Asset management / lighting
Making the switch3 December 2012
This summer, Palo Verde replaced some sections of lighting with 130 new energy-saving LED fixtures. And, as LED prices continue to fall, more nuclear power plants are likely to follow suit.
The Palo Verde nuclear generating station, located near Phoenix, Arizona comprises three Combustion Engineering pressurized water reactors with a combined capacity of almost 4000 MW.
As well as keeping the lights on in Arizona, Palo Verde has lights of its own to maintain, which can come at a significant cost. This could be what has driven the plant to turn to LED (light-emitting diode) technology. US-based lighting firm Albeo Technologies recently supplied 130 new LED light fixtures to Palo Verde, including primarily 98 high bay fixtures, 30 sealed fixtures and three linear fixtures. The switch to this LED technology at Palo Verde is expected to reduce maintenance and electricity costs and offset fixture and installation costs within the next two years, according to the vendor. Arizona Public Services, operator and largest stakeholder in the plant along with six other utilities, told NEI that the project is still ongoing and declined to comment.
“Companies are always looking to improving their lighting…whether it be for energy efficiency, productivity or for maintenance reduction,” says Jeff Bisberg, co-founder and CEO of Albeo, which designs, specifies, manufactures and assembles components and sub-assemblies at its 35,000 square foot facility in Boulder, Colorado. Its lights are tested, inspected and certified to meet national electricity code standards for electrical and thermal safety, and for low-electromagnetic emissions. Although the company does not offer traceable components, it does offer a five-year guarantee.
“There are a couple of key factors that are pushing businesses towards LED technology; one is efficiency and the other is maintenance,” says Bisberg.
Albeo estimates that LEDs are typically 15%-35% more efficient than fluorescent and high-intensity discharge (HID) lighting technologies, although it says that the latter two are highly variable in wattage and lumen output. The highest LED efficiency is currently around 95 lumens per watt (lm/W). Efficiency is constantly improving, says Bisberg, noting that the US Department of Energy predicted in its August 2012 Solid State Lighting Road Map that LED efficiency will more than double by 2020.
How customers spend the energy savings created by LED lights’ greater efficiency depends on the project goals, Bisberg says; many install lower-powered lights than before to save electricity, unless the area has been underlit in the past.
Albeo’s LED high-bay fixtures comprise multiple 120 W modules (the power is limited by thermal dissipation). Each module is capable of delivering 11,000 lumens of light (120 W x 95 lm/W). Lights run on voltages from 120V-480V, and on both 50 Hz and 60 Hz AC. Inside each module, 24 LEDs are connected in series and in parallel to optimize voltage and current. Each LED requires only 3V to turn on. At the fixture level, modules are driven in parallel at constant voltage. The LEDs come on instantly, although the fixtures (depending on power supply) can take up to a couple of seconds to start up. Albeo says it is working with vendors to minimize that delay.
The second factor driving the shift towards LED technology is longer lifetime and the lack of maintenance (there is none, although individual modules in the fixture can be replaced).
LED lifetime is measured and calculated from standardized tests (Illuminating Engineering Society of North America LM-80-2008) performed at nationally-certified laboratories and extrapolated with a standardized procedure (IES TM-21-2011). “The most critical test is the in-situ temperature test that shows the maximum temperature the LED will hit and is used in the TM21 calculation,” Bisberg says. In simple terms, the higher the temperature, the shorter the life.
An LED degrades by very slowly dimming over time, with the level of degradation depending on the actual amount of use. (The installation of motion sensors increases lifetime). The average life expectancy for an LED is around 100,000 hours, Bisberg told NEI. This compares with a life expectancy of about 10,000 hours for a fluorescent fixture. However, these standards measure life in different ways. End-of-life for a fluorescent bulb is the time for 50% of lights in a test sample to fail; but end-of-life for LEDs is when test lights dim to 70% of original light output.
On top of longer lifetime, LEDs are inherently more robust than traditional lights, which have filaments or glass that could break through shock or thermal cracking, according to Bisberg. LEDs have two categories of failure modes: components and assemblies. Generally failure is loosely linked to architecture, Bisberg says. Components fail because of physical damage, electrostatic discharge or backwards assembly. Assembly failures occur because of shorts, opens, or physical damage.
The total cost of the fixtures is the major factor holding back the widespread implementation of LED lighting, Bisberg says. LED lighting currently costs around three times that of a conventional fluorescent fixture.
But price parity is not needed for the switch, Bisberg says, likening it to the transition from cathode-ray tube to flat screen televisions. When the up-front cost falls to under two times the cost of traditional lighting, which may be in the next few years, the balance could tip in favour of widespread adoption of LED technology.
This article first appeared in the November 2012 issue of Nuclear Engineering International magazine.