1 Abstract—The development of energy storing devices with high density power has become an area of major interest to wide range of applications. Therefore, ultracapacitors have been in the spotlight because, beyond its high power density, it also has a lot of advantages when compared to other devices of energy storage available in nowadays. Its characteristics have been explored since the beginning of the 21st century, which made ultracapacitors conquer a significative market share (and still increasing) in the market of energy storage devices. This work has been done in the framework of an investigation project in the electrochemical area, and it pretends to study a redox ultracapacitor prototype with an aqueous electrolyte. This work aims to study its electrical characteristics, in order to develop and improve even more the prototypes of ultracapacitors using this kind of materials. The final objective of this work is to characterize a prototype electrically, estimating its capacity, internal resistance and self-discharge characteristic. It was also simulated its behaviour when applied in a DC/DC converter. The results obtained showed a lot of potential in the redox ultracapacitors technology, and that the prototype has similar characteristics when compared to carbon based ultracapacitors, which are usually available in the market. In spite of this results, were identified aspects that could be improved, which is in line with the objectives of this work. Keywords – Ultracapacitor, Capacity, Internal resistance, Self- discharge, DC/DC converter I. INTRODUCTION LETRICAL and electronic devices have an increasingly important role in the population quotidian and, as a result of that, its growth has increased over the last years. Among the most common energy storage devices are ultracapacitors. This type of devices have, simultaneously, comparable energy and power densities when compared to batteries. Ultracapacitors main advantages when compared to batteries are: high rates of charge/discharge, low degradation over hundred thousand cycles, high efficiency and good reversibility. Among the main disadvantages, the quantity of stored energy per weight unit is relatively low, the voltage varies with the stored energy and the dielectric has a high absorption rate. [1] Figura I.1 - Ragone chart [2] A. Proposed work As referred in the previous chapter, ultracapacitors have been growing in the electrical energy storage market. However, there are still a lot of limitations and a long way to go. Therefore, ultracapacitors are subject to an improvement phase of its technology. The present work comes under a project on the electrochemical area, whose main objective is to develop an ultracapacitor prototype using stainless steel electrodes with electrodeposited transition metal oxides, manufactured in IST’s laboratory of electrochemical technology. This prototype should have its electrical properties characterized and quantified. It was performed a computer simulation of the prototype, to test this device as a part of a DC-DC converter. B. Applications Ultracapacitors are still not being used in a lot of its potential applications. Initially, were limited by its low energy and power densities, being used only in low power and energy applications. Due to the technological advancements, this characteristics have been improving, and the application for this type of devices has been increasing rapidly. The main ultracapacitors applications are: Military (for engines starting and substitution of missiles batteries); Memory Backup (ultracapacitors provide energy right after the power cut, until the generator isn’t working); Testing a hybrid supercapacitor using stainless steel electrodes with electrodeposited transition metal oxides João André Gama Correia, Instituto Superior Técnico, November 2015, Lisbon, Portugal, [email protected]E
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1
Abstract—The development of energy storing devices with high density power has become an area of major interest to wide range of applications. Therefore, ultracapacitors have been in the spotlight because, beyond its high power density, it also has a lot of advantages when compared to other devices of energy storage
available in nowadays. Its characteristics have been explored since the beginning of the 21st century, which made ultracapacitors conquer a significative market share (and still increasing) in the market of energy storage devices.
This work has been done in the framework of an investigation project in the electrochemical area, and it pretends to study a redox ultracapacitor prototype with an aqueous electrolyte. This work aims to study its electrical characteristics, in order to
develop and improve even more the prototypes of ultracapacitors using this kind of materials.
The final objective of this work is to characterize a prototype electrically, estimating its capacity, internal resistance and self-discharge characteristic. It was also simulated its behaviour when applied in a DC/DC converter. The results obtained showed a lot of potential in the redox ultracapacitors technology, and that the prototype has similar
characteristics when compared to carbon based ultracapacitors, which are usually available in the market. In spite of this results, were identified aspects that could be improved, which is in line with the objectives of this work. Keywords – Ultracapacitor, Capacity, Internal resistance, Self-discharge, DC/DC converter
I. INTRODUCTION
LETRICAL and electronic devices have an increasingly
important role in the population quotidian and, as a result
of that, its growth has increased over the last years.
Among the most common energy storage devices are
ultracapacitors. This type of devices have, simultaneously,
comparable energy and power densities when compared to batteries.
Ultracapacitors main advantages when compared to
batteries are: high rates of charge/discharge, low degradation
over hundred thousand cycles, high efficiency and good
reversibility. Among the main disadvantages, the quantity of
stored energy per weight unit is relatively low, the voltage
varies with the stored energy and the dielectric has a high
absorption rate. [1]
Figura I.1 - Ragone chart [2]
A. Proposed work
As referred in the previous chapter, ultracapacitors have
been growing in the electrical energy storage market.
However, there are still a lot of limitations and a long way to
go. Therefore, ultracapacitors are subject to an improvement
phase of its technology.
The present work comes under a project on the
electrochemical area, whose main objective is to develop an ultracapacitor prototype using stainless steel electrodes with
electrodeposited transition metal oxides, manufactured in
IST’s laboratory of electrochemical technology. This
prototype should have its electrical properties characterized
and quantified.
It was performed a computer simulation of the prototype, to
test this device as a part of a DC-DC converter.
B. Applications
Ultracapacitors are still not being used in a lot of its
potential applications. Initially, were limited by its low energy
and power densities, being used only in low power and energy
applications. Due to the technological advancements, this
characteristics have been improving, and the application for
this type of devices has been increasing rapidly.
The main ultracapacitors applications are:
Military (for engines starting and substitution of
missiles batteries);
Memory Backup (ultracapacitors provide energy
right after the power cut, until the generator isn’t
working);
Testing a hybrid supercapacitor using stainless steel
electrodes with electrodeposited transition metal
oxides
João André Gama Correia, Instituto Superior Técnico, November 2015, Lisbon, Portugal,