Abstract:The Southern African Development Community's (SADC) water and energy sectors are under increasing pressure due to population growth and agricultural and industrial development. Climate change is also negatively impacting on the region's water and energy resources. As the majority of SADC's population lives in poverty, regional development and integration are underpinned by water and energy security as the watercourses in the region are transboundary in nature. This paper reviews the region's water and energy resources and recommends policies based on the water-energy nexus approach. This is achieved by reviewing literature on water and energy resources as well as policy issues. Water resources governance provides a strong case to create a water-energy nexus platform to support regional planning and integration as SADC countries share similar climatic and hydrological conditions. However, there has been a gap between water and energy sector planning in terms of policy alignment and technical convergence. These challenges hinder national policies on delivering economic and social development goals, as well as constraining the regional goal of greater integration. Regional objectives on sustainable energy and access to clean water for all can only be achieved through the recognition of the water-energy nexus, championed in an integrated and sustainable manner. A coordinated regional water-energy nexus approach stimulates economic growth, alleviates poverty and reduces high unemployment rates. The shared nature of water and energy resources requires far more transboundary water-energy nexus studies to be done in the context of regional integration and policy formulation.

A passive solar still with separate condenser has been modeled and its performance evaluated. The system has one basin in the evaporation chamber and two basins (middle and upper) in the condenser chamber, with a glass cover over the evaporator basin and an opaque condensing cover over the upper basin. The evaporator, middle and upper basins yield the first, second and third effects respectively. The top part of the condensing cover is shielded from solar radiation to keep the cover relatively cool. Water vapor from the first effect condenses under the glass cover while the remainder of it flows into the condenser, by purging and diffusion, and condenses under the liner of the middle basin. The performance of the system is evaluated and compared with that of a conventional solar still under the same meteorological conditions. Results show that the distillate productivity of the present still is 62 % higher than that of the conventional type. Purging is the most significant mode of vapor transfer from the evaporator into the condenser chamber. The first, second and third effects contribute 60, 22 and 18 % of the total distillate yield respectively. It is also found that the productivity of the solar still with separate condenser is sensitive to the absorptance of the evaporator basin liner, mass of water in the evaporator and middle basins, and wind speed. The mass of water in the upper basin has a marginal effect on distillate production. Other results are presented and discussed in detail.

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...

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