Solar dryer with thermal storage and biomass-backup heater

Abstract

The Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. Madhlopa, A. and Ngwalo, G. (2007) Solar dryer with thermal storage and biomass backup heater. Solar Energy, 81 (4). pp. 449-462. ISSN 0038-092Xhttp://strathprints.strath.ac.uk/16428/ This is an author produced version of a paper published in Solar Energy, 81 (4). pp. 449-462. ISSN 0038-092X. This version has been peer-reviewed but does not include the final publisher proof corrections, published layout or pagination.Strathprints is designed to allow users to access the research output of the University of Strathclyde. Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (http://strathprints.strath.ac.uk) and the content of this paper for research or study, educational, or not-for-profit purposes without prior permission or charge. You may freely distribute the url (http://strathprints.strath.ac.uk) of the Strathprints website.Any correspondence concerning this service should be sent to The Strathprints Administrator: eprints@cis.strath. AbstractAn indirect type natural convection solar dryer with integrated collector-storage solar and biomass backup heaters has been designed, constructed and evaluated. The major components of the dryer are biomass burner (with a rectangular duct and flue gas chimney), collector-storage thermal mass and drying chamber (with a conventional solar chimney).The thermal mass was placed in the top part of the biomass burner enclosure. The dryer was fabricated using simple materials, tools and skills, and it was tested in three modes of operation (solar, biomass and solar-biomass) by drying twelve batches of fresh pineapple (Ananas comosus), with each batch weighing about 20 kg. Meteorological conditions were monitored during the dehydration process. Moisture and vitamin C contents were determined in both fresh and dried samples. Results show that the thermal mass was capable of storing part of the absorbed solar energy and heat from the burner. It was possible to dry a batch of pineapples using solar energy only on clear days. Drying proceeded successfully even under unfavorable weather conditions in the solar-biomass mode of operation. In this operational mode, the dryer reduced the moisture content of pineapple slices from about 669 to 11% (db) and yielded a nutritious dried product. The average values of the final-day moisture-pickup efficiency were 15, 11 and 13 % in the solar, biomass and solar-biomass modes of operation respectively. It appears that the solar dryer is suitable for preservation of pineapples and other fresh food...

Energy sustainability through integrated solar thermal systems

“…Madhlopa and Ngwalo [1] studied an indirect solar dryer with biomass backup heaters. The biomass burner was made of brick and consisted of rock pebbles which acted as a thermal storage.…”

“…The biomass gasifier consists of a shell and fin heat exchanger configuration and the heat delivery and combustion rate could be controlled using a butterfly valve at the primary air inlet. Among the biomass fuel materials that have been reported in biomass burner application are coconut shells (Serafica and del Mundo [8]), woodchips (Bhattacharya, et al [9], and Madhlopa and Ngwalo [1]), charcoal (Prasad et al [4]), paddy husk (Thanaraj et al [2]), fuel wood (Prasad and Vijay [3], Bena and Fuller [6], and Tarigan and Takasakul [5]), and briquetted rice husks (Mastekbayeva et al [10]). …”

Development of prototype solar-biomass hybrid dryer and its performance evaluation using salted fish (Cynoglossus spp.)

“…As the product is enclosed in the dryer, it is protected from dust, insects, birds, rodents and animals (Sharma et al, 2009). Solar dryer has the limitation that it can be used only during daytime and the drying process has to be continued next day which leads to inferior product and limits production (Madhlopa and Ngwalo, 2007). To get better quality product, it is necessary to provide solar dryer with any form of back-up heating.…”

Evaluation of hybrid solar – biomass dryer with no load

“…The temperature recorded at the bottom tray was 59.5ºC. An indirect type natural convection solar dryer with integrated collectorstorage solar and biomass-backup heaters has been designed, constructed and evaluated by Madhlopa and Ngwalo [2]. The major components of the dryer are biomass burner, collector-storage thermal mass and drying chamber.…”