Browsing by Author "Rulazi, Evordius"

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    Development and Performance Evaluation of a Novel Solar Dryer Integrated with Thermal Energy Storage System for Drying of Agricultural Products
    (American Chemical Society, 2023-11-14) Kivevele, Thomas; Kichonge, Baraka; Marwa, Janeth; Rulazi, Evordius
    Passive solar dryers play a crucial role in reducing postharvest losses in fruits and vegetables, especially in regions like sub-Saharan Africa with low electrification rates and limited financial resources. However, the intermittent nature of solar energy presents a significant challenge for these dryers. Passive solar dryers integrated with thermal energy storage (TES) can reduce intermittence and improve the drying efficiency. Currently, phase change materials (PCMs) are popular heat storage materials in dryers, and paraffin wax dominates. The main problem with the use of PCMs is that it is necessary to closely constrain the temperature range of the process during charging and discharging. This can be a difficult condition to meet in simple solar dryers due to the variable availability of solar radiation. Instead, solid-phase materials, such as sand and rocks, are often used. Soapstone is one of the natural rocks with good thermal properties, but it has yet to be used as a TES material in solar dryers for drying agricultural products. Therefore, the main objective of the present study was to develop a novel solar dryer integrated with soapstone as a TES material and evaluate its performance. The proximate analysis to examine the quality of dried products using the developed technology was also carried out. The comparative experiments for the developed dryer were conducted in two modes: dryer with TES materials and without TES materials, and the results were compared with open sun drying (OSD) by drying 50 kg of fresh pineapple and carrot at different times. The drying times for pineapples in the dryer with TES, without TES, and OSD were 13, 24, and 52 h, respectively. However, the drying times for carrots in the dryer with TES, without TES, and OSD were 12, 23, and 50 h, respectively. Notably, the dryer integrated with TES materials could supply heat for around 3–4 h after sunset. The thermal efficiency of the dryer, collector efficiency, and storage efficiency of TES materials were calculated and found to be 45, 43, and 74.5%, respectively. Proximate analysis indicated that the dryer integrated with TES materials effectively maintained the quality of the dried products compared to OSD. Solar dryer integrated with soapstone showed great promise as sustainable and efficient solutions for reducing postharvest losses and enhancing food security in resource-constrained regions like sub-Saharan Africa.
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    Development and Performance Evaluation of a Solar Dryer Integrated with Thermal Energy Storage Materials for Drying Agricultural Products
    (NM-AIST, 2025-03) Rulazi, Evordius
    Passive solar dryers are essential in reducing post-harvest losses of vegetable and fruits particularly in developing countries in Africa. Most simple passive solar dryers are being developed in developing countries, but the challenge is the sporadic nature of solar energy, resulting in reduced performance and rendering them ineffective during periods without sunlight. In addition, Techno-economic analysis (TEA) and Life cycle assessment (LCA) have been neglected in most of the studies on solar dryers (SD). In this study, a novel solar dryer incorporating soapstone as a thermal energy storage (TES) system to prolong the drying time was designed, constructed, and evaluated for its performance in terms of TEA and LCA. Experiments were carried out to compare the performance of the developed dryer in two configurations: With and without thermal energy storage (TES) materials. The results were evaluated alongside open-sun drying (OSD) with 50 kg of fresh carrots as well as fresh pineapples on separate occasions. The drying durations were recorded as 12 hours for the dryer with TES, 23 hours for the dryer without TES, and 50 hours for OSD. Notably, the TES integrated dryer could provide energy for approximately 3–4 hours after sunset. The dryer was found to have a thermal efficiency of 45%, a collector efficiency of 43%, and a storage efficiency of 74.5%. The dryer combined with TES materials proved to be more efficient in retaining nutrients in the dried products compared to the dryer without TES materials and OSD based on proximate study. The economic analysis showed that the annual savings for the dryer's 20 years of operation are $ 9814.5 for pineapple and $ 9121.2 for carrots. The cumulative present worth was $ 62 232.7 for pineapples and $ 57 836.3 for carrots. It was found that the pineapples payback period was 1.5 years, whereas for carrots payback was 1.6 years. The LCA revealed that steel materials had higher environmental impact items in material extraction and fabrication compared to aluminum materials for both the midpoint and endpoint categories. Based on techno-economic TEA and LCA assessments, the fabricated solar dryer is economically feasible and environmentally friendly. Solar dryers incorporating soapstone have demonstrated potential as efficient technology for minimizing post-harvest losses especially in developing countries in Africa.