Optimization of the geometry of double-chamber basin-type passive solar stills to maximize yield

Developing countries require simple low-technology methods to desalinate drinking water. Passive solar stills are an example of a simple low-technology innovation that can desalinate saline water for small populations. Compared to single-chamber solar stills, double-chamber solar stills have the potential of increasing the yield of solar stills due to an increased condensation surface area. An experiment was carried out to determine the optimal angle of double-chamber solar stills. The set-up comprised double-chamber solar stills with angles of 10°, 20°, 30° and 40°, with a control set-up of a 20° single-chamber solar still. The experiment was conducted in January 2022 at Juja in Kiambu County, Kenya. The double-chamber solar stills comprised an evaporation chamber and a condensation chamber. The dimensions of the chambers were 0.5 m × 0.5 m with a height of 0.25 m. The main assumptions were that there existed steady-state conditions and that the solar still was leakproof. The research found that the 40° double-chamber solar still had the highest yield of 3.756 l/m2/day and the 10° double-chamber solar still had the least yield of 1.644 l/m2/day. Comparing the 20° double-chamber still and the 20° single-chamber still (control), the double-chamber solar still had a higher external efficiency. HIGHLIGHTS The configuration of the double-slope single-chamber has not been experimented on before.; The geographical location is unique (Kenya (1°north of the equator)).

Reducing Cooling Demands in Sub-Saharan Africa: a Study on the Thermal Performance of Passive Cooling Methods in Enclosed Spaces

The paper aims to explore the effect of different passive cooling measures using thermal modelling and predicting. Solar shading, green roofs and cool paints were incorporated as passive cooling measures to evaluate their combined effects on indoor environment, thermal comfort and its importance in energy conservation. A field experiment study was conducted in the sub-Saharan climate of Kiambu, Kenya where microclimate indicators were measured for validating and predicting the thermal behaviour. For this study, both mechanical and natural ventilation were restricted. Modelling and prediction were done in Design Builder and EnergyPlus software. The computer model was validated with data measured for 20 days on the field. A correlation value of 0.85 between the predicted values and the observed values was recorded. This result shows that this energy prediction process can provide reasonable predictions in cooling loads and the effect of passive cooling in reducing indoor temperature gains

Performance assessment of hybrid recuperative heat exchanger for diesel engine generated exhaust gas

In this study, the use of supplemental heat energy from exhaust gas of a stationary diesel engine was assessed to explore a new method of drying black nightshade seeds in a solar-exhaust gas greenhouse dryer. The energy recovery potential of a hybrid recuperative heat exchanger (HRHE) was demonstrated with the objective of utilizing the recovered energy from an engine on milling operations to heat a fluid stream of drying air. The results show that 4.45 kW of thermal energy was available in exhaust gas of a diesel engine operated at 2500 rpm when mass flow rate was 45.07 kg/h at a temperature of 357.36 °C. The rate of heat utilized for solar-exhaust gas mode ranged from 40.49 to 685.94 J/m2.s and from 21.69 to 668.11 J/m2.s in exhaust gas mode of drying. The heat exchanger raised the dryer temperature by an average of 11.78 °C when temperature differences between inside and outside were compared in solar-exhaust gas mode of drying. The average hourly rise in temperature inside the dryer was 8.04 °C with a minimum rise of 3.7 °C and a maximum of 9.41 °C when exhaust gas was utilized to provide heat energy. The performance of the solar-exhaust gas greenhouse dryer improved when thermal energy was used as a supplement in drying and as a result the drying time for black nightshade seeds was significantly reduced from 11 h in solar mode to 10 h in solar-exhaust gas mode of drying. Moreover, the seeds were dried for 14 h when exhaust gas mode of drying was performed without utilizing solar energy. The percent internal uncertainty for experimental measurements of relative humidity (γ) was 4.1% and 17.5% for temperature (T) observations. The three proposed thermal models for temperatures and moisture evaporation performed better with low RMSEs in exhaust gas mode compared to the other modes of drying

Realising the cross-cutting potential of sport in situations of forced displacement

Editorial: Realising the cross-cutting potential of sport in situations of forced displacement</p