Energy Storage-a prerequisite for harnessing renewable energy

Dr. P. C. PantDr. P. C. PantSolar Energy CentreSolar Energy Centre

Ministry of New and Renewable EnergyMinistry of New and Renewable Energypcpant@nic.inpcpant@nic.in

Nature of renewable energy supplies and real challenge

Renewable energy supplies are continuing or repetitive Renewable energy supplies are continuing or repetitive current of energy occurring in natural environmentcurrent of energy occurring in natural environment

The initial input power from renewable energy supplies The initial input power from renewable energy supplies therefore is outside our control; and matching supply therefore is outside our control; and matching supply and demand in the time domain is a real challengeand demand in the time domain is a real challenge

Two ways to overcome this challenge are :Two ways to overcome this challenge are : Matching the load to the availability of Matching the load to the availability of

renewable energy supply or hybridize it with an renewable energy supply or hybridize it with an auxiliary energy supply system auxiliary energy supply system

Storing the energy for future use i.e. keeping it Storing the energy for future use i.e. keeping it available when it is wantedavailable when it is wanted

Methods of energy storage

Chemical Chemical : hydrogen, ammonia: hydrogen, ammonia Heat Heat : hot water, steam: hot water, steam ElectricElectric : Capacitors, : Capacitors,

electromegnetselectromegnets Electro chemicalElectro chemical : Batteries, fuel cell : Batteries, fuel cell GravitationalGravitational : water reservoir : water reservoir MechanicalMechanical : Flywheel: Flywheel

Battery: Introduction

An electrochemical apparatus-used for An electrochemical apparatus-used for accumulating charge for use at later stage and accumulating charge for use at later stage and that’s why called “charge accumulator”that’s why called “charge accumulator”

Stores electrical energy in the form of chemical Stores electrical energy in the form of chemical energy and then converts this chemical energy to energy and then converts this chemical energy to electrical energy when needed: essentially an electrical energy when needed: essentially an electrical energy storage deviceelectrical energy storage device

Introduction contd….

A source of ‘portable' electrical powerA source of ‘portable' electrical power Capable of delivering very large quantities of Capable of delivering very large quantities of

power for short period and being recharged at power for short period and being recharged at low rate for extended timelow rate for extended time

Reliable source of emergency power, Reliable source of emergency power, instantaneouslyinstantaneously

A source of pure direct current for laboratory A source of pure direct current for laboratory

andand other other specific purposesspecific purposes

Features to study

Must be discussed from three points of view:Must be discussed from three points of view: ChemicalChemical PhysicalPhysical PracticalPractical

All three are interrelated and are necessary All three are interrelated and are necessary to understand the nature and performance of to understand the nature and performance of storage batteriesstorage batteries

Cell and battery

Cell: Cell: basic building block that convert basic building block that convert chemical energy into electrical chemical energy into electrical energy; a energy; a cell consists of an assembly cell consists of an assembly of of

two two dissimilar electrodes dissimilar electrodes (anode and (anode and cathode), seperated by seperators, cathode), seperated by seperators,

immersed in an immersed in an electrolyte in a suitable container electrolyte in a suitable container

having terminals coming out of having terminals coming out of electrodes for connecting to external electrodes for connecting to external circuit. circuit.

Battery:Battery: An electric battery consists of two or An electric battery consists of two or more cells connected in series or more cells connected in series or

parallelparallel

Classification of cells:

Primary cells: Primary cells: capable of converting chemical capable of converting chemical energy into electrical energy energy into electrical energy and in this process gets and in this process gets exhausted. The chemical exhausted. The chemical reaction is irreversible.reaction is irreversible.

Secondary cells: Also called storage cells. Convert Secondary cells: Also called storage cells. Convert chemical energy into electrical chemical energy into electrical energy or vice versa by reactions energy or vice versa by reactions that are essentially reversiblethat are essentially reversible

Various types of secondary cells:

Lead Acid Lead Acid Nickle-Cadmium (Ni-Cd)Nickle-Cadmium (Ni-Cd) Nickle-matel-hydride (NiMH)Nickle-matel-hydride (NiMH) Nickle polymerNickle polymer Lithium ion (Li-ion)Lithium ion (Li-ion)

Lead-Acid :Fundamental Principle Fundamentally very simple to makeFundamentally very simple to make On hanging 2 metallic lead strips in and on opposite sides On hanging 2 metallic lead strips in and on opposite sides

of a small glass jar filled with dilute sulphuric acid, of a small glass jar filled with dilute sulphuric acid, connecting these strips called ‘plates’ with a source of connecting these strips called ‘plates’ with a source of direct current and allowing them to ‘charge’, the colour of direct current and allowing them to ‘charge’, the colour of one strip becomes increasingly dark brown , called one strip becomes increasingly dark brown , called positive plate; and other retains its original colour called positive plate; and other retains its original colour called negative platenegative plate

On removing the charging source, a voltage of about two On removing the charging source, a voltage of about two volts is shown by a sensitive voltmeter across the two volts is shown by a sensitive voltmeter across the two plates called electrodes.plates called electrodes.

Fundamental Principle

A battery formed this way has no practical A battery formed this way has no practical value because of low surface area of the value because of low surface area of the strip to accumulate sufficient ‘active strip to accumulate sufficient ‘active material’ i.e. brown lead peroxide of the material’ i.e. brown lead peroxide of the positive plate and metallic ‘sponge’ lead of positive plate and metallic ‘sponge’ lead of the negative.the negative.

Fundamental Principle The increase in effective area of plates for The increase in effective area of plates for

achieving greater and greater capacity for achieving greater and greater capacity for industrial use is one of the requirements for useful industrial use is one of the requirements for useful design of the battery. design of the battery.

This can be accomplished by:This can be accomplished by:Casting plates with complex ridges or Casting plates with complex ridges or

groovesgroovesMechanically furrowed to obtain greater Mechanically furrowed to obtain greater

surfacesurfaceSeparate corrugated lead ribbons are rolled Separate corrugated lead ribbons are rolled

into spiral buttons and inserted in lead alloy into spiral buttons and inserted in lead alloy frames.frames.

Fundamental Principle

Type of plate affects the characteristics and performance of battery.Type of plate affects the characteristics and performance of battery. All types have lead di oxide (PbOAll types have lead di oxide (PbO22)in the positive plate applied during )in the positive plate applied during

manufacture and porous sponge lead (Pb) on negative plate.manufacture and porous sponge lead (Pb) on negative plate. The positive plates are welded to form a plate group and negative The positive plates are welded to form a plate group and negative

plates are assembled in the same manner. plates are assembled in the same manner. The plates of different polarity are insulated from each other by The plates of different polarity are insulated from each other by

separators. separators. The complete plate group assembly is immersed in dilute sulphuric The complete plate group assembly is immersed in dilute sulphuric

acid in a container.acid in a container. Thus an electrochemical couple of two different plates or electrodes Thus an electrochemical couple of two different plates or electrodes

(PbO(PbO2 2 and Pb) in an acid electrolyte (Hand Pb) in an acid electrolyte (H22SOSO44) are all that is required to ) are all that is required to

make a rechargeable, or storage battery.make a rechargeable, or storage battery.

Classification of battery according to +ve plate type

Flat plate type: Flat plate type: different type of grid different type of grid structure structure

Tubular plate typeTubular plate type

-ve Plate is always flat plate of sponge lead -ve Plate is always flat plate of sponge lead

Classification of battery as per electrolyte type

FloodedFlooded Valve Regulated Lead Acid BatteryValve Regulated Lead Acid Battery

Absorbed Glass Mat type (AGM)Absorbed Glass Mat type (AGM) Gel typeGel type

Classification of battery as per use StarterStarter CyclicCyclic

Ampere-Hour Rating

The rating assigned to the cell shall be the capacity expressed in ampere-hours (after correction to 27oC) stated by the manufacturer to be obtainable under specified condition. Generally for flooded battery it is taken at 10 hr rating and for VRLA it is at 20 hr rating.

Charge-discharge curve of a VRLA battery C20 rating

  

    

Reasons of battery loosing capacity SulphationSulphation SedimentationSedimentation StratificationStratification

THANKYOU