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The drying process in agriculture is energy-intensive and traditionally relies on fossil fuels, which are becoming less reliable and more expensive. This study designed and simulated a hybrid solar hot plate dryer system using the computer to reduce reliance on fossil fuels. The system's main components are a flat plate collector, photovoltaic panels, and a wind turbine. This system was simulated in three cities of Iran, including Bushehr, Kerman, and Shahrekord, from May 22 to October 23. Results showed that Bushehr had the best wind turbine performance, producing 1.35 × 109 W annually. Shahrekord was ideal for solar energy, reaching solar radiation levels of about 4540 kJ/m2hr in September and generating 6660 W of solar-heated water. Finally, by comparing the yearly yield, it was concluded that Bushehr had a higher yield than the other two cities due to its geographical location, which was 0.301. The results of this research indicated that Iran, with its sunny days and wind energy potential, will be a very suitable place for installing and operating the hot plate solar dryer system. Future studies should look at longer-term simulations, use real-time data, and consider cost-benefit analyses to improve system efficiency and applicability. [ABSTRACT FROM AUTHOR]

The drying kinetics and physical and chemical characteristics of Leucaena esculenta seed drying using a forced convection solar dryer are described. The drying kinetics behavior is examined for three experiments under climate conditions of three different winter days in central Mexico, observing significant effects related to the reported pH levels of the seeds with values of 6.34, 5.98, 5.97, 5.82, and 6.07. The airflow measurements inside the drying chamber were observed, including the geometric dimensions, color, appearance, weight, and moisture loss, and the effective diffusivity coefficient D e f f of Leucaena esculenta with values between 1.23 × 10−7 and 8.09 × 10−9  m 2 s . Solar drying, with the technology used in this study, is a viable alternative to give added value to Leucaena esculenta. This study can be the basis for developing alternatives to preserve seeds for animal and human consumption. [ABSTRACT FROM AUTHOR]

The aim of the current research is to dry apples using a solar dryer with a desiccant cycle in two modes: direct radiation -convection and indirect radiation -convection. Two types of drying methods, direct and indirect with desiccant and without desiccant, moisture content, and drying in open air were used. Pre - prepared apple slices (flavored with cinnamon) were placed on a specific -sized mesh, the initial weight of the samples was measured, and they were placed inside the solar dryer with a desiccant cycle in two modes: direct radiation -convection and indirect radiation -convection. During the drying process, the evaporation rate, texture, wrinkling, water reabsorption, vitamin C retention, color changes, and sensory characteristics at different treatment levels (30% sucrose and without sucrose, 0.5%, 1%, and 2% cinnamon) were examined. Additionally, several samples were dried as controls without cinnamon flavoring using the solar dryer. Data analysis was conducted using a completely randomized factorial design and the statistical software SPSS version 26. The results of the study showed that in both direct and indirect methods, with and without desiccant, the moisture removal rate in samples without sucrose was higher compared to samples with sucrose and cinnamon. Comparing control samples in both methods with and without desiccant moisture showed that the evaporation rate of samples with desiccant moisture was significantly higher. Furthermore, in samples with sucrose, the evaporation rate was lower in the desiccant method, and in direct sunlight drying, the drying rate was significantly lower compared to solar dryer drying. The results of evaporation rates in the indirect drying method also indicated that similar to the direct method, the evaporation rate of samples with cinnamon treatment and without sucrose was higher than that of samples with sucrose and controls. Tissue analysis results also indicated that the highest firmness was observed in the direct method without desiccant for samples without sucrose, with no significant difference in means. Cinnamon also increased the firmness in samples without desiccant moisture in the indirect drying method, and samples with sucrose had less wrinkling, with an increase in cinnamon concentration leading to more wrinkling, with the highest increase observed in the direct method without desiccant at 2% cinnamon and in the direct method with desiccant at 1% cinnamon concentration. The water reabsorption rate in both direct and indirect drying methods showed that samples with sucrose had better water reabsorption conditions, and the vitamin C degradation rate indicated that the use of sucrose improved vitamin C retention. Color change analysis also showed that samples with sucrose had more favorable conditions in both methods. Therefore, the results related to sensory evaluation characteristics indicated that samples with sucrose and different cinnamon concentrations received the highest sensory evaluation scores. Hence, it can be stated that samples dried with osmotic solution and sucrose generally had better acceptability in terms of physical appearance, color, taste, and flavor . [ABSTRACT FROM AUTHOR]

A drying technique utilizing solar energy on shredded apples as raw material for apple infusion has a reduced emission risk while also producing high-quality drying products.This study aimed to determine the optimum semi-theoretical mathematical model for drying shredded apples after blanching and non-blanching treatments utilizing three simple mathematical models: Newton, Henderson, Pabis, and Page. The results showed that blanched shredded apples dried using the Convective Solar Drying (CSD) method had the highest rate of decrease in the moisture ratio compared to those dried in the open sun drying (OSD). The three semi-theoretical models examined can be used to forecast the rate of decline in the water content ratio of dry shaved apples in all treatment combinations, as demonstrated by a value of R2 more than 0.9. Based on a comparison of the validity of each semi-theoretical model utilized, Page's model is the best model for characterizing the drying kinetics of shredded apples for both blanching CSD, non-blanching CSD, blanching OSD, and non-blanching OSD drying. The information acquired will be important in selecting an appropriate apple pretreatment handle and drying model for shredded apples.

Solar dryers are solar thermal devices which increase the drying temperature and aid in moisture removal from the load, leading to faster drying of the agri-product as compared to the open sun drying. Conversion of grapes to raisins can be effectively achieved through solar dryers, and efforts are ongoing to improve the efficiency and further reduce the drying time. Usually in order to reduce the drying time for the conversion of grapes to raisins several pre-treatment methods with the use of chemicals are employed. In the present work pre-treatment in the form of blanching of grapes is adopted without the use of any chemicals to study the effect on the drying time in the solar dryer. The experimental results have been compared with the study of conversion of grapes to raisins with the same solar dryer without blanching. It is found that pre-treatment in the form of blanching resulted in a reduction in drying time to almost half. Experimental observations for the temperature profile studies relating to ambient temperature, air temperature inside the dryer, base plate temperature and solar radiation are presented in the form of graphs and calculations have been carried out for the estimation of drying rate and efficiency.

In this study, a solar dryer incorporating a flat plate heat exchanger to recover heat from exhaust air was investigated to explore the usability of different types of collectors in the system. Their usability was further evaluated through economic and environmental analyses. Moreover, the thermodynamic performance of the solar dryers was evaluated under two weather conditions in Nepal. Apple drying experiments were conducted for 8 h from 09:00 to 17:00 from February to April 2023 on solar dryers and with open sun drying (OSD) in Dhulikhel, Nepal. The results showed that the low emissivity (low-e) coated aluminum collector was more efficient in terms of collector efficiency and drying rate than collectors with flat or v-corrugated GI absorbers. The average collector efficiency and drying rate were found to be 89 % and 107 g/(h × m2) using the low-e coated aluminum collectors, while the values were 50 % and 84 g/(h × m2) for the GI sheet collector. The results indicated a slight improvement in the performance of v-corrugated collectors, with values of 53 % and 89 g/(h × m2). The drying rate for OSD was found to be 78 g/(h × m2), which was lower than for the dryers with all collectors used in this study. In terms of economic analysis, the dryer equipped with the low-e coated collector was found to be superior, with a payback time of 1.61 years compared to the dryers with flat or v-corrugated GI collectors. Reducing the thermal losses due to radiation by using the low-e coated absorber was shown to be more important than increasing the absorber area using v-corrugated GI sheets.

In line with the aim of drying food products of high quality in the shortest time and with the least energy consumption, in this study, peach slices of three different thicknesses were dried in three different dryer types. The drying of peaches was carried out using a solar energy drying system, a thermal energy storage solar dryer, and a dryer with a heat pump. The drying performances of peach slices of three different thicknesses were investigated. SMER, MER, and SEC values, which relate to the amount of removed moisture and the amount of consumed energy at the end of the drying studies, were calculated. Food analyses, such as moisture, color, texture, and water activity were performed. Considering the amount of energy consumed, it is seen that the heat pump system consumes more energy than the solar energy system. In addition, by using the heat storage system, the drying time is shortened and the energy consumption is reduced. A decrease in SEC values was observed with the activation of the heat storage solar dryer.

Traditional open sun drying methods face issues such as weather dependence, contamination risk, inconsistent drying rates, and nutrient loss. This study investigates a novel photovoltaic (PV)-integrated solar dryer designed to improve seaweed drying efficiency by effectively removing moisture content. Addressing the needs of Malaysian seaweed growers for a reliable and efficient drying method, this research compares conventional open sun drying with solar drying by evaluating key parameters such as moisture removal rate, drying rate, and dryer efficiency. Using a sample size of 100 grams, experimental results demonstrated that moisture loss was higher with solar drying, resulting in significantly lower final weights for Sargassum polycystum (43.8 g) and Cystoseira barbata (40.1 g) compared to open sun drying (55.81 g and 52.9 g, respectively). The drying rate for seaweed in the solar dryer was also higher, with Sargassum polycystum at 7.03 g/hr and Cystoseira barbata at 7.5 g/hr, compared to 5.52 g/hr and 5.89 g/hr for open sun drying. Additionally, the drying efficiency of the solar dryer outperformed open sun drying, with Sargassum polycystum achieving 9.52 % and Cystoseira barbata 10.13 %, compared to 7.4 % and 7.9 %, respectively, for open sun drying. Economic analysis revealed an estimated annual profit of USD 2270, indicating the economic viability of the proposed system. The findings suggest that the PV-integrated solar dryer offers a promising alternative to traditional drying methods, providing enhanced efficiency and economic benefits for seaweed farmers.

Fruits and vegetables are an important part of human diet. In the present study, the thermal performance of a solar greenhouse dryer for drying Solanum lycopersicum (Tomatoes) was analyzed. The drying pattern at various locations of the drying chamber and different levels of the dryer was evaluated. The life cost analysis for drying the tomatoes in the dryer for 25 years of service was evaluated. The greenhouse solar dryer was developed with a structure base of galvanized iron pipes and a covering of a 2 mm thick polycarbonate sheet. The experiment was carried out for drying the tomatoes at various locations in the dryer using the trays and trolley system. The maximum thermal efficiency of the dryer is 26.66 % while drying out 5.8 kgs of tomatoes in one day. The economic analysis of the greenhouse solar dryer shows that the payback period of such a system can be attained in only 1.6 years which terms the dryer feasible and economically viable in the current agro-drying market. The embodied energy for the dryer was calculated at 3154.71 kWh for the system. The CO2 emission for the greenhouse solar dryer was found to be around 6.62 tonnes for a lifespan of 25 years. The net CO2 mitigation was calculated at around 41.62 tonnes which would generate an earning from 46766 INR to 62355 INR worth of carbon credits. [ABSTRACT FROM AUTHOR]

Drying process has been employed since ancient times to preserve agricultural products by reducing the moisture content. Solar dryer is one of the most commonly used dryers due to its availability, reliability, and environmentally friendly nature. It is practical in rural areas since solar dryer can be fabricated with a simple design. Despite its potential, designing a long-term, feasible solar dryer is challenging without a good understanding of its performance parameters, such as energy, exergy, economic, environmental (4E) aspect, and its impact on product quality. Therefore, many attempts have been dedicated to conducting these analyses. Nonetheless, the information obtained is only one-dimensional, and they do not reflect the actual behaviour of a solar dryer. This paper aims to provide a comprehensive and critical review of the additional 3E parameters, namely energoeconomic, exergoeconomic, and enviroeconomic. Moreover, the effect of solar drying on product quality parameters (Q) will be discussed. Furthermore, a new idea to perform energy, exergy, environmental, economic, energoeconomic, exergoeconomic, and enviroeconomic (7E) and quality analysis (7E + Q) is proposed and outlined to improve the operability of the solar dryer. It is envisaged that 7E + Q analysis will pave the way for more effective and efficient solar dryers. [ABSTRACT FROM AUTHOR]

In this study, a novel adaptive solar dryer with a coating of polymer-dispersed liquid crystals (PDLC) was designed, built, and characterized to evaluate its optical properties and thermal performance by modulating the transmission of solar radiation toward the drying chamber. PDLC films can electrically switch between opaque and transparent states, making them ideal for controlling solar radiation. Unlike conventional direct dryers, the proposed solar drying system takes advantage of direct solar radiation, known for its rapid drying process, while minimizing the impact on product properties. The results show that the PDLC coating exhibited a significant difference in transmittance between the “on” and “off” states under ambient conditions. At 400 nm, the transmittance varied by 20 %, increasing to 30 % at 450 nm. The solar dryer with dynamic control of solar irradiance constantly maintained a temperature range of 52.19 °C–57 °C. Lower relative humidity values were achieved compared to the uncontrolled solar dryer, resulting in a uniform irradiance distribution within the drying cabinet. The solar dryer with dynamic control of solar irradiance (acrylic and PDLC film) presents a total thermal resistance (0.02817 mK/W) exhibiting better heat permanence inside the drying cabinet compared to polycarbonate (one of the materials most used for drying systems). The system's thermal efficiency ensures reliable operation regardless of weather conditions, efficiently capturing and converting solar energy into heat.

This study was aimed to investigate an air-flow distributer of a solar dryer. This study was contained two factors: First, the air outlet throttle (three angles, 30°, 60°, and 90°). Second, the design of the air inlet with three levels (new design (I2), without (I1), and half-opening air inlet gate of the new design (I3)). The results show significant effects on these parameters, where the highest efficiency (51.7%) was obtained at (I1) and (30°) angles. While the temperature changes between the inlet and outlet had a significant effect on the pressure difference, the pressure difference increased, reaching (1.65 Pa). Also, the drying rate was affected by the temperature and the amount of air entering the dryer. The highest drying rate gave (0.165 kg/h) when used the air discharge angle (30°) with the (I3), where this increased the temperatures of the air in the dryer reduced the air entering. [ABSTRACT FROM AUTHOR]

Aloe Barbadensis Miller, commonly known as Aloe vera, has been widely used in different applications, such as medicinal treatments and cosmetic products. However, its transportation and handling present challenges due to oxidation and property loss caused by direct environmental exposure. A strategy to mitigate these effects is dehydration, where different industrial-scale methods such as freeze-drying, spraying, refractory windows, and convective drying can be applied. Despite their effectiveness, those dehydration techniques are both energetically and economically costly. Solar drying technology offers a cost-effective, lower-energy alternative addressing sustainability, socioeconomic, scientific progress, and integrated sustainable development challenges. Nevertheless, solar drying through direct sunlight exposure has been minimally explored for drying high-water-content products like Aloe vera, potentially due to the inherent challenges of drying under uncontrolled environmental conditions. In response, this paper introduces a methodology for pre-treating and pre-drying Aloe vera gel using a low-cost solar dryer prototype, achieving up to 50% water activity reduction in experimental tests under uncontrolled conditions in Colombia, South America. The proposed prototype features a drying cabinet with energy autonomy and forced convection. The experimental evaluation compares the quality of pre-dried Aloe vera gel with freeze-dried samples, demonstrating comparable attributes under favorable environmental conditions. The results demonstrate the feasibility of pre-drying Aloe vera gel within 13 to 48 h, with a maximum drying rate of 0.38 g/min. During this process, water activity decreased from an initial value of 0.975 to a final value ranging between 0.472 and 0.748. Furthermore, the quality of the dehydrated gel was assessed through color analysis, comparing it with a freeze-dried sample. Subsequent color analysis of the freeze-dried samples revealed minor changes in product quality compared to those dried using the proposed solar drying method. These results demonstrate the effectiveness of the proposed solar dryer in pre-dehydrating Aloe vera gel, yielding characteristics similar to those achieved through conventional methods. [ABSTRACT FROM AUTHOR]

The present work presents the effective application of waste heat rejected from window air conditioning (AC) in a waste heat dryer (WHD) for drying plantain banana slices. The comparison between drying with the waste heat dryer coupled with an AC unit (ACWHD) and a natural convective indirect solar dryer (SD) reveals significant differences in drying kinetics, supply air conditions, and thermodynamic performance. The drying kinetics of banana slices obtained with ACWHD and SD were validated by revisiting the concepts of dryer performance index (DPI) and generalized drying curve. The temperature of the hot air supplied to the drying chamber in ACWHD was 48 °C while the relative humidity of the supply air was below 30 %. The thermodynamic performance assessment revealed that the exergetic efficiency was about 45 % and 16 % for ACWHD and SD respectively. The results of exergy based sustainable index and environment impact factor indicated the potential application of the waste heat of residual air from AC units for drying applications. Thus, the results of the present study imply that this novel idea has appreciable potential for commercialization with large-scale central air conditioning units in commercial complexes and industries where the magnitude of heat rejection will be multi-fold.

Drying assumes a pivotal role in the preservation of high-moisture products over extended durations. Despite the widespread utilization of solar dryers owing to their energy-efficient nature, they are often plagued by prolonged drying durations, subsequently impacting the quantity of dried products. This investigation endeavors to introduce an innovative technique aimed at augmenting the efficacy of solar drying processes. Specifically, the study integrates forced convection solar drying with electrohydrodynamic (EHD) drying. The experimentation entails the drying of pineapple slices conducted between December 2023 and January 2024 in Nakorn Pathom, Thailand. The pineapple slices, featuring a ring-shaped geometry, are subjected to varying corona voltages ranging from 7 to 10 kV. The findings reveal a direct correlation between the corona voltage and the diffusion coefficient of the pineapple slices, wherein an escalation in corona voltage leads to an elevation in the diffusion coefficient, consequently resulting in a reduction of moisture ratio during the drying process. Consequently, the novel drying approach exhibits superior efficiency compared to traditional solar drying techniques, particularly as corona voltages increase. Moreover, the study employs Buckingham-Pi terms to predict the fluctuations in the diffusion coefficient, yielding a diffusion coefficient function with an R2 value of 0.996. Subsequently, a novel kinetics model for the drying process is proposed, boasting an average R2 value of 0.98. This model is envisioned to serve as a vital tool for enhancing and advancing forced convection solar-EHD dryers in forthcoming industrial applications.

This research presents the prediction of temperatures in the chamber of a solar dryer using artificial neural networks (ANN). The dryer is a forced-flow type and indirect. Climatic conditions, temperatures, airflow, and geometric parameters were considered to build the ANN model. The model was a feed-forward network trained using a backpropagation algorithm and Levenberg–Marquardt optimization. The configuration of the optimal neural network to carry out the verification and validation processes was nine neurons in the input layer, one in the output layer, and two hidden layers of thirteen and twelve neurons each (9-13-12-1). The percentage error of the predictive model was below 1%. The predictive model has been successfully tested, achieving a predictor with good capabilities. This consistency is reflected in the relative error between the predicted and experimental temperatures. The error is below 0.25% for the model’s verification and validation. Moreover, this model could be the basis for developing a powerful real-time operation optimization tool and the optimal design for indirect solar dryers to reduce cost and time in food-drying processes.

Drying is the process of moisture removal which is applied to many foodstuffs including fruits and vegetables for preservation and storage purposes. Since solar energy is one type of environmentally friendly renewable energy, open-type solar dryers, natural convective type solar dryers and greenhouse type solar dryers were designed and fabricated in this study for the preservation of fruits and vegetables. A comparative study among various solar drying methods was performed to study the drying performance by maintaining the quality and texture of the dried foodstuffs. Factors such as solar radiation, ambient temperature, moisture in the air, materials used for glazing, inclination, etc., were considered during the fabrication of the solar dryer so that a better estimate of the performance of the solar dryer could be obtained. The lowest drying rate was observed when convective drying was used as an indirect mode of heating. The maximum drying rate observed in open drying was 0.088 kg/kgh, whereas in convective drying under the same conditions, it was 0.03 kg/kgh, which was almost 65% less. This in turn also resulted in the dried samples displaying a better texture and better color. The shrinkage effect on the samples was less pronounced for those samples in the convective dryer than it was for those in the open and greenhouse dryers, as the method uses indirect drying. Comparing convective and greenhouse drying, more shrinkage and a greater browning effect were observed for the open drying method. Out of three types of solar dryers, the greenhouse dryer was selected to study thermal performance because of its better drying rate. DHT11 sensors controlled through Arduino programming were employed in this study to record the temperature and moisture at various locations in the greenhouse dryer setup. The range of energy efficiency of the greenhouse solar dryer was estimated to be from around 15% to 25% on average. This might be due to a greater extent of energy losses. No significant difference was observed in the energy efficiency with respect to the samples used for drying. [ABSTRACT FROM AUTHOR]

The preservation of perishable foods through their transformation is always a major challenge for producers. Several methods are applied for this purpose, and progresses are recorded by improving these processes or by finding new means. In our work, the method of dehydration and natural drying of tomatoes using a natural dryer with indirect solar energy with air circulation by extractor is used to describe and then predict the process of obtaining the finished product in the form of tiny dried fragments or powder. This is the novelty of this research, which uses the unconventional design of experiments. This consists of finding a mathematical model based on the interaction of 3 parameters that interact with each other, namely the trays temperature, the drying speed and the relative humidity in the solar dryer. The interference of the values of one of these 3 parameters on the 2 other parameters acts directly on the result of the drying process. The matrix treatment of the data of several carried out experiments in the resolution of 13 equations gives us the required responses and permits us to draw the graphs, the contours and the responses surfaces that access us to a more detailed analysis. [ABSTRACT FROM AUTHOR]

In geopolymer bricks (GPBs), fly ash content, which is waste from power plants, is converted into bricks by chemical treatment. GPBs can be dried by using appropriate curing methods. Conventionally, electric oven curing is one of the prominent methods. Using a solar dryer instead of an electric oven provides the added advantage of saving high-grade electrical energy. So, in this work, a solar dryer with the phase change material (PCM) paraffin wax and without a PCM is used for curing applications. GPBs gain an added advantage when compared to conventional bricks like cement and sand bricks in terms of strength. A GPB has been taken as a specimen for comparing the compressive strength, tensile split strength, and flexural strength of electrical-energy-based curing and solar-energy-based curing. It has been experimentally observed that solar-energy-based curing with and without a PCM exhibits higher compressive strength, higher tensile split strength, and flexural strength when compared to electrical-energy-based curing. Solar curing with a PCM shows higher compressive strength, higher tensile split strength, and higher flexural strength when compared to solar curing without a PCM. Open solar curing is a traditional technique, but nowadays, aggressive climatic conditions can lead to severe damage to geopolymers. The novelty of this work is the study of the effect of PCMs like paraffin wax in solar drying on the curing time and the mechanical properties of GPBs. [ABSTRACT FROM AUTHOR]

This research presents the prediction of temperatures in the chamber of a solar dryer using artificial neural networks (ANN). The dryer is a forced-flow type and indirect. Climatic conditions, temperatures, airflow, and geometric parameters were considered to build the ANN model. The model was a feed-forward network trained using a backpropagation algorithm and Levenberg–Marquardt optimization. The configuration of the optimal neural network to carry out the verification and validation processes was nine neurons in the input layer, one in the output layer, and two hidden layers of thirteen and twelve neurons each (9-13-12-1). The percentage error of the predictive model was below 1%. The predictive model has been successfully tested, achieving a predictor with good capabilities. This consistency is reflected in the relative error between the predicted and experimental temperatures. The error is below 0.25% for the model's verification and validation. Moreover, this model could be the basis for developing a powerful real-time operation optimization tool and the optimal design for indirect solar dryers to reduce cost and time in food-drying processes. [ABSTRACT FROM AUTHOR]

In the central jungle region of Peru, within the wet processing of coffee, the coffee pulp is discarded. This objective is to design a dual solar and gas dryer with continuous operation, for the dehydration of waste from wet processing of coffee for human use. The proposed objective is part of a broader project to apply the circular economy in the use of waste from wet coffee processing financed by Pro Ciencia. The following procedure was followed. At first, a 100 kg/Bach capacity gas and solar system dryer was designed applying the proposed technology development methodology in mechanical engineering and secondly arriving at the construction of the prototype. The results are to have a design methodology and the built prototype of the dual dryer (solar and gas) of continuous and semi-automated operation that has a control panel to allow programming and monitoring the drying process in real time. At the end of the project, the proposal will allow a continuous dehydration of the coffee pulp with quality, low cost and the industrialization of its by-products such as coffee pulp flour, filters and functional drinks.

The use of solar energy for drying is considered one of the most environmentally friendly ways to reduce dependence on fossil fuels. The purpose of this experimental study is to determine how absorption plate design affects the evaporation rate of a solar food dryer in Baghdad, Iraq. Tests were performed on four different absorbent panel models. This dryer design consists of a section for heating solar air and one for preserving food. There is insulation at the back of the dining cabinet, which is made of wood. As food samples, orange slices were selected. Except for the absorb plate design, all four models have identical measurements. Matte black aluminum absorbent plate is featured on the Model-1. Both Models 2 and 3 have perforated cylindrical fins arranged uniformly and vertically in Model 2 and horizontally in Model 3. Model 4 uses horizontal fins and an absorber plate coated with 15 % silicon content. A fruit cabinet holds sliced fruit in five movable mesh trays. According to experimental results, the shape of the absorbent plate directly affects the temperature of the outlet air, which in turn affects the rate at which water is evaporated from fruit slices and the overall drying process. Model-1 solar air heaters could be improved by approximately 17 % by coating them with 15 % silicon. The efficiency of Models 2, 3, and 4 is increased by 20 %, 40 %, and 65 % by adding fins and tint over Model 1. Models 1, 2, 3, and 4 had moisture contents of 28 %, 25 %, 20 %, and 18 %, respectively, at 15 p.m. A solar dryer has been demonstrated to be suitable for successfully drying fruits and vegetables in Iraq's atmosphere through practical experiments.

Background: In the past 30–40 years, conflicts over limited conventional energy sources and the negative climate change caused by them have attracted researchers and analysts to new, clean, and green energy technologies. Thereby reducing the consumption of conventional fuel and the negative impact on the climate. The production of alternative energy in the form of thermal energy storage using phase change materials (PCMs) is one of the techniques that not only reduces the gap between the supply and demand of energy but also increases the stability of the energy supply. The tendency of PCMs to melt and solidify over a wide temperature range makes them more attractive for use in many applications. The effective and efficient storage of solar energy by PCM has the potential to significantly advance the use of renewable energy. Methods: Organic non-paraffin compound beeswax (BW) mixed with other non-paraffin compounds stearic acid (SA), Palmitic acid (PA), Myristic acid (MA), and Lauric acid (LA) in different compositions with the help of magnetic stirrer at 50–60°C for 3–4 hours to prepare BWSA, BWPA, BWMA, and BWLA eutectic PCM. Results: Prepared eutectics melt and solidify in the temperature range 36–56°C and with latent heat in the range of 155–211 kJ/Kg. Conclusions: Due to suitable temperature and good latent heat storage range, it is a good choice as thermal energy storage, for solar drying applications.

Energy and environomical analysis play important role in designing a solar thermal drying system as these analyses identify the high energy-consuming area, formulate energy-saving measures and evaluate the size of any potential savings. In this study, a greenhouse solar dryer with a double-pass multi-hollow collector for leaf drying was evaluated using environmental-economic analysis. Environmental analysis includes the determination of embodied energy, energy payback time (EPBT) period, as well as CO2 emissions per year, carbon mitigation and carbon credit. The embodied energy of a passive dryer is 606.86 kWh and EPBT of 16.68 years, while for an active dryer, the values are determined at 636.17 kWh and 10.39 years, respectively. CO2 emission for the passive dryer is 47.17 kg per year, net CO2 mitigation of 124.6 kg, and earned carbon credit of RM 2.58 – RM 12.38. The active dryer has CO2 emission of 47.14 kg, net CO2 mitigation of 594 kg, and earned carbon credit of RM 51.95 – RM 247.66. Economic analysis of this dryer shows that the energy cost associated with its operation ranges from RM 1.59 to RM 4.77, monthly.

In solar drying, the moisture content of a product is reduced through the use of sunlight. Solar drying is practiced since civilization for the drying of crops. The dried crop has a longer shelf life and requires less storage space. For crop drying, hot air is required in the moderate temperature range of 40 to 75℃. Solar dryer makes it possible to obtain better product quality. Over the past 20 years, numerous experimental projects have been carried out in the field of solar dryers. Most conventional dryers are not able to operate continuously during the off sunshine time. However, attempts were made to develop uninterrupted solar drying systems by incorporating an energy storage facility and a hybrid mode of operation. Sensible and latent heat storage methods are widely used to store solar energy. Heat storage materials store energy in the form of heat during sunshine and release it whenever it is required. Biogas backup, Chemical heat pump, Photo Voltaic, and Fluidized bed methods were integrated with solar dryers for uninterrupted operation. In this article, the discussion is made about different dryers. Also, the challenges and scope in the area of the solar dryer are highlighted.

With ever expanding population and accelerating energy challenges, the ultimate need to adopt green-energy solutions for the preservation and storage techniques for fruits and vegetables has become vital. Sun drying is an age-old method to preserve food and it has revived the popularity within the industrial sector to overcome the high energy consuming operations. This work presents the experimental investigations of a solar dryer with integrated thermal storage chamber. The thermal storage chamber employed paraffin wax as a phase change material (PCM). Incorporating PCM enhances the efficiency and efficacy of the solar dryer. PCM absorbs heat, causing it to melt during peak sunshine hours. Then, during periods of reduced sunlight, the PCM releases the stored heat, enabling continuous product drying. Particularly, the solar dryer successfully dried onions, apricots, and peas, with moisture removal percentages of 69.6 %, 65 %, and 75 % respectively from the total mass.

A solar air heater that operates in the mixed-mode double pass and an absorber plate has aluminum cans at the top and bottom of the absorber for red pepper drying experiments was conducted in Bahir Dar, Ethiopia climatic conditions. A total dying period of red pepper in a mixed-mode solar greenhouse dryer takes less time than an open solar drying system. From the experiment, the average daily dryer chamber temperature ranges between 39.93 0C and 47.02 0C and the average daily ambient temperature ranges between 24.890C and 27.530C. Solar insolation reached 973 W/m2 when the sun was at mid-day and minimum solar insolation was 220 W/m2 and 0.0383 kg per second of air are expelled. A newly designed mixed-mode double pass, integrated with an Aluminum can dryer and the traditional open sun dryer, achieves an efficiency of 46% and 28%, respectively. In the open sun dryer system and the mixed-mode solar dryer, the drying rates are 0.0003395 kg/s and 0.0000365 kg/s respectively. On eleven mathematical models, Microsoft Excel was used to perform the statistical analysis. Logarithmic models were found to be the best explanation of red pepper behavior in both mixed-mode and open-sun solar dryer systems. These models were tested by comparing the maximum value of the coefficient of determination R2 and the minimum value of reduced chi-square X2 and root mean square error RMSE between experimental and predicted moisture ratios.

Agriculture contributes to large export earnings for many countries and provides food all over the world. However, most agricultural products need some post-harvest processing, such as drying, to extend their shelf life while still maintaining their respective nutrient quality. One popular post-harvest processing method is drying using solar energy. It is a type of renewable energy that is abundant and free. Conventional dryers use grid electricity and can be expensive to operate. Consequently, there is a growing need for cost-effective solar-powered agricultural dryers that is reasonable for smaller-scale farmers. Although current solar dryers are still not on par with modern electricity-powered dryers, solar dryers have lower running costs and are sustainable and able to generate electricity. They can also be used practically anywhere with abundant solar energy. As numerous solar drying technologies have been proposed over the past decade, it is necessary to assess the current state of solar drying technology in the agricultural sector to identify current advancements and potential research gaps. In this paper, a review of existing solar dryers mechanism and the state of the art of solar drying technology research for agricultural products is presented. [ABSTRACT FROM AUTHOR]

The current study examined reduction of moisture from agricultural energy and food crops in a conventional oven to a solar dryer at various treatment periods at temperature between 40 ± 10 oC. Sugarcane bagasse and Phragmites Australis had initial moisture of 50.8 % and 6.07 % by dry weight, respectively, with higher heating values (HHV) 6548.5 kJ/kg and 17653.02 kJ/kg respectively. The moisture content of bagasse and phragmites were decreased by 51.31% and 68.69% respectively using oven drying, while the moisture content of bagasse and phragmites was reduced by 48.01% and 66.22% respectively, using solar drying with 5 hrs treatment time. Corresponding increase in HHV’s observed in bagasse to 11195.6 KJ/kg (oven drying) and 10998.1 KJ/kg (solar drying), while HHV of phragmites increased to 18706.79KJ/kg (oven drying) and 18685.36KJ/kg (solar drying). Green chillies had a moisture content reduction by 33.69 % (oven) and 8.28 % (solar), whereas grapes had a reduction by 31.20 % (oven) and 7.88 % (solar) with 5 hrs treatment time. The oven drying approach revealed higher carbohydrate content in food crops when compared to solar drying, while both treatments showed a similar drop in protein, fat, and vitamin C contents. Statistical and energy analysis observed that comparing solar drying; the oven drying eliminates slightly higher moisture content and have less drying energy requirements. The amount of heat energy required for drying unit mass of bagasse was 0.476 kJ/kg (oven) and 0.556 kJ/kg (solar), for phragmites it was 0.074 kJ/kg (oven) and 0.092 kJ/kg (solar), for chilles 0.524 kJ/kg (oven) and 0.576 kJ/kg (solar) and for grapes 0.123 kJ/kg (oven) and 0.157 MJ/kg (solar). According to the results solar drying required greater quantity of heat energy than oven drying. Mass transfer analysis showed drying constant of bagasse and phragmites were higher initially, then showed reducing trend with respect time. Furthermore, it was observed that the effective diffusivity and mass transfer coefficient were found reducing with respect to increasing drying treatment time. The research findings of renewable solar drying, on the other hand, are comparable to those of oven drying, demonstrating that there is still enough untapped heat energy available for its utilization in biomass thermo-chemical conversion methods.

Agricultural technological development is a crucial strategy for agricultural commercialization and socio-economic transformation in Africa. However, a key challenge to technology use in agriculture remains the limited farmer acceptance of unfamiliar technologies. This paper uses a sample of 245 okra farmers drawn from northern Uganda to assess the drivers of the farmer acceptance of solar drying technology. On the basis of drying performance, farmers perceive the solar dryer to perform better than the open sun-drying method. Structural equation modelling results show that the drying rate and perceived product quality are the main determinants of farmer perceptions on product marketability. Further, product marketability drives acceptance of solar dryers among farmers. We conclude that acceptance of solar dryers is dependent on: i) the drying rate, ii) favorable perceptions towards product quality, and iii) perceived marketability of the solar-dried product. We call for policy action on intensification of efforts that promote solar drying technology, including supporting local artisans to fabricate dryers, to enable increased value addition and consumption of nutritious foods.

This present work deals with experimental investigation of photovoltaic thermal collector design and development with solar dryer (PVTCSD). An solar experimental investigation is done on coriander seeds by natural, forced and open sun drying to estimate different parametric investigations such as solar radiation intensity, removal of moisture and the air outlet in the collector. Solar radiation is utilized as a source of energy to propel the photovoltaic thermal collector dryer; which was analysed in a drying testing chamber temperature in the range of 32°C to 59°C to dry 4 kg of coriander seeds. From the experimental study, it was understood that coriander seeds posses much more starting moisture 68% by weight and also the results proved that final moisture content has been decreased by 9% by weight during six bright days in the month of May 2021. The PVTCSD was used during the 9 a.m. to 4 p.m. In terms of understanding PVTCSD, solar sun drying with the forced convection achieved superior results than other two modes of operation. [ABSTRACT FROM AUTHOR]

India like other developing countries adopts many food preservation technologies using fossil fuels. But the fossil fuel resource depletes over the years and is non-renewable. Therefore, solar drying technology is preferred as a sustainable method for food preservation. The present study is aimed at a sustainable livelihood initiative for drying fruits and vegetables through solar technology intervention using an indirect forced convection type solar dryer. Such a dryer of 15 kg capacity has been designed and fabricated for drying mangoes. Performance indicators such as instantaneous collector efficiency, drying efficiency, drying rate, COP, heat utilization factor, and moisture content on a dry basis are evaluated as 59%, 32.25%, 0.15178 kg/hr, 0.77, 0.229, and 2.55, respectively by considering maximum outlet collector temperature, drying chamber temperature and atmospheric temperature. Economic indicators such as pay-back period and cost-benefit ratio are also evaluated as 1.439 and 2.0008, respectively. The dryer can be used by rural people of Odisha for earning their livelihood. [ABSTRACT FROM AUTHOR]

It is estimated that in Portugal per year, 132 kg/person of food is wasted due to imperfections in weight, shape and due to their perishability, resulting in foods that cannot be marketed. Solar drying can be used to extend food life. However, it usually does not meet the current productivity and quality requirements of the dried product. Solar energy is renewable, very available in Portugal, which can make an important contribution to reducing the specific energy consumption and carbon footprint intensity associated with drying. This work aims to optimize the drying process using a solar dryer with electric support. The conditions of temperature and humidity in the dryer and their influence on the physical and chemical properties of blueberries and raspberries were studied, namely the ash, protein, fat, sugars, total phenolic compounds content and antioxidant capacity.It was concluded that the blueberries and raspberries, after drying underwent slight changes in some chemical parameters, namely the reduction of fats and phenolic compounds. The results of the drying tests showed a strong dependence on atmospheric conditions. Under the most favorable conditions, it was possible to record reductions in electricity consumption of 35%.

Photovoltaic-thermal (PV-T) solar air/water collectors have received increasing attention in recent years. Efficiency is the most important parameter usually considered in PV-T technologies. The present paper expressed energy efficiency and thermal-electrical exergy of PV-T collectors, and compared the studies of researchers on the performance of these systems. The figures are provided to give an overview of how PV-T performance is improved. Changes in heat transfer fluid play a major role in electrical and thermal efficiency. A brief overview of the most promising fluids used in PV-T is reported in this article. Nowadays, improving PV- T performance by optimizing the adsorbent plate and cooling fluid and using nanofluid has been considered by researchers. The application of these schemes in implementation, especially in agriculture, can help significantly in increasing the efficiency of solar radiation. Therefore, future work should be aimed at increasing efficiency and reducing costs to increase their competitiveness and use as a renewable and environmentally friendly energy device.

In this article the energy & exergy analysis of forced convection solar dryer for drying of garlic has been investigated. The exergy parameter, air velocity has been taken to conduct the experiments and its effect on thermal efficiency. Forced draft fans were used in all the two working conditions. During the two conditions, with and without sensible heat storage system, the average air-velocities were 4.5, 9.5 and 11.4 m/s selected as ideal and subsequently its entire effect on thermal efficiency and outlet. The ambient temperatures were between (17-25) °C during the month of October and November. A DC fan is directly connected to the photovoltaic cell in the solar dryer. The thermal energy storage bed was packed with gravels with 1.5 in of thickness up to the surface of flat plate collector, the storage system becomes space-efficient. The average thermal efficiency with sensible heat storage materials was high as compared to system without sensible heat storage. The highest thermal efficiency of 61% was achieved. The maximum collector temperature obtained was 55 °C, with a mean temperature of 42 °C in the drying chamber. The collector’s greatest exergy loss was 30.38 kJ/kg and highest exergy efficiency was 70%.

This recent study evaluated a hybrid solar-assisted heat pump dryer (HS-AHPD) for drying paddy and its product quality. R22 is used as a working fluid in the heat pump system during the drying experiment. The HS-AHPD decreased the paddy's weight from 420 kg (31.67% db) to 370.60 kg (16.18% db) in 5.5 h with an average air temperature of 62.9 °C and an average relative humidity of 16.1% at a mass flow rate of 0.195 kg/s. The average drying rate, specific moisture extraction rate (SMER), and specific energy consumption (SEC) were 8.34 kg/s, 0.44 kg/kWh, and 4.69 kWh/kg, respectively. The HS-AHPD's average thermal efficiency and the exergy efficiency of the drying section were found up to 29.1% and 18.4%, respectively. The furnace and the solar collector contributed 19.7% and 12.9% of energy to the HS-AHPD, respectively. The improvement potential (IP) was in the range of 628.8–824.4W. The drying resulted in higher-quality products due to higher head rice yield (93.10 ± 1.044%), lower broken rice (4.41 ± 0.737%), and lower rice grouts (1.11 ± 0.271%).

The treatment and disposal of sewage sludge is one of the most important and critical problems of wastewater treatment plants. 8.7 million tonnes of dry matter of sewage sludge were produced annually in the European Union in the year 2020. Due to the fact that sewage sludge contains a large number of substances that are not beneficial for human health, the conditions for sludge management will be significantly tightened in the EU countries. One option for sludge liquidation is the production of biofuel in a form of granules or pellets from sewage sludge enriched by waste celluloses. The achieved results show that the resulting quality of such alternative biofuel is fully comparable to conventional fossil fuels. The economic analysis is based on the simulation of cash flows associated with the implementation of the project over the lifetime and the calculation of levelised cost (LCOE). Results shows (under the current economic situation) that solar dryer technology ensures the lowest LCOE at the level of 26 EUR/GJ in fuel. If the LCOE of the alternative biofuel includes the price of the saved emission allowance and the future costs of sewage sludge disposal, the resulting price is directly competitive with lignite. The results thus clearly show that there is an ecological and economically competitive substitute for solid fossil fuels, which may be an important step for the future use of local combustion sources such as district heating plants. [ABSTRACT FROM AUTHOR]

Drying of agricultural food products in a solar dryer equipped with a PV/T air collector is a frequent research topic. Consequently, an experimental and numerical study has been conducted on MSD to examine the distribution of the temperature and airflow. Moreover, COMSOL Multiphysics software is used to solve a 3D temporal non-isothermal flow for the system invented. Further, the improvement of the mass flow rate dropped approximately the average PV temperature experimentally from 60 °C to 43 °C and from 63 °C to 47 °C numerically. Furthermore, the average outlet temperature of the PV/T reaches 60,5 °C in the experience and 62 °C in the simulation in the case where the mass flow rate is 0,012 kg/s, but it is dropped to 44 °C in the experience and 45 °C in the simulation for the highest mass flow rate of 0,0235 kg/s. Hence, the best recorded average thermal efficiency of the PV/T was 53% for the maximum mass flow rate (0,025 kg/s), while the average thermal efficiency of the PV/T was 29% when the mass flow rate decreased to 0,012 kg/s. Consequently, the recorded temperature in the drying chamber reaches 55 °C in the experimental data and in the simulation.

Optimised solar air dryers, in terms of efficiency and performance, can solve some major concerns in the agro-industrial processing sector. Solar air dryers can reduce the large share of energy costs of a final product and can provide sustainable energy in rural areas where access to energy is often limited. In this study, a pilot scale v-groove double pass solar air collector has been analysed thermodynamically with real time solar radiation and mass flow rate (0.021–0.061 kg/s) inputs and validated experimentally in terms of first and second law efficiencies. Performance of the process was assessed using experimental drying measures including final moisture content, drying rate and exergy efficiency for drying of Pink Lady apples. Energy payback time and specific energy consumption were calculated to reveal the techno-economic value of the system. The maximum thermal efficiency of the collector was observed to be 88.8 % at 0.061 kg/s having exergy efficiency of 6.6 % which shows an efficient sourcing for the operation. In terms of the performance of the dryer, mass flow rate of 0.041 kg/s offers a higher moisture removal. Specific energy consumption (SEC) was 3.096 kWh/kg. Thermodynamic model was validated with matching experimentation with acceptable RMSE for the range of investigated measures. Energy payback period time calculated by the embodied energy of the system was obtained to be 0.78 years which implies that the system is capable of addressing a large capacity drying if it is to be scaled-up.

Background: In the past 30–40 years, conflicts over limited conventional energy sources and the negative climate change caused by them have attracted researchers and analysts to new, clean, and green energy technologies. Thereby reducing the consumption of conventional fuel and the negative impact on the climate. The production of alternative energy in the form of thermal energy storage using phase change materials (PCMs) is one of the techniques that not only reduces the gap between the supply and demand of energy but also increases the stability of the energy supply. The tendency of PCMs to melt and solidify over a wide temperature range makes them more attractive for use in many applications. The effective and efficient storage of solar energy by PCM has the potential to significantly advance the use of renewable energy. Methods: Organic non-paraffin compound beeswax (BW) mixed with other non-paraffin compounds stearic acid (SA), Palmitic acid (PA), Myristic acid (MA), and Lauric acid (LA) in different compositions with the help of magnetic stirrer at 50–60°C for 3–4 hours to prepare BWSA, BWPA, BWMA, and BWLA eutectic PCM. Results: Prepared eutectics melt and solidify in the temperature range 36–56°C and with latent heat in the range of 155–211 kJ/Kg. Conclusions: Due to suitable temperature and good latent heat storage range, it is a good choice as thermal energy storage, for solar drying applications.

In the present work, a forced convective hybrid photovoltaic thermal (PV-T) solar dryer assisted with an evacuated tube collector (ETC) is set up to investigate the thin layer drying of potato slices. The drying experiment is compared with the traditional sun drying method without PV-T system under the meteorological conditions of Thanjavur, Tamilnadu. The initial moisture content of potato slices used for the study is 91% (wb). The drying experiment was carried out at different air temperature levels of 50, 55 and 60 °C. Nine numerical models are used to study the drying kinetics of untreated potato slices. Using IBM SPSS 23 statistical package, non-linear regression analysis was performed to estimate correlation coefficient (R2), reduced chi-square (χ²) and root mean square error (RMSE). The model developed by Midilli et al., is the most appropriate one to describe potato slices thin layer drying behavior in a hybrid dryer. The effective moisture diffusivity (Deff) determined using Fick's second law of diffusion was found to vary from 2.12463×10-8 to 2.79233×10-8 m²/s. The activation energy (Ea) determined using the Arrhenius equation was found to be 16.4276 KJ/mol for drying of potato slices. [ABSTRACT FROM AUTHOR]

The current study examined reduction of moisture from agricultural energy and food crops in a conventional oven to a solar dryer at various treatment periods at temperature between 40 ± 10 °C. Sugarcane bagasse and Phragmites Australis had initial moisture of 50.8 % and 6.07 % by dry weight, respectively, with higher heating values (HHV) 6548.5 kJ/kg and 17653.02 kJ/kg respectively. The moisture content of bagasse and phragmites were decreased by 51.31% and 68.69% respectively using oven drying, while the moisture content of bagasse and phragmites was reduced by 48.01% and 66.22% respectively, using solar drying with 5 hrs treatment time. Corresponding increase in HHV's observed in bagasse to 11195.6 KJ/kg (oven drying) and 10998.1 KJ/kg (solar drying), while HHV of phragmites increased to 18706.79KJ/kg (oven drying) and 18685.36KJ/kg (solar drying). Green chillies had a moisture content reduction by 33.69 % (oven) and 8.28 % (solar), whereas grapes had a reduction by 31.20 % (oven) and 7.88 % (solar) with 5 hrs treatment time. The oven drying approach revealed higher carbohydrate content in food crops when compared to solar drying, while both treatments showed a similar drop in protein, fat, and vitamin C contents. Statistical and energy analysis observed that comparing solar drying; the oven drying eliminates slightly higher moisture content and have less drying energy requirements. The amount of heat energy required for drying unit mass of bagasse was 0.476 kJ/kg (oven) and 0.556 kJ/kg (solar), for phragmites it was 0.074 kJ/kg (oven) and 0.092 kJ/kg (solar), for chilles 0.524 kJ/kg (oven) and 0.576 kJ/kg (solar) and for grapes 0.123 kJ/kg (oven) and 0.157 MJ/kg (solar). According to the results solar drying required greater quantity of heat energy than oven drying. Mass transfer analysis showed drying constant of bagasse and phragmites were higher initially, then showed reducing trend with respect time. Furthermore, it was observed that the effective diffusivity and mass transfer coefficient were found reducing with respect to increasing drying treatment time. The research findings of renewable solar drying, on the other hand, are comparable to those of oven drying, demonstrating that there is still enough untapped heat energy available for its utilization in biomass thermo-chemical conversion methods. [ABSTRACT FROM AUTHOR]