Integrated spectral nanofluid filtering and thermal management for PVT-LFR systems with hybrid nanofluid cooling and novel finned channel arrangement

The growing global demand for high-efficiency solar technologies has intensified the need for photovoltaic-thermal (PVT) systems capable of extracting more useful energy from the same solar footprint. One of the most effective strategies to improve PVT performance is optical concentration; however, increasing the solar flux on the panel significantly elevates its temperature, leading to a drop in electrical output. This challenge highlights the importance of advanced thermal management and spectral-control techniques, which remain insufficiently explored in integrated PVT applications. To address this gap, the current work investigates a new concentrated PVT configuration that combines Linear Fresnel reflectors, a spectral-selective nanofluid filter, and fin-enhanced hybrid-nanofluid cooling channels to improve both electrical and thermal efficiencies under realistic operating conditions. In this system, ground-mounted mirrors are arranged beneath the panel to achieve two concentration ratios (CR ≈ 1.5 and 2.5), where the spatial distribution of concentrated heat flux is determined using SolTrace ray-tracing software. The MgO–water nanofluid serves as the working medium in the spectral filter placed over the PV surface. This filter selectively transmits electricity-generating wavelengths while absorbing the infrared portion of the spectrum, reducing PV overheating and simultaneously capturing additional thermal energy. The cooling subsystem consists of finned channels carrying MgO–ZnO–water hybrid nanofluid, modeled as a single-phase mixture due to the low nanoparticle volume fraction. The numerical model is developed, incorporating real meteorological data for a summer day in Babol, Iran, and evaluating the system at three characteristic times (08:00, 12:00, and 14:00). The influence of reflectors, spectral filtering, fin geometry, and coolant inlet velocity on electrical efficiency (ηPV), thermal efficiency (ηth), and total energy output (Etot) is systematically assessed. Model validation against published studies demonstrates good accuracy. Results show that ηth increases about 50.08% with rise of solar irradiance from morning to noon but ηPV reduces by 1.96%, while Etot at noon becomes 2.27 times higher than at 08:00. The addition of reflectors (CR = 2.5) increases ηth by 2.73% but causes a modest 1.55% drop in ηPV due to higher temperatures. Incorporating fins significantly improves heat removal, raising ηPV by 3.11%, ηth by 17.13%, and Etot by 10.91%. The spectral nanofluid filter shows the strongest effect: under CR = 2.5 and without fins, ηPV, ηth, and Etot increase by 7.11%, 71.71%, and 43.03%, respectively. Interestingly, the filter's benefit grows in the presence of optical concentration but decreases slightly when fins are utilized, as fins already reduce temperature. The filter also enhances temperature uniformity by 27.42% at noon, minimizing thermal hotspots. Increasing the hybrid-nanofluid inlet velocity further strengthens convective cooling; with reflectors and fins at noon, ηth and Etot rise by 8.82% and 5.76%. However, when the spectral filter is active, the influence of velocity becomes less pronounced because the filter absorbs a substantial portion of the heat load before reaching the PV layer. Economic analysis indicates that the proposed system can generate annual revenue of $615.11, with a short payback period of approximately 8.1 months. Overall, the findings reveal that combining spectral management, engineered cooling, and solar concentration offers a powerful approach for advancing next-generation PVT systems. The proposed design not only mitigates the thermal challenges associated with optical concentration but also significantly boosts electrical, thermal, and total energy output, establishing a promising pathway for more efficient and compact solar energy technologies.