Powering LED Grow Lights with Solar DC

What is an LED Driver?

LED chips need DC power to operate. The electronic device that provides DC power is called an LED driver. For commercial grow lights LED drivers are typically powered by utility AC power. Here’s how it works: AC is converted to DC, then converted to high-frequency AC and then converted to a regulated DC to power LED chips.

LED Driver Efficiency: 90% to 95%

The efficiency of LED drivers ranges typically from 90% to 95%. In other words, 10% to 5% electrical energy is wasted in the form of heat.

Solar Inverter Efficiency: 95% to 97%

Solar panels produce DC power which is converted to AC power by means of a solar inverter that has a power conversion efficiency, ranging from 93% to 97%. Therefore, LED grow lights that are powered by solar panel-based renewable energy during the day, solar inverters and AC LED drivers combined, can waste as much as 15% energy in the form of heat.

DC powered LED drivers save over 12% energy and Cost Less

When LED lights are driven by DC power directly, it can save over 12% electrical energy by eliminating AC and Inverter circuit losses. This is significant. It will reduce cost and space for solar panels proportionately for controlled environment agriculture such as ZEFAB.

How it Works?

Raw DC power from solar panels could be fed into a high-efficiency DC to DC converter to power LED chips. DC to DC converters is much cheaper to make and smaller in size than AC LED driver.

Cloudy and Off-Peak Hours Operation

What happens when solar panels cannot supply power when operating outside of peak hours or on a cloudy day. Under these conditions depending on the available DC power, only a certain portion of the LED grow lights can be operated by DC power and the remaining lights with AC power.

The following is a specific example:

LED Grow light power rating: 100W
Number of lights: 10
Total power needed for 10 lights: 1,000W
Useable sunlight hours per day, 8 am to 4 pm: 8
Peak hours: 4
Solar panel average peak power generation capacity during peak hours: 1,000W
Solar panel minimum power generation capacity outside of peak hours butwithin useable sunlight hours: 200W

Therefore,

Number of LED lights can be operated with DC power during peak hours: 10
Number of LED lights can be operated with DC power outside of peak hours but within useable sunlight hours: 2

How to Mix DC solar Power with Utility AC Power

How many LED lights will be driven by AC utility power and what number of LED lights can be operated with DC power outside of peak hours but within useable sunlight hours are detected and operated by mixing by means of, for example, a transfer switch as follows:

High voltage DC: high voltage DC power from solar panels with high voltage rectified DC power from AC power source.
Low voltage DC: Low voltage DC power from solar panels low voltage DC power from a DC-DC converter after the rectified DC.

These are shown in the following block diagrams, respectively.