Closed-Loop Digital Twins for Building-Integrated Photovoltaics: A Focused Review

The decarbonization of urban environments relies on Building Integrated Photovoltaics (BIPV) to turn structures into active energy prosumers. However, traditional "Digital Shadows" utilize unidirectional data flows that fail to address real-time performance losses from urban shading, soiling, and degradation. This review explores closed-loop digital twins (CLDTs), which shift BIPV management from passive observation to autonomous, cyber-physical synchronization. By synthesizing 12 core studies (2013-2025), this paper maps a technological stack integrating Building Information Modeling (BIM), IoT sensing, and AI engines like LSTM and CNNs. Key findings highlight feedback mechanisms such as UAV-based robotic maintenance and multi-objective optimization (ANN-MOGA) to balance energy yield with occupant comfort. While CLDTs can reduce cooling energy and improve self-absorption, deployment is challenged by 5G or 6G latency, cybersecurity risks, and model drift from biological corrosion. We conclude with a roadmap for blockchain-secured, interoperable protocols to enable self-adaptive, resilient energy infrastructure.