Evaluation of an all-sky meteorological radiation model against long-term measured hourly data

With the proliferation of cheap, high performance desktop computers, the building services profession is demanding detailed (hourly or sub-hourly) weather data for simulation, optimum plant sizing and design of buildings which may use passive solar and/or natural ventilation features. Even in a developed country, such as the United Kingdom, there is a dearth of measured long-term solar radiation and daylight data. Herein, a simple and precise meteorological radiation model (MRM) is presented, which enables computation of horizontal beam and diffuse solar radiation to be accomplished, given four basic meteorological parameters-hourly dry-and wet-bulb temperatures, atmospheric pressure and bright sunshine duration. These data are available worldwide for very many locations. The present model is of a semi-general nature as demonstrated by its applicability to ten widespread locations in the United Kingdom. The model enables computation of hour-by-hour insolation. Statistical analysis of 100 station-years hourly data indicates that the MRM can compute insolation with an average error of 9% for clear skies and 25% for overcast conditions. On a monthly-averaged hourly and daily basis, this error reduces to 3%. (C) 1997 Elsevier Science Ltd.