Physical and sensory quality of Java Arabica green coffee beans W B Sunarharum, S S Yuwono, N B S W Pangestu et al. Abstract. Drying agricultural product is a post-harvest process that consumes significant energy. It can affect the quality of the product. This paper deals with literature review and field survey of drying methods of coffee beans of Indonesia farmers. The objective is to supply the necessary information on developing continuous solar drier. The results show that intermittent characteristic of sun drying results in a better quality of coffee beans in comparison with constant convective drying. In order to use energy efficiently, the drying process should be divided into several stages. In the first stage when the moist content is high, higher drying air temperature is more effective. After this step, where the moist content is low, lower drying air temperature is better. The field survey of drying coffee beans in Sumatera Utara province reveals that the used drying process is very traditional. It can be divided into two modes and depend on the coffee beans type. The Arabica coffee is firstly fermented and dried to moisture content of 80% using sun drying method, then followed by Green House model of drying up to moisture content about 12%. The latter typically spends 3 days of drying time. On the other hand, The Robusta coffee is dried by exposing to the sun directly without any treatment. After the coffee beans dried follow by peeled process. These findings can be considered to develop a continuous solar drying that suitable for coffee beans drying.
This study investigates the performance of a solar adsorption refrigerator using activated alumina and methanol adsorption pair. The experiments were carried out for 24-hour. The refrigeration was completed during seven cycles with varying weather conditions. A flat plate type collector was used with an area of 0.25 m 2 and tilt angle of 30 o . Theoretical calculations show that, the maximum collector efficiency is 47.15% when the maximum solar radiation obtained is 936.9 W/m 2 . In this research, the maximum value of the COP is 0.0991 when the total solar energy is 16.485 MJ/m 2 and the minimum value obtained is 0.0919 when the total solar energy is 7.609 MJ/m 2 . The experiment results show that the adsorption pair system can deliver an evaporator temperature of about 9.92°C and the cooling load can be achieved by a heat source with a temperature range of 83.95°C and 95.39 o C.
Abstract. The characteristics of absorber plate of a flat plate solar collector play an important role in the improvement of the performance. In this work, a numerical analysis is carried out to explore the effect of absorptivity and emissivity of absorber plate to the performance of the solar collector of a solar water heater. For a results comparison, a simple a simple solar box cooker with absorber area of 0.835 m 0.835 m is designed and fabricated. It is employed to heat water in a container by exposing to the solar radiation in Medan city of Indonesia. The transient governing equations are developed. The governing equations are discretized and solved using the forward time step marching technique. The results reveal that the experimental and numerical results show good agreement. The absorptivity of the plate absorber and emissivity of the glass cover strongly affect the performance of the solar collector. IntroductionIn order to avoid the catastrophe of the globe due to global warming, emission of Greenhouse gas gases to the atmosphere must be reduced. One of the potential solutions is to enhance the use of renewable energy resources. Solar energy is known as a potential renewable energy resource. It is convinced, it will play an important role in the future energy demand. In a year, the globe is exposed by 3,400,000 Exa-Joule of solar energy. This is a vast amount of energy. It can fill the present world energy consumption by only 1 hour 15 minutes of irradiation [1]. However, at the present time, only a very little portion of the human energy consumption is filled with the solar energy. According to REN21, since 2030 solar energy application will increase significantly. Thus, studies on solar energy have increased significantly [2]. Industry related to solar energy application is developing constantly in all over the world. This is because of twofold, increasing energy demand and limitation on major energy source the fossil fuel. Indonesian islands have a big potency of solar energy. It is also constant in every year [3]. The solar energy can be harvested by solar photovoltaic and solar thermal methods. In the solar thermal method, the solar energy can be collected and used as a heat energy for several applications such as solar drying process [4], solar adsorption refrigeration [5], solar desalination [6,7,8], solar water heater [9], solar cooker [10], etc.
Abstract. In the present work, the performance of an adsorption refrigerator driven by a solar collector was investigated. The adsorbent used in this study was 6.5 kg ordinary granular activated carbon of coconut shell produced in the Sumatera Utara province of Indonesia, 3 liters of methanol as adsorbate and 4.5 litres of water as the medium that was cooled. The experiments were carried out under varying weather conditions during seven cycles with total solar radiation about 2.681-3.918 kWh/m 2 /cycle. In this study, the values of the coefficient of performance (COP) obtained were about 0.0827-0.1271. The values of specific cooling power (SCP) obtained were in the range of 0.01839-0.01883 kW/kg. The experimental results show that the adsorption refrigerator system can deliver an evaporator temperature of about 2.81-13.61°C.
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