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CEBus aims to cut power use
Power companies could turn off home appliances on a rotating basis
By Deana Colucci, Associate Editor -- Design News, July 7, 1997
Newton, MA--We all know leaving lights, appliances, and other equipment on means higher electric bills. But how many of us realize the broad negative effects of our conspicuous consumption?
For example, generating electricity requires burning fossil fuels, which in turn releases harmful pollutants into the air. According to the U.S. Environmental Protection Agency (EPA), electricity generation accounts for 35% of all carbon dioxide emissions in the U.S., 75% of sulfur dioxide, and 38% of nitrogen oxides. Reducing energy consumption not only saves money, it can help combat smog, acid rain, and climate change by decreasing air pollution.
To address the problem, the EPA developed several Energy Star Programs to encourage the production and use of energy-efficient equipment. Manufacturers who have partnered with the EPA have created efficient models of products ranging from office equipment to homes to commercial heating and cooling systems.
An Energy Star home, for example, uses at least 30% less energy than required by the national Model Energy Code while maintaining or improving indoor air quality. Expected commitments from program partners by the year 2000 will provide home buyers with $1.8 billion in utility-bill savings, and pollution prevention equivalent to removing more than 50,000 cars from U.S. roads, the EPA says.
Several other energy-saving initiatives are underway around the country as well. For example, the Photovoltaic Design Assistance Center at Sandia National Laboratories (Albuquerque, NM) and the National Park Service (NPS) have partnered to promote energy conservation and increase the use of renewable energy at NPS facilities.
A driving force behind the initial 25 parks project was to replace diesel-powered generators with photovoltaic power systems, which convert sunlight to direct-current electricity. The generators are noisy, costly to operate, produce considerable emissions, and have potential for soil and water pollution associated with fuel storage and transportation.
The photovoltaic systems have replaced 11 diesel generators so far. Seven projects provide electrical power where none was previously available. Three systems have been installed in association with local utility companies that provide photovoltaic systems as a customer service option.
"This approach uses the existing energy supply structure in a non-conventional way to provide a win-win situation for the NPS, its visitors, the local energy supplier, and for photovoltaic technology," says Hal Post of Sandia's Photovoltaic System Applications Department.
Perhaps the biggest step toward conserving energy would be widespread adoption of the CEBus standard, say its advocates. CEBus (Consumer Electronic Bus) is a set of open-architecture-specification documents that defines protocols for how to make products communicate through power line wires, low voltage twisted pairs, coaxial cable, infrared, RF, and fiberoptics. A CEBus network provides a standard communication base for exchanging control information and data among devices and services in the home.
In essence, CEBus-compliant devices "talk" to each other and exchange valuable information about product function, energy use, etc. Some 21 trials are taking place around the country using the standard to communicate between homes and power companies. The goal is to modify power consumption either through homeowner-initiated conservation based on time-of-day pricing or through load shedding taking place at the utility company.
As with telephone bills, time-of-day pricing enables consumers to pay less for electricity during certain hours of the day. In order for utilities to put such programs into effect, they must be able to track a consumer's use of electricity to determine prices at specific times, something possible through CEBus communication.
A CEBus network would also enable load shedding: A power company could turn off devices within appropriately equipped homes during peak demand times. In a neighborhood of 17 homes, for example, the utility company could cycle energy use so that certain devices in every tenth home would be off for 15 minutes on a rotating basis.
The lapse of power during that time would be barely noticeable to the consumer because it would affect devices such as water heaters, pool pumps, and heating or cooling units. But the utility company could significantly decrease the overall demand for electricity and eliminate such problems as brown outs. Continued development with the standard is underway by the CEBus Industry Council (CIC), a non-profit organization comprising firms such as Microsoft, IBM, Compaq, AT&T, Honeywell, Panasonic, Sony, Thomson Consumer Electronics, Leviton, and Pacific Gas & Electric. The CIC is developing a non-profit testing laboratory where manufacturers will be able to verify conformance of their product and its performance in a home network environment.
"Communication between the power company and the consumer is the way conservation will take place in the future, and CEBus is one of the best vehicles to achieve that,"says Kurt Kyvik, director of marketing communication at Intellon Corp., the Ocala, FL-based manufacturer of CEBus chips.
Other applications for CEBus
CEBus can handle control-communication requirements for a wide range of residential applications. In addition to energy management, CEBus is well suited for:
Remote control
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Status indication
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Remote instrumentation
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Security systems
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Entertainment device coordination
Behind the CEBus specs
In 1984, members of the Electronics Industry Association (EIA) identified a need for standards that included more than just ON, OFF, DIM, BRIGHT, ALL LIGHTS ON, and ALL LIGHTS OFF controls. Engineering representatives from several companies developed the CEBus standard and introduced it to the world in 1992.
CEBus (Consumer Electronic Bus) is a set of open-architecture-specification documents that defines protocols for how to make products communicate.
The standard includes such things as spread spectrum modulations on a power line. Spread spectrum involves starting a modulation at one frequency, and altering the frequency during its cycle. The CEBus power line standard begins each burst at 100 kHz and increases linearly to 400 kHz during a 100-ms duration. Both the burst (the superior state) and the absence of burst (the inferior state) create similar digits, so a pause in between is not necessary.
A digit 1 is created by an inferior or superior state that lasts 100 ms; a digit 0 is created by an inferior or superior state that lasts 200 ms. The resulting transmission rate varies, depending on the number of 1s and 0s in the transmission. The average rate is 7,500 bits per second.
CEBus transmissions are based on strings or packets of data that also vary in length, following the amount of data included. Some packets can be hundreds of bits in length. The minimum packet size is 64 bits which, at an average rate of 7,500 bits per second, will take about 1/117th of a second to be transmitted and received.
The standard involves device addresses that are set in hardware at the factory and include 4 billion possibilities. It also offers a defined language of object-oriented controls that include commands such as volume up, fast forward, rewind, pause, skip, and temperature up or down one degree.
Currently, all of the communications hardware, language, and protocol is available on a chip produced by Intellon Corp. (Ocala, FL). Manufacturers can purchase the chip for use in their products, or purchase a developer's kit. Intellon also manufactures private label and OEM products using the CEBus standard.
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