In this study, a greenhouse solar dryer with double-pass multi-hollow collector for leaf drying was design, constructed, and evaluated. From the result, the double pass solar air collector with multi-hollow tube is capable of increasing air temperature by 5.5℃-10.8℃ compared to ambient air temperature. Thermal efficiency of the dryer was evaluated for passive and active modes, where 47.2% and 50% are recorded respectively. The moisture reduction on mass basis in passive and active dryer recorded was 44% and 74%, respectively. The specific moisture extraction rate (SMER) and specific energy consumption (SEC) of passive dryer was determined to be 0.198 kg per kWh and 5.047 kWh per kg, and active dryer at 0.210 kg per kWh and 4.769 kWh per kg, respectively.

The renewable energy source potencies in Indonesia are needed to be utilized to fulfill the electricity requirement in rural or remote area that not yet get electricity. One of the potency is biomass waste. Therefore, this paper discusses about the electricity generation preliminary design of Organic Rankine Cycle (ORC) system with corn cob biomass waste burning as heat source, so it can be obtained the theoretic corn farm area requirement, electricity power, and thermal efficiency at heat source temperature and flow rate variations. Corn cob burning temperature can heat up the heating fluid that is heated by boiler with corn cob as the biomass fuel. Furthermore, that heating fluid is used as ORC electricity generation heat source. The independent variables in this study are the heating fluid temperature which varied between 110, 120, and 130oC, and the heating fluid flow rate that varied between 100, 150, and 200 liter/minute. R141b is selected to be the working fluid, palm oil is used for heating fluid and water as cooling fluid. The calculation results that the theoretic electricity power, thermal efficiency, and corn farm area requirement, respectively, are in the range of 3.5-8.5kW, 9.2-10.3%, and 49.5-101.1hectare/year. All of the highest range values are resulted at the highest temperature and flow rate, 130oC and 200 liter/minute. This result shows that corn cob burning heat is potential to be utilized as electricity generation heat source for rural society, particularly for some areas that have been studied

Solar chimneys (SCs) utilize solar-induced buoyancy to enhance natural ventilation; however, design recommendations remain challenging because of differences in modelling assumptions, thermal boundary conditions, and operating environments. This study investigates the thermal–flow characteristics and ventilation performance of a wall-mounted building-integrated SC under representative Indonesian humid-tropical conditions using OpenFOAM. The thermal predictions of the numerical model were validated against published experimental temperature data, with a maximum deviation of 3.36%. Parametric analyses of chimney cross-sectional area, height, and air gap were conducted at a constant absorbed heat flux of 500 W/m², followed by hourly quasi-steady evaluation. Chimney cross-sectional area had the greatest effect on ventilation performance, producing an air change per hour (ACH) range of 0.5–30 h⁻¹, compared with 7.7–8.6 h⁻¹ for height and 7.4–7.7 h⁻¹ for air gap. The selected configuration, with a 0.09 m² area, 3 m height, and 0.3 m air gap, achieved 4.0–10.7 h⁻¹ during hourly evaluation. The model assumes quiescent ambient conditions and dry-air Boussinesq properties; thus, wind-pressure effects and humidity-induced changes in air properties and buoyancy are not represented. These findings provide quantitative guidance for the design and assessment of building-integrated SCs in humid tropical climates within the adopted modelling assumptions.