This study aims at determining the effect of the torrefaction process on the fuel quality of biomass pellets made from oil palm empty fruit bunches (EFB). The torrefaction process was carried out using a rotary reactor, which has a cylinder with a diameter of 15 cm and a length of 15 cm made from an iron plate. The cylinder was heated externally using a horizontal heater fueled with LPG. The reactor cylinder was filled with 1.5 kg of clean sand to homogenize the heat transfer and prevent pellets from colliding during the process. The torrefaction process was conducted with a load of 300 grams of EFB pellets at temperatures around 240-310 °C at variations of reaction time (20, 30, and 45 min.) and the reactor cylinder rotation speed (16, 31, and 37 RPM). The results showed that the torrefaction process improved the quality of the EFB pellet fuel. This was reflected from the very low moisture content (0.32-0.52 %) of torrefied pellets and its calorific value, which increased from 15.82 MJ/kg (without torrefaction) to 17.59 MJ/kg (with torrefaction for 45 minutes). Torrefied pellets showed good hydrophobicity where the pellet was not broken when immersed in water for 24 hours. Pellet without torrefaction was destroyed in water just in one minute.

Rubberwood (Hevea brasiliensis) and Jabon (Anthocephalus cadamba) are two promising species that is widely planted in industrial plantation and community forests in Indonesia. The objective of this study was to improve the properties of rubberwood and jabon pellets through torrefacation. Torrefaction was performed at a temperature of 300°C and a residence time of 3 min, using Counter-Flow Multi Baffle (COMB) Dryer/Pyrolizer. The properties of torrefied wood pellets as equilibrium moisture content (EMC), density, and heating value. Black pellets were succefully obtained after torrefaction using COMB Dryer/Pyrolizer. The EMC of the black pellets from rubberwood and jabon was 3.54% and 2.85%, which is remarkably lower that their initial EMC of 12.25% and 12.76%, for rubberwood and jabon pellets, respectively. The density of black pellets from rubberwood and jabon and decreased 16.18% and 13.44% compared to control. Torrefaction using COMB Dryer/Pyrolizer also increased high heating value of wood pellets to 18.32% and 79.70%, for rubberwood and jabon pellets, respectively. Consequently, torrefaction using the COMB Dryer/Pyrolizer could improve the bioenergetic properties of jabon and rubberwood pellets.

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The night air temperature which is below or equal to the temperature of human thermal comfort is very potential to be used to help reduce the thermal load of the room. This utilization can help minimize the electrical energy consumption of air conditioning systems. Phase change material (PCM) can be used to utilize the potential of cold air at night as latent heat thermal energy storage (LHTES). One model of the application of PCM is the heat exchanger. PCM fills one part of the heat exchanger. The characteristics of heat transfer need to be known so that it can know the cooling rate and the time required in the process. The variable used in this study is the inlet air velocity. In this research, a staggered fins-type heat exchanger which contains PCM with paraffin material is used in the cooling process. The results showed that an increase in speed would accelerate the cooling rate. At a velocity of 3 m.s−1, the average cooling rate of the PCM mass unity was 6.4 °C.hr’.kg−1. With this rate of cooling, the potential for cold night air for about two to three hours can be utilized for the PCM freezing process.

A flat-plate thermal collector combined with a PV panel also called a PV/T collector is a device that converts solar irradiation into thermal energy and electrical energy simultaneously. The unused thermal energy of the PV/T collector is absorbed by the flat-plate thermal collector. This may then contribute directly to an enhancement of the electrical efficiency of the PV/T collector. In the present study, the effect of geometry and Reynolds Number on the thermal performance of flat-plate thermal collectors is numerically investigated. Thereafter, CFD simulation is then implemented to characterize the thermal performance in terms of absorber temperature and convection heat transfer coefficient. To disturb the fluid flow pattern in this work the 45o inclined fins are attached underneath the surface of the collector model and they act as an absorber. Monthly average weather data of inlet fluid temperature and ambient temperature as well as solar irradiation level implemented in this study were obtained from the Meteorological, Climatological and Geophysical Agency of Bandarlampung regency. Several different cases have been considered by varying the fin height from 20 to 80 mm, fin thickness from 1 to 4 mm, and Reynolds number from 1500 to 6000. The results show that increasing the fin geometry (the fin thickness and fin height) and Reynolds Number reduce the flat-plate surface temperature due to the more conductive and convective heat transfer process. However, in terms of the convective heat transfer coefficient parameter, the Reynolds Number implemented has a dominant effect compared to the fin geometry. Moreover, by increasing Reynolds Number by four times, there is a decrease in the mean surface temperature by 26% and an increase in the mean convective heat transfer coefficient of 146% compared to the initial conditions