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November 26, 2003
Internet-Based Control Systems for Building Energy Efficiency

Developing internet-based control systems
to improve the energy efficiency of buildings
is one of the key elements of the recently
concluded High-Performance Commercial
Buildings Systems (HPCBS) research program funded by the California
Energy Commission. This article, the second in a three-part series,
concentrates on lighting.

"Previous research here taught us that lighting controls can reduce lighting energy
consumption in a variety of ways," says researcher Francis Rubinstein of Berkeley Lab's
Environmental Energy Technologies Division (EETD). Rubinstein leads a project to improve
energy efficiency through flexible control systems that make optimum use of natural lighting.

Letting the sun shine in on energy use

The window office — that most coveted of office spaces in the modern commercial building — is also a naturally energy-efficient office, because the occupant needs less electric lighting when sunshine streams in. Most of us prefer natural light to artificially created light anyway, one reason these offices are so desirable.

In California, 40 percent of the electricity used by commercial buildings is consumed by electric lighting, the largest single load in these buildings. Throughout the rest of the country, in spite of variations in climate that make heating a larger overall piece of the pie, lighting always uses a substantial percentage of building electricity.

If architects and engineers designed buildings to use daylighting as an integral part of their lighting system, lighting energy use could decrease substantially. But while there has been much progress in the last 20 years in improving the efficiency of electric lights, bringing daylighting into the fold as an energy efficiency strategy has been more difficult.

"It requires careful integration of lighting and window systems, architectural design that recognizes the importance of daylighting, and a control strategy for turning down electric lights automatically as natural light levels increase," says Stephen Selkowitz, head of EETD's Building Technologies Department.

Of course architects do design buildings that bring in more daylight than the sunless canyons of downtown might suggest, with their massive, blocky structures with deep interiors. Unfortunately systems that automatically dim electric lights as daylight increases are expensive to purchase and install. And because these systems also require careful commissioning to operate efficiently, achieving sustainable energy savings has been an elusive goal.

"We know we can use photosensors to integrate daylight and electric light — and occupancy sensors and scheduling to reduce lighting of unoccupied spaces," Rubinstein says. "A third strategy is giving occupants control of their local lighting. Together these three methods can reduce lighting energy consumption substantially, even compared to a state-of-the-art, efficient lighting system with electronic ballasts."

IBECS is a practical networking system that takes advantage of a building's existing IT infrastructure to control off-the-shelf lighting components and other building equipment through the internet.

Rubinstein, his colleagues Eleanor Lee, Dennis DiBartolomeo, Jim Galvin, Judy Jennings, and Pete Pettler of Vistron, a private-sector partner in the project, set out to develop IBECS, an "integrated building equipment communications network" that would allow building lighting and envelope systems to respond automatically to changes in occupancy, daylight levels, and energy costs — while at the same time giving occupants more control over their workspace environment. Their goal is to achieve, by 2015, lighting-related electricity-consumption savings of 59 percent in new construction and 43 percent in major retrofits.

In developing the IBECS network, LBNL researchers applied recent developments in networking techology known as embedded device networks. Microchip manufacturers can now produce embedded devices that incorporate a microprocessor, unique IP address, controller, and simple local-area-network communications at a very low cost per control point. These devices are "embedded" into electronic components like lighting ballasts, which adds a modicum of intelligence to components while allowing them to communicate digitally over a simple network. The IBECS project applies a general-purpose embedded device network from Dallas Semiconductor/MAXIM to building lighting and envelope controls.

"By designing IBECS so that it works with existing products, such as dimming ballasts, it is much easier for lighting manufacturers to adopt the technology to their advanced product lines," says Rubinstein, so he and his team developed the IBECS network to be compatible with existing lighting and envelope components. In addition to hardware development, the researchers worked on control algorithms that would manage the process of taking input from photosensors and deciding when to dim lights, and by how much.

Another area of the work, led by Berkeley Lab's Eleanor Lee, focused on daylighting. Her group used the IBECS networking and control devices to develop a system that allows facilities operators and end-users to control motorized shades and switchable, variable-transmittance, electrochromic windows — an advanced window now in commercial development that darkens and lightens when a small electric current is applied.

IBECS for Lighting Control

"We developed network control hardware," says Rubinstein, "and we built a working system in our office building at Berkeley Lab to test it out." Rubinstein and Pete Pettler of Vistron developed IBECS ballast network interfaces for controlling dimming ballasts (part of fluorescent lighting systems) from the network, an IBECS-enabled wall switch to fit in a standard wall box, provide bi-level switch control, and an IBECS-ready environmental sensor capable of measuring key environmental variables — occupancy, light level and temperature.

An IBECS ballast/network interface incorporating a digital potentiometer dims a 0- to 10-volt ballast over the ballast control circuit.
Above: An IBECS addressable power switch, embedded in a standard wall switch, allows an operator to turn the switch off remotely through IBECS.
A prototype workstation multisensor measures light levels, temperature, and occupancy, and sends digital data to the IBECS network.

Rubinstein and his team tested the system successfully in a fully-configured IBECS network installed in a building at Berkeley Lab. The demonstration network includes all the IBECS-compatible technologies they developed for lighting, automated shades and Venetian blind systems, sensors and power measurement. Office workers can control their overhead lights and motorized blinds by internet. The network is a demonstration site for potential industrial partners to evaluate the technology. Potential partners will be able to observe the system's performance using a secure web link.

"Adding digital smarts to analog electronics products has been a mainstream business goal for many companies in this field. IBECS technology presents new business opportunities, markets and employment potentials for these companies," says Rubinstein.

The team is working with two ballast manufacturers who have already decided to use IBECS technology in their products. A digital-lighting-network products manufacturer will embed the IBECS ballast network interface in their network connector, and another firm will put IBECS technology in occupancy sensors and daylight control photosensors.

IBECS for Daylighting

Eleanor Lee and Dennis DiBartolomeo applied the IBECS components to controlling dynamic window systems for better lighting-energy efficiency. The networked control technology can regulate direct current-motorized Venetian blinds or roller shades, alternating current-motorized blinds or shades, and electrochromic windows. The first full-scale demonstration in the U.S. of an integrated electrochromic window and dimmable fluorescent lighting system was conducted in a federal office building in Oakland, California, with more tests continuing in a new laboratory at Berkeley Lab.

Interior view of test room on a partly cloudy day. The electrochromic windows are in the clear state under diffuse light conditions (left). When sun enters the window, the electrochromic switches within five minutes to its fully colored state (right).

"The commercial prototype electrochromic window and lighting system reduced total energy use significantly," according to Lee. "Our monitored study proved that perimeter zone daily lighting energy use can be reduced by 6 to 24 percent when compared to a standard window transmitting 11 percent with the same daylighting control system. Simulations indicate that total primary energy use" — cooling, heating, and lighting energy — "can be reduced by 14 to 30 percent in all climates compared to advanced spectrally-selective, low-emissivity windows with no daylighting controls in a typical commercial office building. Bench-scale testing also showed that the electrochromic IBECS network interface operated reliably."

Electrochromic windows and lighting systems are controlled in real time to meet an illuminance range and to control solar heat gains and glare. (A) On a cloudy day, the electrochromic window is at its maximum transmission level, and the lights are at minimum power. (B) When the sun comes out from behind a cloud, the window starts to darken to control solar heat gains and glare. (C) After about five minutes of sunshine, the electrochromics are fully darkened and the electric lighting has been increased slightly to provide sufficient interior light.

The team also successfully tested the IBECS interface on motorized Venetian blinds. Using an off-the-shelf software package, they created a virtual control panel from which they could control the tilt, raise and lower functions of the blinds on west-facing windows in an open-plan, occupied office. The system has been working reliably for more than a year.

A Venetian-blind system at a Berkeley Lab office building is equipped with a "virtual instrument" panel for IBECS control of blinds settings.

Reducing Energy on Demand

Ultimately, the tools developed in this research will go beyond saving energy — they could also help building operators respond to electricity grid emergencies, and to money-saving opportunities when energy costs are high. Many states, including California, now have or are looking seriously at real-time electricity pricing, to reflect the true cost of generating power as demand rises and falls throughout the day.

"Building operators, among others, will be able to use this technology to reduce their power consumption when the real-time price of electricity starts to rise," says Rubinstein. They can also respond quickly to shut down energy-consuming equipment when the electricity grid is threatened by outages or other reliability problems."

If IBECS technologies are installed in 20 percent of available building stock in California, and assuming that the energy saving is about 40 percent, the savings potential to California businesses could be 2.4 Terawatt-hours(trillion watt-hours)/year, or $250 million in avoided energy costs. For the U.S. as a whole, although technical estimates are not available, the savings could be an order of magnitude higher.

Personal control of lighting in a worker's individual space also makes the office a more pleasant place — it might reduce the number of complaints building staff have to deal with, and free up their time for long-term maintenance. Finally, the researchers believe that writing control software for building systems is a frontier industry that could generate new software jobs.

In the next issue of Science Beat, the third and final article in this series will examine the results of research on improving the air quality and energy efficiency of temporary classroom structures found in schools throughout the country.

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