You may have heard that shading can reduce the electric production of solar electric modules (panels). The major cause of the lower output is because traditional solar PV systems use string inverters which convert the module output into usable house electric current. A string inverter is a separate unit that generally serves between 8 to 12 solar modules. If a module is shaded, its output expectedly drops. Worse yet, the entire set of modules served by the same inverter is equally and adversely affected. It is not uncommon to see output of solar electric systems drop by 30% or more where shadings occur.
Then came the micro inverter technology. A micro inverter serves only one module. Shading on one module only reduces output of that module. The output of modules not shaded are not affected. Thus the overall output of a solar electric system can be kept closer to its rating in spite of some shading.
For a long time, the big concerns about micro inverters were cost and reliability. It has taken a few years for manufacturers to improve the micro inverters to the point of market acceptance.
At the July 2012 North America Intersolar Conference in San Francisco, quite a number of micro inverter companies, including the market leading inverter manufacturers, exhibited their micro inverter products. In addition, many module manufacturers either showed pre-market modules or talked about modules that will be shipped with micro inverters already integrated.
The integrated modules will make the job of solar installers easier for they do not have to find matching micro inverters for the modules and then individually wire them for each module. More importantly, the module manufacturers plan to include the micro inverters in their modules’ typical 25-year warranty, which should remove the angst of micro inverter failures.
While the cost of micro inverters may still be slightly higher than that of string inverters, the better output can more than offset the additional cost. This is particularly true in places where an unavoidable and small amount of shade that moves across the set of modules over the course of a day.
Shading should be avoided as much as possible. However, the availability of string and micro inverters provides you options to suit your particular situation.
