Design and Simulation of a Renewable Energy – Solar Powered - Tobacco Curing System

∗ Corresponding author: Nicholas Tayisepi Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. Design and Simulation of a Renewable Energy – Solar Powered - Tobacco Curing System Timukudze Ndlovu, Nicholas Tayisepi *, Albert Nkulumo Mnkandla and Destine Mashava Department of Industrial and Manufacturing Engineering, National University of Science and Technology, Bulawayo, Zimbabwe. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074-095 Publication history: Received on 18 July 2025; revised on 30 August 2025; accepted on 3 September 2025 Article DOI: https://doi.org/10.30574/gjeta.2025.24.3.0252 Abstract Tobacco, colloquially termed the golden leaf, contributes, significantly, towards sustaining the Zimbabwean economy, wherein its annual contribution to the Gross Domestic Product – through substantial revenue and exports earnings - had averaged more than 10% for a period stretching more than five decades to date. Production, curing and processing flue cured tobacco in Zimbabwe is substantially energy demanding. The principal energy sources utilised in the mercantile tobacco processing, in Zimbabwe, are coal, wood and grid electricity. Wood is the main source of energy used in the tobacco curing process in the country side farms where deforestation acceleration is reported to be a major problem attributable to tobacco processing, in those regions where there is no alternative fuel, to wood, for curing the golden leaf. This study present the results of a proposed design of renewable energy (solar energy) fuelled tobacco curing system in a barn for bulk tobacco curing. The designed system utilises solar thermal collectors to generate the heat energy for physical curing of the tobacco and accumulating thermal storage reservoir during the day. The design of the automated solar-powered tobacco curing system aims to provide a sustainable and cost-effective solution for tobacco farmers by reducing their reliance on non-efficient traditional curing methods that rely on fossil fuels and the use of extensive manual labour. The automated system is designed to optimise energy use and minimise costly wood use and manual intervention by utilising an Arduino Uno controller for automated system elements actuation. The design prototype simulation results are promising. Keywords: Solar Radiation; Design Efficiency; Parabolic Collector; Modularity; Sustainable Energy; Renewable Energy 1. Introduction Utilisation of renewable energy resources to address the energy demand challenge has reached peak priority consideration in human societies the world over [1], and indeed in the Zimbabwean farming community in particular, in their quest to achieve and secure a sustainable energy transition during the curing of tobacco in the production season. This research designed a solar energy powered, micro grid for driving the thermal energy system in the uninterrupted continuous batch bulk drying of flue cured tobacco, enabled by an integrated renewable thermal energy storage system. Flat plate solar thermal collectors were used to circulate hot air through the bulk drying tobacco barn during the day whilst the parabolic solar thermal collector is used to concentrate solar thermal energy onto the rock bed thermal energy storage system, for use in the tobacco barn hot air circulation during the night. Tobacco, colloquially termed the golden leaf, contributes, significantly, towards sustaining the Zimbabwean economy, wherein its annual contribution to the Gross Domestic Product (GDP) – through substantial revenue and exports earnings - had averaged more than 10% for a period stretching more than five decades to date, [2]. Table 1 show a Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 75 snippet of the tobacco crop GDP contribution to be the Zimbabwean economy in the recent past few years over a few conveniently selected years. Table 1 Tobacco crop contribution to the Zimbabwe economy GDP Year GDP contribution in the Economy % 2000 8.2 2008 24.2 2016 11 2018 10 2020 10 2021 10 2022 10 2023 2.4 2024 5.44 It is apparent that tobacco has a significant contribution to the Zimbabwe economy, despite the observed attendant challenges of deforestation from the cutting down of trees for firewood to fuel the tobacco curing barns. Projectedly this tobacco influence shall continue to occur for a foreseeable future Thus, energy resources use optimisation strategies [3] and methodologies have to be developed in the tobacco processing business. Producing, curing, and processing of tobacco is energy demanding, [4, 5]. The principal energy sources utilised in the business of tobacco processing, in the developing economies, are coal, wood and grid electricity. Deforestation is a major challenge in tobacco producing areas where no fuel substitute, to firewood, is available for use during tobacco curing. Figure 1 typifies the nature of deforestation occurring in the Zimbabwe tobacco farmlands where wood is used as the main fuel for curing tobacco. Figure 1 Extensive deforestation prompted by wood cutting for tobacco curing [6] The Zimbabwe flue cured tobacco processing enterprise, is dominated by the use of firewood fuel and this significantly contribute to the challenge of deforestation in the farming lands where wood is the main fuel driving the curing energy Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 76 [7]. Figure 2 shows the remarkable thermal insolation map of Zimbabwe. The map shows promising potential for solar energy utilisation in the country due to its wide spread availability across the greater part of the country. Figure 2 Countrywide solar irradiation resource map of Zimbabwe [8] The other forms of energy fuel, rarely, used in the advanced farms are coal and grid electricity, [9]. The report on coal use in tobacco curing show that it brings the challenges of combustion instability, which results in elevated energy consumption, hence expensive, and poses environmental pollution [10]. The use of firewood and manual labour for tobacco curing is expensive and unsustainable and could be mitigated by the creation and utilisation of alternative renewable energy systems. In concurrence with this observation, Shati, et al., [6] asserted that there is now imperative need to shifting away from the use of fire wood as the main fuel energy source utilised in curing tobacco. The same research reported on the unanimous supportive stance among tobacco farming interest stakeholders, surveyed, on the requirement of the pursuit of implementation of renewable sustainable energy system solutions in the tobacco curing facilities. Thus, the design in this study was inspired by the requirement to minimally contribute towards reducing the current tobacco–curing fire-wood-cutting driven deforestation and contributing towards fostering long term sustainability in the business of tobacco curing. In an effort to tackle the elevated tobacco curing costs, a solar energy driven automated bulk tobacco curing barn system was designed, modelled and simulated to confirm the thermal energy distribution profile of the curing barn system. The potential application utility of solar energy in agro-processing systems of fresh cash crops is increasing, [11] in the recent times due to the affordability of solar technology resources. This design study investigated the technical practicability of utilising solar energy generated hot air to thermally cure tobacco in a bulk tobacco curing barn. The evolution of the microcomputer technology, in the recent past, offered increased feasibility of automating and controlling solar energy driven agricultural produce processing operations by utilising micro-controllers, [4, 12]. Performance optimisation and thermal efficiency of the system are anticipated to be realised through precise solarenergy based heat supply automatic control of the curing operation through employing the micro-computer control technology. Tobacco is an extremely labor-intensive cash crop when compared to most crops grown locally. The tobacco flue-curing process involves heating and drying tobacco leaves and the process requires 43 m3 of fuel wood of 15 000 kg to produce an average of 1 400 kg and therefore high labor for cutting down trees for firewood and supplying of wood into the furnace [13]. Domestic labor for tobacco production and curing is expensive making up about 50% of the total cost [14]. The tobacco is allowed to dry over a period between one to eight weeks, therefore during this period there should be more labour input to continuously supply firewood into the barn for maintaining the optimum temperatures required in the drying chamber. The inability to mechanise such a complex operation that eliminates the tobacco curing optimum temperature maintenance problem, as well as the use of firewood, is a key solution point for the large labor requirements in tobacco production. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 77 The country, Zimbabwe, has 4,130,000 hectares of arable land, with animal and manual draught power used to cultivate 25% of it. A significant part of the population are farmers who dependent on tobacco farming for their livelihoods [15]. Among the major cash crops that are exported from Zimbabwe, tobacco, the golden leaf, contributes the highest foreign currency earnings from the agricultural sector, dominating 50% of the total income from overall agricultural exports [16]. Though the industry is lucrative, it still lacks an automated solar system for tobacco curing to increase the quality of cured tobacco, the efficiency of the barn curing process system - through energy sustainability - and decrease labour intensity which are drawbacks to the industry’s operations. Figure 3 show the minimum time taken to completely cure a leaf of tobacco using direct or indirect heating relative to the temperatures involved per each stage. The flue tobacco curing process uses 43 m3 of fuel wood of 15 000kg and produces an average of 1 400kg of cured tobacco [13]. Using a rocket barn the ratio of firewood to cured tobacco is 9 kg : 1 kg respectively. The indirect (flue-curing) process lasts for at least 200 hours to completely cure a leaf of tobacco whilst direct (fire) tobacco curing last for at least 270 hours to completely cure a leaf of tobacco, [2] . Despite the large amounts of firewood being used, the lack of automation and non-manual monitoring systems increases the time for curing and makes the system job very hard. Figure 3 Tobacco curing process [9] Figure 4 shows that monitoring and control are very crucial in tobacco curing for the best quality and good grade of tobacco. Temperature and humidity or moisture of both the leaf and surrounding of the leaf should be monitored thoroughly at each stage of the curing process. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 78 Figure 4 Temperature against humidity during curing [9] In much of the world, awareness is growing about renewable energy technologies having a major role in the extension of technologies to farmers in developing countries to improve their productivity [17]. The development of a reliable, fairly air-blown automatic solar system that can be mass-produced and used for tobacco curing would greatly aid the introduction of clean natural energy for tobacco curing. Apart from the prevention of deforestation, land degradation, and air pollution, introducing a solar tobacco curing system that is automatically controlled will also reduce curing time as it eliminates human error in trying to maintain the optimum temperatures in the drying chamber. Due to the use of fire for curing tobacco leaves will always be smelling smoke from the fire burning but introducing this proposed solar energy-based curing system will eliminate this contamination factor and enhance the final leaf quality of the tobacco. Compared with a direct curing barn, the energysaving rate can reach up to 50% when compared to the current curing regime [18]. Therefore, a heating source like an automated solar heat pump is projected to be more energy-efficient than direct firewood based natural airflow heating. It could have a non-negotiable, significant role to play in the advancement of sustainable use of energy. 1.1. Tobacco Curing Tobacco curing is a deliberate controlled man-made effort intent on creating a favourable condition for the tobacco leaf to biologically physically mature. The two key goals targeted, are firstly, in the curing of tobacco relate to the provision of temperature and humidity conditions that will promote the subsistence of the physical biological and chemical changes occurring in the tobacco leaves, and secondly, timeous dehydration of the tobacco leaves so that they are preserved, [7]. The process is typically aimed at developing three key quality aspects of the tobacco, viz, the aroma, the colour and enzymatic changes in the tobacco leaf. Tobacco curing methodology involves the removal of chlorophyll from the tobacco leaves, causing them to turn yellow (see the leaf colour change transitions shown in Figure 5). According to tobacco handling personnel, colour accounts for 75% of the market value of tobacco. This is a process which is carried out at a temperature range of 30-40°C from an elevated humidity level of 85%, [11]. Tobacco leaves are dried or cured when heat is distributed uniformly inside a tightly closed barn using a heat exchanger at a temperature of 40-50°C, and finally, the main leaf stem is dried by exposing the tobacco to a higher barn temperature of 65-70°C with declining humidity for a determinate time duration, [19]. The leaves are loosely hung inside the barn to allow for an easy flow of hot air. Natural convection is the primary mode of heat transfer to the leaves. Wood, coal, solar energy, and LP gas are all common fuels used in curing tobacco, [2]. Figures 5 depict the three clear views of the fundamental curing process stages taken by the tobacco leaf during the curing process, [20]. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 79 Figure 5 Three stages of tobacco curing [20] There are four curing processes namely • Flue or indirect curingThe barns' flues come from furnaces or fireboxes that are fed externally throughout the curing process. These fireboxes are employed to provide heat without exposing the tobacco to smoke for curing in the barn [20]. The tobacco that is produced has a high sugar content and medium to high nicotine levels. • Fire or direct curingTobacco is strung in vast barns, and a constant fire of wood, coal, or charcoal is maintained burning beneath the tobacco. The tobacco produced has a low sugar content and a high nicotine content [21]. • Sun curingInvolves exposing tobacco directly to the sun until the leaves are brown and withered. The tobacco produced is low in both sugar and nicotine [19]. • Air curingTobacco is hung in a well-ventilated barn and allowed to dry over a period of four to eight weeks. The tobacco produced is low in sugar, high in nicotine, and has a sweet flavour [21]. 1.2. Solar heat collectors There are numerous types of solar collectors. Solar heat collectors are classified as either stationary or nonconcentrating and concentrating. A list of the numerous subcategories and traits of thermal energy collectors is presented in Table 2. Table 2 Solar energy collectors Motion Collector type Absorber shape Concentration ratio Indicative temperature range oC Stationary Flat plate collector (ETC) Flat 1 30-80 Evacuated tube collector (ETC) Flat 1 50-200 Compound parabolic collector (CPC) Flat 1-15 60-200 Tubular 10-40 80-300 Single-axis tracking Linear Fresnel reflector (LFR) Tubular 15-45 80-250 Parabolic trough collector (PTC) Tubular 10-50 80-300 Parabolic trough collector (PTC) Tubular 100-1000 80-300 Cylindrical trough collector (CTC) Tubular 100-1500 100-500 Two axis tracking Parabolic dish reflector (PDR) Point 100-1500 150-2000 Heliostat field collector (HFC) Point 100-1500 150-2000 Courtesy: [22] Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 80 The flat-plate solar collector is a device used to convert solar energy into thermal energy. It consists of a box-like structure with glass sheets covering the top surface [22]. The glass transmits shortwave solar irradiation but increases the glass temperature by trapping long-wave radiation within it. This trapped radiation is then absorbed by the surface absorbent, which is usually made of a material with high thermal conductivity such as copper or aluminium. The absorber plate heats up and transfers its heat to a fluid that flows through it, which can be water, air or some other fluid depending on the application. Durability, energy transmission, non-degradability, and strength are all important characteristics. According to research findings reported by Himanshu , et al., [23], a larger component of solar irradiance energy impinging on a transparent-material-covered blackened surface of high absorbency behaviour, is transmitted into the transportation media in the pipes and gets conveyed to the storage or use point. Figure 6 shows a typical schematic image of a flat plate solar collector. This was considered in the curing barn design for the portion responsible for direct heating air supply feeder line into the barn during the day. Figure 6 Flat plate solar collector [24] 1.3. Solar thermal energy storage Thermal conductivity, thermal diffusivity, and heat capacity of materials are all important properties in determining the efficiency of a thermal system, [25]. Thermal energy storage is one of the utmost effective methods of warehousing astral energy when a fluid (air, water or other media) is incorporated into contact with solar air heater. Thermal energy accumulation facilities enable the collection and accumulation of solar energy systems for utilisation in the convenient future [23]. This technology enhances flexibility and efficiency, in operation processes, by storing the heat energy for eventual uses as may be deemed convenient by the users, [26, 27]. Thermal accumulation (storage) systems exterminate intermittent energy status between the supply and demand sides. Solar energy storage system could be stored as sensible or latent heat, where respectively, the thermal energy could be stored inside the storage medium by raising the storing body temperature which does not change its material phase, [23], whereas, in latency form the stored energy causes the storing body phase to change its state. According to Clerjon and Perdu [26], solar energy based thermal energy storage systems accumulate thermal energy into the thermal storage material before sunset and the thermal energy shall be used to heat the material at a later time even after the sun had long set. Currently thermal storage systems are integrated to accumulate thermal energy for use in greenhouses, [23]. The schematic representation process chain, illustrated in Figure 7 denotes the conversion principle of energy from solar irradiation to usable and storage warehousable thermal energy. Irradiance – the insolation energy in the electromagnetic wave form per unit surface area of the earth measured in kW/m² - is the key fundamental factor enabling the utility of solar thermal energy system application, [6]. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 81 Figure 7 Solar irradiance to thermal energy conversion process schematic representation chain [28] In light of the abundance, of solar energy availability in Zimbabwe, during the tobacco curing season, the objective of this research included designing and analysing the performance of the solar thermal energy tobacco bulk curing system, wherein solar energy heated hot air is circulated through the curing ban to provide tobacco curing process as desired. The amount of heat energy (Q) transferred, balance for short term and long-term storage requirements during an insolation exposure process, is given by equation 1, thus: 𝑚𝑚𝑐𝑐𝑝𝑝𝛿𝛿𝛿𝛿 𝛿𝛿𝛿𝛿 =𝑄𝑄𝑢𝑢−𝑄𝑄𝐿𝐿−𝑄𝑄𝑠𝑠 (1) Where, m - the mass; Cp - its specific heat; T - the temperature; t - the time; Qu - solar energy rate which charges the storage; QL - the energy rate required by a curing barn; and Qs is the energy loss rate to the surroundings, then also 𝑄𝑄𝑢𝑢=𝑙𝑙𝑎𝑎 (2) Where, la - actual solar insolation The collector efficiency is given by equation 3, thus: 𝜂𝜂=𝑄𝑄𝑛𝑛 𝑄𝑄=𝑎𝑎(1−𝑔𝑔)−𝐶𝐶𝛥𝛥𝛿𝛿 𝑄𝑄 (3) Where, Q - where solar radiation density normal to the collector plate (W/m2); Qn - net heat absorption (W/m2), g - reflection and absorption loss in the cover plate; a - absorption coefficient for solar radiation of a black body; Tpl - absorber surface/black plate temperature (K); Tgl - surrounding air/glass cover temperature (K); g = 0.15; a=0.09 The projected profile of daily insolation curve and the associated solar insolation collector efficiency is represented in Figure 8. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 82 Figure 8 Summer time daily insolation curve and collector efficiency estimate, [6] The useful energy gain by the collector, under steady state, is given by equation 4: 𝑞𝑞𝑢𝑢=𝐹𝐹𝑅𝑅𝐴𝐴𝑐𝑐[(𝜏𝜏⍶)𝐼𝐼 −𝑈𝑈𝐿𝐿(𝑇𝑇𝑖𝑖−𝑇𝑇𝑎𝑎)] (4) Where, 𝜏𝜏⍶ - is the absorbance transmittance product; 𝑈𝑈𝐿𝐿 – is the overall heat transfer coefficient (J/m2K); 𝑇𝑇𝑖𝑖 – Temperature at inlet; L – is the bed length (m); 𝐹𝐹𝑅𝑅 – Collector removal factor. The long-established sensible heat storage computation formula, which makes use of a variety of common materials, wherein, the mode of thermal energy transfer is by conduction through heat exchangers, is summarised in equation 5, [29]. 𝑞𝑞=𝑚𝑚𝑐𝑐𝑝𝑝(𝑇𝑇𝑓𝑓−𝑇𝑇𝑖𝑖) (5) Where, m - the mass (given by equation 6); Cp - its specific heat; Tf – final temperature; Ti – initial temperature, And, 𝑚𝑚=𝑉𝑉 𝜌𝜌 (6) Wherein, V – volume, and ρ - density Therefore, 𝑞𝑞=𝑉𝑉 𝜌𝜌 𝑐𝑐𝑝𝑝(𝑇𝑇𝑓𝑓−𝑇𝑇𝑖𝑖) (7) Heat capacity (ρcp), is the combination of density and specific heat, and in order to store solar energy in another medium, the thermal conductivity of that medium is also important, leading to the parameter known as thermal diffusivity [5], which is in equation 8: k ρc𝑝𝑝 (8) The energy storage materials performance behaviour depends on the heat capacity and thermal diffusivity, [23, 30]. Table 3 shows common storage materials. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 89 a variety of applications, as well as its high processing speed. Figure 13 shows the control system, design concept, of the automated solar-powered tobacco curing system. The circuit design presented, in Figure 14, depicts the connections for all of the electronic components that constitute the automated solar powered tobacco barn curing system control. 3.2. System functionality simulation and modelling results The barn prototype model was constructed. The prototype was developed using different tools, keeping the design objectives in mind. Samples, of tobacco, were dried in the barn and measurements, of the drying process, were recorded. The barn curing process was also simulated and results were recorded and compared, of the simulation model as well as the physical model curing process. The tobacco barn heat distribution simulation was performed to quantify the variability of temperature and humidity within the curing barn, which influences the tobacco leaf quality. Figure 15 shows the computational fluid dynamics (CFD) simulation planning flow chart of the tobacco curing barn heating process. The control system pseudo code text instructions is detailed in Appendix 1. Figure 15 Design CFD simulation plan flow diagram of the solar energy curing system Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 90 Figure 16 results show the thermal distribution gradient map simulation of the interior environment of the curing barn. It is apparent, from the heat distribution map that the heat energy reasonably saturates the barn’s interior such as to cause the dehydration of the tobacco hung inside it adequately. Figure 16 Curing barn interior thermal map system simulation The heat distribution simulation was performed to quantify the variability of temperature, within the curing barn, which influences the distribution of tobacco leaf quality. The simulation results for a five-day curing schedule is presented in Figure 17(a) whilst results presented in Figure 17(b)show the relative humidity variation inside the curing barn during the same period. The temperature variation results indicate the adequacy of the temperature elevation within the barn to the maximum soaking temperature of 70 oC required to cause the drying of the leaf midrib after the main leaf body which dries sufficiently at lower temperatures. Figure 17 (a) Curing temperature and (b) relative humidity, respectively, vs time plots The relative humidity change, of the curing barn interior shown in Figure 17(b) indicate good drying capacity of the designed curing barn system as reflected by the comparability of the live curing and simulation curing humidity reduction curves over the assessment time period of 5 days. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 91 Comparison graphs for six days drying curing process schedule results, graphically presented in Figure 18(a) graphs, respectively, of the physical model temperature and simulated system temperature, as well as the physical model humidity and simulated system humidity, results shown in Figure 18(b). Figure 18 (a) Curing temperature and (b) relative humidity, respectively, vs time plots Graph results presented in Figure 18(b) show the comparative curves of the simulated and practical (physical model) profiles of relative humidity over a six-day curing schedule. 3.3. Solar driven tobacco curing system design implementation costs This section deals with project costing. It is carried out to evaluate the costs associated with project implementation in order to assess the financial feasibility of project implementation. It involves an analysis of various components and economic evaluation to ensure financial feasibility. Economic evaluation of the solar energy systems design is implemented in order to establish the least expenditure of providing the sustainable renewable energy-based tobacco curing system. The costing details of implementing the prototype development are presented in Appendices 2 and 3. The project implementation cost is estimated at US$1300.00 and the payback period is two (2) years. 4. Conclusion In conclusion, the development of an automated solar-powered tobacco curing system represents a viable solution for long-term and cost-effective curing process in tobacco production. The design limitation though is in the design process assuming that there shall not be extended periods of overcast cloud cover weather patterns during the tobacco curing periods when extensive energy resources shall be required. The design research strives to strengthen farmers’ capability in harnessing the renewable solar energy and storing the energy for continued use in curing tobacco during periods when there is no clear sunshine. This is anticipated to benefit the farmers, through increasing the efficiency in tobacco curing. Further work relate to building more real-life prototypes and carrying out more tests and gathering more data for easier of future predictions. Compliance with ethical standards Acknowledgments The authors express their profound gratitude to the Industrial and Manufacturing Engineering Department Board, of and the National University of Science and Technology, for extending funding support to this research. Disclosure of conflict of interest The authors were not conflicted and had no conflict to declare. Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 92 References [1] Mihramane R l, Ech-Charqaouy S S, Saifaoui D, Ech-Charqaouy N, Ech-Charqaouy A. Management and Optimization of a Renewable Energy Hybrid System Integrated into a Microgrid, Considering Constraints Related to Voltage Stability and Service Continuity. International Journal of Renewable Energy Research (IJRER). 2025 Jun 29; 15 (2):213-25. [2] MOAG. National Agricultural Policy Framework 2018-2030. Ministry of Lands, Agriculture and Rural Resettlement (MOAG). Government of Zimbabwe, Harare: 2024. 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Bulletin of the Torrey Botanical Club. 1937; 64 (3) 117-131. Appendices Appendix 1 Software Design: Pseudo Code for automated tobacco curing barn process control Among the three areas of this design, the software design for an automated solar-powered tobacco curing barn is the most critical. Software is the brain that instructs the system to meet the specified parameters. Several factors were carefully considered to ensure that the software operates flawlessly. The designers used the knowledge base of tobacco expert curers as a reliable parametric source to design the software. Arduino Uno was chosen to carry out the required controller operations. This section of the design also received presentations from all relevant algorithms. In some cases, pseudo codes were also provided to assist with the proper design and programming of the specific automated solar- Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 94 powered tobacco curing barn operation. The entire code was developed in the in C++ language, to implement the set of instructions texturally presented in the section’s headings below 4.1. Leaf colouring stage • If the temperature is less than 30 °C, turn on the fan to raise the temperature. • If the temperature is between 30-40 °C, turn off all actuators while rotating the leaf hangers once every onehour interval. • If the temperature exceeds 40 °C, turn on the blower and the heat reduction fan, and turn on the motor to rotate the leaf hanger while the heat increasing fan is turned off. • If the humidity level in the barn is less than 70%, open the valve to increase moisture in the barn and turn on the motor to rotate the leaf hanger every 1-hour interval. • If the humidity level exceeds 75%, turn on all actuators to reduce moisture while maintaining motor rotation and temperature. 4.2. Lamina drying stage • If the temperature is less than 40 °C, turn on the fan to raise the temperature in the curing barn. • If the temperature is between 40 °C and 60°C, turn off all actuators while the motor is running to rotate the leaf hangers every 1 hour. • If the temperature exceeds 60 °C, turn on the blower and the heat reduction fan, and turn on the motor to rotate the leaf hanger while the heat increasing fan is turned off. • If the humidity level in the barn chamber falls below 30%, turn on the valve to maintain the humidity level while maintaining the hanger rotation. • If the humidity level exceeds 35%, turn on all actuators and rotate the leaf hanger every 1 hour. 4.3. Stem drying • If the temperature is less than 60 °C, turn on the heat blower to raise the temperature in the curing barn. • If the temperature is between 60-70 °C, turn off the actuators while rotating the motor for the leaf hangers once every one-hour interval. • If the temperature rises above 70 °C, turn on the blower and fan while the motor of the leaf hanger remains turned on. • If the humidity level is below 20%, turn on the valve while the leaf hangers continue to rotate once every onehour interval. • If the humidity level reaches 18%, turn on the buzzer to indicate curing cycle completion and maintain the leaf hanger in rotation. Appendix 2 Table Bill of materials Qty Item Description Price Total Cost (US$) 5m2 Transparent glazing $ 2.10 $ 10.50 5m2 Absorber plate $ 100.00 $ 500.00 4 Light Dependent Resistor (LDR) $ 1.25 $ 5.00 1 Legging insulation $ 50.00 $ 50.00 2 Servo motor $ 5.00 $ 10.00 1 Geared motor $ 30.00 $ 30.00 10 Light Emitting Diode (LED) $ 0.20 $ 2.00 1 Breadboard $ 6.00 $ 6.00 2 DHT11 Humidity and Temperature Sensor $ 6.00 $ 12.00 Global Journal of Engineering and Technology Advances, 2025, 24(03), 074–095 95 1 Arduino Nano $ 15.00 $ 15.00 1 Arduino Wemos D1 Wifi Uno ESP8266 $ 25.00 $ 25.00 1 Arduino power supply $ 10.00 $ 10.00 1 Push button $ 1.00 $ 1.00 1 Fan $ 6.00 $ 6.00 1 Buzzer $ 1.00 $ 1.00 1 Jumper cables $ 5.00 $ 5.00 1 Housing Materials $ 200.00 $ 2000.00 Total $ 898.50 Appendix 3 Table Total cost estimation Expenditure description Total cost (US$) Total Material Costs $ 898.00 Total Labour Costs $ 280.00 Overhead Costs $ 122.00 Total Capital Investment Cost $ 1300.00