Solar exergy evaluation and empirical model establishment; case study: Iran

Area of Science:

• Renewable Energy Engineering
• Thermodynamics
• Environmental Science

Background:

• Iran possesses significant solar energy potential due to abundant sunshine.
• Previous research has not addressed the solar exergy status in Iran.
• Understanding solar exergy is crucial for assessing solar energy quality.

Purpose of the Study:

• To investigate and quantify solar radiation exergy in Iran.
• To establish empirical models for predicting solar exergy based on sunshine duration.
• To evaluate the performance of these models across diverse climatic conditions.

Main Methods:

• Utilized long-term meteorological and solar data from eight Iranian capital provinces representing five climatic conditions.
• Calculated monthly average daily solar radiation exergy on a horizontal surface.
• Developed and calibrated five empirical models (linear, quadratic, cubic, exponential, power) dependent on relative sunshine duration.
• Evaluated model performance using eight statistical indicators.

Main Results:

• Determined a consistent annual ratio of solar exergy to energy of approximately 0.87 for Iran, independent of location and month.
• Identified the best-performing predictive models for solar exergy in each studied province, varying in functional form (cubic, power, exponential, linear, quadratic).
• These models demonstrate simplicity and applicability to similar climates.

Conclusions:

• The solar exergy to energy ratio in Iran is remarkably stable at 0.87.
• Accurate and simple empirical models for solar exergy prediction have been developed and validated for various Iranian climates.
• The findings provide valuable insights for optimizing solar energy utilization and planning in Iran and similar regions.