The cell-string optimizers are highly integrated DC/DC converters that replace the bypass diode and perform maximum power point tracking (MPPT) deep inside the PV module.
By replacing each diode with a MPPT device, the on-off response to performance mismatch is eliminated; every cell-string contributes maximum power without interfering with the power production capability of others. This enhanced degree of flexibility leads to increased energy production; eliminating collateral performance loss due to module mismatch, degradation, soiling, localized shading, and row shading loss mechanisms.
The illustration shows the principle; when panel segments are linked by bypass diodes, partial shading or a section takes the output of that group of cells below the point at which the entire section contributes to the total. Using DC/DC converters allows the shaded panel still to feed power to the output, but at a lower level.
A white paper (" Solar Cell Optimization: Cutting Costs and Driving Performance " (PDF)) and a video (" Solar Cell Optimizers Offer Huge Gains in Energy Harvesting ") are also available.
Advantages claimed are:
- increases energy harvest: offers optimum shade mitigation, providing 30% additional power over diodes
- extends reliability: eliminates hotspots and minimizes the impact of power degradation mechanisms
- enables flexible design: higher degree of flexibility to incorporate multiple string lengths, multiple orientations, and expanding modules into partially shaded areas
- simplifies operation: fully integrated solution simplifies design by requiring no additional hardware, specialized inverters, or data services
Maxim Integrated: www.maximintegrated.com