Carnegie Mellon reports that DC power is cheaper for LED lighting
27 Apr 2012
Researchers at Carnegie Mellon University have published a paper evaluating the cost of energy for lighting systems and concluded that a DC grid is far less expensive powering LED lighting.
The debate over AC or DC power grids will apparently continue into a third century as researchers have documented significant energy savings potential in commercial buildings when LED lighting is powered by a DC grid. Carnegie Mellon University researchers say DC power could save $24,000 a year in a 48,000-ft2 building lit by solid-state lighting (SSL).
The university team published the research in the scientific journal Energy Policy. A DC grid was not identified as an advantage for fluorescent lighting, but the advantage for SSL is clear. Moreover in a building equipped with solar cells that generate DC power, the savings escalate another $5000 per year.
The savings documented by the researchers is over and above the baseline energy savings attributable to LED-based lighting. The documented savings are purely attributable to the efficiency of the power grid and the power conversions needed to drive the lighting.
In reality, the report is hardly a surprise. Fluorescent lighting was designed for AC-powered applications. LEDs require an AC-DC conversion, and generally a second, constant-current DC conversion to operate from the AC line. Every conversion wastes energy and a DC grid eliminates a conversion stage. And in the case of the additional savings in a solar installation, those DC solar cells also minimize conversions.