• Applied Thermal Engineering (https://www.sciencedirect.com/journal/applied-thermal-engineering/about/aims-and-scope)
• Energies (https://www.mdpi.com/journal/energies/about)
• Energy (https://www.sciencedirect.com/journal/energy/about/aims-and-scope)
• International Journal of Thermodynamics (https://dergipark.org.tr/en/pub/ijot)
• Journal of Cleaner Production (https://www.sciencedirect.com/journal/journal-of-cleaner-production/about/aims-and-scope)
• Journal of Energy Resources Technology (https://asmedigitalcollection.asme.org/energyresources)
• Renewable Energy (https://www.sciencedirect.com/journal/renewable-energy/about/editorial-board)
• Thermal science (https://thermalscience.vinca.rs/About)

The authors present a numerical study of concentrated photovoltaic-thermal solar collectors with spectral beam splitters. I really enjoyed reading the manuscript and how the information was presented. However, I think the work could be improved if the following comments are considered:
– How was the collector geometry selected?
– A figure with the mesh and boundary conditions applied would help clarify how the numerical simulations were performed.
– Was a mesh independence study done?
– Are geometries of other works comparable? Maybe adding a table with their characteristics and the ones of the present study could highlight the validity of the comparisons.

The authors present a numerical study of concentrated photovoltaic-thermal solar collectors with spectral beam splitters. I really enjoyed reading the manuscript and how the information was presented. I have added some comments that I hope will improve their work and how the information is presented.

This is a really good contribution to the ECOS 2023 conference.
The paper is well structured and detailed and you have a very good discussion.
I recommend this paper for oral presentation

• Andres Meana-Fernandez

• Beatriz del Río

Concentrated hybrid photovoltaic thermal (CPVT) solar collectors can generate thermal energy and electricity simultaneously. Conventional CPVT collectors are usually constrained by the silicon solar cells that they employ to operate at temperatures below 70-90 °C. To overcome this limitation, CPVT systems have been proposed and explored that feature spectral beam splitters (SBSs). A SBS acts as an optical filter which, for a collector with silicon cells, allows wavelengths between ~500-1100 nm to pass through onto the cells while reflecting the rest to a separate thermal absorber. The filtering acts to reduce the operating temperature of the cells, thereby improving their electrical performance. The reflected rays from the SBS filter, which mostly consist of the UV and IR part of the solar spectrum, are directed onto an absorber whose purpose is to extract high-grade thermal energy, thereby improving the potential of thermal energy extraction. In this work, SBS-based CPVT systems are explored. Ray-tracing simulations are performed to optimise the geometrical arrangement of the thermal absorber and SBS, while computational fluid dynamics (CFD) modelling is used to estimate the benefits of the CPVT system with the SBS compared to those without the SBS. The effects of solar irradiance and inlet water temperature are studied in detail. Preliminary results show that for a solar incidence of 1000 W/m², the SBS  is able to reduce the solar cell operation temperature by 10-12 °C, leading to potential electrical efficiency benefits of ~7.5%.