Although LED drivers for commercial grow lights are powered by utility AC power, LED chips are run by DC. Typically, AC is converted to DC, then converted to high-frequency AC and then converted to a regulated DC to power LEDs. The efficiency of LED drivers ranges typically from 90% to 95%.
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 95% 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. This can be reduced to 2% to 3% if the LED lights are driven by DC power directly. Saving 12% to 13% waste energy is significant. It will reduce cost and space for solar panels proportionately.
Raw DC power from solar panels could be fed into a high-efficiency DC to DC converter to power LED chips. There is another benefit of running LED chips with a DC driver. It is cheaper and smaller in size than AC LED driver.
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 example will make it more clear:
- 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 but within useable sunlight hours: 200W
- 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 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 1) High voltage DC: high voltage DC power from solar panels with high voltage rectified DC power from AC power source and 2) 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.