How to Overcome Solar Shading Problems

Solar panels are linked in strings, usually between 7-15 panels long.  If just one panel in a string gets shaded, the whole string has to suffer.  As drill sergeants and sports coaches are known to say, “We’re only as strong as our weakest member.” So it is with solar panels stringed in series.  The current in the weakest panel becomes the current in all the panels.  Regular string inverters, which are the lowest cost, are limited in their power output if shade becomes a problem.

In instances where there is major shading involved, like a huge tree by a house or a chimney that could block sunlight , a more robust solution is needed.  Microinverters are a great way to overcome solar shading problems.  A microinverter is a tiny inverter that rests right underneath the solar panels.  Microinverters are a bit like individualistic overachievers, so to speak.  They don’t really care how well the panels around them are doing, as long as they are doing their best.  Microinverters have built in MPPT that optimizes the voltage of each panel, not just the entire string.  The output of the microinverters is alternating current, and the total current from all the panels is added together without them needing to match up.  We recently completed a design featuring the APSystems YC500 microinverter.  This component hooks up to two panels at once, which helps to reduce cost.  Also, this is an ideal component in situations where two different buildings need to be fed with power.  One of our recent installations was roof mounted on a barn separate from the house.  The output of the microinverters tied into the electric system in such a way that fed both the barn and the house.

DC optimizers serve a very similar purpose as microinverters.  They are a voltage controller for every individual panel.  However, unlike microinverters, they don’t convert the power from DC to AC on the spot.  In humorous terms, it’s like a little boy continuously raising and lowering a magnifying glass in the sunlight to create the most focused laser beam possible (to fry an ant or start a fire or whatever).  Every panel will be at the ideal voltage to supply the right amount of current to the string, and the DC string is converted to AC at the inverter which is normally mounted near the electrical meter.  Systems like the Solar Edge 7600 Hybrid inverter require a DC optimizer on every panel.  As we’ve mentioned before, a hybrid inverter is the only kind that will enable your solar panels to keep producing power if the grid goes down.  They are compatible with backup batteries like the LG Chem Resu or the Tesla Powerwall.  DC optimizers are an extra investment, as is a complete hybrid solar system. Those who choose to invest in battery backup can be assured that they are getting a system that will function ideally no matter what shading or other obstructions may block their panels’ output.