Solar Charging Batteries: Advances, Challenges, and Opportunities

Energy for a sustainable future motivates today's R&D, enabling technologies such as smart consumer electronics, electric vehicles, and smart grids. These technologies demand the use of batteries. Sunlight, an abundant clean source of energy, can alleviate the energy limits of batteries, while batteries can address photovoltaic intermittency. This perspective paper focuses on advancing concepts in PV-battery system design while providing critical discussion, review, and prospect. Reports on discrete and integrated PV-battery designs are discussed. Three key technical challenges, namely energy density, efficiency, and stability, toward further advancement of integrated PV-battery systems are discussed. We present a perspective on opportunities and future directions, highlighting key strategies on developing such PV-battery systems. Key focus should be on the development of innovative designs that incorporates high-capacity, efficient, and stable materials, emphasizing the demonstration of practical viability of such integrated PV-battery systems. Today's world is energy driven and batteries have become an integral part as an energy source considering the technological advances in consumer electronics to electric vehicles, renewables, and smart grids. Batteries are energy limited and require recharging. Recharging batteries with solar energy by means of solar cells can offer a convenient option for smart consumer electronics. Meanwhile, batteries can be used to address the intermittency concern of photovoltaics. This perspective discusses the advances in battery charging using solar energy. Conventional design of solar charging batteries involves the use of batteries and solar modules as two separate units connected by electric wires. Advanced design involves the integration of in situ battery storage in solar modules, thus offering compactness and fewer packaging requirements with the potential to become less costly. This advancement can be advantageous for consumer electronics where space, size, and packaging requirements hold greater value. Three major metrics, namely energy density, efficiency, and stability, have been addressed by presenting relevant challenges and potential opportunities. The integrated design is still in the early R&D phase. There is a need for innovative designs that explore high-capacity, efficient, and stable materials. Meanwhile, to demonstrate its practical viability, this integrated design should also focus on real-world applications such as wearables that demand specific requirements of energy and power. This perspective provides insights into battery-charging designs using solar energy. Advances in conventional-discrete-type and advanced-integrated-type systems are summarized. Three key challenges of such integrated-type systems, namely energy density, overall efficiency, and stability, are discussed while presenting potential opportunities to overcome them. Finally, the perspective provides some practical considerations that would guide future efforts.