Full year performance analysis and steady state operation model for a stationary Shadeless solar thermal collector with a horizontal aperture for steam generation

This work documents a full-year performance of a new design of a non-tracking zero-latitude-tilt external compound parabolic concentrator (XCPC) solar thermal system called Non-tracking Asymmetric Shadeless (NASH) concentrator. The system has a horizontal-aperture design that offers several advantages in terms of land use efficiency because of zero row-to-row spacing, reduced capital costs, and improved heat management. The horizontal aperture (no tilt) design enables it to be scaled to a large area easily without lost area from row-to-row shading as experienced by a tilted design. The system was tested at the University of California Merced, Castle test facility for a full year. The data are analyzed to investigate the system efficiency and thermal energy generated during the year. The system generated 766 kWh/m² during 2022 with annual efficiency of 41 %. A steady-state model is developed to predict the system performance based on the direct- and diffuse-light optical efficiencies, radiative and manifold heat losses, and observed soiling rate. The system efficiency decreased by up to 14 % over a month due to soiling in this test location. The model gives a good estimation of the steady-state operation during July and predicts the general annual trend of the generated thermal energy.