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Cycle 9 (2020 Deadline)

Solar dryer integrated with energy storage system: An energy efficient and environmentally friendly technology for drying biomaterials in Tanzania

PI: Thomas Kivevele (, Nelson Mandela African Institution of Science and Technology (NM-AIST)
U.S. Partner: Sunghwan Lee, Purdue University
Project Dates: July 2021 - July 2023

Project Overview:
Over 40% 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. Biomaterials, which are traditionally sun-dried, are often of poor quality due to the complexity in controlling drying parameters. Presently, most farmers in Tanzania use biomass and natural sun for drying their farming products, but biomass is becoming increasingly scarce and farmers, especially woman, have to walk long distances to fetch firewood (Mwema and Gheewalaa, 2011). Tanzania receives abundant solar radiation that can be used for drying agricultural produce. Solar dryers have the potential to exploit this renewable resource, and the technology is attractive because of its ability to rapidly, uniformly, and hygienically meet drying standards with zero energy costs. Despite development of solar drying technology in sub-Saharan Africa, most countries like Tanzania have seen limited market penetration because of a need for further research. Many solar dryers are only useful on sunny days and useless at night or during cloudy days. To facilitate drying in the absence of sunlight, dryers must have the capacity to collect and store heat for later use (e.g., overnight drying). This project is intended to develop an inexpensive, effective, and reliable solar dryer integrated with a thermal energy-storage system made of locally abundant and affordable materials (rocks) with favorable thermal and mechanical properties. The dryer prototype will include a solar collector and bed storage made of carbonate (dolomite and limestone) and granitic rocks. The project will further theoretically and experimentally investigate in-situ performance and economic feasibility of the developed dryer. Successful execution of the project will decrease wood-burning for drying purposes, thereby protecting the environment and reduce postharvest loss. The U.S. Government-supported partner is expected to use his expertise in solar energy conversion to provide guidance in the research design, data analysis, and review of manuscripts and patents resulting from this project. Also, he will facilitate access to lab equipment at Purdue University to characterize energy storage materials.

The Tanzanian government is promoting industrialization with the goal of achieving middle income by 2025. It is therefore important for institutions like the Nelson Mandela African Institution of Science and Technology to support these initiatives, especially with regard to developing technologies that will assist in reducing postharvest loss, which is one of the outstanding problems in the country. Agriculture is the backbone of the national economy of Tanzania in terms of food production, employment, production of raw materials for industries, and generation of foreign-exchange earnings. The national objective is to enhance production of quality products to improve market competitiveness of agricultural produce. This project is aligned with this policy for increasing productivity and reducing postharvest loss through drying. The proposed drying technology uses solar energy, which decreases deforestation problems resulting from using fuelwood for drying purposes in line with the Tanzania National Forest Policy of 2008 and the National Climate Change Strategy of 2012. This research will contribute to increased high-quality dried products such as fruits and vegetables, which are market-competitive and hence improve farmers’ livelihoods and national income in general. The project will also engage three graduate students (two MS and one PhD) and take into consideration the gender equality aspects at various stages of project implementation. The proposed technology will have a significant impact on the drying activities of fruits and vegetables, which mostly involve women. The project will also train women how to use the drying technology thereby promoting adoption and acceptability of the technology during and after the planned training workshops.

Summary of Recent Activities:

In this first quarter of 2023, the team completed data collection from the prototype solar dryer and completed modifications to the dryer to improve its performance. The developed dryer is installed at Tanzania Horticultural Association (TAHA) training Centre which is located at Tengeru area, Arusha where tests were being carried-out before it will be moved to a group of small-scale farmers involved in drying agricultural produce for piloting.

The second manuscript “Development and performance evaluation of a solar dryer integrated with thermal energy storage system for drying of agricultural products” based on the collected data was prepared and is currently undergoing internal review before journal submission. The first manuscript on “Experimental investigation of soapstone and granite natural rocks as energy-storage materials for concentrated solar power generation and solar drying technology” was submitted previously to the journal ACS OMEGA and the second response to reviewers' comments was submitted this quarter and is currently under review.

In the coming quarter, the team expects to complete the final two studies on the dryer, the techno-economic assessment and life cycle analysis using collected data, file patents and conduct the final project workshop to share findings of the project with key stakeholders and engage farmers on the use of the developed dryer.

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