G.B.M.A. Litjens

Outdoor Characterization of Three PV Architectures under Clear and Shaded Conditions

Building Integrated and Building Applied Photovoltaic (BIPV, BAPV) systems often suffer from low performance due to partial shading. New system arch itectures have been proposed to optimize the energy yield. The common approach of these new architectures is to tr ack the Maximum Power Point (MPP) of every solar mo dule individually. Three independent PV systems were ins talled in Eindhoven, a reference string inverter sy stem, a power optimizer (PO) system and a micro inverter system. We designed a sophisticated monitoring system that allows for a detailed comparison of the three PV systems. We cal culated system and component efficiencies and foun d a good agreement with data sheets provided by the manufact urers. Additionally, we analyzed the performance ra tio for DC and AC of the systems for different weather types b a ed on the clearness index. A pole shading coverin g 1 to 2% of the total system surface has been used to evaluate sys m performance under a specific type of partial shading. Module Level Power Electronics (MLPE) are capable of increasing the Performance Ratio (PR) up to 35% under certain partial shading conditions. However, the st ring inverter system outperformed MLPE under unshad ed operation conditions.

On the influence of electricity demand patterns, battery storage and PV system design on PV self-consumption and grid interaction

New policies supporting photovoltaics (PV) self-consumption and reduced feed-in power flows are advocated in many countries. Consequently, knowledge about the influences of demand patterns and battery energy storage on PV self-consumption and grid impact is required. This study analysed these influences for 400 residential and 26 commercial systems from the Netherlands. Results show larger self-consumption rates for commercial systems than residential systems. Batteries increase the self-consumption rate depending on the PV size and the battery size. Averaged curtailment losses are larger for residential systems than commercial systems and decrease with the addition of a battery to the system.

Annual Yield Comparison of Module Level Power Electronics and String Level PV Systems with Standard and Advanced Module Design

This study focuses on the partial shade-mitigating effects related to the insertion of additional ideal bypass diodes in residential-scale photovoltaic (PV) systems. For this purpose, quantification of the resulting energy yield benefits is carried out in a representative residential environment. It is widely recognized that partial shading inflicts disproportional losses to the energy output of PV systems. Increased granularity levels in cell groups are perceived as a potentially promising measure to increase the shade-tolerance of photovoltaic devices. The past years, introduction of module level electronics promise to reduce further shading losses. The developed model includes a shading evaluation of the installation with means of 3D modeling, insertion of additional by pass diodes resulting in smaller cell groups, irradiance calculations, PV cell modelling and finally an empirical power conversion model. Results suggest that in the reference case of 3 by pass diodes the micro inverter system is performing the best under partial shading. By increasing the cell group granularity the string inverter systems seems to benefit due to the wide maximum power point voltage window.

Yield modelling for micro inverter, power optimizer and string inverter under clear and partially shading shaded conditions

Building Integrated and Building Attached Photovoltaic (BIPV, BAPV) systems may suffer from lower performance than predicted as a result of unwanted partial shading. New system architectures have been proposed to optimize performance. The common approach of these new architectures is to track the Maximum Power Point (MPP) of every solar module individually. A simulation model is developed to quantify the benefits and drawbacks of different PV system architectures. The model includes a shading evaluation of the installation with means of 3D modeling, irradiance calculations, PV cell modelling and finally an empirical power conversion model. The energy yield of three leading architectures is confirmed (string inverter, power optimizer, micro inverter) for clear and partial shading conditions by means of an outdoor field test. Results show that there is a clear benefit for MLPE systems at higher irradiance when partial shading is present. The analysis method can be used by PV installers and system designer to determine which is the optimal system architecture for maximum energy yield especially when partial shading is present.