Performance Evaluation of a Pebble Bed Solar Crop Dryer

The design, development and test performance evaluation of an integrated of passive solar energy crop drying system was undertaken. The solar crop dryer consists of an imbedded pebble bed solar heat storage unit/solar collector and crop drying chamber measuring 67 cm x 110 cm x 21cm and 50 cm x 90 cm respectively. The crop-drying chamber is made of drying trays of wire gauze while the roof is made of transparent glazing. Test performance evaluation of the solar crop dryer indicates that maximum absorber temperature of 72 0C, heat storage bed temperature of 58 0C and chamber temperature of 57 0C were obtained using the dryer when the maximum ambient temperature was  34 0C. Further test using cassava, showed a moisture reduction from 73% initial moisture content to 10.2% final moisture content in 3 days of drying process while open air sun drying was 22.2% under the same period of drying.Products dried under the passive solar crop dryer were of high quality while there were mould build up on the open air sun dried products. This indicates that drying under solar crop dryer offers high quality products and is time saving than the open-air sun drying

DESIGN AND ANALYSIS OF A MULTIPOINT TEMPERATURE DATALOGGER

 In this work, a low cost six- multipoint temperature data logger was developed. It was designed using LM35 as the sensor, and arduino Uno as the data processing element. The response time of the sensor was observed to be between three and four minutes. The comparative evaluation of the system with other established thermometers show that no two temperature meters gave the same values. However the most important thing is that all the systems recorded the same temperature flow pattern. This indicates that the systems actually senses change in the surrounding effectively. In relation to the alcohol thermometer, the designed system shows an accuracy of +0.4oC at temperatures below 300C and +1.850C at temperatures above 300C. The system gives room for effective and adjustable temperature data logging procedure. Hence, the system is recommended for use in monitoring low temperature systems. http://dx.doi.org/10.4314/njt.v35i2.3

Germination capacity and viability of threatened species collections in seed banks

Facing the current biodiversity crisis, the value of ex situ conservation has been increasingly acknowledged in international treaties and legislations. Seed banks are a good way of conserving biodiversity, providing that seeds are of high quality and at maximum viability. However, despite the number of established ex situ facilities, there is little information on seed viability in botanic garden seed banks. This paper analyses the status of the seed collection of the National Botanic Garden of Belgium by determining the germination capacity and viability of seeds that have been stored for 1-26 years. It aims at: (1) ensuring that existing storage conditions provide effective ex situ conservation of threatened species; (2) providing viability data on threatened species; (3) planning future collection and storage efforts for seeds of West European species of conservation value. Results from this study showed that the germination and viability percentages of the 250 tested species reached on average 59 and 79% respectively. Some families typically performed better than others. Within a species, consistent results were not always obtained. Over a quarter of accessions exhibited some degree of dormancy. Considering the current lack of knowledge in seed germination and dormancy of many rare and threatened species, we believe that the quality of a seed collection should be estimated by its viability and not by its germination percentage. This study calls for further research in order to better understand the biology of a range of threatened native species. © Springer Science+Business Media B.V. 2009.SCOPUS: ar.jinfo:eu-repo/semantics/publishe