Antoine Zelenka

COMPARING SATELLITE REMOTE SENSING AND GROUND NETWORK MEASUREMENTS FOR THE PRODUCTION OF SITE/TIME SPECIFIC IRRADIANCE DATA

In this article, we compare the accuracy of satellite-derived time/site specific hourly irradiances, with that of irradiances obtained via extrapolation and/or interpolation of nearby ground-measuring stations. A comprehensive study undertaken by the International Energy Agency [Zelenka et al. Final Report of International Energy Agency Solar Heating and Cooling Program (1992)] had addressed this question, but had limited its scope to daily total irradiances. The present study focuses on hourly data.

Making full use of the clearness index for parameterizing hourly insolation conditions

An enhanced parameterization of insolation conditions based only on the knowledge of global irradiance is presented. Two limitations associated with the current approach using the clearness index are pointed out: its dependence on solar elevation and its inability to differentiate between different conditions that produce the same global irradiance. Suggestions are provided which could overcome part of these limitations. Arguments are substantiated with solid experimental evidence. It is further shown that noticeable gains in accuracy for the decomposition of global into direct and diffuse irradiance are possible if one makes optimum use of the information available within a global irradiance time series.

Climatic evaluation of models that predict hourly direct irradiance from hourly global irradiance: Prospects for performance improvements

This paper presents a comprehensive evaluation of recent models designed to predict direct from global irradiance on a short time step basis. Three models are selected for the present evaluation. These were proposed by Erbs et al., Skartveit and Olseth, and Maxwell. Model validation is performed against a large array of experimental data: A total of over 60,000 global and direct data points from 14 sites in Europe and the United States. Environments range from humid oceanic to desertic, including humid continental, high altitude, subtropical, and polluted. It is found that specific models are better adapted to certain climatic types than others. However, each model is found to have a “generic” insolation-dependent error pattern across all climates. This error pattern may be deterministically corrected and yield substantial performance improvement without additional input data.

Using satellite-derived insolation data for the site/time specific simulation of solar energy systems

In this paper, the question of satellite-derived irradiance is addressed on two levels. First, the question of physical accuracy is addressed by comparing satellite-predicted hourly/daily global and direct irradiance with controlled ground measurements in climatically distinct environments. This accuracy is compared to the error made as a function of distance when extrapolating the needed data from the closest ground measurement site. Second, the question of end-use accuracy is addressed by comparing satellite-derived, photovoltaic-utility load-match benchmarks with actual benchmarks for three US electric utilities where ground measurements were available.

Solar radiation transposition models applied to a plane tracking the sun

Many solar radiation transposition models, from a horizontal plane to any fixed inclined surface, have been compared with measurements from different sites. The tests here were carried out for four top-ranked models and with measurements taken on a plane tracking the sun. The best precision obtained in this study is ±7% on the global solar radiation and ±20% on the diffuse solar radiation with a zero bias.