Lumens/Watt

Samplings of a table entitled Efficiencies of Illuminants from the CRC Handbook of Chemistry and Physics 59th Edition

Lamp Efficiency	lm/lamp W (Lumen pre Watt)
Tungsten filament, gas filled (3200 K)	33.5
Flourescent (cool white) Rapid start (T12)	78.8
Mercury vapor (E-37) Deluxe White	56.3
High-pressure sodium (Lucalox) 400 Watt	125.0
Electric arc, High intensity	31.4

When it comes to energy efficiency you just can't beat good ol' high voltage AC. Electrochemical processes such as in car batteries are anything but efficient. Batteries are good for backup power, but if efficiency is the name of the game better keep them out of the loop most of the time. The light panels can be wired to run off either 120V AC or 12V DC. The power levels involved are too high to consider running off low voltage. A 50 kW light would require over 4000 amps at 12 Volts. You don't use limiting resistors in the design, the LEDs are just strung together until they form the appropriate voltage drop. For example I am using a typical LED with a Voltage drop of 2.2V at 20 milliamps, so to come up with say 12V you would string about seven of them together. They will operate within a wide range of voltage, although if you want to prolong the life of the LEDs don't exceed their rating for too long.

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