A novel concave-wall absorber for enhanced heat flux distribution and thermal stability in linear Fresnel solar receivers

The long-term reliability of Linear Fresnel Reflector (LFR) systems is critically limited by thermomechanical stress, which arises from heterogeneous solar flux on the receiver tube. To address this challenge, this work investigates the optical performance of two new Concave-Wall Design, of 45° and 90° orientations, evacuated receivers. A comparative analysis against a conventional circular absorber was conducted using high-fidelity Monte Carlo ray-tracing across diverse geographic and seasonal conditions. The primary finding is that the Concave-Wall Design of 90° orientation geometry provides a substantial enhancement in thermal management; heat flux non-uniformity was reduced by up to 15 %, a result achieved by geometrically dividing the concentrated flux to eliminate damaging hotspots. While optically competitive, the Concave-Wall Design designs also showed a minor efficiency gain (2–4 %) at low solar angles. This study demonstrates that a strategic geometric redesign can solve a key failure mode in linear Fresnel reflector technology, showing that a negligible trade-off in peak optical performance yields a crucial improvement in thermal stability and receiver durability.