THERMAL PERFORMANCE ANALYSIS OF GLAZED AND UNGLAZED RECEIVER OF SCHEFFLER DISH

Dnyaneshwar Malwad,Vinod Tungi̇kar

doi:10.18186/thermal.799450

Abstract

The impact of reradiation and convection losses from the receiver is substantial on the performance of solar parabolic dish concentrator. In this paper, an experimental and theoretical study to compare the performance of the glazed and unglazed receiver of Scheffler dish for direct steam generation is presented. Tempered glass cover is provided on aperture to reduce the reradiation and convection losses from the receiver. Improvement in the efficiency of the Scheffler dish is found due to suppressed heat losses from the receiver front surface. Overall heat loss coefficient, useful energy transfer rate to water, steam flow rate, and efficiency of the system with and without glass cover on the receiver are evaluated and compared. The average solar beam intensity during experimentation was 569 W/m2 and 600 W/m2 with the glazed and unglazed receiver respectively. The average temperature at the receiver with glazing is recorded as 425oC, even at low solar beam intensity in comparison with the unglazed receiver. Overall heat loss coefficient at the front surface of the receiver is reduced to 6.04 W/m2K. It has been observed that the Scheffler dish with a glazed receiver achieves thermal performance above 50.00% within the solar beam intensity range of 600-650 W/m2. The enhancement of 8.74% in the average thermal efficiency, with glass cover on the receiver is achieved.

Highlights

Solar energy is an encouraging source of renewable energy
Recent studies have shown that glass cover on the receiver plays an important role in the performance enhancement of the Concentrated solar power (CSP) system ; the use of transparent glazing has been made for only low-temperature systems
We have evaluated the performance of Scheffler dish with a hollow convex receiver in glazed and unglazed conditions

Summary

INTRODUCTION

Solar energy is an encouraging source of renewable energy. Development in solar energy harvesting technologies plays an important role in the replacement of fossil fuels for electricity generation and heat applications. Providing transparent glass cover on absorber eliminates the effect of varying convective heat transfer coefficient of wind on receiver temperature. Researchers have focused on receiver size and shape, absorber coating, glass glazing, and use of nanofluids as phase change material to utilize the maximum energy received from the concentrator. Recent studies have shown that glass cover on the receiver plays an important role in the performance enhancement of the CSP system ; the use of transparent glazing has been made for only low-temperature systems. Overall heat loss coefficient, useful power available for heat transfer fluid and efficiency of the system is compared for direct steam generation. Glazing glass, which acts as transparent insulation for Scheffler dish receiver, is tested above 500oC to justify the importance of transparent glazing for high-temperature point focus solar thermal systems.

Glazing glass transmitivity

Anemometer

RESULT

Findings

CONCLUSIONS