A comprehensive review of solar photovoltaic thermal technology: Performance evaluation and recent discoveries

Abstract

In the field of simultaneous electricity generation and thermal energy recovery, photovoltaic thermal (PVT) systems represent a promising solution; however, their performance is strongly dependent on the strategy used for recovering the heat, the choice of the working fluid, the stability of the materials, and the operating conditions. This structured critical review fills the gap in previous review literature, which tended to consider phase change materials (PCM) integration, nanofluid cooling, the design of the absorber, and the use of air-/water-based collectors separately. The novelty of this review is to build a comparative framework that categorises the recent developments in PVT into air-based, water-based, nanofluid-enhanced, PCM-integrated, and hybrid PVT systems and correlates the performance indicators with technical limitations, reliability, cost, and scalability. A review of approximately 250 published papers from 2000 to 2024 found that the following systems are compared, thermal management strategies are reviewed, and operating conditions and reported performance trends are discussed. The synthesis reveals that air-based PVT systems are still the simplest and costliest systems, with the reported efficiency range of 30–45%. Water-based and nanofluid-based systems are better at heat removal, with electrical efficiencies of 12–16% and thermal efficiencies of 50–75%, primarily because of the enhanced convective heat transfer and decreased PV cell temperature. Currently, PCM-integrated systems have been found to have thermal efficiency of 55–80% and offer passive thermal stabilisation; however, their long-term feasibility is compromised by low thermal conductivity, degradation, leakage risk, cost, and cycling reliability. Hybrid systems with the combination of nanofluids, absorber optimisation, and PCM generally exhibit the best overall performance, with some studies reporting overall efficiencies of up to 88.86% under optimal operating conditions. However, the advantages do not appear in all studies and are influenced by pressure drop, pumping power, and stability of the nanofluid, degradation of the PCM, testing conditions, and definitions of efficiency. Standardised testing, long-term outdoor validation, techno-economic assessment, durable low-cost materials, and intelligent monitoring and control strategies for scalable PVT deployment should be prioritised for future research.