Importance of Time Averaging Conventions
Abstract
Original or raw solar radiation data is preferably created at relatively high temporal resolutions, such as one-minute values for direct measurements. However, and especially when combining different sources or with different kinds of data, the data actually seen by end users is frequently already averaged at some other temporal resolution, commonly 15-, 30- or 60-minute averages. One also commonly missing piece of information is how those averages were obtained; in particular, what the timestamps actually mean; for example, does the hourly value marked as 10 am include 9:01 to 10:00, or 10:00 to 10:50, or something else? This study presents an estimation of errors, using real measurements, resulting from a user assigning the 'wrong' interval to the timestamps, at different averaging scales, from 5 to 60 minutes.