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LD+A The Magazine of the Illuminating Engineering Society of North America

Lighting Research & Education

Solid-State Lighting in the Office Environment

Demonstrations at the NRC-IRC lab showcase three systems for testing LED viability

BY ERHAN DIKEL

T he lighting industry and academia are investing millions of dollars to develop solid-state lighting (SSL) technology, especially LEDs. Most of the effort has focused on the technology and its costs. However, there is one major question largely unanswered, and its answer will determine the success or failure of this lighting revolution: How ought we to motivate the end-user to adopt SSL technology? No matter how energy-efficient SSL is, if there is an initial cost premium it must offer a remarkable functionality that cannot be achieved by fluorescents.

Our group at the National Research Council of Canada, Institute for Research in Construction (NRC-IRC) has been exploring these questions with laboratory experiments and field demonstrations. The project began in 2008 with a design charrette at which lighting designers, industry leaders and NRC researchers imagined the future of SSL for offices. This led, through iterations, to the prototypes and field demonstrations described here, which focus on color and controllability features that SSL can provide but other technologies cannot.

LED DEMONSTRATIONS
We designed and built two types of luminaires to display novel ideas such as using LEDs to create an artificial skylight and as part of a building’s emergency system in real offices. We are now testing their performance on the bench and we will commission them in an office building this fall. After installing them, we hope to share our experience with a follow-up article.

Although LEDs, with their small form factors, allow us to design flexible and low-profile luminaires, we kept luminaire designs as simple as possible with the most common luminaire form in office spaces to fit into existing ceiling grids: 1-by-4 and 4-by-4 ft sizes. We carefully adjusted the light distribution by using reflectors and diffusers, so they look like regular fluorescent lensedtroffers and the novel light source is not obvious. Our focus is on how people respond to the light effect and not to the knowledge that the source is an LED.

Artificial Sky Demonstration. Access to windows and the knowledge of exterior conditions is highly prized, but many buildings have large areas where this is not possible. We designed an artificial sky panel specifically for these spaces. Connected to a webcam elsewhere, the artificial sky can inform occupants about outdoor conditions as if the space had a real skylight. Some companies install LCD panels to play high-resolution movies of recorded skies. However, their light output is not high enough to be a light source. Our panel, with a higher light output, is of value for the occupants and is a potential energy-saving strategy for the building managers.

Figure 1.

The 4-by-4 ft panel houses 289 individually controlled Philips Color Kinetics iColor LMX RGB LED nodes with transparent lens covers (Figure 1). The Barrisol membrane acts as a diffuser, so the individual LED nodes do not present hot spots. The distance between the LEDs and the diffuser is critical: For some demonstrations, we need to see the individual pixels, whereas for others the light should perfectly blend for a natural effect. The working principle of the demonstration is straightforward: A camera captures the actual sky and by using image-processing software, the LED panel plays back the image. This panel also has the capability to display text, images or other valuable information for the occupants. For instance, in case of a fire, the individually controlled LEDs can strobe in red and show the direction to the nearest fire exit to the occupants with a scrolling arrow. This is a valuable option for people with hearing impairments.

A control rack houses all the drivers and control equipment such as DMX communication devices and a computer. It also acts as an interface for the demonstrator to push the preset buttons to trigger shows. The total power consumption of this luminaire, including the electrical components in the control rack is 420 watts. The light output of the luminaire is 2,400 lumens when the three channels of each LED node are set to maximum light output. The LEDs used in this demonstration were not designed for general illumination, so it does not offer an efficacious solution. However, future iterations should be able to reach to higher efficiency.

The artificial sky luminaire will be installed in a windowless cafeteria which is located at the basement of an office building. The occupants of the space will spend time under that panel to refresh and eat their lunches during the breaks. We will conduct surveys to collect data about occupant’s impressions about the light source.

Figure 2.

Rectangular Luminaire. We will install eight rectangular LED luminaires in the main circulation area of an existing office building which is currently lit by 1-by-4 ft fluorescent troffers with prismatic lenses (Figure 2). The LED luminaires match with the rest of the luminaires in the ceiling layout in size and appearance. Among other simulations, the main purpose of this installation is to demonstrate the emergency lighting idea, so we specifically chose the location to be near a fire exit. The rectangular luminaires will be installed end to end to form a single row. In normal operation these luminaires will deliver white light, but in an emergency they will switch modes, allowing people to find the fire exit by following a red light, scrolling from one luminaire to another. It is impossible to have this level of flexibility and resolution with fluorescent lighting.

Each luminaire has seven DMX-controlled Philips Lexel DLM 1100 RGBW LEDs, which enables us to create different lighting effects by adjusting the intensity of one of the three RGB channels and tune the spectral power distribution. Our software can control red, green and blue channels, but a built-in sensor inside the LED engine automatically adjusts the white channel to guarantee a constant light level and color quality. The total power consumption of each luminaire is approximately 200 watts with an approximate light output of 3,500 lumens.

The 1-by-4 ft luminaires will be in a busy circulation area. Office workers won’t spend too much time under the light, but they will experience the quality of light and the fire exit information during drills or demonstrations.

Figure 3.

Portable Demonstration Booth. Full-scale demonstrations of novel lighting concepts are expensive and can reach only a limited audience. We decided to make a 1/10 scale model of an office space entirely lit by 150 Philips Color Kinetics iColor LMX LED nodes to demonstrate various control concepts (Figure 3). Currently under construction, we will install the model chamber inside a portable booth, which will allow it to be carried it from one space to another. The design of the model is minimal, but realistic. The walls will have openings like windows, fire exit and entrance doors to support the scenarios. There will also be defined sitting areas with furniture and accessories such as bookshelves and plants.

The demonstration booth will support several scenarios such as the artificial sky and emergency lighting, as described above. There will also be interactive demonstrations that use a 1/10-scale human figure. For example, discussions in our initial design charrette suggested a “following light” idea; a computer program controls the LEDs in the model chamber with the signals received from 105 magnetic switches installed on the base of the model. The magnet underneath the figure triggers the switches when the doll moves over them. The light level of LEDs above and in front of the figure will be higher than the level elsewhere in the space. When the figure moves, the area with higher light output follows it. We envision that in the near future buildings will use smart ID badges or multiple motion sensors to identify occupants, and to tailor lighting to their preferences and location.

The “medical alert” idea demonstrates the LEDs’ reaction if the figure falls, simulating a person in trouble and needing help. In that case, the system senses the position of the figure and activates the LEDs in a specific pattern to indicate the emergency. This could help people and paramedics to locate the sufferer as fast as possible; together with the smart ID badge, it would provide more information than is currently possible.

The booth may be used as a portable human factors laboratory, enabling us to collect data from people observing different lighting scenarios in the scale model.

October 2011