Micro-Inverters gaining an edge over the traditional String Inverters

The National Renewable Energy Laboratory of US Department of Energy has created a test protocol which can create a real shade condition and can tell with a great accuracy the effect shading has on the solar array. The good thing is that the test protocol can simulate any type of shading condition.

The use of the system shows that in typical shading conditions that micro-inverters can increase the performance of the system by upto 12% as compared to the traditional string inverters. The research was carried out by senior engineers of NREL which was funded by DOE.

As a known fact that shading can seriously hamper the performance of a photovoltaic system. The effect of performance depends on various factors such as the configuration of the PV module as well as the shading on the system. Currently there is a lack of test protocols in the market which can calculate the average shading per year on various shading conditions. The report of NREL describes a test protocol which can analyse the yearly data and the measurements can be used to calculate annual performance.

The parameters for measurements taken for the shading analysis for the report consisted of 60 residential properties and shading was classified into three categories “light”, “moderate” and “heavy”. The data collected from these systems along with the annual shade loss and  inverter CEC efficiency will allow software such as PV Watts and system advisor model will allow for an accurate performance analysis.

Under the normal conditions for a 8-KW system it was found that micro-inverters increased the production by 3.7% under light shading, 7.8% under moderate shading and 12.3% under heavy shading as compared to string inverters.

This research will provide a major step in establishing new PV systems providing a better performance considering the shading effect.

 

(Author: Mohd. Arif)