Several simplified design procedures for solar energy systems require monthly average meteorological data. Monthly average daily totals of the solar radiation incident on a horizontal surface are available. However, radiation data on tilted surfaces, required by the design procedures, are generally not available. A simple method of estimating the average daily radiation for each calendar month on surfaces facing directly towards the equator has been presented by Liu and Jordan [1]. This method is verified with experimental measurements and extended to allow calculation of monthly average radiation on surfaces of a wide range of orientations.

Calculation of monthly average insolation on tilted surfaces

Solar radiation data plays an important role in solar energy research. These data are not available for location of interest due to absence of a meteorological station. Therefore, the solar radiation has to be predicted accurately for these locations using various solar radiation estimation models. The main objective of this study is to review Artificial Neural Network (ANN) based techniques in order to identify suitable methods available in the literature for solar radiation prediction and to identify research gaps. The study shows that Artificial Neural Network techniques predict solar radiation more accurately in comparison to conventional methods. The prediction accuracy of ANN models is found to be dependent on input parameter combinations, training algorithm and architecture configurations. Further research areas in ANN technique based methodologies are also identified in the present study.

Solar radiation prediction using Artificial Neural Network techniques: A review

Solar radiation is a primary driver for many physical, chemical, and biological processes on the earth’s surface. Solar energy engineers, architects, agriculturists, hydrologists, etc. often require a reasonably accurate knowledge of the availability of the solar resource for their relevant applications at their local. In solar applications, one of the most important parameters needed is the long-term average daily global irradiation. For regions where no actual measured values are available, a common practice is to estimate average daily global solar radiation using appropriate empirical correlations based on the measured relevant data at those locations. These correlations estimate the values of global solar radiation for a region of interest from more readily available meteorological, climatological, and geographical parameters. The main objective of this study is to chronologically collect and review the extensive global solar radiation models available in the literature and to classify them into four categories, i.e., sunshine-based, cloud-based, temperature-based, and other meteorological parameter-based models, based on the employed meteorological parameters as model input.

Furthermore, in order to evaluate the accuracy and applicability of the models reported in this paper for computing the monthly average daily global solar radiation on a horizontal surface, the geographical and meteorological data of Yazd city, Iran was used. The developed models were then evaluated and compared on the basis of statistical error indices and the most accurate model was chosen in each category. Results revealed that all the proposed correlations have a good estimation of the monthly average daily global solar radiation on a horizontal surface in Yazd city, however, the El-Metwally sunshine-based model predicts the monthly averaged global solar radiation with a higher accuracy.

Empirical models for estimating global solar radiation: A review and case study

The tilt angle of a solar energy system is one of the important parameters for capturing maximum solar radiation falling on the solar panels. This angle is site specific as it depends on the daily, monthly and yearly path of the sun. The accurate determination of the optimum tilt angle for the location of interest is essential for maximum energy production by the system. A number of methods have been used for determining the tilt angle at different locations worldwide. Keeping in view the relevance of the optimum tilt angle in energy production and reducing the cost of solar energy systems, the present study has been undertaken. This paper provides the update status of research and applications of various methods for determining solar panel tilt angle using different optimization techniques. The study shows that for maximum energy gain, the optimum tilt angle for solar systems must be determined accurately for each location. The review will be useful for designers and researchers to select suitable methodology for determining optimal tilt angle for solar systems at any site.

Tilt angle optimization to maximize incident solar radiation: A review

For the optimal design and selection of solar energy conversion systems, as well as for other fields of interest, such as architecture, agriculture, hydrology and ecology, the knowledge of accurate global solar radiation data is extremely important. However, due to the cost and difficulty in solar radiation measurements these data are not easily available for many countries. Therefore many empirical models have been developed by various researchers to predict global solar radiation from readily available data. The number of developed models is relatively high, which makes it difficult to choose the most appropriate one for a particular purpose and site. There are several studies in which authors evaluate different models for specific location. However, there is no comprehensive study in which these models are evaluated in case of global use. The main objective of this study is to evaluate different solar radiation models on global scale, which might be helpful in the selection of the most appropriate and accurate model based on the available sunshine data. Using the radiation data corresponding to 924 sites throughout the world we conducted a detailed statistical analysis of 101 different solar radiation models that are available in literature. Ten statistical indicators were used to assess models performance. In addition, we introduced specific global performance indicator (GPI), by means of which all analyzed models are depicted with a single parameter and easily ranked.

Review and statistical analysis of different global solar radiation sunshine models

Simple correlation for estimating the global solar radiation on horizontal surfaces in India

A comparative study to estimate daily diffuse solar radiation over India

Energy is considered as a key source for the future and plays a pivotal role in its socioeconomic development by raising the standard of living and the quality of life, not only for India but also for the world. In view of the scarce fossil fuel reserves, solar energy is one of the important sources of renewable energy used in India because of the suitable climate conditions. It receives about 5485.17 Wh/m2 day of solar insolation with an annual total of about 19, 74, 661.2 Wh/m2. Except for the monsoon months, solar radiation incidence is very encouraging, from the application point of view. For the efficient functioning and better performance of solar energy device, the information of solar radiation and its components at particular location is very essential for designing the solar energy devices. Therefore, over the years, several empirical correlations have been developed in order to estimate the more appropriate solar radiation in India as well as around the world. Here we present a review of different solar radiation models which predict global solar radiation and discussed the long-term plan to meet future energy demand with renewable energy due to economy growth.

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A Review of Solar Radiation Models—Part I

A note on diffuse solar radiation on a tilted surface

In order to grasp the significance of the work accomplished by the author, it is necessary to keep abreast of the present developments in this field. The research work reported in the paper is an attempt to get knowledge to assess the solar energy potential for practical and efficient utilization in India. Our work is centered on estimating realistic values of solar (global and diffuse) radiation on horizontal and tilted surfaces using measured meteorological data and geographical and geometrical parameters for India.

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Chanchal Kumar Pandey

Papers

Simple correlation for estimating the global solar radiation on horizontal surfaces in India

A comparative study to estimate daily diffuse solar radiation over India

A Review of Solar Radiation Models—Part I

A note on diffuse solar radiation on a tilted surface

Solar Radiation: Models and Measurement Techniques