Efficient Power Solutions
Inverters are a critical component to maximize the power from a solar PV power system or a wind power system. Inherent to solar panel and wind turbine technology, the power and voltage vary with the intensity of the sun or the velocity of the wind. The inverter plays a key role in converting the power from these renewable sources to AC power (alternating current) to be compatible with the voltage and frequency required to power buildings or to feed in power to the utility power grid. The efficiency of the inverter is the ratio of the AC power out of the inverter to the total power produced by the solar panels or wind turbine that is the input to the inverter. Inverter manufacturers including Power-One publish the peak efficiency of the inverter typically measured at the maximum rated output power. Power-One is a leader in high efficiency design with the popular AURORA® UNO and AURORA TRIO inverters having a peak efficiency over 97%.
Another parameter often provided by inverter manufacturer’s to aid the selection of efficient power solutions is the weighted efficiency of the inverter. In actual use, the insolation of the solar panel fluctuate and will not be optimal due to shading, cloud conditions, angle of the sun and other factors. A model has been adopted by the California Energy Commission that assumes that the inverter is operating at power levels from 10% to 100% of its maximum rated power with the majority of the operation at 50% to 75% of full power. The efficiency at various power levels from 10% to 100% are multiplied by the models estimate of the percent of time that the inverter is operating at that power level. Due to the varying power levels of inverters in actual use, it is an advantage to select an inverter that has high efficiency while operating over a wide range of power levels. Power-One has patented innovative circuits to operate at ever increasing efficiency and to have high efficiency over a wide range of output power. To select an inverter for a highly efficient power solution, care should be taken to examine the published efficiency curves over a range of output power and not only a published efficiency figure.
Another aspect in designing a highly efficient power solution is to consider overall architecture of the solar installation. For an architecture with one inverter per solar panel, the inverter, known as a micro-inverter will be a lower efficiency due to the economies of scale for the power conversion. This one to one relationship of solar panel to inverter does allow the inverter to select the optimum power level for that solar panel and not for the average of multiple solar panels connected in parallel. The AURORA MICRO -0.3-I offers 95.5% maximum efficiency and is installed on each solar panel in an installation.
In addition to inverter performance parameters, care must be taken in the maintenance of the entire power installation to ensure that it operating as an efficient power solution. The AURORA Vision product offering includes AURORA Environmental so that the meteorological conditions can be evaluated alongside the inverter’s power output. The internet accessible data from AURORA Vision alerts the user to underperformance of the system, and maintenance or repairs needed to maintain the high efficiency of the system.