Generation of Hourly Design-Day Weather Data

ASHRAE Research Project 1363 to develop procedures for developing hourly design-day temperature and solar profiles.

The first part of the project used weather data from 21 cities of a variety of climatic conditions to develop a daily profile which describes the variation of dry bulb and wet bulb temperature on design days.  The profile defines the hourly temperature as a fraction of the difference between the daily high and low, as described by the design temperature and the design daily range.  A single profile was found to be applicable to all climates and times of the year for both dry bulb and wet bulb profiles.  Dewpoint temperature variations were found to be highly variable, such that no single profile can provide reliable predictions.

In addition, we developed profiles for direct normal irradiance, diffuse radiation, and ground reflected radiation.  The analysis was based on the use of a complex solar model, REST2.  These three values are determined from straightforward equations using solar position and sets of three parameters which will need to tabulated for location and month.  These parameters are dependent on turbidity, water vapor, and altitude, and separate sets of parameters are needed for direct normal irradiance and diffuse radiation.  Diffuse radiation is used with ground reflectance and solar position values to find ground reflected radiation.