Home Automation Systems
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Introduction
Since the mid-1980s, several major participants in the housing, large appliance, and electrical control industries have pursued the idea of an integrated home automation system. Ideally, such a system monitors and operates many different functions within the home. Lighting, heating, cooling, ventilation, appliances, entertainment, and security can all be operated automatically. The homeowner programs, controls, or monitors the house by a computer or even by telephone. These systems have many similarities with building automation systems used in commercial buildings. Systems for the residential market, however, require mass production and simple installation before they will begin to make major inroads to the residential market. A minimal amount of custom engineering and installation is desirable. In many cases, automatic control is economically justified for only a few functions.
Types of Systems
There are three types of home automation controls: individual control devices, distributed-control systems, and centrally controlled systems.
Individual devices control only one appliance or function. Examples include programmable setback thermostats, motion detectors, occupancy sensors, photocell lighting controls, and timers. Individual control devices have a wide variety of successful applications. These range from outdoor lighting to security sensors. The familiar television remote control unit often falls into this category. Remote control devices are not truly home automation devices, however, since they require conscious thought and human effort (however small) to operate.
A distributed-control system uses standard power line wiring, telephone wire (4 pair), video wire (dual coaxial), radio frequency (RF) signals, and infrared (IR) signals. This makes it easier to retrofit the system into existing homes. Microchip controls (actuators, interfaces, and sensors) must be installed in appliances or outlets. The system allows individual appliances to communicate with each other over the existing electrical wiring without a central controller (although keyboard entry is possible using telephones or personal computers). Users can use a television set to monitor the system's status. These form a local area network or home LAN. Compatible appliances are necessary, but currently it is up to the individual manufacturers to decide how to make them compatible. The major development in this direction has come from the Electronic Industries Association (EIA). The Association developed a standard communications protocol (CEBus) which will allow appliances and modems from different manufacturers to communicate with each other. Individual semiconductor manufacturers have developed microchips that could be installed in appliances. You can obtain information about CEBus-compatible appliances from the CEBus Industry Council (see referral below).
A centrally controlled communication system routes signals between a central computer and appliance controllers or environmental sensors. The main advantage of this system is that it can control some "dumb" appliances as well as "smart" appliances. If the controller fails, however, the whole system fails. The major distinction in "smart" home technology is the way electricity is distributed throughout the home. A central control system allots incoming household electricity to a distribution unit in each room of the house. The distribution unit (or network box) does not provide power to the room's outlets indiscriminately, as in a conventional home. The new outlets contain microprocessor chips that only provide power upon request by a "smart" appliance. "Smart" appliances have microprocessor chips that enable them to "communicate" their identity, power demands, and functional status to the network box when the appliance is plugged in. If the computer system determines that all is well, the network box sends power to that outlet. If the network senses potential danger, such as a frayed cord, or appliance incompatibility, the system denies power to the outlet. An outlet is only "live" when utilized by a compatible appliance.
These systems perform similar functions with natural gas appliances. Gas outlets can be placed strategically throughout the house, using easy-to-install semi-rigid stainless steel piping. Any appliance requiring gas, like a stove, outdoor grill, or clothes' dryer, could be "plugged in," accessing gas from the system as it requires it. The "smart gas" outlets constantly monitor for leaks, improper connections, and other malfunctions, and shut off gas to the outlet when the situation is unsafe. The most attractive feature of this system is that the interactive household system would automatically detect smoke and shut off the flow of gas from the main valve. This prevents gas-fueled house fires or explosions.
The idea of a "smart house" package for new homes was conceived by the National Association of Home Builders (NAHB) in 1984. Research and development have been continued by an offshoot of that project called the Smart House Limited Partnership. They currently sell a complete wiring system for new smart house construction. Although they have developed and marketed a number of complete intelligent systems, with a variety of options, complete systems can be very expensive. Except for low-end security systems with some lighting and climate control added, they are targeted at the new luxury home market.
Energy Savings from Home Automation Systems
Much of home automation system marketing is based upon its "space-age" technology. (Security, fire safety, and home entertainment systems figure prominently in brochures and advertisements in magazines that describe this technology.) Vendors believe that the technology of home automation systems will also save significant amounts of energy. Direct savings come from automatic shut-off features and occupancy sensors. The potential for indirect savings through participation in utility load-shifting programs or time-of-use rates is even greater.
Photosensor, Occupancy, and Remote Control of Lighting and Appliances
When used as individual device controllers, these technologies have a proven track record of energy savings. They are also the first energy-saving applications in home automation systems. Occupancy sensor technologies save the automated house owner energy and money by limiting lighting, appliance, and space conditioning use when rooms or zones are unoccupied for a certain length of time. Photosensors adjust the lighting in a room to take advantage of daylight. When tied to a home automation system, heating, cooling, and ventilation systems (HVAC) can be adjusted to account for passive solar heat gains. Systems connected to a home automation system can also be turned on by telephone, so the home is comfortable when the owner arrives.
Load Shifting and Load Management
One energy-saving option is peak-load shifting. Many "smart" appliances are programmable, so that homeowners can take advantage of lower utility rates at times when the demand on the utility is low (some utilities already offer off-peak rates to certain customers). Further developments are expected. In the future, houses with home automation will "communicate" with utilities so that certain appliances (washers, water heaters, heating, ventilation, and cooling) are automatically deactivated during the peak demand periods. Some utilities already provide their customers incentives for putting control devices on individual appliances such as water heaters and air-conditioners, and during peak demand periods the utility shuts down these appliances for a specific amount of time.
Many utilities are experimenting with real-time pricing methods. This concept involves directly tying the marginal price of electricity to the marginal cost of producing it. Your home automation computer would receive the real time price of electricity (or gas) from the utility. It would then operate the house in the most cost-effective way (according to pre-programmed instructions).
Staged Power Return
Another utility interactive feature that home automation supporters expect to be popular with utilities is an option for "staged power return" after blackouts. It requires a great deal of energy for utilities to restart a power plant after a power failure, particularly in summer when many air conditioners run continuously. With a staged return of power, utilities can control the rate at which power returns after a blackout, first issuing electricity to essential home appliances, such as heating or refrigeration, then to the remaining appliances.
Thermal Storage
Heat, generated by conventional or renewable means during off-peak hours, can be stored in ceramic bricks, water, or other storage media. Chilled water tanks or ice storage provide a similar function in summer cooling seasons. Optimization of storage and release of thermal energy by computers is a common strategy for large commercial and industrial facilities. Home automation systems would make it more feasible to operate such systems on a residential scale.
Zoned and Programmable HVAC
Home automation systems also control temperature within different zones of a home. They operate as programmable thermostats and regulate household temperatures on a room-by-room basis, instead of the whole house. For example, rooms in which the family spends a great deal of time can be allotted heat on a more regular basis than seldom-used rooms. When hooked up to occupancy sensors, the zones are only activated when occupied. In one high-tech application, people carry sensors that are programmed to their personal preferences. The system reads these when people enter a room and adjust the environment accordingly. The possibilities are limited only by the imagination.
Air Quality
In many tightly constructed, energy-efficient homes, air quality and ventilation are a concern. While heat recovery ventilators recover most of the heat from exhausted air, a home automation system could control the ventilation system to operate only when the house is occupied. Additional sensors could control the humidity as well.
