|Michigan Tech's Open Sustainability Technology Lab.|
Search terms[edit | edit source]
- Ultracapacitors and solar PV
- Hybrid battery-ultracapacitor charging
- Constant current charging
- Constant power charging mode
- Hybrid energy storage
Journals[edit | edit source]
- Science Direct
- Solar Energy
literature[edit | edit source]
Uninterruptible power supply for short-time power back-up using ultracapacitors[edit | edit source]
Abstract: This paper presents an uninterruptible power supply capable of proving power for several seconds. Ultracapacitors are used as the storage method since they are suitable for pulse power applications and longer life time. Selection of ultracapacitors and controller design for associated power electronic converters are presented in this paper. Further simulation results of the proposed uninterruptible power supply are also included in the paper.
Ultracapacitors: why, how, and where is the technology[edit | edit source]
Abstract: This paper covers all the basics of Ultra capacitors from why we need them, their advantages, their working and a detailed comparison of various features of Ultra capacitors with that of batteries. Various concerns like the cost issues and the manufacturing problems of the technologies involved are discussed.The present status and the future scope of the technology is also covered.
Effective charging method for ultracapacitors[edit | edit source]
Abstract:One of the advantages of ultracapacitors is its high power capability, which is applicable for high rate of charging and discharging operation like motor starting and regenerative braking of an electric vehicle. This paper presents a new charging method for ultracapacitors. Comparing with batteries, ultracapacitor can accept a wide range of charging current and can be fully charged within a few minutes. Common chargers for ultracapacitors are usually equipped with current transducers and closed loop circuitry for current control, which are expensive and complicated. The proposed circuit consists of a minimum number of components. It does not require any current transducer or dedicated voltage/current control circuitry. A simple open-loop control system is applicable for the whole charging stage. It is free of stability problem and protects itself from being overloaded by ultracapacitor with zero initial charge. This paper presents the design and operation of the hardware circuit. Both simulation and experimental results are included.
Use of Super-Capacitor to Enhance Charging Performance of Stand-Alone Solar PV System[edit | edit source]
Abstract:The battery charging performance in a stand-alone solar PV system affects the PV system efficiency and the load operating time. The New Energy Center of National Taiwan University has been devoted to the development of a PWM charging technique to continue charging the lead-acid battery after the overcharge point to increase the battery storage capacity by more than 10%. The present study intends to use the super-capacitor to further increase the charge capacity before the overcharge point of the battery. The super-capacitor is connected in parallel to the lead-acid battery. This will reduce the overall charging impedance during the charge and increase the charging current, especially in sunny weather. A system dynamics model of the lead-acid battery and super-capacitor was derived and the control system simulation was carried out to predict the charging performance for various weathers. It shows that the overall battery impedance decreases and charging power increases with increasing solar radiation. An outdoor comparative test for two identical PV systems with and without supercapacitor was carried out. The use of super-capacitor is shown to be able to increase the lead-acid charging capacity by more than 25% at sunny weather and 10% in cloudy weather.
Maximum power transfer tracking for a photovoltaic-supercapacitor energy system[edit | edit source]
Abstract:It is important to maintain high efﬁciency when charging electrical energy storage elements so as to achieve holistic optimization from an energy generation source (e.g., a solar cell array) to an energy storage element (e.g., a supercapacitor bank). Previous maximum power point tracking (MPPT) methods do not consider the fact that efﬁciency of the charger varies depending on the power output level of the energy generation source and the state of charge of the storage element. This paper is the ﬁrst paper to optimize the efﬁciency of a supercapacitor charging process by utilizing the MPPT technique and simultaneously considering the variable charger efﬁciency. More precisely, previous MPPT methods only maximize the power output of the energy generation source, but they do not guarantee the maximum energy is stored in the energy storage element. Note that the load device takes its energy from the storage element so it is important to maximize energy transfer from the source into the storage element. We present a rigorous framework to determine the optimal capacitance of a supercapacitor and optimal conﬁguration of a solar cell array so as to maximize the efﬁciency of energy transfer from the solar cells into a bank of supercapacitors. Experimental results show the efﬁcacy of the proposed technique and design optimization framework.
A novel charging control scheme for super capacitor energy storage in photovoltaic generation system[edit | edit source]
Abstract:A control scheme is described to charge series-connected super capacitors for photovoltaic generation systems. Based on the features of the super capacitors charge, the control scheme consists of three modes, i.e., the constant current charge mode, the constant power charge mode, and the constant voltage charge mode. The shift of three modes can be realized by controlling the duty of IGBT in the Boost-Buck converter system. Meanwhile, the high voltage, which is more suitable for application, can be obtained. Compared with the normal charge method with series-connected current-limiting resistance and the charge method with the constant current charge mode and the constant voltage charge mode, the proposed charging control scheme can shorten the charging time and improve the usage of the electric power generated from the PV arrays. The advantage described above is verified by simulations.
Research on Supercapacitor Charging Efficiency of Photovoltaic System[edit | edit source]
Abstract:the model of supercapacitor and its charging performance with constant voltage charging mode, constant current charging mode and constant power charging mode were studied. A numerical method to calculate the efficiency of these charging modes was inducted. To analyze the storage performance of supercapacitor in PV system, using this method, the maximum charging efficiencies of supercapacitor when its terminal voltage raise from zero to the rated voltage with different charging modes were presented. The multi-stage charging efficiency curves were retrieved, which indicated that the constant power charging mode is more suitable when supercapacitor are charged in PV system. A MPPT plus constant power control charging strategy using two-stage Buck-Boost converter to charge supercapacitor in PV system was proposed. The simulation results showed that this strategy effectively ensure the charging efficiency of the system.
Technology Research Of Novel Energy Storage Control For The PV Generation System[edit | edit source]
Abstract:Recent years, technologies for new energy have developed rapidly since the energy crisis and the environmental pollution got worse. And the solar energy generation technology tends towards the stage of a large number of applications in engineering from the research stage. This paper designed a grid-connected PV system firstly, then introduced the operation principle of the various parts as well with the control strategy of the power flow. The design of energy storage is of great significance as the output power of PV cells array is greatly affected by the light intensity and the temperature change. Battery is used as the energy storage device normally in the traditional energy storage system. In this paper, it used the Ultracapacitor as the energy storage device after comparing with the battery, and designed the charge-discharge control strategy according to the characteristics of the ultracapacitor. Finally it verified the feasibility of the energy storage control strategy through the simulation models which was built based on the PSCAD/EMTDC platform.
Using Ultracapacitors in Photovoltaic Systems. A technical proposal[edit | edit source]
Control of Bidirectional DC-DC Converter for Supercapacitor Automotive Application[edit | edit source]
Abstract: The purpose of this paper is to study a sliding- mode controller to regulate the voltage and current a bidirectional DC-DC converter . The converter is placed between a supercapacitor array (SA) and a DC-link �xed at 42V. Supercapacitor array is re- garded as powered system with high current and low voltage source. The DC-DC converter is bidi- rectional: it is a Boost converter when the SA pro- vides the power requirement of the DC link and a Buck converter when SA is charged from the DC link. The output voltage ( Boost case) and the inductor current (Buck case) are regulated at con- stant values using a sliding mode approach.
MCU Controlled DC-DC Buck/Boost Converter for Supercapacitors[edit | edit source]
Abstract: This work is focused on DC to DC conversion, what is a crucial function to enable the use of supercapacitors for energy storage. A theoretical study and comparison of methods, algorithms and techniques for software controlled DC-DC converters have been used to develop a system what can step up or down a DC variable voltage and transform it into a steady state voltage. As a result a new control theory based on Bang-Bang control has been developed with an ARM LPC1768 processor. It was implemented to solve the commercial converters problems because they cannot work with supercapacitors due to their low internal resistance. The outcome is a device what can provide a programmable voltage between 4.5 V and 25 V, hardware can support up to 6 A and it is able to control the operating current owing through the converter. It can be used with the supercapacitors as shown in this work but it can also be used as a general platform for voltage and energy conversion. Furthermore, the designed hardware has the potential to work with smart grids via Ethernet connector, solar panels with MPPT algorithms and, at last, manage energy between di�erent kinds of DC voltage sources and devices.
Isolated Bidirectional DC–DC Converter for SuperCapacitor Applications[edit | edit source]
Abstract: This paper proposes a new bidirectional DC/DC converter for supercapacitor applications. The proposed converter has a parallel structure in supercapacitor side (where voltage is low and current is high) and a series structure in the other side. This structure increases efficiency of the converter. For current sharing in the parallel side of the proposed converter, two different methods are recommended and compared in this paper: Current balancing transformer (CBT) and two separate inductors (TSI). Simulation and experimental results show performance of the proposed converter.
MODELING BATTERY-ULTRACAPACITOR HYBRID SYSTEMS FOR SOLAR AND WIND APPLICATIONS[edit | edit source]
Abstract: The purpose of this study was to quantify the improvement in the performance of a battery with the addition of an ultracapacitor as an auxillary energy storage device for solar and wind applica- tions. The improvement in performance was demonstrated through simulation and modeling. A ceraolo battery model and a third order ultracapacitor ladder model were implemented in Mat- lab/Simulink. Sample battery load cycles for solar and wind applications have been obtained from literature and the corresponding C-rates were quanti�ed. The C-rate for the solar load cycle was found to be 0.3C and 0.2C for the wind load cycle. The performance of the battery- ultracapacitor system was checked for the sample solar and wind load cycles and compared with the performance of the battery system without an ultracapacitor. A reduction of 50.5% in bat- tery RMS currents was found for the solar load cycle and 60.9% for the wind load cycle. This reduction in battery RMS currents was found to be directly proportional to the ultracapacitor contribution. Given the low C-rates for the sample load cycles it was deduced that the addition of an ultracapacitor will not signi�cantly improve the battery life to justify the high initial costs.
Sizing Ultracapacitors For Hybrid Electric Vehicles[edit | edit source]
Abstract: An efficient energy storage medium is essential in all hybrid electric vehicles. The advances in double layer electrolytic capacitor technology have opened new areas to complement batteries as a storage medium. In this paper we will review some of the present applications of ultracapacitors as well as to provide guidelines for sizing ultracapacitors for minimal mass in hybrid electric vehicles. Equations for both constant current as well as constant power discharge are discussed. An iterative method for determining the minimum number of ultracapacitor cells is introduced. The effects of ultracapacitor sizing on the rating of interface power electronics are examined.
ULTRACAPACITOR/ BATTERY HYBRID FOR SOLAR ENERGY STORAGE[edit | edit source]
Abstract: All stand alone photovoltaic systems require an energy buffer to bridge the mismatch between available and required energy. Battery technology, chiefly the lead acid battery, is the most popular form of energy storage utilized. Nevertheless in a photovoltaic application, the storage battery generally has the highest life time cost in the system, it has a profound effect on the systems reliability and global performance. Photovoltaic panels are not an ideal source for charging batteries as the output is unreliable and heavily dependent on weather conditions an optimum charge/ discharge cycle cannot be guaranteed. Using an ultracapacitor and battery hybrid system it is aimed to prolong the lifetime of the battery, making the overall system more efficient and reliable. The ultracapacitor/ battery hybrid system will be controlled by an energy management system (EMS) implemented in labview. The EMS will implement maximum power point tracking (MPPT) and the chosen battery charging algorithm.
Ultracapacitor Energy Storage for MicroGrid Micro-generation[edit | edit source]
Abstract:A microsource interface with energy storage would help to realise the plug and play functionality of a MicroGrid. This paper discusses the energy storage interface. Selection and sizing of the energy storage unit is explained. A bi-directional converter is used to interface the storage, and a controller is implemented to keep the output voltage of the converter approximately constant. The energy storage unit was connected to a PV system in simulation. The system response to the irradiance, temperature and load variations were analysed in this paper.
TurboCap: A Batteryless, Supercapacitor-based Power Supply for Mini-FDPM[edit | edit source]
Abstract: This paper describes TurboCap, a batteryless, supercapacitor-based power supply subsystem for a handheld, laser-based breast cancer detector named the Mini-FDPM. Supercapacitors have high power density and are a better match with the power usage pattern than batteries. However, the multivoltage requirement poses a new problem on the selection of supercapacitor topology for conversion efficiency and for formfactor minimization. Experimental results show that our design can efficiently power the Mini-FDPM system for energy-efficient, untethered operation in a compact size while supporting fast recharge.
Energy Harvesting by Sweeping Voltage-Escalated Charging of a Reconfigurable Supercapacitor Array[edit | edit source]
Abstract: EscaCap is an energy harvester that uses a boostup charge pump to perform maximum power-transfer tracking (MPTT) while charging a reservoir supercapacitor array (RSA) with a reconfigurable topology. Unlike buck-down type harvesters, the voltage-doubling charge pump of EscaCap enables the sensor nodes to operate under low ambient power conditions. The supercapacitors in the RSA can be dynamically configured for series or parallel topologies by means of a switch array for not only minimizing leakage of the supercapacitors but also improving the charging speed. Furthermore, the RSA of EscaCap is modular and can be easily expanded. Experimental results show that EscaCap can harvest energy efficiently under low and high solar irradiation conditions, achieve shorter charging time, and demonstrate flexibility and robustness.
Efficient Charging of Supercapacitors for Extended Lifetime of Wireless Sensor Nodes[edit | edit source]
Abstract: This paper describes an efficient charging method for a supercapacitor-operated, solar-powered wireless sensor node called Everlast. Unlike traditional wireless sensors that store energy in batteries, Everlast’s use of supercapacitors enables the system to operate for an estimated lifetime of 20 years without any maintenance. The novelty of this system lies in the feed-forward, pulse frequency modulated converter and open-circuit solar voltage method for maximum power point tracking (MPPT), enabling the solar cell to efficiently charge the supercapacitor and power the node. Experimental results show that by its low-complexity MPPT, Everlast can achieve over 89% conversion efficiency with lower power overhead than the state-of-the-art by two orders of magnitude, while enabling charging a supercapacitor up to 400% faster than direct charging. This makes Everlast particularly applicable to miniature-scale, high-impedance energy harvesting systems.
A new simplified model of Double-Layer Capacitors[edit | edit source]
Abstract: The paper introduces a simplified model, named “two branches model”, to characterize the electrical behaviour of the DLCs (Double Layer Capacitors). The new model is very similar to many others in literature from the circuital point of view, however the process of identification of its parameters is easier and faster. This new identification process can be followed in other some model proposed in literature. Experimental charge tests have been executed on supercapacitors of two different labels (Epcos and Maxwell) and size (between 100F to 600F). The experimental results and the performed simulations have been reported in order to verify the validity of the new identification proposed method.
Modeling and Simulation of Supercapacitors[edit | edit source]
Abstract: In this paper we present some models for supercapacitors. The supercapacitors are used more and more in high level industries such as: traction systems, automotive industry, aerospace industry, telecommunications etc. Undestanding supercapacitors operation mode is necessary so we can be able to determine the applications which require these components, and to be able to choose between supercapacitors and other energy storage devices. In this paper were used some models for the implementation of supercapacitors, and the simulations made in Orcad 9.2 to determine their operation, are in time and frequency domain. Also, the models were implemented in Simulink 7.5 and the simulation results prove the models accuracy. Two test measurements on the ECOND Pscap350 supercapacitor were realized and using the measurement data, two methods to compute the parameters are presented.
High Power DC-to-DC Converter For Supercapacitors[edit | edit source]
Abstract: The purpose of this paper is to present Solectria’s approach to the design and realization of a high power, nonisolated DC-to-DC converter for supercapacitors. The study focuses on supercapacitor specific design rules and on how to integrate the unit into a system with other energy storage devices and converters. Two applications are presented to illustrate the validity of the suggested approach: An electric vehicle with supercapacitor load leveling, and a 50 kW pulse power source.
Time domain validation of ultracapacitor fractional order model[edit | edit source]
Abstract: In this paper, the modeling of the ultracapacitor using fractional order model is shown. The derivation of time domain response of the ultracapacitor and system with the ultracapacitor is presented. The results of frequency domain identification were used to validate the response of the ultracapacitor in time domain. All theoretical results are compared with the response of the physical system with the ultracapacitor. Then the issue of capacity for the ultracapacitors is shown and discussed.
A physical based model of power electric double-layer supercapacitors[edit | edit source]
Abstract: Recent developments in the field of supercapacitors have led to the achievement of high specific energy and high specific power devices. Due to capacitances of severai hundred farads and serial resistances of less than one milliohm, these new components are suitable for energy storage in high power electronic applications, especially in the field of management of embarked electrical power (hybrid power sources, energy recovery). This paper presents theory, characterisation and experimental validation of an accurate electric double-layer supercapacitor model based on the physics of phenomena governing charges storage, which theoretically leads to a transmission line with voltage dependant distributed capacitance.
PSiM Based Electric Modeling of Supercapacitors for Line Voltage Regulation of Electric Train System[edit | edit source]
Abstract: Supercapacitor can be used for energy storage and peak power control in order to increase the efficiency and the life cycle of the system. Recent developments in the field of supercapacitors have led to the achievement of high specific energy and high specific power devices. Due to the capacitances of several hundred farads and serial resistances of less than one milliohm, these new components are suitable for energy storage in high power electronic applications, especially in the field of management of embarked electrical power (hybrid power sources, energy recovery). This paper presents a method to identify the equivalent circuit parameters of supercapacitor by the experimental results. In order to validate this method, parameters of a Maxwell BCAP 3000F are extracted from the experiment and then the equivalent circuit model using parameters is implemented by using the PSiM software. Finally, experimental and simulation results are compared to verify the electric modeling of some supercapacitors.