Optical performance of wall-mounted inverted absorber asymmetric compound parabolic concentrators for air heating solar collectors

• 3D ray tracing models optical performance of solar air heating concentrators. • Inverted absorber design minimises convective and radiative heat losses. • Smaller, elongated concentrators enhance efficiency and reduce material use. • Multiple smaller collectors outperform fewer large ones in building integration. • Design optimisation balances optical efficiency, size, and material requirement. The optical performance of inverted absorber asymmetric compound parabolic concentrators (IACPCs) for solar air heating applications is analysed. An inverted absorber concentrates incident solar energy on to a downward-facing transpired surface from which convective and radiative heat losses can be minimised. Three-dimensional ray tracing is used to model optical behaviour, simulating solar radiation pathways and interactions with reflective surfaces. The variations of optical efficiency and effective concentration ratio with reflector geometry, truncation and collector length are analysed. Findings indicate that smaller, elongated concentrators maximise optical performance and reduce material requirements when integrated over a fixed façade area. Design configurations that optimise aperture width optimise a trade-off between collector compactness and optical performance.