An Experimental Study of Solar Cooker Performance With Thermal Concentrator System by Spot Fresnel Lens

Abstract

The study to investigate the thermal performance of solar cooker using a spot Fresnel lens for concentrators of solar thermal energy is conducted. The main objectives of the present work are: a) to develop a new design of the cooking pot of solar cooker as an absorber of solar thermal from a spot Fresnel lens; b) to analyze the relationship of several temperature parameters in the cooking pot with the thermal efficiency of the Fresnel solar cooker (FSC); c) to conduct field test by heating test and cooling test to obtain a performance characteristic of FSC. The experimental test was conducted at Brawijaya University (7.9553°S, 112.6145°E), East Java, Indonesia during August – September 2019. The Fresnel lens operation method uses the azimuth manual tracker to concentrate direct normal irradiance (DNI). The measurement of Direct Normal Irradiance (DNI) was made by the SM 206 Solar Power Meter and placed on the FSC frame. A new design of solar cooking pot has been developed. That is a cylindrical shape for boiling water and food cooking with a cone cavity as a solar collector. While on the cooking pot, the temperature sensor is placed: 1) ambient temperature; 2) cooking pot temperature; 3) focal point temperature on the receiver surface; 4) water temperature in the solar cooking pot. It is connected to the Digi-Sense 12 CH-Scanning Benchtop Thermometer for temperature data acquisition system. The measurement of wind speed was made by Cup Anemometer ABH-4224. The procedure for testing the FSC was developed based on existing international testing standards. The receiver/cooking pot was tested for thermal performance characteristics of cooking by conducting the following tests: 1) no-load test; 2) water heating and cooling tests. The experimental results show that the average stagnation temperature in a cooking pot with a conical cavity receiver was 267.35 °C. The receiver shape with a conical cavity has better heat transfer capability and low heat losses, hence, making it suitable for applications on FSC. DNI ±850 W/m² produces a focal point temperature of 1064 °C, a heat removal factor of 7.39 W/m². °C, and an optical efficiency factor of 0.312. Therefore, the thermal efficiency of the FSC is 27.72 %. The thermal efficiency tends to decrease until the end of the process due to the influence of the optical efficiency factor