HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Energy and Power Management, Distributed Control Trendsis supplied to the unit by a built-in solar cell with battery backup. Thesensor would then start broadcasting using infrared, radio wave, ormicrowave. The computer will recognize the sensor and assign a pointnumber.The system will map the location of the sensor using triangulationof the signal and its internal map of the building. The system can thenstart a self-optimization routine to search for the optimum control strategyto utilize this new sensor.Direct Digital ControlDirect Digital Control (DDC) has evolved from the growth stage ofthe late 1970s which were triggered as a result of the energy price hikesof 1973 and 1977. Control system technology had been evolving but anumber of factors combined to make computer-based control technologymore viable. One of these was the decreasing cost of electronicswhich made control systems more affordable. At about the same timethe interest in energy savings jumped and a number of incentives andtax credits became available which stimulated the market. These factorsresulted in a demand for technology that would allow building ownersto save energy. These newly developed systems came to be known asEnergy Management and Control Systems (EMCS).The main computer in use at that time was the minicomputer, orcentral processing units (CPUs). These systems utilized energy savingfeatures for optimizing equipment operation, offsetting electrical demandand the shutdown of equipment when not in use.Next in this evolution was the application of Direct Digital Control.Although this technology was used in industrial process control, andeven for some building applications as long ago as the 1950s, it was notuntil much later that it became an acceptable technique for HVAC systems.DDC refers to a closed loop control process that is implemented bya digital computer. Closed loop control implies that a condition is controlledby sensing the status of that condition, taking control action toensure that the condition remains in the desired range and then monitoringthat condition to evaluate if the control action was successful(Figure 2-2).©2001 by The Fairmont Press, Inc. All rights reserved.