Int. Journal of Renewable Energy Development 9 (1) 2020: 131-139 Page | © IJRED – ISSN: 2252-4940.All rights reserved 131 Contents list available at IJRED website Int. Journal of Renewable Energy Development (IJRED) Journal homepage: http://ejournal.undip.ac.id/index.php/ijred Energy Analysis of a Hybrid Solar Dryer for Drying Coffee Beans Suherman Suherman * , Hasri Widuri, Shelyn Patricia, Evan Eduard Susanto and Raafi Jaya Sutrisna Department of Chemical Engineering, Faculty of Engineering, Diponegoro University, Jl. Prof. Soedarto, Tembalang, Semarang, Jawa Tengah 50275, Indonesia ABSTRACT. In this study, hybrid solar drying of coffee beans was performed, and energy analysis was carried out, to assess the system’s performance, in terms of energy efficiency, compared to solar drying and the open sun drying method. The dryer has three compartments: solar collector for collecting solar radiation, drying chamber, and a Liquid Petroleum Gas burner, which acted as an auxiliary heater to assist the thermal energy. The drying chamber has four trays for placing the dried product. The initial moisture content of coffee beans was 54.23% w.b and was reduced to the final moisture content between 11-12% w.b. The coffee beans dried faster when subjected to the solar hybrid drying method, compared to other methods, with the dryer temperature of 40°C, 50°C, and 60°C. Results indicated that the coffee beans’ drying times varied from 10 to 14 hours. However, at temperature 50°C and 60°C for the 1st tray, the water content was reduced more rapidly compared to the other tray. From the results of this study, we can see the different efficiency of solar collector that shows of 54.15% at variable temperature 60°C for drying time 12:00 to 14:00 p.m for hybrid solar drying and for the solar drying process is 50.07% at the range of drying time 12:00 to 14:00 p.m. Mathematical modelling shows that Page model is the most suitable for describing the coffee beans’ drying behaviour using a hybrid solar dryer. The effective diffusivity values found in this experiment are all in the acceptable range for most agricultural products. ©2020. CBIORE-IJRED. All rights reserved Keywords: Solar Drying, Hybrid Solar Dryer, Coffee Beans, Energy Analysis, Mathematical Modeling Article History: Received: October 16, 2019; Revised: January 15, 2020; Accepted: February 10, 2020; Available online: February 15, 2020 How to Cite This Article: Suherman, S., Widuri, H., Patricia, S., Susanto, E.E., and Sutrisna, R.J. (2020) Energy Analysis of a Hybrid Solar Dryer for Drying Coffee Beans. International Journal of Renewable Energy Development, 9(1), 131-139. https://doi.org/10.14710/ijred.9.1.131-139 1. Introduction According to the Coffee Market Report in December 2018, Indonesia was the fourth largest coffee-producing country, with a total production of 10.2 million tons in 2018 (International Coffee Organization, 2018). Over the last few years, market demands have increased, considering that daily coffee consumption has also increased. Studies had shown that coffee may have health benefits, including promoting calming effects and weight loss, and may prevent or delay diabetes by Greenberg et al. (2006). According to the Indonesia Standardization Body (2004), and Hanif et al. (2014), coffee with good quality has a moisture content of 11-12% w.b. The drying factor must be determined to achieve the desired water content. Both Aissa et al. (2014) and Dong et al (2019) have the same understanding of drying; it is a complex process that involves the transfer of heat and mass between the product and the surrounding media. The purpose of drying is to partially eliminate the moisture content from the products to reach the safe limit so it cannot become a medium for spreading * Corresponding author: suherman.mz@che.undip.ac.id microorganisms, which may decrease the coffee bean quality (Suherman et al. 2018). Solar drying has been used for the preservation of food, agricultural, and marine products for a long time. This was particularly called natural convection drying under the direct sun. However, this natural convection drying is a relatively slow process in decreasing the water content in the product. There are many obstacles in small industries during the drying process, such as contamination or insect infestation, depending on the availability of sunshine and inability to control the weather. This process causes the coffee bean’s moisture content to be non-uniform. Therefore, the new technology for the drying process was developed to solve the problems mentioned above. This new technology is called a hybrid solar dryer, with sunlight as the main energy of the process supported by means of additional heating (Bennamoun et al. 2012; Kassem et al. 2011). Several researchers have studied the application of the hybrid solar dryer for various products. A hybrid solar dryer system, which combines natural convection solar drying and a biomass burner, was studied experimentally Research Article