Our Impact

Solar-assisted heat pump dryer with energy storage for drying biomaterials

Thematic Area: Minerals, mining and materials engineering

University: The Nelson Mandela African Institution of Science and Technology (NM-AIST)

Project Leader: Dr Thomas Kivevele

Collaborating Partners: Alpha Thermal Process, LLC (ATP); US Department of Agriculture (USDA), Eastern Regional Research Center, USA; Empowering Africa Consulting Group LLC, USA ; Innovative Technology and Energy Center (iTEC), Arusha Tanzania

Duration: 3 years

Project Overview

Fruits, medicinal herbs and vegetables which are traditionally sun-dried, are often of poor quality due to the complexity in controlling the rate of drying and the extent of cell damage. Over forty percent of agricultural produce in developing countries is wasted, not only due to lack of storage and processing facilities, but also due to limited knowledge of processing technologies. Economic considerations, environmental concerns and product quality aspects are the three main goals of drying process research in the food industry. In many cases, the drying process is applicable to seasonal biomaterials, so that they can be stored for as long as possible and be available out of season. Apart from direct sunlight drying, many farmers in Africa use firewood and fossil fuel burning, electrical and diesel engine heating, these methods result in smoke and other emissions which have negative effects on human health and contribute to climate change.

The technology

This project is proposing a solar-assisted heat pump dryer integrated with thermal energy storage system for drying fruits, medicinal herbs and vegetables. The technology can further be used for drying grains, fish and etcetera. Heat pump dryer has been proven as energy efficient method for drying thermally sensitive agricultural produce. This method is more efficacious than most of the traditional industrial and agricultural drying methods. This technology is not well-known in sub-Saharan Africa, however, developed countries have been using at advanced stage based on their specific climatic conditions which cannot be directly applied to a different region like sub-Saharan Africa. Hence the need to do an analysis of such technology especially for sub-Sahara African region is inevitable.

Expected Impact

The technology will be developed using locally available materials which are cheaper and readily available. The use of passive solar dryers which are mostly available in sub-Saharan region is limited because drying process is not possible in the absence of sunlight. Thus, integrating heat pump and thermal storage systems to the solar dryer will enable the system to work even when the sun is not active mostly in the evening and nighttime. Solar-assisted heat pump dryer uses renewable solar energy which reduces the deforestation problems resulting from cutting trees (fuelwood) for drying purposes. The proposed technology has short payback period and low cost of production due to high energy saving potential and low maintenance cost. The technology is also addressing the problem of postharvest loss in the region through drying. It is expected to increase the quality of dried products leading to improved farmers’ livelihoods and the national income at large.