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Act Solar’s Powerstring power management system boost PV system yield

Product Briefing Outline: Act Solar, Inc., a power management optimization company, has launched, ‘PowerString’ a patent-pending system that complements central inverters by dynamically re-circulating small amounts of electricity, as needed. ‘Injection Boost’ technology, actively maintains the balance of the array, which assures maximum power output. The system combines two capabilities—power optimization and remote diagnostics—that when applied together can more than double the lifetime productivity of most PV arrays. The company claims that field testing yield improvements of 6-11% and are projected to cumulatively deliver 40–80% more total power over 25–40 years of operation.

Problem: Generally, monolithic systems have minimal instrumentation beyond the AC output as measured at a utility meter and the summary DC input reported by the inverter. If the system’s output is diminished it might be noticed at the AC meter, but there’s no practical way to identify the cause. This is a result of primary losses in a few excessively worn components combined with the fact that accumulated variations across all of the system components has a magnified penalty on system output due to secondary losses at the string level and tertiary losses at the array level. Not only is power lost from worn or broken components, but substantial power is lost from the remainder of a PV system’s components since many can no longer achieve maximum power.

Solution: PowerString breaks a single large monolithic array into multiple independent strings. These strings are truly independent, and their power is tracked and optimized locally such that each panel and solar cell can run at its individual maximum power point. Each string can have different electrical characteristics, different conditions, different solar angles and can even utilize different panel technologies. This adds tremendous flexibility to system design, independently optimizes the power of each string and localizes any degradation to the directly-impacted panel, preventing a fault from impairing power output from the rest of the system.

Applications: All types of medium to large scale PV systems.

Platform: The PowerString Active Power Management system gathers and analyzes real-time data from millions of components including panels, strings, trackers, inverters and weather instruments.  Symmetry analysis incorporates voltage, current, energy, temperature, insolation, trend data and I-V curve measurement simultaneously from multiple sites and components. A signature is developed based on that data which can discriminate failed panels, dirty panels, corroded connectors, degraded wiring, shade, bypass diodes, fuses, inverter degradation, ground faults, etc.

Availability: February 2009 onwards.