NIST has been monitoring three grid-tied photovoltaic arrays for over a year to create a database of performance data that can be used for increased understanding of system performance, model validation, and fault detection. Such understanding is important for designers, financers, and operators of photovoltaic systems to reduce the uncertainties in operation and to ultimately lower the cost and risk of these installations.
The systems have been monitored to provide data on the DC output, AC output from the inverters, temperatures of the modules, and meteorological conditions in the vicinity of the arrays at 1-second intervals. Images of the arrays are taken at 5-minute intervals to observe shading, snow and any obstructions or signs of damage. Additionally, a weather station having a more extensive suite of measurements is installed on a building on the NIST campus along with a test station to get more detailed data on representative modules' performances.
Chart of Monthly Output
The systems produced a total of 872 MWh of electricity over the course of the first year of monitoring. This amount of energy would meet the electric needs of 80 typical US households over the course of the year. Given an average commercial electricity rate in the United States of $0.1075 per kWh in the year 2014, this electric output amounted to $93,715 without including peak demand charge reductions.