ABSTRACT

Solar energy can meet a largevariety of the small-scale decentralized energyneeds of a region. The design of solar devices depends on the global and diffuse solar radiation data. Estimation of solar radiation for Uttara Kannada district is done on the basis of solar and other climatological data available at stations located at Karwar, Honnavar, Shirali, Mangalore, and Goa. A variety of empirical equations for estimating monthly global solar radiation exist in the solar energyliterature..The most commonly used empirical formula is the one that relates sunshine duration and global radiation, also referred to as Angstrom's equation. We have used this relationship to estimate global radiation based on 20 years of data at Mangalore and 25 years of data at Goa provided by the India Meteorological Department. It is seen that computed and measured values (actual values) of global radiation (GR) agree within the range of 2-5% for most months.

Data at Goa and Mangalore have been analyzed in order to improve accuracy and to establish the role of other climatological parameters, such as mean daily temperature, relative humidity, specific humidity, minimum and maximum temperature, and rainfalL Based on the R² value and the least value of the standard error of the Y estimate, the empirical formula consisting of mean temperature, sunshine duration, and specific humidity is the best relationship to estimate GR with the available climatological information. The computed and estimated values are within the range +or- 5%. With this empirical relationship, GR is estimated (kWh/m²) for Karwar (with 37 years of climatological data), Honnavar (with 50 years of climatological data), and Bhatkal (Shirali, with 15years of climatological data). Karwar has a GR range of 5.5-6.5 for January-May and is in the range of 4-5 during the monsoon months, July-September, while at Honnavar the GR range during January-May is 5.47-6.5 and is minimum during the monsoon months. Thus this study, covering five locations of the coastal belt of the western Ghats region, demonstrates that good solar energypotential is available in this region during most months of the year.

The amount of solar energythat could be harnessed by utilizing 5% of the present wasteland in coastal taluks as a solar collector area, is found to be of the order of 95.72 million units (mkWh) annually from the coastal belt of the Uttara Kannada district alone- That means the solar energy can meet at least 32.5% of the present electricitydemand of Uttara Kannada. This study suggests that solar conl-ersiontechnologies have considerable potential for application, provided that questions of storage and the monsoon season requirement can be adequately addressed through other options. The abundance of solar resources can be illustrated by comparing the land requirements of solar projects (thennal or photovoltaic) with those of hydro or energyplantation projects. Except for run-of-river projects and for high head sites in deep gorges, the land requirements for hydel projects at coday's concersion efficiencies average around 25-45 times that required for solar projects- This means that solar energy is capable of supplying 5-10 times the electricity demand of Kamataka State while occupying a land area less than that currently used by hydel projects.

KEYWORDS

diffuse radiation, global solar radiation, solar energy potential, solar thermal devices, specific humidity, sunshine duration, temperature