Simply put, MPPT is a feature built into inverters to find the “sweet spot” in solar array performance.  Basically, solar panels put out current and voltage.  But it’s the product (V x I) that gives what matters; power.   The challenge is that current and voltage vary based on sun, load and temperature.

Under short circuit conditions, current is max (Isc), but voltage is zero, and V x I is zero power.  On the other hand, if the load is open circuit, voltage is max (Voc), but current is zero, and V x I is zero power.  You need to be somewhere in the middle of the range to have non-zero power.  Based on the physics of the materials used in solar cells, the I-V curve of a solar module is non-linear (i.e, not a straight line).  There is actually a ‘knee is the curve’ that gives the best I x V.

This is illustrated on the I-V curves for my favorite panel; the Canadian Solar 265W module which is taken from the spec sheet.

 

I-V curve for Canadian Solar 265W Panel

I-V curve for Canadian Solar 265W Panel

You can see that the sweet spot (a.k.a., the “MPP”) is really the knee of the curve.  You can also see that the point moves with different sun powers (e.g., cloud cover) in W/m2 and also for different temperatures.  The inverter’s electronics continuously vary the load to track the MPP to always give you the max power under all conditions.

So why should you care? Well, that’s just it- you don’t have to care.  Just know that this marvel of engineering has been built in to all modern inverters.

Just appreciate it!