Thesis (M.Sc.)-Cairo University, 2023.

Bibliography: pages 58-53.

Vanadium Redox Flow Batteries (VRFBs) lifetime prediction is essential for renew-
able energy integration at a large-scale. Since renewable energy sources are unpredictable
and intermittent, energy storage systems became essential to provide power shaving of
load when there is a peak demand and power smoothing of generation when there is an
excess renewable generation. The cost of energy generation and storage in kilowatt hours
delivered includes all costs from investment through maintenance. Thus, the lifetime and
operational costs are important economic assessment parameters. VRFB lifetime is de-
termined by the battery chemistry, layout and design. Since the laboratory experiments
are not practical due to their high price and their time consumption, a high precision two-
dimensional Multiphysics model for a VRFBs that captures the coupling relationships
between the electrochemical reactions and the thermodynamics under dynamic load vari-
ations shall be considered. The temperature is feedbacked to the electrochemical model
as it affects the diffusion coefficient and the ionic mobility of vanadium ions. Mean-
while, the heat generated by the ohmic resistance, the electrochemical reactions and the
activation losses also result in the temperature rise of the stack temperature. In addition
to this, the impact of renewable energy applications, which are characterized by being
highly varying power profiles, on the battery performance and health have rarely been
studied in the literature. Although there are few studies with varying load profiles, it re-
mains unclear how the dynamic pulse profile affects the cycle life of VRFB. Therefore,
a statistical long-term varying power profile is compared to a continuous current load
with the same average current in order to draw conclusions about battery lifespan under
severe load variations. Although the system efficiency was poorer in case of discontin-
uous power profile, equal state of health values were resulted after the operation of the
variable and the constant profiles. The obtained results assert that VRFB is a propitious
grid-based renewable energy storage system

يعد التنبؤ مدى الحياة لبطاريات تدفق الفاناديوم واالخت ازل )VRFBs( ضرورًيا لتكامل الطاقة
المتجددة. في هذه األطروحة ، تم تطوير نموذج متعدد الفيزياء عالي الدقة ثنائي األبعاد لـ VRFB الذي يلتقط عالقات االقت ارن بين التفاعالت الكهروكيميائية والديناميكا الح اررية. بعد ذلك ، تتم مقارنة ملف تعريف الطاقة المتغير اإلحصائي طويل المدى بالحمل الحالي المستمر بنفس متوسط الطاقة من أجل استخالص استنتاجات حول عمر البطارية في ظل االختالفات الشديدة في الحمل. على الرغم من أن كفاءة النظام كانت أقل في حالة ملف تعريف القدرة المتقطع ، إال أن الحالة المتساوية للقيم الصحية نتجت بعد تشغيل المالمح المتغيرة والثابتة. تؤكد النتائج التي تم الحصول عليها أن
VRFB هو نظام تخزين طاقة الشبكة الواعد للطاقة المتجددة.

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