Theoretical and Experimental Study on Co-suppress Resistive and Mismatch Losses of Concentrating Photovoltaics by Non-Equal-sized Series Cell Connection

Concentrating photovoltaic (CPV) technology enhances energy flux density by focusing sunlight, offering potential for high-power generation coupled with heat recovery. However, it faces dual challenges in practical applications: significant increase in series resistance loss under high concentration and current mismatch caused by non-uniform radiation distribution. This study evaluates the performance and loss mechanisms of series-connected small-size sliced cells and innovatively proposes a non-equal-size cell series packaging scheme. The scheme aims to actively adapt to non-uniform radiation distribution through differentiated cell size design, thereby synergistically suppressing resistance loss and current mismatch. A high-precision three-dimensional optical-thermal-electrical multiphysics coupled simulation model is developed and validated with outdoor experiments. Results show that cutting conventional sized PV cells into equal-size units for series packaging can effectively reduce performance degradation from resistive loss, temperature rise, and non-uniform temperature distribution. However, this approach aggravates current mismatch loss due to radiance non-uniformity and lowers the fill ratio owing to increased inter-cell gaps. After non-equal-size optimization, current consistency among cells improves significantly, with the maximum current deviation in modules consisting of four and eight cells reduced to 0.03 A and 0.06 A, respectively. Maximum output power increases by 5.3% and 19.6% compared to the equal-size design. The study further clarifies the synergistic relationship among cell size, concentration ratio, and cable specification, providing guidance for optimal module selection. Under various cooling conditions, non-equal-size modules exhibit superior electrical and exergy efficiencies. A two-day outdoor experiment verifies the effectiveness of the proposed design: the average electrical and exergy efficiencies of a module with four equal-size cells increase by 51.2% and 33.3%, respectively, compared to a conventional full-size module, while thermal efficiency decreases by only 4.2%. After non-equal-size optimization, the average electrical and exergy efficiencies are further enhanced by 4.5% and 3.4%.