An affordable LED grow light for off grid operation.
Step 1: Concept
With the current availability of both higher power white LED's and inexpensive DC to DC Converters, it is now possible to construct your own LED grow lights that can be directly powered off of your Solar Panels and keep your plants growing off grid. No other electronics (such as inverters or timers) are needed as you will just use the sunlight as it is available. The concept is simple:
Solar Panel ---> DC to DC Converter---> LED
Step 2: Devices
Both the DC to DC converters and LED's are readily available and inexpensive. The DC to DC converters are the step down types that can take a wide range of input (8 volts to more than 40 volts) and then set a given voltage/current for each LED. The white LED's are a 10 watt chip either as Cool White or Warm White color temperature. We have found that a mixture of these two types of white LED's comes closest to matching the plant photosynthesis curves to allow for good plant growth. The DC to DC converters are set for 8.8 to 9.0 volts to get the best operation of the LED's.
The good news is that the prices for the DC to DC Converter and 10 watt LED have fallen to about $1 (US) each, so that a nice fixture can be fabricated cheaply. Parts can be found on eBay, Amazon, or other electronic supply houses.
Step 3: Mounting
We took the DC to DC converters and LED's and mounted these to aluminum heat sink material. We went a bit overboard with the size of the heat sink, but felt it was better to be larger than needed than too small. Mounted LED's using 2-56 hex head hardware into tapped holes on the heat sink. Used heat sink compound to help with the heat transfer. Got to keep the LED's cool and get the excess heat away from the LED's
Step 4: Wiring
Wiring is very simple. Just keep the + and - wiring straight. It's all DC wiring...just two wires in and out of devices: the plus and the minus.
The pairings of DC to DC Converter and LED can then be paralleled up into a large fixture as shown. Just remember to keep track of the total power requirement of your finished units. Each LED will need 10 watts each and the power required will add with each LED. Keeping track of the power will be important when hooking the lamps to the Solar Panels. Keep the power requirement of the LED's under the power output of the solar panel. We have found that 120 watts of LED's works well with Solar Panels rated for 200 watts
Step 5: End Results
With this setup it is possible to grow plants entirely off grid. With roughly 120 watts of power off of a Solar Panel, you can create 8000+ lumens of light for plant growth. Here's some of our setups. More projects like ours can be found at www.earthineer.com