Ola Subhi Waheed Al-Qasem

Discussion Committee: 
Prof. Marwan Mahmoud / Supervisor
Dr. Abdel Karim Daud/ External Examiner
Dr. Muneer Abdo / Internal Examiner
Prof. Marwan Mahmoud
Ola Subhi Waheed Al-Qasem
Storage batteries are indispensable in all standalone solar electric systems (PV power systems). Their efficiency and life time affects significantly the overall PV system performance and economics. Batteries specified especially for use in PV systems have to be distinguished with standing of a very deep discharge rate and high cycling stability. The most proper types of storage batteries (rechargeable batteries) are discussed, and the most important characteristics of lead acid batteries necessary for evaluation of their performance are presented and discussed in this thesis. Selecting the optimum conditions of lead acid battery to obtain the maximum efficiency and maximum ampere hour and watt hour capacities by implemented measurements on a lead acid battery are presented in this thesis. The internal resistance of the battery is a reliable key for determination of its state of charge. The value of this resistance increases almost linearly with increasing of the stored energy. At the same time the specific gravity of the electrolyte decreases linearly with the degradation of ampere hour capacity. The experiments have shown that the battery internal temperature doesn’t change significantly from the ambient temperature during charge and discharge process. The implemented experimental tests have proved that a regular battery cell will be not more rechargeable if it is fully discharged. This issue requires using always a controllable battery charger within the PV power systems to protect the storage batteries against deep discharge and extremely over charge. Such equipment will extend the life time of the battery and consequently improve the economic feasibility and reliability of the PV power systems. In addition the tests have shown that the watt hour efficiency of a battery is considerably less than the ampere hour efficiency, which advices to depend more on the watt hour efficiency when designing storage battery systems to secure higher reliability. Moreover, depending on an earlier developed algorithm for determination of the ampere hour capacity of a battery cell, a new similar algorithm based on specific gravity and cell voltage have been developed which enables also the determination of the ampere hour capacity from the implemented tests on the new battery. This algorithm enables the correct settings of the limits of charge - discharge hysteresis of the battery charger in order to avoid extremely deep discharge and over charge of the battery. Moreover, this thesis presents a construction of an equivalent circuit for lead acid battery using MATLAB program, defines all the components that the circuits consist of and defines the components equations and the parameters with their constants that the equivalent circuit depends on. The final simulation results related to this circuit are also presented. A simulation of the battery on the MATLAB has shown that a realization of an equivalent circuit for a battery cell is possible. With respect to battery characteristic functions, it was found that simulation and practical testing results are almost similar.
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