Abstract
Energy resources and their utilization intimately relate to sustainable development. In attaining sustainable development, increasing the energy efficiencies of processes utilizing sustainable energy resources plays an important role. The utilization of renewable energy offers a wide range of exceptional benefits. There is also a link between exergy and sustainable development. Exergy analysis has been widely used in the design, simulation, and performance evaluation of various energy systems as well as renewable energy sources. In this regard, determination of exergy of solar radiation is very crucial for various solar energy-related applications and is based on the relative potential of the maximum energy available from radiation. The efficiency factor limiting the gain of the maximum useful energy from the solar radiation is significantly similar to that of the Carnot efficiency for the heat engines. The main objectives of this study are two-fold, namely, (i) to comprehensively review various solar exergy models used in solar energy-related applications, and (ii) to determine the solar exergetic values for some regions of Saudi Arabia and Turkey, which are taken as two illustrative examples to which various models have been applied and compared. In this regard, the ratios of solar radiation exergy to solar radiation energy (exergy-to-energy ratio) for northeastern Saudi Arabia are calculated to be on average 0.933 for both approaches of Petela and Spanner and 0.950 for Jefer's approach at outside air temperatures between 16.18 and 33.01°C. These ratios for Izmir, Turkey are obtained to be on average 0.935 and 0.951 for the same approaches at a temperature range of 15-22°C, respectively. The values found using Jefer's approach appear to be 2% larger than the approaches of Petela and Spanner, while those are very close to the value of 0.95 proposed by Nobusawa.