity batteries could power medical sensors in the body, for example sensing glucose for diabetes management. A miniature, case-less Zn-Ag/AgCl battery would consist merely of a zinc anode and a bioinert gel-coated Ag/AgCl cathode, if both operated efficiently in the interstitial fluid. Such a battery has not previously been built, primarily because of rapid corrosion of Zn. We show that the corrosion of zinc is significantly reduced by growth of Zn2+-ion-conducting, O2-impermeable, hopeite [Zn3(PO4)2.4H2O] lamellae on the Nafion-coated Zn anode. The hopeite lamellae allow discharge of the Zn anodes over three weeks at 86% current efficiency in physiological buffer and at 60% efficiency over two weeks in serum. The Zn|physiological buffer|Ag/AgCl cell operates at 1.00 V at 13 muA cm-2 and at 0.94 V at 0.2 mA cm-2 anodic current density.