Energy storage Devices

Background

Storage devices are an essential units that stores electric

energies produced by different manners.

Storage devices takes an important part in the electricity

storage systems for households, the medium-size system

for industrial/commercial use, and the extra-large system

for power plants and substations.

DIFFERENT ENERGY GENERATION AND STORAGE TECHNOLOGIES

• Pumped storage• Batteries• Superconducting magnet energy storage• Flywheel energy storage• Regenerative fuel cell storage • Compressed air energy storage

Pumped storage Hydroelectric Power Plant

In a pumped storage hydro plant, water is

pumped during off-peak times and may be

utilized to generate electricity. Hydro power

plant store electricity in Megawatts (MW)

or even Gigawatts (GW).

In hydroelectric power station potential and kinetic energy of stored water is converted into electric energy.

For hydro power station factors like rainfall,steam flow available head and storage are very important.

25% of electricity generation capacity in world is provided by hydel power plant.

In India 25.32% of total electricity generation capacity is produced by hydel power plant.

BASIC ELEMENTS OF HYDEL POWER PLANT

ADVANTAGES OF HYDEL POWER PLANT

• This plant is free from pollution.

• Its operation and maintenance cost is less.

• Unit cost of power is less.

• Hydraulic turbines can be started speedily.

• The plant has longer service life.

• No fuel is required.

Disadvantages of hydel power plant

• Initial cost of dam and plant is high.

• The availability of power from it is not much

reliable.

• Loss of forest creates environmental problems.

• Due to evaporation , considerable water is lost.

• Time required for construction of hydro project is

more.

BatteriesA mobile source of power that makes many modern conveniences possible.

History behind this storage concept

In ancient times, the generation of electricity was purely accidental.

By rubbing certain materials together, static charges can be accumulated.

Ancient Greeks rubbed amber on hair to generate electricity. In fact, the word elektron comes from the greek word for amber By the mid 1600’s, static electricity could be readily generated by rubbing insulating materials together: fur/cloth, sulfur, amber, etc.

But in the 1600’s, scientists did not really know much aboutelectricity or how to use it.

In 1745, scientists (Musschenbroek and Cunaeus) noticed that one could “charge” up a glass filled with water and get a shock by touching a metal nail Shortly thereafter, this was simplified to just metal foil wrapped around the inside and outside of a jar with a chain connecting the inner layer.

Leyden Jar

We know these devices as capacitors, but they work by storing charge ELECTROSTATICALLY

1746: Nollet assembled a line of 200 monks each holding the end of a wire to test if electricity can travel faster than human communication. Without warning he connected a Leyden Jar tothe ends …

1747-1753 Cavendish used Leyden Jars to discover many of the fundamental physics laws of electricity Inverse square law for force, electric potential, capacitance, resistance But he could not published all his study and these discoveries were rediscovered by Faraday, Ohm, Coulomb, Maxwell

1786: Galvani’s famous experiments on frog legs

He took two dissimilar metals (Zn, Cu) and touched them to theends of a dead frog’s leg and surprisingly, the leg moved and Galvani attributed this to bioelectricity

But the scientist, Volta did not believe that the electricity came from the frog.

He believed the electricity came from the metals.

In 1799, Volta tried a experiment by combining different metals that are separated by a salt or acidic solution it was possible to generate electricity.

First commerciallyavailable battery

How does all of this work ?

It’s all electrochemistry!!

For today, we’ll focus on batteries for portable energy storage

The redox (oxidation-reduction) reactions that occur at these electrodes convert electrochemical energy into electrical energy.

Batteries definition:

Two or more electrochemical cells, electrically interconnected, each of which contains two electrodes and an electrolyte.

In everyday usage, 'battery' is also used to refer to a single cell. The solid-state batteries are the batteries in which the electrolyte is in solid state, which is responsible for the conduction of ions from one electrode to other electrode. 

In 1800, Alessandro Volta invented the first modern battery.

1.Introduction

There are two common types of batteries

1. Primary1. Primary 2. Secondary2. Secondary

The materials inside the battery were the prime source of the electric power it delivered.

The materials inside the battery were the prime source of the electric power it delivered.

First it had to receive a charge before they could deliver any power. It also called as Rechargeable batteries.

First it had to receive a charge before they could deliver any power. It also called as Rechargeable batteries.

1. Primary batteriesIn primary batteries, the electrochemical reaction is not reversible. During discharging the chemical compounds are permanently changed and electrical energy is released until the original compounds are completely exhausted. Thus the cells can be used only once.

2. Secondary batteries

In secondary batteries, the electrochemical reaction is reversible and the original chemical compounds can be reconstituted by the application of an electrical potential between the electrodes injecting energy into the cell. Such cells can be discharged and recharged many times.

If there is a spontaneous chemical reaction then the generated chemical energy can be further used to do some useful work.

To exploit this energy, the reaction must be split into two separate parts reactions:

1.Oxidation

2.Reduction

The reactions will be into two different containers and a conductive wire is used to drive the electrons from one side to the other.

In doing so, a Voltaic/ Galvanic Cell is created.

Fundamental of Cells

Fundamental of Cells continues

In case of general Voltaic/ Galvanic Cell the redox reactions which include all chemical reactions in which atoms have their oxidation state changed;

Such reactions involve the formal transfer of electronsSuch reactions involve the formal transfer of electrons

A net loss of electrons A net loss of electrons A net gain in electronsA net gain in electrons

The increase in oxidation state of an atom through a chemical reaction

The decrease in oxidation state of an atom through a chemical reaction.

OxidationOxidation Reduction

Daniell cell,

Copper and Zinc electrodes are immersed in a solution of copper sulfate and zinc sulfate respectively.

At the anode, zinc is oxidized as per the following half reaction:

Zn(s) → Zn2+(aq) + 2e- (Required energy for this reaction : -0.76 volt)

At the cathode, copper is reduced as per the following reaction:

Cu2+(aq) + 2e- → Cu(s) (Required energy for this reaction : 0.34 volt)

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s).

Net delivered Energy ENET = E (Cu2+ / Cu ) - E (Zn2+

/ Zn ) = 0.34 - (-0.76) Volt =1.1 Volt

The total reaction being:

Batteries have become a most important and most used

equipment in these days. Batteries are used where power

supply is not regular, where low voltage is required like

watches, mobiles many small equipments which require

lesser voltage mainly run on batteries.

The main advantage of batteries are that they can be charged

and used if the capability of supplying power reduces. Cells

are the unit of batteries, many cells complete a battery.

There are mainly two types of batteries,

I) Alkaline batteries

II) Lead-acid batteries

The first Alkaline battery was brought into market by Eveready Battery, Toronto.

It was developed by Lew Urry in 1949, one of the chemical engineer in the same company.

Alkaline batteries in the starting was five to eight times as long as zinc-carbon cells, their predecessors.

Alkaline Batteries

In any kind of batteries, electrolysis has very important role of running of a battery. Electrolysis means basically chemical reaction while conducting current through a mixture. The alkaline Batteries are basically introduced to overcome the weight and mechanical weakness of the lead plates.

The main working principle of the alkaline batteries is based on reaction between zinc (Zn) and manganese dioxide (MnO2).

Alkaline battery is so named because the electrolyte used in it is potassium hydroxide, a purely alkaline substance

Alkaline battery is so named because the electrolyte used in it is potassium hydroxide, a purely alkaline substance

Construction of Alkaline Battery

Construction:

The body of the battery is made of a hollow steel drum. This drum contains all materials of the battery and it also serves as cathode of the battery. The positive terminal of the battery is projected from the top of this drum.

Fine grained manganese dioxide (MnO2) powder mixed with coal dust is molted to the inner peripheral surface of the empty cylindrical drum. This molded mixture serves as cathode mixture of the alkaline battery.

The inner surface of the thick layer of cathode mixture is covered with paper separator.

The central space, inside this paper separator is filled by zinc powder with potassium hydroxide electrolyte. The zinc powder serves as anode.

The paper separator soaked with potassium hydroxide, holds the electrolyte in between cathode(MnO2) and anode(Zn).

A metallic pin (preferably made of brass) is inserted along the central axis of the alkaline battery to collect negative charge. This pin is called negative collector pin. This pin is in touch with metallic end sealed cap.

There is a plastic cover just inside the Metallic end sealed cap and this plastic cover electrically separates positive steel drum and negative end cap of alkaline batteries.

In an alkaline battery cell, the powder zinc serves as anode, manganese dioxide serves as cathode and potassium hydroxide serves as electrolyte.

An alkaline battery cell is rated for 1.5 V. A new non discharged alkaline cell shows a voltage of 1.50 to 1.65 V. The average voltage under load condition may be 1.1 to 1.3 V. AA alkaline cell is generally rated for 700 mA.

There are various types of alkaline batteries depending on various parameters. Depending on the composition of the active materials of the plates there are four types of batteries.

a) Nickel iron (or Edison)

b) Nickel- cadmium (or Nife)

c) Silver zinc

d) Alkum batteries

Use of Alkaline Batteries

Various types of these batteries are there and different batteries are used for different purposes. Like, nickel iron batteries are used for propulsion of industrial trucks and mine locomotives. In air conditions also, this type of batteries are used. Another type of batteries alkaline battery is Nickel-cadmium batteries, they are used in commercial airlines, military aeroplane for initiating main engine. So, we can say that the alkaline batteries are mainly used in moving vehicles and industrial purposes.

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Lithium battery

• Lithium is the lightest of metals and it can float on water.

• The electrochemical properties of lithium are excellent and it is also a highly reactive material.

• These properties gives Lithium the potential to achieve very high energy and power densities in high-density battery applications such as automotive and standby power.

• Lithium batteries are primary batteries in which lithium metal (or) lithium compound acts as a Anode. A lithium cell can produce voltage from 1.5 V to about 3 V based on the types of materials used.

Characteristics

They use nickel hydroxide Ni(OH)2 for the positive electrode (cathode), cadmium Cd as the negative electrode (anode) and an alkaline potassium hydroxide KOH electrolyte.

Their small size and high rate discharge capacity made portable tools and other consumer applications practical for the first time.The cells are sealed and utilise a recombinant system to prevent electrolyte loss and extend the useful life. 

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There are two types of lithium-based batteries available.

1. Lithium batteries2. Lithium-ion batteries

• In lithium batteries, a pure lithium metallic element is used as anode. These types of batteries are not rechargeable.

• In lithium-ion batteries, lithium compounds are used as anode.

These batteries are known as re-chargeable batteries. Therefore,

Lithium ion batteries are considered as best than pure Lithium based batteries.

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Lithium-ion battery (Li-ion Battery)

Li-ion batteries are secondary batteries.

• The battery consists of a anode of Lithium, dissolved as ions, into a carbon. • The cathode material is made up from three electro-active oxide

materials,

• Lithium Cobalt-oxide (LiCoO2 )• Lithium Manganese-oxide (LiMn2 O4 )• Lithium Nickel-oxide (LiNiO2)

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Principle

During the charge and discharge processes, lithium ions are inserted or extracted from interstitial space between atomic layers within the active material of the battery.

• Simply, the Li-ion is transfers between anode and cathode through lithium Electrolyte.

Li-Ion battery Principle

Li- ion Electrolyte

Cathode Anode

Construction • Li-ion cell has a four-layer structure.

• A positive electrode made with Lithium Cobalt Oxide has a current collector made of thin aluminum foil - cathode

• A negative electrode made with specialty carbon has a current collector of thin copper foil – anode

• A separator is a fine porous polymer film.

• An electrolyte made with lithium salt in an organic solvent.

Construction cont..

• The electrolytes are selected in such a way that there should be an effective transport of Li-ion to the cathode during discharge.

• The type of conductivity of electrolyte is ionic in nature rather than electronic

Working

The traditional batteries are based on galvanic action but Lithium ion secondary battery depends on an "intercalation" mechanism.

This involves the addition of lithium ions into the crystalline lattice of the host electrode without changing its crystal structure.

These electrodes have two key properties. One is the open crystal structure, which allow the insertion or extraction of lithium ions and the second is the ability to accept compensating electrons at the same time. Such electrodes are called intercalation hosts.

Working Cont…

The chemical reaction that takes place inside the battery is as follows, during charge and discharge operation:

The lithium ion is inserted and exerted into the lattice structure of anode and cathode during charging and discharging

During discharge current flows through external circuit and light glows

During charging, no the electrons flows in the opposite direction

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• During charging, lithium in positive electrode material is ionized and moves from layer to layer and inserted into the negative electrode.

• During discharge Li ions are detached from the anode and migrate across the electrolyte and are inserted into the crystal structure of the host compound of cathode.

• At the same time the compensating electrons travel in the external circuit and are accepted by the host to balance the reaction.

• The process is completely reversible. Thus the lithium ions pass back and forth between the electrodes during charging and discharging.

• Because of this reason, the lithium ion batteries are called ‘ Rocking chair, ‘Swing’ cells.

• A typical Li-ion battery can store 150 watt-hours of electricity in 1 kilogram of battery as compared to lead acid

batteries can sore only 25 watt-hours of electricity in one kilogram

• All rechargeable batteries suffer from self-discharge when stored or not in use.

• Normally, there will be a three to five percent of self-discharge in lithium ion batteries for 30 days of storage.

PH 0101 Unit-5 Lecture-7 51

Advantages• They have high energy density than other rechargeable batteries• They are less weight• They produce high voltage out about 4 V as compared with other batteries.• They have improved safety, i.e. more resistance to overcharge• No liquid electrolyte means they are immune from leaking.• Fast charge and discharge rate

Disadvantage• They are expensive• They are not available in standard cell types.

5. Advantage, disadvantage and applications

PH 0101 Unit-5 Lecture-7 52

Applications

• The Li-ion batteries are used in cameras, calculators

• They are used in cardiac pacemakers and other implantable device

• They are used in telecommunication equipment, instruments, portable radios and TVs, pagers

• They are used to operate laptop computers and mobile phones and aerospace application

Primary batteries are capable of one-time use: use it until it’s depleted and then dispose of it.

The most common primary batteries are alkaline D, C, AA, AAA and 9-volt batteries.

Applications:

Portable devicesLightingToysMemory back-upWatches/clocksHearing aidsRadiosMedical implantsDefence related systems such as missiles

Advantages:

InexpensiveConvenientLightweightGood shelf lifeHigh Energy density at low/moderate discharges

Disadvantages:

Can only be used onceLeads to large amount of waste batteries to be recycledBatteries put into landfill sites have severe environmental impact

Continued