Long-term stability and performance of solar system instrumentation

Abstract

SYNOPSIS In an attempt to improve the quality and reliability of methods used for long-term performance evaluation of solar systems, detailed information is provided about the long-term (typically 2 years) performance and stability of a relatively large number of instruments used in the performance monitoring of a well-instrumented solar heating project. The calibration methods are also described. The instruments include resistance temperature detectors, several types of flowmeters, wattmeters, pyranometers, wind anemometers, a humidity meter, a barometer, differential temperature solar system controllers, and an automatic data acquisition system used to scan, convert and store the data. Recommendations for good instrumentation of solar systems are also provided. It was found that the critical instruments for performance evaluation, and most of the instruments overall, have performed very well over the long term, allowing thermal performance evaluation with an accuracy better than 3% with only one calibra...