Photovoltaic Systems Engineering Ali Karimpour Assistant Professor Ferdowsi University of Mashhad Reference for this lecture: Photovoltaic Systems Engineering Third Edition CRC Roger Messenger, Jerry Ventre
Lecture 7 Energy Storage 2
Energy Storage The Lead-Acid Storage Battery Batteries The Nickel Cadmium Storage Battery Other Battery Systems Hydrogen Storage The Fuel Cell Potential energy stored, Compressed air, flywheels, Superconducting magnets,. 3
The Lead-Acid Storage Battery Chemistry of the Lead-Acid Cell Charging process Over charging Gassing Discharging process Sometimes it is ok. Deep discharging is not ok since cell performance may be affected. 4
The Lead-Acid Storage Battery Lead-acid battery is still the most common for relatively economical 5 storage of electrical energy.
The Lead-Acid Storage Battery Properties of the Lead-Acid Storage Battery Charging efficiency is around 95%, Discharging efficiency is around 95%, Overall efficiency is around 90% High charging rate or discharging rate leads to lower efficiency. The amount of energy in a battery is commonly measured in Ah and shown by C. Charging rate or discharging rate is shown by C/x. 6
The Lead-Acid Storage Battery Properties of the Lead-Acid Storage Battery Higher discharge rate less charge being available as energy to a load. Higher charge rate it takes more energy to fully charged. 7
The Lead-Acid Storage Battery Properties of the Lead-Acid Storage Battery Effects of discharge rates and temperature on the relative amount of charge that a battery can deliver. 8
The Lead-Acid Storage Battery Properties of the Lead-Acid Storage Battery Shallow discharge Small amount of calcium combined with the lead to import greater strength to the otherwise pure lead. Thinner plates with greater area higher starting current Should not be discharged to less than 75% of their capacity. Less lead less expensive. Deep discharge Use antimony to strengthen the lead. Can be discharged to 20% of their capacity. Thicker plates with less area lower level current. Marine application, electric forklifts and PV system use. 9
The Lead-Acid Storage Battery Properties of the Lead-Acid Storage Battery Deep of discharge affects the number of operating cycles. Trade off between: - More batteries, shallower discharge and extend the overall lift or - Fewer batteries with dipper discharge rate and lower initial cost. 10
The Lead-Acid Storage Battery Properties of the Lead-Acid Storage Battery Where maintenance is inconvenient, maintenance-free, sealed deep-cycle batteries exist, but at least double the price. Valve regulated to recombine gases. The temperature at which the electrodes of batteries will freeze is very important 11
The Lead-Acid Storage Battery Properties of the Lead-Acid Storage Battery Specific gravity is the most accurate measure of the state of the charge of a battery. An advantage of removable caps is that it is possible to measure specific gravity. 12
The Nickel Cadmium Storage Battery Chemistry of the Nickel Cadmium Storage Battery Nickel hydroxide for the anode plates. Cadmium oxide for the cathode plates. Potassium hydroxide for the electrolyte. Charged cell is 1.29 V. Specific gravity of the electrolyte changes very little during battery operation. 13
The Nickel Cadmium Storage Battery Properties of the Nickel Cadmium System More robust than lead acid They can survive freezing and high temperature. They can fully discharged. Less affected by overcharging. Elimination of charge controller. Very low internal resistance. Can be discharge at the rates up to C over a wide range of temperature range, while still providing more than 90% of its capacity Unreasonable to expect it last twice as long as its lead-acid counterpart. (25 year good condition to 8 years in bad.) 14
The Nickel Cadmium Storage Battery Properties of the Nickel Cadmium System Disadvantages Memory effect. Memory effect is predominant in sealed batteries and is not a problem in some other types. It is hard to determine state of charge. Toxicity of the cadmium. Higher price compare to lead-acid. 15
Electrolysis of Water (H 2 O) http://www.gm.com/company/gmability/edu_k-12/9-12/fc_energy/make_your_own_hydrogen_results.html
Hydrogen Storage lecture 2 17
Hydrogen Economy Schematic
Hydrogen Energy Cycle http://en.wikipedia.org/wiki/hydrogen_economy
Hydrogen Storage 20
Hydrogen Storage 21
Hydrogen Storage lecture 2 It can be used as a engine fuel to power a vehicle. Hydrogen + air water + heat (No pollution but small NO x ) Hydrogen + air + Fuel cell water + heat + electricity High energy density 2 ft 3 gasoline is around 614 Kwh 5*60 Ah 12 V batteries is around: 3.5 Kwh Fuel_cell.FLV fuel_cell2.flv 2 ft 3 of gaseous hydrogen is around: 27.5 Kwh 2 ft 3 of liquid hydrogen is around: 140 Kwh Storage and transport of the gas is an engineering challenges. 22
The Fuel Cell 23
How does a Hydrogen Car Work? In a hydrogen car, its primary source of power is from one of two ways: Combustion chamber Fuel Cell
Hydrogen-Powered Autos fuel_cell_car_4.flv
Hydrogen-Powered Aircraft Hydrogen powered passenger aircraft with cryogenic tanks along spine of fuselage. Hydrogen fuel requires about 4 times the volume of standard jet fuel (kerosene). But less weight 200 ton 70 tone http://planetforlife.com/h2/h2vehicle.html
Hydrogen Future http://www.unido-ichet.org/ichet-transition.php
Hydrogen Future