Apr 10, 2018

With every last watt being squeezed out of lighting, will codes even be needed?
By Willard Warren

Has the adoption of LEDs and other solid-state devices influenced the mechanical design of buildings beyond the energy savings in lighting? Let’s look at the factors involved. Architects, engineers and lighting consultants who design buildings now come from all over the world and they employ innovative energy-saving systems being used worldwide. Our DOE is the strongest factor in the U.S. for promoting energy conservation codes, not designers, while state and municipal legislators decide which versions of the many energy codes available get enacted into law. But the compliance of energy codes is left to the local authorities having jurisdiction (AHJs). In-state public service commissions regulate the distribution of electricity by utilities under a monopoly in the areas they serve. Traditionally, building codes establish a minimum level of compliance for public safety, not for design. Until the early 1950s, incandescent sources with efficacies of 10 lumens per watt prevailed, and the electric code required that the main feeders allow 6 watts per sq ft in feeder cable capacity just for lighting in new non-residential buildings.

But as technology advanced, fluorescents and HID sources with efficacies of 50 lumens per watt became dominant, and the feeder capacity allowance for lighting was lowered to 3.5 watts per sq ft. Current SSL sources get 100 lumens per watt in efficacy; they are now the statutory lighting source that must be used in the lighting power density (LPD) calculations in the ASHRAE 90.1-2016 energy code. And cooler colored LEDs with 200 lumens per watt will soon be available. Add to that, if some daylight is brought indoors and simple lighting controls are used, 0.5 watts per sq ft will be sufficient to provide the recommended illuminances in the IES Handbook for visual task performance. With the advent of renewable sources of sun and wind for the generation of electricity, we will soon approach net-zero energy for lighting.

In California, under its Title 24 energy code, when the LPD in a non-residential facility drops below 0.3 watts per sq ft, the lighting energy code may be ignored under certain conditions. Additional energy savings are being reaped through more efficient electric motors and innovative HVAC ventilation systems, which portend that an alternate means of generating and distributing electric power may now be economically justifiable. One suggested solution is the use of microgrids that generate electricity onsite, store enough electricity when not needed by the facility and eliminate the need to be on the grid. That’s happening now in Puerto Rico where 75 percent of the grid was destroyed by two hurricanes, never to be restored because it is being replaced with solar panel generators and battery storage.

Furthermore, regulated utilities are reluctant to extend towers and power lines past the existing “end of the line,” because the ROI is long, and it’s the weak link in system resilience, which is critically important to grid users. A report by the Rocky Mountain Institute in January concluded that regulators have to consider balancing the monopoly franchise that utilities enjoy with the competitive marketplace for a new electric era to emerge. This includes whether or not utilities should be allowed to own microgrids and distributed energy resources. But new construction only adds about 1 percent to the existing infrastructure annually and SSLs are now being used for upgrading lighting in older existing buildings, many of which still have incandescent, fluorescent and HID legacy light sources. Where daylight has also been introduced liberally into interiors, plus sophisticated lighting controls, and photovoltaic rooftop panels installed on low rise buildings, the demand level for electricity has lowered significantly.

California will probably be the first state to set the example on how to encourage the use of regulated and/or non-regulated microgrids, allowing other states to follow its example, and hopefully, render lighting energy codes unnecessary. We now have some experience with on-site generated 48-V DC power from renewable sun and wind sources for existing buildings, not only to directly drive LED lighting, but also DC computing equipment, controls and brushless DC motors, and in addition provide the segregated AC and DC electrical systems, and their respective electric panels to allow us to measure and verify usage data for benchmarking different electrical systems. Changes are coming and the sharp drop of 90 percent in lighting load density over the last 50 years has certainly helped make it easier to justify those changes economically.


Willard Warren

Willard Warren

Willard L. Warren, PE, LC, Fellow IES, DSA, is principal of Willard L. Warren... More info »