ŞENER OKTİK

Quo Vadis: Intermittent Power of Solar Photovoltaic + Electrochemical Storage

Abstract

As of 2026, the experimentally recorded efficiencies for single-junction crystalline silicon heterojunction solar cells with back-contact architectures under standard test conditions (AM1.5G) are reported above 27% (NREL) approaching the maximum theoretical efficiency of approximately 33% for single p-n junction solar cells (the Shockley-Queasier   limit). Recent advances in photovoltaic materials and device architectures aim to overcome this fundamental limitation by improving spectral utilization and reducing recombination losses. Among these approaches, multi-junction and tandem solar cells represent the most successful pathway. By stacking absorbers with different bandgaps, tandem structures can capture a broader portion of the solar spectrum and reduce thermalization losses. In 2025, perovskite–silicon tandem solar cells achieved certified efficiencies of 34.85%, surpassing the theoretical SQ limit for single-junction devices and demonstrating the viability of tandem architectures for next-generation photovoltaics. (2). Unprecedented cost reductions driven by technological advances together with increasing global market volume have been accelerating deployment of solar photovoltaic (PV) systems for transforming global electricity generation. By 2026, global solar PV installed capacity is approaching 3 TWp with  the Levelized Cost of Electricity (LCOE)” for utility-scale solar PV has declined dramatically by nearly 90% over the past decade to approximately 24–50 USD/MWh, while conventional baseload generation typically remains in the 50–150 USD/MWh range depending on the energy source (3) and  yet an inherent intermittency of solar PV power  poses critical challenges for grid stability and reliability. SolarPV -plus-electrochemical storage (PV+BESS) systems are expanding rapidly, with annual growth rates exceeding 40% and global battery storage capacity surpassing 100 GW, dominated by lithium-ion technologies according to recent assessments by the International Energy Agency and International Renewable Energy Agency (4). These developments suggest that integrated solar-storage systems could transform solar energy from an intermittent resource into a reliable cornerstone of future power systems.

This paper explores the question “Quo Vadis?” by examining the integration of electrochemical energy storage primarily lithium-ion and emerging battery technologies with PV systems to enable dispatchable and flexible power generation.

A system-level analysis is presented, focusing on PV–battery energy storage systems (PV-BESS) and their role in mitigating temporal mismatches between generation and demand. Electrochemical storage is evaluated in terms of efficiency, response time, scalability, and lifecycle performance. The study highlights how PV-BESS configurations enhance capacity value, reduce curtailment, and provide essential grid services, including frequency regulation and peak load management. Economic implications are discussed through the lens of levelized cost of electricity and system value, emphasizing the transition from energy-centric to flexibility-driven market structures.

The findings indicate that the synergistic coupling of PV and electrochemical storage is a cornerstone of future low-carbon base load electrical energy productio. Despite ongoing challenges in cost, degradation, and recycling, continued technological advancements and supportive policy frameworks are expected to accelerate the transition toward resilient, decentralized, and sustainable power systems.

Biography

Prof. Dr. Şener Oktik received his PhD in 1982 from the Department of Applied Physics and Electronics at Durham University (U:K. He was awarded the title of Associate Professor in 1986 and Professor in 1995. Throughout his academic career, he has held positions internationally at Durham University (UK), the University of Lecce (Italy), and the University of Stuttgart (Germany); and nationally at Selçuk University, Muğla University, and Kadir Has University, serving as a faculty member, researcher, senior research specialist, and senior administrator/executive managements.

Prof. Dr. Oktik served as the Rector of Muğla University during its third and fourth terms between 2002 and 2010. He  founded the Clean Energy Research and Development Center  in 1996 at Muğla University and with his team  members  been carried out  a  pioneering studies in materials, devices, and systems for photovoltaic conversion technologies.

Within the scope of industrial research, he has served internationally as a senior scientist, senior technologist, and senior executive at BP Solar (Sunbury), Imperial Chemical Industries, Durham University Industrial Research Laboratories (UK), and ZSW (Germany); and nationally at organizations such as Anel Group, Arıkanlı Holding, and Şişecam R&D.

Prof. Dr. Oktik held the position of President of Research and Technological Development at the Şişecam Group from January 2012 to March 2020, and subsequently served as a Member of the Şişecam Board of Directors from March 2020 to March 2024.

Throughout his career, Prof. Dr. Oktik has taken active roles in numerous professional and non-governmental organizations. He currently continues his academic work as a faculty member at the Faculty of Engineering and Natural Sciences at Maltepe University, as Chairman of the Industrial Commission, and as an affiliated senior researcher at the Middle East Technical University (METU) Solar Energy Research and Application Center.

At the international level, he serves as Vice President of the Balkan Physical Union; a member of the International Advisory Boards of the International Commission on Glass (ICG), the International Conference on Coatings on Glass and Plastics (ICCG), the Society of Vacuum Coaters (SVC), and the Center for Functional and Surface Functionalized Glass; and as a member of the Scientific Committee of the European Photovoltaic Solar Energy Conference (EU-PVSEC).

At the national level, he serves as Honorary Chairman of the Turkish Solar Energy Industry Association, a Board Member of the Clean Energy Foundation (TEMEV), a member of the General Assembly of the Turkish Basic Sciences Research Foundation, and a member of the General Assembly of the Muğla Sıtkı Koçman Foundation. He also continues his industrial engagements as a Board Member of Birleşim Energy.

Prof. Dr. Oktik has supervised numerous PhD and MSc theses in the field of photovoltaics and is the author or co-author of over one hundred national and international scientific publications, as well as two international patents.