Power optimizer

Overview Power optimizers are a technology developed to maximize the energy harvest from solar photovoltaic systems. They do this by maximizing the output from each solar module in a string. Because solar modules are usually wired sequentially within an array, when one fails, the entire system can see electricity generation significantly reduced. By avoiding this problem, power optimizers can increase the performance of solar systems, improving an owner’s return on investment (ROI). They can also increase the available installation area for a PV system, particularly in sites prone to partial, temporary shading.

Disproportionate power loss Because of their sequential wiring, power mismatch between PV modules within a string can lead to a drastic and disproportionate loss of power from the entire solar array, in some cases leading to complete system failure (the problem is partially analogous to Christmas tree lights; when one goes out, they all go out). For example, shading of as little as 9%% of the entire surface array of a PV system can, in some circumstances, lead to a system-wide power loss of as much as 54%.

Mismatch can be caused by a range of real-world phenomena including mis-performing solar cells, particularly in older systems where the cells have been in situ for a period of years. Another key cause of mis-matching panel performance is shading from falling leaves, bird droppings or accumulated dust particles, or in some cases structural objects such as trees or handrails. Over time, this power loss can have significant impacts on a solar array owner’s return on investment (ROI), impacting the economic rationale for solar power.

Power optimizer solution Power optimizers can recoup up to around 50% of this lost energy. They do so by harvesting the maximum potential power of each module individually. They can thus significantly enhance the ROI for the array owner. They can also increase the available surface area for the installation of a solar array, particularly in situations where there may be structural shading of the array at certain hours of the day or during certain seasons of the year. Manufactured by National Semiconductor, of California, under the proprietary name of Solar Magic power optimizers, they will be commercially available from May 2009.