Page 107 - Solar Power in Building Design The Engineer's Complete Design Resource

CENTRAL MONITORING AND LOGGING SYSTEM REQUIREMENTS 77

■ AC current
■ AC voltage
■ AC kilowatt-hours
■ Solar plane of array irradiance
■ Ambient temperature
■ Wind speed

The calculated parameters displayed include:

■ AC power output
■ Sunlight conversion efficiency to ac power
■ Sunlight conversion efficiency to dc power
■ Inverter dc-to-ac power conversion efficiency
■ Avoided pollutant emissions of CO ,SO ,NO gases
2
x
x
The preceding information and calculated parameter are displayed on monitors and
updated once every second. The data are also averaged every 15 minutes and stored in
a locally accessible database. The software includes a “Virtual Array Tour” that allows
observers to analyze the solar photovoltaic component of the photovoltaic array and
monitoring system. It also provides an optional portal Web capability whereby the
displayed data could be monitored from a remote distance over the Internet.
The monitoring and display software can also be customized to incorporate descrip-
tive text, photographs, schematic diagrams, and user-specific data. Some of the graph-
ing capabilities of the system include the following:

■ Average plots of irradiance, ambient temperature, and module temperature that are
updated every 15 minutes and averaged over one day.
■ Daily values or totals of daily energy production, peak daily power, peak daily
module temperature, and peak daily irradiance plotted over a specified month.
■ Monthly values of energy production; incident solar irradiance; and avoided emission
of CO ,NO , and SO plotted over a specified year.
x
x
2
GENERAL DESCRIPTION OF A MONITORING SYSTEM
The central monitoring system discussed here reflects the actual configuration of the
Water and Life Museum project, located in Hemet, California, and was designed by the
author. This state-of-the-art monitoring system provides a real-time interactive display
for education and understanding of photovoltaics and the solar electric installation as
well as monitoring of the solar electric system for maintenance and troubleshooting
purposes.
The system is made up of wireless inverter data transmitters, a weather station,
a data storage computer, and a data display computer with a 26-in LCD screen. In the
Water and Life Museum project configuration, the inverters, which are connected in
parallel, output data to wireless transmitters located in their close proximity. Wireless
transmitters throughout the site transmit data to a single central receiver located in