Presentation on theme: "Dr. Dave Irvine-Halliday"— Presentation transcript:
1 Dr. Dave Irvine-Halliday ENERGY STORAGE Part IIDr. Dave Irvine-HallidayENEL 581
2 Chemistry of Lead Acid Batteries When the battery is discharged:Lead (-) combines with the sulfuric acid to create lead sulfate (PbSO4),Pb + SO4 PbSO4 + 2e-Lead oxide (+) combines with hydrogen and sulfuric acid to create lead sulfate and water (H2O).PbO2 + SO4 + 4H + 2e- PbSO4 + 2H2Olead sulfate builds up on the electrodes, and the water builds up in the sulfuric acid solution.When the battery is charged:The process reverses; lead sulfate combining with water to build up lead and lead oxide on the electrodes.Lead Acid Batteries Consist of:Lead (Pb) electrode (-)Lead oxide (PbO2) electrode (+)Water and sulfuric acid (H2SO4) electrolyte.PbSO4 + 2e- Pb + H2SO4PbSO4 + 2H2O PbO2 + H2SO4 + 2e-
3 Sealed Lead Acid (SLA) Batteries Instead of water and sulfuric acid the SLAs have the acid in form of a gelThe battery is valve regulated to prevent the build up of gases which are produced during charging.Maintenance freeSafer against leakage
4 Using SLA batteries in a Solid State Lighting System Deep discharging will shorten the battery life timeSafe limit - do not discharge the battery more than 20% of its full capacityKeep the battery charged all the timeNever short circuit the battery terminalsLet the users be aware about the proper handling of the batteryOperating Temperature Limits(-30º C to 65º C)Heat can kill the batteryCold slows down chemical reactions inside in the batteryEnd ENEL Lecture # 30 (Wed22Nov2006)
5 Discharge Pattern of SLA batteries in a Solid State Lighting System Example:A 12V 7.2 Ah battery can store*E = Voltage (13.2v) x Capacity (7.2 Ah)E = 95 Wh or 342 KJA luxeon lamp takes 110 mA when battery voltage is at 13.2 VThenPconsum = V x 110 mA = 1.4 WAssuming 75 % power transfer efficiency from battery to lamp)Tdisch = Capacity / consumed current x 0.75= [7.2 Ah / 110 mA] x = horTdisch = Energy / Power consumption= [95 Wh /1.4W] x = hEnd ENEL 581 Lec. # 17 (Tues. 4Nov2008 “President Obama Day”)Capacity of a battery (C) is measured in Ampere-hours (Ah)
7 Discharge Pattern of SLA batteries in a Solid State Lighting System End ENEL Lecture # 14 (Mon. 29Oct2007)
8 Electrochemically Stored Energy II. Fuel Cells: Convert chemical energy into electric energyChemistry of a Fuel CellChemical Process:1.- Platinum Catalyst (electrode) Separates Hydrogen gas into electrons- and Ions+.2.- Hydrogen Ions+ pass through membrane only.3.- With help of the Platinum catalyst Hydrogen Ions- combine with electrons and oxygen to form water.Proton ExchangeMembraneNet reaction: 2H2 + O2 2H2O + Electricity + Heat
9 Electrochemically Stored Energy Reversible Fuel Cells/ Electrolizer:Chemical Process:1.- Platinum Catalyst Separates Water into Oxygen and Hydrogen electrons and Ions+.2.- Hydrogen Ions+ pass through membrane only.3.- With help of the Platinum catalyst, Hydrogen molecules are formed when hydrogen Ions- and electrons are combined.ElectrolizerProton ExchangeMembraneNet reaction: 2H2O + 4H+ + 4e- 2H2 + O2
10 Fuel CellsUsually named according to their electrolyte and categorized according to their operation temperature.Low temperature fuel cells (< 200°C):Polymer Electrolyte Membrane Fuel Cell (PEMFC)Direct Methanol Fuel Cell (DMFC)Phosphoric Acid Fuel Cell (PAFC)Alkaline Fuel Cell (AFC)High temperature fuel cells(600° to 1000° C):Solid Oxide Fuel Cell (SOFC)Molten Carbonate Fuel Cell (MCFC)
13 Electric Energy Storage I. Capacitor: is an electrical device which serves to store up electricity or electrical energy.C = x10-12 K · A / dC = Capacity (farads) K = dielectric constant A = area of one plate (square centimeters) d = distance between plates (centimeters)AQ = CVdQ = charge (Coulombs) V = voltage (Volts)Stored energy: E = ½ C · V2e.g μF at 35 volts will store Joules(enough to power 1 W WLED lamp for ~ 0.5 seconds, assuming90% power transfer efficiency and 1.2 W of lamp consumption)
14 Electric Energy Storage II. Ultracapacitors or Supercapacitors: Similar to a normal capacitor, a supercapacitor or ultracapacitor stores energy electrostatically by polarizing an electrolytic solution. Highly porous carbon-based electrodes increases the area to be charged as compared to flat plates.NegativeelectrodeCapacitance: FaradsVoltage: 2.5 VCharging/Discharging Efficiency: 90%Charging/Discharging Cycles:Stored Energy:E = ½ C · V2E = 7.81KJ to KJEnough to power a 1W WLED lamp for ~ 1.6 to 3.2 Hours(assuming 90% energy transfer efficiency and 1.2 W lamp consumption)Ion-donorelectrolyteToyota Prius Cars and Chinese Buses in Shanghai use SupercapsPositiveelectrodeUltracapacitor cross section view when is being charged
15 Lead Acid Batteries vs Ultracapacitors Lead Acid Batteries Ultracapacitors1000 Charging Cycles K – 500K Charging Cycles (Years?)Lifetime 10 years Deteriorates 80% in 10 years*Require discharge controllers *Not require charge controllers*Toxic compounds (H2SO4, Pb) *No toxic compoundsSlow charge and discharge Safe fast charge and dischargeHigh energy density Low energy densityLow power density High power density*Cost – US $0.11/ Wh (Initial) *Cost US$ 12.8 / Wh (Initial)Efficiency 75% to 80% Efficiency 95%End ENEL Lecture # 31 (Fri24Nov2006)
16 Supercapacitor powers a 1 W Luxeon WLED for more than 1 hour Feb. 2002
17 Show IEEE Spectrum article: “The Charge of the Ultracapacitors”
18 More Power. More Energy. More Ideas. The new HC family of products includes compact, cost-effective, 25-, farad cells, all rated at 2.7 volts. Key features and benefits include:Reliable performance for 500,000 or more charge/discharge cyclesZero maintenance over estimated 10-year operating lifetimeBroad operational temperature range (-40 to +65C)High power and energy density in low-volume, lightweight packageTwo-pin radial design for easy mountingResistant to reverse polarityScalable to higher voltages via multi-cell configurationsToday more than ever, system designers recognize that ultracapacitors enhance energy efficiency and functionality and provide 'life of the application' durability for virtually any electronic device or system. The new HC product family responds to growing demand by delivering Maxwell's industry-leading technology in new form factors that are suitable for a broader range of electronic applications. Typical applications benefiting from ultracapacitor cells in the 25-to-150-farad range include:Robotics and factory automationUninterruptible power supply (UPS) systems for industrial and telecommunications installationsRenewable energy systems, including solar and wind energy generation systemsCordless power toolsConsumer electronicsVisit our website, for more information on this and other exciting new developments from Maxwell Technologies.
20 Superconductive Magnetic Energy Storage (SMES) In SMES, Energy is stored in the magnetic field produced by a current passing through a superconductive coil immersed in liquid helium vessel.L = Coil Inductance (H)I = Current (A)Superconductive no resistive losses0.1% of stored energy is used for thecooling system, needed to mantainsuperconductivity in the coil (~ -200°C).Rapid response for either charge/dischargeIt is claimed that SMES are 97-98% efficient.Commercial SMES systems are able to store up to about 6 MJ.
21 Superconductive Magnetic Energy Storage (SMES) Advantages:SMES systems are environmentally friendlyCapable of releasing megawatts of power within a small period of timeRecharges within minutesCan repeat the charge and discharge sequence thousands of timesDisadvantages:Complex expensive parts & maintenanceBig sizeCost
22 References: Mechanically Stored Energy Flywheels –Air Compression -II. Electrochemically Stored EnergyBatteries -Fuel Cells –III. Electric Energy Storage DevicesCapacitors -Ultracapacitors -Superconductive Magnetic -End ENEL Lec. # 19 (Mon. 17Nov2008) ; End ENEL 669 Lec. # 18 (16Nov2009)End ENEL 581 Lec. # 20 (17Nov2009)
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