Improving optical efficiency of linear Fresnel collectors in the Sahel via position and length adjustment

• Weekly adjustments offer about 1 % efficiency gain over monthly adjustments. • Practical feasibility favors a monthly frequency for adjusting receiver position. • Optical efficiency increases from 35 to 47 % with receiver position adjustment. • Annual efficiency reaches 49 % with 15 % longer receiver and monthly adjustment. • 75 % of the receiver's length is not illuminated in winter by solar incident flux. Linear Fresnel concentrators are promising technologies for solar thermal applications, but their performance is often hindered by end losses and inefficiencies related to receiver design and placement. This study aimed to enhance LFC optical performance under the specific solar conditions of the Sahel region by exploring dynamic receiver displacement and tailored receiver length extension. The methodology involved calculating the maximum non-illuminated receiver length analytically for each solar condition and simulating various displacement frequencies (weekly, biweekly, and monthly) using the Tonatiuh ray-tracing tool. The combined strategies of dynamic receiver adjustment and analytically optimised receiver length were evaluated in terms of annual optical efficiency and flux stability. Key findings reveal that the dynamic displacement strategy improved average annual optical efficiency by 13 percentage points, corresponding to a 38 % relative increase compared to fixed receiver positions. Weekly adjustments provided the highest efficiency, while monthly adjustments offered a practical alternative, achieving similar performance with four times fewer interventions. Extending the receiver to match the calculated maximum non-illuminated length yielded an additional 3 % improvement in annual efficiency and a 75 % reduction in flux variability. These results highlight the advantages of adapting receiver design and positioning strategies to regional solar profiles, particularly in intertropical regions like the Sahel. The proposed methods enhance both the optical performance and economic feasibility of LFCs, offering practical insights for optimising solar thermal technologies in diverse climates. Future work could explore automated adjustment mechanisms to further reduce operational demands and improve scalability.