Monday, September 26, 2011

DOE Gateway report indicates viewers prefer LED-illuminated artwork

DOE’s second study on track lighting using LED lamps as replacements for halogen bulbs showed that in addition to energy savings, viewers preferred LED-illuminated artwork.

The US DOE has published a final report from a retrofit of track lighting used to accent a gallery exhibition at the Jordan Schnitzer Museum of Art (JSMA) in Eugene, Oregon. The project involved the replacement of fifty-four 90W halogen narrow flood lamps with 12W LED lamps, allowing energy savings of over $500 per year and a payback period of 9 years.

This is the second such project this year, with the first Gateway study reporting superior quality of light and lower energy use using 12W LED lamps relative to 15W and 23W CFLs and also 90W halogen lamps. This new study is similar in that 12W LED lamps were again tested. Fifty-four lamps were installed in January 2011 in the Coeta and Donald Barker Special Exhibitions Gallery to illuminate the digital photographs from artist Chris Jordan.

Energy use and ROI

The 54-lamp LED system uses 14% of the energy and offers a ten times longer lifetime than the halogen lamps. The present value life-cycle cost of the LED system was $12,124 compared to $16,670 for the halogen system.
Energy use for the 54 track heads LED lamps was estimated at 1403 kWhr per year compared to 9851 kWhr with the estimated number of halogen lamps required for the same lighting effect (44 lamps). At the electrical rate of $0.06 per kWhr, which is low because of the local hydroelectric power source, this translates to an estimated savings of $506.84 per year for the gallery.

Simple return-on-investment (ROI) occurs in year 9 of operation at the $0.06 per kWhr rate. At $0.10 per kWhr, simple payback drops to less than 6 years; at $0.15 per kWhr, payback occurs in less than 4 years.
Payback rates are expected to improve further as the industry works to reduce the price of LED replacement lamps.

Preference for LED-illuminated art

In this study, a separate comparison was set between the museum’s standard halogen lamp and three LED replacement lamps from three different manufacturers to asset the acceptability of LED lighting. In the nearby Gordon Gilkey Study Center Gallery, sets of similar art were mounted on a single gray wall, including an oil painting, a black-and-white photographic print, and a color-checker card. Every set was illuminated with one of four lamps, the halogen, one of the LED lamps, all with color temperatures ranging between 2638K and 2821K.
Artists, museum staff and visitors answered a survey regarding smoothness of light pattern, appropriate warmth/coolness of light for the art, color rendering, visual clarity and suitability of the lighting for the artwork.

The artists and museum staff preferred a different LED lamp than the visitors did, but neither party preferred illumination of the halogen lamp. Observers said they appreciated how the LED lamps improved the ability to see blue colors.

Interestingly, the rank order of preference of lamps for color rendering did not correspond to the rank ordering of lamp CRI. This indicates that a new or modified color rendering metric may be needed for lighting designers who are illuminating artwork in galleries or similar environments.

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