CHEMICAL ENERGY STORAGE

Batteries

• A device that converts the chemical energy into electrical

energy.

• “Combination of individual cells”

• Cell is chemical combination of material and electrolyte

constituting the basic electrochemical energy storer.

• Battery a black box into which electrical energy is put,

stored electrochemically, and later recovered as

electrical energy.

Classification of batteries

Batteries

Primary Secondary

Primary batteries

Primary batteries / non-chargeable – e.g. dry cell - chemical reaction are non reversible• Can produce current immediately

• These are most commonly used in portable devices that have low current drain, such as in alarm and communication circuits

• the chemical reactions are not easily reversible and active materials may not return to their original forms

Secondary batteries

Secondary batteries / rechargeable – e.g. lead acid battery- chemical reaction are reversible• Chief interest of solar electrics

• Storage batteries

• Generally portable, common mobile sources of energy,

• Ex. Starting-lighting ignition (SLI) of automobiles, other applications in mines locomotives, forklift trucks,

golf carts, road vehicles and submarines

Basic battery theory

• Two electrodes (anode and cathode) immersed in electrolyte

• Electrical load connected between electrodes

• The electrons flows through external load and ion through in the electrolyte recombining at other electrodes

• Electrolysis

• A chemical process in which

bonded elements and

compounds are dissociated

by the passage of an electric

current.

• The electrolysis of water:

2H2O + energy = 2H2 + 2O2

Battery - During Charge

ElectrolyteAnode + Cathode -

Charger

Current

Voltage and energy increases

Energy

Heat

Heat

chemical reaction

electrolyteAnode + Cathode -

Load

Current

Voltage and energy decreases

Work

Heat

Heat

Chemical reaction

Battery - During Discharge

Definition of fundamental quantities • Energy capacities of batteries 1)Energy stored(watt-hr) 2)Energy stored per weight (watt-hr/kg) 3)Energy stored per volume(watt-hr/m³)• Power capacity It is the rate at which stored energy can safely be taken out of

a battery and restored• Specific Power The maximum rated power output/ kg the battery can supply• Energy efficiency - useful energy out (watt-hr)/ recharge

energy (watt-hr)• Cycle life It is number of times the battery can be charged and

discharged under specified condition

Classification of batteriesA) Conventional batteries e.g. lead acid, nickel cadmium, nickel iron, nickel zinc,

silver cadmium, zinc bromine

B) Metal gas batteries e.g. iron-air, zinc-air, zinc-oxygen, zinc-chlorine, nickel

hydrogen etc.

C) Alkali-metal-high temperature batteries e.g. sodium-sulfur, sodium-chlorine, lithium-sulfur etc.

Lead acid battery

• Invented by Gaston Plante in France in 1859

• First practical storage battery

• Lead-acid batteries having a very low energy-to-weight ratio

and a low energy-to-volume ratio, their ability to supply high

currents means that the cells maintain a relatively large

power-to-weight ratio.

• These features, along with their low cost, make them

attractive for use in motor vehicles to provide the high current

required by automobile starter motors

Working principle

• + ve electrode : Lead-di-oxide (PbO₂)

• - ve electrode : Metallic lead (Pb)

• Electrolyte : sulphuric acid solution

• PbO₂ + Pb + 2 H₂SO₄ ↔ PbSO₄ (+) + PbSO₄ (-) + 2H₂O

Working of a lead acid battery

• Positive electrode (anode) made from lead alloy and lead dioxide

• The negative electrode (cathode) is made from pure lead and both electrodes are immersed in sulphuric acid

While charging• Lead oxide-anode, pure lead- cathode, liberating H2So4

in water• On charging sulphuric acid is produced and the specific

gravity of the electrolyte increasesDischarging • When the battery is discharged water is produced,

diluting the acid and reducing its specific gravity

Lead acid battery

• Wet cell stand-by (stationary) batteries designed for deep discharge are

commonly used in large backup power supplies for telephone and computer

centers, grid energy storage and off-grid household electric power systems

• Lead-acid batteries are used in emergency lighting in case of power failure

• Large lead-acid batteries are used to power the electric motors in diesel-

electric (conventional) submarines and are used on nuclear submarines as

well

• Motor vehicle starting, lighting and ignition (SLI) batteries (car batteries)

provides current for starting internal combustion engines.

• Lead-acid batteries were used to supply the filament (heater) voltage (usually

between 2 and 12 volts with 2 V being most common) in early vacuum tube

(valve) radio receivers.

Applications

Advantages

• Inexpensive and simple to manufacture

• Reliable and well-understood technology

• Low self-discharge

• Low maintenance requirements

Disadvantages

• Cannot be stored in a discharged condition

• Low energy density

• Allows only a limited number of full discharge cycles - well suited for standby

applications that require only occasional deep discharges

• Environmentally unfriendly - the electrolyte and the lead content can cause

environmental damage

• Transportation restrictions on flooded lead acid

• Thermal runaway can occur with improper charging

Nickel-iron cell battery• By Thomus A. Edison in early 1900 • Anode – Nickel oxide - hydroxide , Cathode – Iron • Electrolyte – Potassium hydroxide• 2NiOOH.H₂O + Fe ↔ 2Ni(OH)₂ + Fe(OH)₂o The active materials are held in nickel-plated steel tubes or perforated

pockets. It is a very robust battery which is tolerant (overcharge, over-discharge and short-circuiting).

o It is often used in backup situations where it can be continuously charged and can last for more than 20 years. Due to low specific energy, poor charge retention and its high cost of manufacture, other types of rechargeable batteries have displaced the nickel-iron battery in most applications

o They are currently gaining popularity for solar voltaic backup applications where daily charging makes them an appropriate technology

• Advantages - used for rail, raod car, mine lighting, industrial trucks• Disadvantages - Upon standing it losses its charge & requires addition

of water time to time

Nickel-Cadmium battery• By W. Junjer in sweden

• The nickel-cadmium battery (NiCd or NiCad) is a type of rechargeable battery

using nickel oxide hydroxide and metallic cadmium as electrode.

• 2NiOOH.H₂O + Cd ↔ 2Ni( OH) ₂ + Cd (OH)₂

• Advantages : longer life, Little loss of water and no evaluation of hydrogen

o Applications : Small NiCd dry cells are used for portable electronics and toys

o When NiCds are substituted for primary cells, the lower terminal voltage and

smaller ampere-hour capacity may reduce performance as compared to

primary cells

o Miniature button cells are sometimes used in photographic equipment, hand-

held lamps (flashlight or torch), computer-memory standby, toys and novelties,

cordless and wireless telephones, emergency lighting and other applications.

Advantages • Fast and simple charge - even after prolonged storage• High number of charge/discharge cycles• Good load performance• Long shelf life • Simple storage and transportation • Good low temperature performanceDisadvantages• Relatively low energy• Memory effect• Environmentally unfriendly - the NiCd contains toxic

metals • Some countries are limiting the use of the NiCd

battery

Lithium ion battery

• One of the most energetic rechargeable batteries

Advantages

• They're generally much lighter than other types of rechargeable

batteries of the same size. The electrodes of a lithium-ion

battery are made of lightweight lithium and carbon. Lithium is

also a highly reactive element, meaning that a lot of energy can

be stored in its atomic bonds. This translates into a very high

energy density for lithium-ion batteries

Lithium ion battery

• The metal case holds a long spiral comprising three thin sheets pressed together:

• A Positive electrode • A Negative electrode • A separator • Inside the case these sheets are submerged in an

organic solvent that acts as the electrolyte. Ether is one common solvent.

• The separator is a very thin sheet of micro-perforated plastic. As the name implies, it separates the positive and negative electrodes while allowing ions to pass through.

• The positive electrode is made of Lithium cobalt oxide, or LiCoO2. The negative electrode is made of carbon. When the battery charges, ions of lithium move through the electrolyte from the positive electrode to the negative electrode and attach to the carbon. During discharge, the lithium ions move back to the LiCoO2 from the carbon.

• A typical lithium-ion battery can store 150 watt-hours of

electricity in 1 kilogram of battery.

• A lithium-ion battery pack loses only about 5 percent of

its charge per month, compared to other batteries

• They have no memory effect, which means that you do

not have to completely discharge them before recharging,

• Lithium-ion batteries can handle hundreds of

charge/discharge cycles.

Disadvantages

• They start degrading as soon as they leave the factory. They will only

last two or three years from the date of manufacture whether you use

them or not.

• They are extremely sensitive to high temperatures. Heat causes lithium-

ion battery packs to degrade much faster than they normally would.

• If you completely discharge a lithium-ion battery, it is ruined.

• A lithium-ion battery pack must have an on-board computer to manage

the battery. This makes them even more expensive than they already

are.

• There is a small chance that, if a lithium-ion battery pack fails, it will

burst into flame.

Sodium–sulfur battery

• Sodium–sulfur battery or liquid metal battery is a type of molten metal

battery constructed from sodium (Na) and sulfur (S).

• This type of battery has a high energy density, high efficiency of

charge/discharge (89–92%) and long cycle life, and is fabricated from

inexpensive materials.

• However, because of the operating temperatures of 300 to 350 °C and the

highly corrosive nature of the sodium polysulfides, such cells are primarily

suitable for large-scale non-mobile applications such as grid energy storage

• The battery has a solid electrolyte membrane between the anode and

cathode, compared with liquid metal batteries where the anode, the cathode,

and also the membrane are liquids.

• Pure sodium presents a hazard because it spontaneously burns/explodes in

contact with water, thus the system must be protected from moisture.

• Corrosion of the insulators was found to be a problem in the harsh chemical

environment as they gradually became conductive and the self-discharge

rate increased.

• NaS batteries are a possible energy storage technology to support

renewable energy generation, specifically wind farms and solar generation

plants.

• In the case of a wind farm, the battery would store energy during times of

high wind but low power demand. This stored energy could then be

discharged from the batteries during peak load periods.

• In addition to this power shifting, it is likely that sodium sulfur batteries could

be used throughout the day to assist in stabilizing the power output of the

wind farm during wind fluctuations.

Zinc-bromine battery

• A solution of Zinc bromide is stored in two tanks.

• When the battery is charged or discharged the solutions

(electrolytes) are pumped through a reactor and back into

the tanks.

• One tank is used to store the electrolyte for the positive

electrode reactions and the other for the negative.

• Zinc bromine batteries from different manufacturers have

energy densities ranging from 34.4–54 Wh/kg

The primary features of the zinc bromine battery are:

• High energy density relative to lead-acid batteries

• 100% depth of discharge capability on a daily basis

• High cycle life of >2,000 cycles at 100% depth of discharge, at which

point the battery can be serviced to increase cycle life to over 3,500

cycles

• No shelf life limitations as zinc-bromine batteries are non-perishable,

unlike lead-acid and lithium-ion batteries, for example.

• Scalable capacities from 10 kW·h (0.036 GJ) to over 500 kW·h

(1.8 GJ) systems

• The ability to store energy from any electricity generating source

• A flow battery is a form of rechargeable battery in which

electrolyte containing one or more dissolved electro-

active species flows through an electrochemical cell that

converts chemical energy directly to electricity

Flow battery

Battery Storage

• Flow batteries store energy in charged electrolytes and

utilize proton exchange membranes similar to fuel cells.

This storage technology is not developed enough at this

point for practical wind energy application. Battery size,

tank capacities, containment, and cell life are the most

critical issues.

Wind-hydrogen storage system

Power GridVariable-speed drive

Rectifier

Electrolyzer

Compressor Storage

Fuel-cell

Inverter

Wind turbine

Storage system efficiency: 25% to 35%

Fuel

e-

e-

e-

e-

e-

e-

H2 H2

H2

e-

H2

BASIC CHARGING METHODS Constant Voltage Cheap battery chargers

Constant Current Switches off at voltage set-point

Taper Current Unregulated constant voltage

Negative Pulse Charge Short discharge pulse

IUI Charging Constant I, constant V, equalize

IUO Charging Constant I, constant V, float

Trickle charge Compensate for self discharge

Float charge Constant voltage below gassing V

Random charging Solar panel

BATTERY CAPACITY

Type Capacity (mAh) Density (Wh/kg)

Alkaline AA 2850 124

Rechargeable 1600 80

NiCd AA 750 41

NiMH AA 1100 51

Lithium ion 1200 100

Lead acid 2000 30

DISCHARGE RATES

Type Voltage Peak Drain

Optimal Drain

Alkaline 1.5 0.5C < 0.2C

NiCd 1.25 20C 1C

Nickel metal 1.25 5C < 0.5C

Lead acid 2 5C 0.2C

Lithium ion 3.6 2C < 1C

HOW TO MAXIMIZE BATTERY LIFE Do not mix with the new batteries used. It reduces the life of

both. Store batteries in room temperature (60 – 90 degrees typical).

For re-chargeable batteries: Do not over charge batteries. It will

reduce the cycle time of battery.

Don’t over drain the batteries as well.

Use the right charger for each type of batteries.

General uses of a battery

• Alarm System• Radios• Clock

• Cameras

• Digital devices

• Hearing aids• Toys • Flashlights

• Calculators • Medical Devices

Cars/Trucks

Computers/Laptops

Motorcycle

Boats

Cordless Phone

Drill packs

Electric Wheel Chair

Ipods/Mobile Sound systems

Advantages of batteries

• Mitigation of oil shortage and import problem

• Lower cost of electric energy

• Lower capital cost

• No envt. Pollution

• Savings in power transmission

• Shorter time for construction

• Reliability In power emergency and regulation

• Batteries can be used for only a limited time, even Rechargeable batteries can be recharged a certain number of times

• Some equipment (high consuming power equipment) become heavier when using batteries

• Some batteries are dangerous and can lead to fire, explosion and chemical pollution

• Some types of batteries need to be maintained and checked periodically

Disadvantages of batteries

Fuel cells

• Fuel cells use a chemical reaction, rather than

combustion (burning a fuel), to produce electricity in a

process that is the reverse of electrolysis.

• In electrolysis, and electric current applied to water

produces hydrogen and oxygen. By reversing this

process, hydrogen and oxygen are combined in the fuel

cell to produce electricity and water.

Working principle• Hydrogen (fuel) is fed into the

anode of the fuel cell. • Oxygen (from air) is fed into the

cathode side. • Encouraged by a catalyst,

electrons are stripped from the hydrogen atom.

• Freed of the electrons, the protons pass through the electrolyte, while the electrons are forced to take a different path to the cathode.

• As the electrons travel their separate path, they create an electric current that can be utilized.

• At the cathode, another catalyst rejoins the hydrogen atom, which then combines with the oxygen to create a molecule of water.

Storage of chemical energy• Energy content about 0.3 cubic meter at STP is one kWh

• Familiar reaction is electrolysis where direct current is passed

through a conducting aqueous solution producing hydrogen at one

electrode and oxygen at the other

• Energy from the wind was converted into electricity (DC) in one

scheme for the electrolysis of water

• Electrolytic cell – Estimated to offer about 60% efficiency and

hydrogen was produced and stored by electrolysis at 211 kg/cm2

• Volume required to store hydrogen at a pressure of 211 kg/cm2,

would be only 0.001 m3 per kWh

Types of fuel cellsClassified on the basis of operating conditions and various electrolytes used.

– Alkaline fuel cells (AFC)– Polymer electrolyte membrane (PEM)– Phosphoric acid fuel cells (PAFC)– Molten carbonate fuel cells (MCFC)– Solid oxide fuel cells (SOFC)– Regenerative fuel cells

Hydrogen Production bySolar Electrolysis

• Solar electric power and/or utility grid power• Power Controller• Electrolyzer• Hydrogen Purifier• Oxygen Purifier• Hydrogen and Oxygen Storage Tanks• Electrolyte Storage Tank and Transfer Pump• Makeup-water Purifier

• Solar electric power is produced by two 16-panel Solar photovoltaic arrays and a gaggle of other smaller panels.

• When the two house battery banks are fully charged, two 50 Amp charge controllers disconnect the PV power, and the PV voltage rises.

• controller senses the voltage rise and transfers the PV power to the electrolyzers to make hydrogen and oxygen.

Advantages• No green house gases• Not much political dependence• More operating time.

Disadvantages• Storage of Hydrogen due to highly inflammable

nature of H2. Though metal hydrides(FeTiH1.7) and NH3 can be alternative.

• High capital cost due to Platinum catalyst used in the process.

Thank you !!!