Published on March 7, 2014
Prepared By: Presented By: Sagar Mali (2067/BEX/133) Rasu Shrestha (2067/BEX/131) Sanid Prajapati (2067/BEX/134) Raushan Mahaseth (2067/BEX/132) Saugat Gautam (2067/BEX/135)
INTRODUCTION Accumulation of energy for future use Accomplished by devices or physical media that stores energy Such devices are also known as Accumulators To balance the supply and demand of energy Major categories are: Mechanical Electrical Chemical Biological Thermal
Energy storing System & Devices 1. Smart Grid Systems 2. Batteries 3. Super Capacitors
1. Smart Grid Systems Modernized and intelligent electrical network Various energy sources are integrated into single grid Acts according to available information & communication technology Information gathered may be: Behaviors of suppliers and consumers Total energy generated Total use of energy Disturbances and problems within grid Currently implemented among European countries
Features of the smart grid Reliability Fault detection Self healing Flexibility in network topology Distributed generation (from hydropower, solar cells, wind turbines etc) Bidirectional energy flow (charging to/from batteries from electric car) Efficiency Storing energy in off-peak time Smart appliances Sustainability Use of renewable energy sources Auto monitor and control system
2. Batteries Energy storing device based upon the principle of Electro-Chemical Reaction Converts stored chemical energy directly into electrical energy Every battery consists of Cathode (+ve terminal) Anode (-ve terminal) Electrolyte (medium for ions)
Principle of Operation Each cell is divided to two parts: Half cell of cathode and electrolytes Half cell of anode and electrolytes Cations are reduced (e- are added) at the cathode during charging Anions are oxidized (e- are removed) at the anode during discharge Basically, Redox reaction powers the battery Each half-cell has an Electromotive force (emf), determined by its ability to drive electric current from the interior to the exterior of the cell The net emf is the difference between the reduction potentials of the half-reactions
Types of Batteries 1. Primary Batteries Disposable batteries (can’t be recharged) because • Chemical reactions are not easily reversible • Materials may not return to their original forms Can produce current immediately on assembly Most commonly used in portable devices Used well away from an alternative power source Ex: Zinc–Carbon batteries and Alkaline batteries
Types of Batteries 2. Secondary Batteries Rechargeable batteries as chemical reaction are reversible Charged by applying electric current Used for power backup as well as in portable devices Example Wet cell: Lead- acid batteries Dry cell: NiMH, NiCad, Li-ion etc.
3. Super-capacitors • A type of electromechanical capacitors • Formerly known as Electric Double-Layer Capacitor (EDLC) or Ultra-capacitors • Doesn’t have a conventional solid dielectric • Can store huge amount of electrical energy (more energy per unit volume)
Energy Storage Mechanism • Store electrical charge in an electric double layer at the interface between high-surface-area carbon electrode and liquid electrolyte. • Double layers are of same substrate and have vanishingly thin (~nm) • These layers can handle only small P.D so super-capacitors have to be connected in series to operate in high P.D. • No need of dielectric layer permits packing of plates with large area into given size resulting in high capacitances.
Comparison of Conventional Storage Technologies
Applications • Stabilizing the supply of power lines. • Provides emergency backup to low power devices such as RAM, S-RAM , Microcontrollers and PC cards in industries. • Delivers power for photographic flashes in digital cameras. • Super-capacitors are used as battery replacement in some pit trains in China to substitute conventional trolleys in coal mines. They bring coal to the surface.
Super-capacitors as Green Electricity • Does not contain harmful chemicals for storing charge. Hence, safe to human. • High number of charge-discharge lifecycle makes sure of less number of disposable parts makes it environmentally friendly.
Benefits • Very high rates of charging and discharging. • Little degradation over hundreds of thousands of cycle. • Good reversibility. • Low toxicity of materials used. • High cycle efficiency( 95% and more).
Limitations • The amount of energy stored per unit weight is considerably lower than that of an electrochemical battery. • The voltage varies with the energy stored. To effectively store and recover energy requires sophisticated electronic control and switching equipment. • Has the highest dielectric absorption of all types of capacitors.
REFERENCES Websites: http://en.wikipedia.org/wiki/Energy_storage http://en.wikipedia.org/wiki/Smart_grid http://science.howstuffworks.com/environmental/green-science/smartgrid.htm http://file.scirp.org/Html/2-6201335/e2908f91-a50c-49e9-a24fa23192a753fc.jpg http://en.wikipedia.org/wiki/Battery_(electricity) http://electronics.howstuffworks.com/everyday-tech/battery1.htm
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