LED Lights in Off-grid Applications

Introduction

At first glance, AC operated LED seem the perfect choice for AC off-grid systems. Their efficiency can reach 120-160 lumen per Watt (as per 2017), their life expectancy is claimed to be between 20'000h and 50'000h, largely exceeding in both regards any competing technology like fluorescent, sodium arc or metal halide. Compared to the latter two, LEDs also are much more scalable (from few Watts to stadium lighting) and demand less careful operations.

Issues with LED lights in AC off-grid applications

Any relatively small amount of LED lights in an inverter based off-grid system (small meaning total power consumption of the LED lights as compared to the total inverter power) poses normally no issues. But since AC LED lights are equipped with an electronic AC to DC converter, their current consumption is not sinoidal (resistive) at all. Often, the necessary energy needed to operate the light during a 10ms halfwave (@50Hz)is drawn in a short current peak, usually at the beginning of the halfwave. After that short peak, for the rear of the halfwave, the power electronics does not draw any more current from the AC supply.

Even worse can be the effests of the inrush current of the AC-DC converters. This becomes relevant, when one is building large lighting systems as off-grid application, where most -if not all- of the loads are LED lights.
Usually, the desired mode of operation of such systems is, that all lights are switched on at the same time, usually timed by a timer or a luminosity detector.
Thus follows, that often all of the LED lights should be switched on at the very same moment, multiplicating the problem of inrush current by the number of lights installed.

References:

Excellent test protocol of LED lamps, at different starting angles:
http://www.olino.org/us/articles/2013/10/22/inrush-current-for-led-light-bulbs