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CENTRAL MONITORING AND LOGGING SYSTEM REQUIREMENTS   75


               Central Monitoring and Logging

               System Requirements


               In large commercial solar power cogeneration systems, power production from the PV
               arrays is monitored by a central monitoring system that provides a log of operation
               performance parameters.  The central monitoring station consists of a PC-type
               computer that retrieves operational parameters from a group of solar power inverters
               by means of an RS-232 interface, a power line carrier, or wireless communication sys-
               tem. Upon receipt of performance parameters, a supervisory software program
               processes the information and provides data in display or print format. Supervisory
               data obtained from the file can also be accessed from distant locations through Web
               networking.
                  Some examples of monitored data are:

               ■ Weather-monitoring data
               ■ Temperature
               ■ Wind velocity and direction
               ■ Solar power output
               ■ Inverter output
               ■ Total system performance and malfunction
               ■ Direct-current power production
               ■ Alternating-current power production
               ■ Accumulated, daily, monthly, and yearly power production

                  The following is an example of a data acquisition system by Heliotronics referred
               to as Sunlogger, which has been specifically developed to monitor and display solar
               power cogeneration parameters.


               SUN VIEWER DATA ACQUISITION SYSTEM

               The following solar power monitoring system by Heliotronics, called the Sun
               Viewer, is an example of an integrated data acquisition system that has been
               designed to acquire and display real-time performance parameters by filed installed
               electric power and atmospheric measurement sensors. The system, in addition to
               providing vital system performance data monitoring and measurement, provides
               the means to view instantaneous real-time and historical statistical energy meas-
               urement data essential for system performance evaluation, research, and education.
               Figure 3.14 depicts a typical presentation of field measurement on a display
               monitor.
                  The system hardware configuration of the Sun Viewer consists of a desk to computer
               based data logging software that processes and displays measured solar power photo-
               voltaic array and atmospheric output parameters from the following sensors and
               equipment:
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