Characterization of selective solar absorber under high vacuum

Area of Science:

• Materials Science
• Renewable Energy Engineering
• Thermodynamics

Background:

• Selective solar absorbers are crucial for efficient solar thermal energy conversion.
• Understanding optical properties (absorption and emission) at elevated temperatures is vital for performance prediction.
• High vacuum conditions minimize convective heat losses, allowing accurate measurement of intrinsic material properties.

Purpose of the Study:

• To measure the total absorption and emission coefficients of selective solar absorbers.
• To determine these coefficients from room temperature up to stagnation temperature under high vacuum.
• To evaluate the solar absorptance and thermal emittance at various temperatures for performance modeling.

Main Methods:

• Selective solar absorbers were tested under high vacuum conditions (pressure not specified).
• Samples were illuminated with a solar simulator at 1000W/m².
• Sample temperature was monitored during heating, equilibrium, and cooling phases to determine stagnation temperature.
• Data analysis was performed to derive absorption and emission coefficients.

Main Results:

• The absorber reached a stagnation temperature exceeding 300°C without solar concentration.
• Solar absorptance and thermal emittance were evaluated at different temperatures.
• The measured coefficients provide insights into the absorber's behavior at operating conditions.

Conclusions:

• The study successfully characterized the optical properties of selective solar absorbers under vacuum and elevated temperatures.
• The obtained data is essential for accurate performance prediction of evacuated solar collectors.
• This research contributes to the development of more efficient solar thermal energy systems.