The meteorological radiation model (MRM): Advancements and applications

Abstract

The estimation of hourly and daily solar radiation on inclined surfaces starts with the determination of the corresponding hourly values on horizontal plane. For this reason the Atmospheric Research Team (ART) at the National Observatory of Athens (NOA) initially developed the so-called MRM (Meteorological Radiation Model; Kambezidis and Papanikolaou 1989; Kambezidis and Papanikolaou 1990a; Kambezidis et al. 1993a,b; Kambezidis et al. 1997). The goal of the development of MRM was to derive solar radiation data at places where these are not available. To do that the implementation in the algorithm of the more widely available meteorological data (viz. air temperature, relative humidity, barometric pressure and sunshine duration) was considered. A solar code with such characteristics is particularly useful for the generation of Solar Atlases in areas with a moderately dense meteorological network. The original form of MRM version one (MRM v1) worked efficiently under clear-sky conditions, but it could not work under partly cloudy or overcast skies. MRM v2 introduced new analytical transmittance equations and, therefore, became more efficient than its predecessor. Nevertheless, this version still worked well under clear sky conditions only. These deficiencies were resolved via the development of the third version of MRM (MRM v3), derived by T. Muneers research group at Napier University, Edinburgh (Muneer et al. 1996; Muneer 1997; Muneer et al. 1997; Muneer et al. 1998) after successful co-operation between ART and his group. MRM v3 was included in the book edited by Muneer (1997). Through the EU JOULE III project on Climatic Synthetic Time Series for the Mediterranean Belt (CliMed), a further development of the MRM was achieved, which is referred to as version four (MRM v4), providing further improvement in relation with partly cloudy and overcast skies. Prof. Hassid, Technion University of Israel, used MRM v4 to make simulations and comparison with Israeli solar radiation data. In using the code, he found some errors mainly in the calculation of the course of the sun in the sky, which were corrected by him. On the other hand, Gueymard (2003) in an inter-comparison study employing various broadband models used MRM v4 and found it not to be performing well in relation to others. Further elaboration of MRM v4 by ART for the purpose of this book resulted in discovering more severe errors in the transmittance and solar geometry equations, which were corrected concluding to a new version of MRM (MRM v5). MRM was successfully used by the Chartered Institution of Building Service Engineers (CIBSE) of UK in 1994 under the Solar Data Task Group (Muneer 1997). Apart from that specific task, MRM can be used in a variety of applications, among of which the most important nowadays are: • to estimate solar irradiance on horizontal plane to be used as input parameter to codes calculating solar irradiance on inclined surfaces with arbitrary orientation, • to estimate solar irradiance on horizontal plane with the use of available meteorological data to derive the solar climatology at a location, • to fill gaps of missing solar radiation values in a historic series from corresponding observations of available meteorological parameters, • to provide algorithms for engineering purposes, such as solar energy applications, photovoltaic efficiency, energy efficient buildings and daylight applications, with needed (simulated) solar radiation data. The objectives of this chapter are (i) to describe the origin, the algorithms, the recent improvements and the test results of MRM; (ii) to show how a detailed statistical analysis of the estimates produced by radiation models can be done to evaluate in depth the performance of solar algorithms such as MRM. © 2008 Springer-Verlag Berlin Heidelberg. All rights are reserved.