Lighting it Right with Smart Dust
The next time you walk into a sunlit, empty meeting room or office, notice whether the lights are on. If the answer is yes, you might wonder why someone-or some automatic system-hasn't turned them off to save energy.
An inexpensive wireless system that can do just that is being developed, by Lawrence Berkeley National Laboratory (Berkeley Lab) researchers collaborating with industry. This new lighting management network is made up of tiny wireless sensors called "motes." The system can dim electric lighting in response to daylight levels, can easily be retrofitted into existing lighting systems, and could save hundreds of millions of dollars annually in lighting energy costs.
Why Dim the Lights?
Lighting of commercial buildings in the United States currently consumes about 3.7 quadrillion British thermal units (Btus) of primary energy a year, equivalent to the output of more than 175 modern power plants. According to Berkeley Lab estimates, if buildings in the U.S. could automatically dim electric lights in daylit spaces, and building occupants could manually dim local lighting according to preference, the energy savings could amount to more than half a quadrillion Btus per year - about 14 percent of total annual energy use for lighting in commercial buildings.
However, the effective use of these strategies requires a smart-building infrastructure - properly located sensors to measure how much daylight is available in a room, lighting fixtures that can respond quickly and reliably to on-demand user control, automated systems with software-based control algorithms, and a network to tie all of these devices and systems together.
First-Generation Daylighting Technology
The wireless lighting management solution that is being designed today is the second generation of lighting sensor and control technology. The first generation, which depends on a wired network, is just now on the verge of appearing in the marketplace, decades after scientists first recognized the large potential for saving energy by taking advantage of daylighting.
Francis Rubinstein, an EETD scientist, has been applying networking systems to daylighting and lighting control problems for years. Starting in 2000, Rubinstein's team of researchers at Berkeley Lab began developing an integrated-building equipment system (IBECS) to allow facilities managers to automatically control devices such as lighting in commercial buildings, using a computer workstation and a wired network.
The team developed a set of prototypes, including a digital interface for dimmable lighting fixtures, a light sensor, switches, and a user interface for controlling the network from a personal computer. Their research demonstrated that automated network control of lighting systems could be cost effective in new construction and major renovation projects where is it relatively easy and inexpensive to run the necessary wiring.
IBECS was recently expanded to allow control of off-the-shelf Digitally Addressable Lighting Interface (DALI) ballasts, which are available in the marketplace now. This enhancement of IBECS allows facilities engineers to customize control systems for their buildings using commercially available lighting products.
If advanced controls are to expand from the new construction and remodel market into the much larger existing-building market, control wiring would have to be eliminated altogether, and the effectiveness of wireless solutions would have to be demonstrated in real settings.
Dust Settles on the Problem
Rubinstein and David Watson of EETD have been working with Dana Teasdale of Dust Networks and Steve Purdy of ELB Electronics Inc. (formerly SVA Lighting Design) on a Department of Energy-funded research project to develop wireless networking technology that can effectively take advantage of daylight to reduce electric lighting energy use in buildings.
"The reason we began looking at wireless technology for lighting control is that wiring and installation costs are barriers to deploying control systems in existing buildings," says Rubinstein. "Existing commercial buildings use over 95 percent of all electricity for lighting, but it is not cost effective to add control wiring to the ceiling to control lighting loads. To capture the energy savings possible from daylighting and other strategies in these buildings requires technology that is reliable and inexpensive enough to be retrofitted to commercial buildings."
Dust Networks provides a wireless mesh networking technology consisting of "smart motes," tiny sensors that create a low-power, connected network of sensors, control devices, computers and other related devices. The company was founded by in 2002 by a team including Kristofer Pister, a professor of electrical engineering and computer sciences at the University of California at Berkeley, who first coined the expression "smart dust" as a way of describing the tiny, expendable sensors that are used in the network.
Smart-mote technology is now finding its way into commercial and industrial applications for making buildings more comfortable, reducing energy costs, and optimizing materials and energy use in industrial processes. Wireless motes can be used in a wide variety of applications to control and monitor systems and processes. Researchers expect them to be widely used to enhance energy efficiency and environmental comfort in buildings once these products appear on the marketplace-which could be in just a few years.
Components for Smart Wireless Daylighting
The project team developed several components for lighting control using Dust Networks' SmartMesh™ technology. These include an analog control module and "mote-integrated dimmable ballasts" (MDBs), which will work in existing lighting systems.
The ballast is the unit in a fluorescent lighting system that provides power to the fluorescent tube at the proper frequency. Located in the lamp's housing, the ballast is a plain metal box containing electronic circuitry. Dimmable ballasts allow lights to be tuned continuously from full brightness to a very low level (usually about five percent of total brightness), to save electricity when less light is needed or to reduce lighting glare.
Berkeley Lab researchers worked with the lighting industry during the 1970s to develop and test the first electronic ballasts as replacements for the less-efficient magnetic versions that prevailed in the market at the time. Today, energy-efficient, nondimming electronic ballasts are common off-the-shelf products, accounting for a majority of the market share of fluorescent lighting ballasts.
Rubinstein's team built prototype MDBs, standard dimmable ballasts that embed Dust Networks' mote technology as an integral component. An antenna on the mote extends outside the fixture, allowing the building control system to communicate wirelessly with that particular mote.
No Wiring Makes the System Cheaper
With mote-embedded MDBs, no low-power wiring is needed, which reduces the cost of installing the control system and makes the technology easier to incorporate in existing buildings. Facilities staff can replace old ballasts with new MDBs over time, adding economical lighting-control capability to the building during routine maintenance.
The lights are controlled wirelessly by the motes, which receive instructions from Dust Networks' SmartMesh Manager, a single-board computer that connects the entire network of motes to a PC running lighting-control software.
"The cost of wiring in advanced lighting systems has traditionally been a major economic impediment to their widespread adoption. The use of wireless technology substantially reduces the installed cost of these systems," says Watson.
An Environmental Sensor Tool
The research team has also developed a wireless environmental sensor that measures the lighting level in a room, tells whether the room is occupied or empty, and transmits this information to the control system through a mote. The multisensor version of this device also contains a temperature sensor to help manage the room's heating and cooling needs.
With the initial phase of technology development completed, the research team will now turn its attention to developing more advanced, second-generation systems and testing these devices in buildings.
Preliminary analysis of the costs and benefits indicates that installing the wireless control system in an existing 16,000-square-foot building costs about 30 percent less than installing a comparable wired system. The wireless system will pay for itself in three years.
If tests of the wireless technology in buildings prove successful, energy management and control in buildings will join the wireless revolution, and the marketplace will have a new wireless solution for saving energy in commercial buildings.
For more information, contact:
- Francis Rubinstein
- (510) 486-4096; Fax (510) 486-4089
- David Watson
- (510) 486-5562; Fax (510) 486-4089
This research was sponsored by the California Energy Commission's Public Interest Energy Research program.
Dust Inc. (Now Dust Networks, April 2008)