In recent years, industrialization has been observed to be the main culprit globally, responsible for the pollution of the atmosphere. This has not only caused global warming, but also affected the transmissivity of the terrestrial region and thereby, severely affected the amount of solar radiation received by the earth. This work is an outcome of an attempt to study the different techniques/models for the estimation of global solar radiation on horizontal surface. The emphasis is on an understanding of the subject as well as on the different methods of calculation. The subject matter has been distributed in to five chapters. In Chapter 1, the introduction of the problem has been outlined. In Chapter 2, detailed formulations for the estimation of solar radiation by sunshine hour duration models have been presented. In Chapter 3, the temperature parameter is taken under consideration for the estimation of solar radiation. In Chapter 4, estimation includes all the other models which include climatic parameters such as latitude, altitude, transmissivity, albedo, humidity etc. In Chapter 5, possible areas of future work have been discussed.