Use Of Solar Dryer Research Articles

Experimental Study and Modeling of Drying Kinetics and Evaluation of Thermal Diffusivity of Sewage Sludge

This article discusses the use of solar dryers as a method for stabilizing and reducing the volume of residual sludge produced by wastewater treatment facilities. The study focused on the convective drying behavior of sewage sludge produced by the wastewater treatment plant of Meknes City under convective solar drying. The study aimed to investigate the drying kinetics of sewage sludge and emphasize the effect of temperature and water content on the evolution of the drying rate. The measured water content values showed a decrease as drying time increased. The results revealed the presence of phase II, which characterizes the decreasing rate drying period, and the absence of phase I, which describes the constant rate drying period.The study developed an empirical model to describe the kinetic behavior of convective solar drying of Moroccan domestic sludge. The model can be used to predict the shape of a drying curve under other aerothermal conditions. Additionally, the study analyzed the thermal diffusivity and activation energy of sewage sludge using an experimental macroscopic method based on Fick's diffusion model and the Arrhenius equation. The measured diffusion coefficient values range from 0,71 10-9 m2.s-1 to 1,47 10-9 m2.s-1, and the value of activation energy was evaluated at 17.54 kJ/mol.

Development of a hybrid mixed-mode solar dryer for product drying

Sun drying in the open air is quite popular worldwide. However, the use of solar dryers to preserve various perishable agricultural products is a relatively new area of study, and the long-term effects of this method are not yet fully understood. The slow drying process in direct sunlight can contaminate the dried materials by soil and insects. To overcome these challenges, we devised a sun drying system that included a heating part, a drying area, a portable stand, fans, and a 50-W photovoltaic panel. An alternate energy source was used to power the drying process during cloudy days and at night. Fresh Freestone peach, Golden apple, and Anaheim chilies weighing 10 kg each with the initial moisture content of 89%, 87%, and 75% on a wet basis (w.b), respectively, were used in the experiments. The final moisture content of the samples was reduced by an average of 16%, 15%, and 11% for Freestone peaches, Golden apples, and Anaheim chilies, respectively. The quality analysis was carried out to determine sample composition, total bacteria, and color of dried products. The results indicated that the dried products met the recommended quality standards for food products in terms of composition, total bacteria, and color. This research supports the use of a hybrid mixed-mode solar dryer for drying a wide range of perishable agricultural products.

Prioritization of potential barriers to the implementation of solar drying techniques using MCDM tools: A case study and mapping in INDIA

In the present scenario, food security is one of the major concerns in the Indian context; engendered due to increased population and other associated anthropological activities. Despite high levels of food production, the current poor ranking of the country in the Global Hunger Index (GHI) has put an alarming trend for policy-makers as well as the contributors working towards food security improvement. The significant post-harvest losses in several durables and perishable food products affect society adversely. The use of solar dryers is one of the most efficient, cost-effective, and sustainable techniques for various food-processing and preservation applications; without any compromise with their morphological structure.Besides having the pre-eminent product quality along with several economic, environmental, and social impacts, the adoptability of solar dryers has not touched a benchmark; as per expectation due to various associated potential barriers. In this work, a systematic framework, utilizing the MCDM tools; has been suggested for the identification and prioritization of several barriers responsible for such a hampered adoption rate. The study comprises three major sections- (a) Identification and categorization of potential barriers, (b) Prioritization of identified barriers using DEMATEL scheme based priority weights, followed by (c) the sensitivity analysis to confirm the robustness of the proposed methodology. The findings suggested that political instability and interference have a significant impact on the adoptability of solar-thermal-based drying technology. Several potential recommendations for the removal of these barriers are also suggested to ensure the contribution towards the achievement of UN sustainable development goals.

Review the Design of the Solar Dryer for the Dryer of Fruit and Vegetable Dryers

Fruits and vegetables are very seasonal and are particularly abundant year-on-year. Preserving these fruits and vegetables can prevent high accusations and can be achieved during the exit period at the cost of pay. Drying out fruits and vegetables is essential for the preservation of food. The technique is done using artificially fossil fuels or placing the fruit and vegetables under the sun. The first method has an expensive and environmentally negative impact, and the second method is entirely dependent on the weather. By contrast, the use of solar dryers is relatively cheap and efficient. Some solar dryers run without electricity or fossil fuels. This paper looks at a variety of solar panels that are widely used today. Active and useless design solar dryers are an environmental influence on solar power (Harness). This plays a crucial role in the solar dryer. They are often easy and relatively cheap to make, often showing efficient and active designs based on low-quality products or the use of compulsory convection. The indirect and direct, design dryers that have shown potential in drying food products in tropical and subtropical countries are reviewed. Such low-cost food drying technologies can be easily introduced in rural areas of developing and developed countries. This technology aims to reduce the quality of production, improve product quality and promote overall sanitation. Therefore, this review should be used to adequately guide individuals by selecting appropriate drying designs for the conditions given to them and later assessing the execution of the system for developing countries such as Ethiopia.

​Food Drying: A Review

Foods are complex biological substances that are obtained from animal or plant origin and because of that they contain high moisture contents which make them highly perishable and thereby requiring preservation in some forms. This review assessed different techniques of drying food and optimization of drying parameters to obtain good and acceptable quality food products. Among the useful processes used in preserving food products reviewed is minimal processing, dehydration or drying. The authors explored the available literature from journals, textbooks and search engines to develop this review paper. Food dehydration or drying is used to reduce losses and improving food commercial value. The use of artificial dryers has been found to reduce drying time when compared with natural drying method although at higher consumption level. Natural drying methods are sun drying and solar drying which could involve the use of solar dryers. Artificial drying methods are radiation, freeze drying, osmotic drying, dielectric drying etc. Novel technologies like microencapsulation and nanotechnology are increasingly used in food drying. Microencapsulation has been found to improve the stability of nutrients, preventing ingredient interactions and degradation as the coating matrix effectively separates particles and prevents them from contacting each other. Nanotechnology has found wide applications in food production, processing and packaging. Nanotechnology is an emerging technology that could impact every aspect of food system from cultivation and production of food to processing, packaging, transportation, shelf life and bioavailability of nutrients in foods.

Design, development and testing of Universiti Malaysia Sabah (UMS) eco-solar dryer

Utilization of solar drying for food preservation would be a step towards sustainable food processing. Even today, most of the agricultural and marine products are dried under open sun-drying. However, this method is associated with several drawbacks, which then leads to the use of solar dryer. Universiti Malaysia Sabah (UMS) has developed a solar drying system with loading capacity of 50kg to enhance the drying process of various food products. Design parameters particularly focused in this project includes the air movement pattern in drying chamber, heating system employed, air circulation ventilation and the airflow configuration in solar heat collector. Results revealed that solar dried products attained desired moisture content in shorter drying time. Temperature profile in updraft and downdraft drying mode indicated that no temperature fluctuation occurred when switching in between. Maximum temperature achieved under complete solar mode were 65°C and 83°C for single-pass and multi-pass solar heat collector, respectively. Under solar-hybrid mode, higher temperature was attained under intermittent ventilation mode. It can be concluded that UMS Eco-Solar Dryer is an environmentally and economically efficient drying system for the food processing industry.

Working Productivity Analysis on the Process of Drying Fish Using Solar Dryers

The process of drying fish using solar energy is strongly influenced by weather conditions. Sunlight is needed by household scale workers because it is cheap. On the other hand, sun drying creates additional workload for workers. Workers are exposed to hot sun during drying. Continuous heat exposure results in an increased work pulse. This affects the level of worker productivity. To anticipate this, a solar dryer is used by utilizing a solar collector as an absorber of sunlight and a drying chamber for the drying process of fish. The use of solar dryers has been shown to increase drying temperatures and reduce workers' sun exposure. This decreases the workload of workers, so that it has an impact on increasing productivity. Worker productivity increased by 133.94%.

Recent advances in solar tunnel dryer for performance improvement in food drying process: a review

The unexpected increase in demand and persistent shortage of fossil fuels continues the search for an alternative source of power. Solar energy is one of the sustainable and renewable sources of power that encouraged various researchers from all over the world. The production of food and its immediate consumption is the biggest problem to reduce the wastages of food. To overcome the wastage, drying is an excellent method to preserve the food grains, fruits and vegetables. For drying, conventional drying system is sun drying which is free and a renewable source of energy. But, there are various limitations e.g. rain, dust, animals, wind and insects. The use of solar dryers can eliminate these limitations significantly and enhance the productivity of farmers towards better revenue earned. This review attempts to provide in brief the recent developments to increase the temperature of drying chamber and applications of drying technology for different foods and agricultural produce, with particular emphasis on the modifications in the dryer and process conditions. This review paper will be helpful to know about the recent trends and different useful aspects of solar tunnel dryer to the new researchers.

Recent advances in solar tunnel dryer for performance improvement in food drying process: a review

The unexpected increase in demand and persistent shortage of fossil fuels continues the search for an alternative source of power. Solar energy is one of the sustainable and renewable sources of power that encouraged various researchers from all over the world. The production of food and its immediate consumption is the biggest problem to reduce the wastages of food. To overcome the wastage, drying is an excellent method to preserve the food grains, fruits and vegetables. For drying, conventional drying system is sun drying which is free and a renewable source of energy. But, there are various limitations e.g. rain, dust, animals, wind and insects. The use of solar dryers can eliminate these limitations significantly and enhance the productivity of farmers towards better revenue earned. This review attempts to provide in brief the recent developments to increase the temperature of drying chamber and applications of drying technology for different foods and agricultural produce, with particular emphasis on the modifications in the dryer and process conditions. This review paper will be helpful to know about the recent trends and different useful aspects of solar tunnel dryer to the new researchers.

A Model Identifying Factors Affecting the Sustainable Use of Solar Dryers: A Case Study

Solar energy has been used to preserve agricultural products which require drying through a consistent application of relatively low heat. In the present study, the feasibility of implementation the solar dryer system in the city of Yazd in Iran is evaluated by examining the effective factors. By identifying factors which may somehow affect the design, construction and operation of solar drying systems, a questionnaire was prepared and distributed. Among the results of the analysis, six main factors were identified: “performance,” “geographical location,” “infrastructures,” “interactions,” “financial support” and “social, cultural and political issues.” According to the results obtained from factor analysis and with Structural Equations Modelling (SEM) method, a model was introduced. Subsequently, the final model was developed with the use of path analysis method and with AMOS. Based on the final model, the three factors of infrastructures (with the coefficient of 0.44), interactions and cultural, social and political issues (both with the coefficient of 0.12) directly affect the possibility of implementing the solar dryer in Yazd. According to the proposed model, it was concluded that authorities should mainly focus their attentions on finance, science, economy and infrastructures to develop and promote use of solar drying systems.

Evaluation of traditional fish preservation method of Masmin from skipjack tuna (Katsuwonus pelamis) in Lakshadweep, India, with respect to nutritional and environmental perspectives

Masmin preparation is a traditional method that has been practiced for many years to preserve skipjack tuna (Katsuwonus pelamis) mainly in Lakshadweep. However, the method is not evaluated scientifically for its quality concerning nutrition and environmental contamination. Thus, in the present study tuna fillets from four stages of Masmin preparation, namely fresh, boiling, smoking, and sun-drying are evaluated for bacterial, nutritional, and heavy metal contents. The analysis revealed no significant difference in bacterial load, proximate nutrition (p = .93) and essential minerals, and heavy metals (p = .94) among all stages, suggesting the final product “Masmin” is nutritionally equivalent to the fresh tuna. However, pathogenic bacteria, such as Vibrio harveyi, Pseudomonas spp. Bacillus spp. are found, indicating poor hygiene during the processing. Heavy metals concentration like Al, Cd, Co, Cr, Mn, Ni, Zn, and Pb has increased with respect to previous reports, indicating an increase in pollution level in the catchment area that demands proper monitoring. Practical applications The findings inform the personnel engaged in Masmin preparation and consumption about the nutritional value of Masmin which is comparable to the fresh tuna even after different processing stages. Thus, the traditional fish preservation method could be applied to other economic important fishes where the cold facility is limited for fish preservation. On the basis of the microbiological analysis, we recommend the use of solar dryer and smokers in a traditional method of Masmin preparation to reduce microbial and dust contamination during processing and also it reduces the processing time that ultimately increases the production rate. Further, the findings from the heavy metal analysis bring into notice the increase in pollution level in Lakshadweep that raises health concern for the island populations and consumers.

Evaluating Economic Viability of Large Fish Solar Tent Dryers

Effectiveness of solar tent dryers in agricultural products has been well documented, but this information may not be generalised for use of solar dryers in all agricultural commodities and for all sizes of solar dryers. As such, we evaluated the economic viability of large capital intensive solar dryer that has been designed to dry small fish species on commercial basis on Lake Malawi. A probabilistic net present value (NPV) analysis was applied to a 15-m-long by 8-m-wide solar tent dryer which costs MK1,513,850 (US$2100) to construct and has a maximum carrying capacity 850 kg of fresh fish. The results show that the base NPV of this solar tent dryer is MWK5, 838,482.11 (US$11,762). When risk and uncertainty are considered, the probabilistic NPV becomes MWK12, 268,503 (US$24,716). The probability of obtaining a positive NPV was 58%, and we found that NPV is highly sensitive to total revenue and total cost but not to their components. We conclude that investments in large solar tent dryers are economically viable and that viability would be enhanced through access to formal fish markets where prices are stable and high.

Kinetics drying of silver banana (Musa spp.) in hybrid dryer

The search for the reduction of production costs and for the diversification of the commercialization of agricultural products is necessary when looking to ensure autonomy and increase income for farmers. The use of solar dryers for the dry fruits production provides an excellent alternative for consideration. However, in order to introduce this technology, one must understand the drying kinetics for a given product. This paper’s purpose was to study the intermittent drying kinetics of banana in a hybrid dryer. The drying was performed in a hybrid dryer composed of a solar collector (photothermal energy), a drying chamber containing Banana-Prata cut into cylindrical and disc shapes and a power-driven exhaust system. The process occurred during four sequential days, totaling 78 h of operation and 12 h of intermittence. The effective drying period took 39 h, with a temperature and relative humidity inside the drying chamber of 43.4 °C and 45.3%, respectively, and an air speed of 1.0 m.s-1. In the first few hours of drying, a sharp decrease in the moisture content was verified. During this period, the maximum and minimum drying temperatures were approximately 42 and 28 °C, respectively. A higher reduction in the moisture content of the disc samples was observed when compared to the cylindrical shape. After the intermittence period, a peak of moisture ratio was observed, followed by a marked loss of water in the fruit in both formats. The results have shown that the Page model is the one that better applies to the experimental data for the intermittent solar drying of banana in both shapes.

Modeling and simulation of moisture transfer during solar drying of carrot slices

AbstractCarrot slices of 0.03 m diameter and 0.005 m thickness were dried in direct, indirect and mixed mode type natural convection solar dryers. Thin layer drying behavior of carrot slices was studied using 10 empirical and semi‐empirical mathematical models. Wang and Singh model described the drying behavior of carrot accurately with maximum values of coefficient of determination (R2) and minimum reduced chi‐square (χ2), and root mean square error (RMSE). The effective diffusivity (Deff) and convective mass transfer coefficient (hm) of carrot slices ranged from 2.59 × 10−8−6.36 × 10−8 m2/s and 3.15 × 10−7 to 4.28 × 10−7 m/s, respectively, with maximum values obtained for mixed mode solar dried samples followed by direct and indirect solar dried samples. The diffusivity of carrot slices dried in direct, indirect and mixed‐mode solar dryer were expressed as a function of temperature using Arrhenius relation. Finite element model was developed using COMSOL Multiphysics software to simulate moisture ratio during drying. The developed model predicted the transient moisture migration phenomenon inside the samples precisely during the drying process.Practical applicationsThe ever increasing worriment on climate change and growing demand for enactment of clean energy technologies in food industries is the motivation for investigating the solar drying behavior of carrot slices. It is well known that the physico‐chemical and sensorial changes during drying are very much dependent on the moisture content of food product. In this regard, proper understanding and controlling of the solar drying process by accurately predicting moisture distribution inside the product will result in superior quality dried products. Moreover, mathematical models will assist in predicting the drying behavior of food product by analyzing the influence of process parameters and will be helpful to minimize the cost of drying process and deterioration of quality attributes of the product. The use of solar dryers is a proven technology and the food industry should promote its practical applications in food processing sector.

Effects of the climatic conditions and the shape on the drying kinetics, Application to solar drying of potato-case of Maghreb's region

Abstract This study focuses on the drying of the same quantity of a food product, cut in three different shapes (cylindrical, cubical and rectangular parallelepipedic). The experiments were carried out, considering the solar drying of potatoes. The results show that, the drying kinetics depend, on the shape and the size of items, which constitute each quantity. Using the diffusion model and experimental curves of the drying kinetics, the internal coefficient of diffusion, is identified for each case. Results show that, due to the shrinkage effect, the calculation of this coefficients modified, between the beginning and the end of drying. Relations between these coefficients and the characteristic dimension, are established. The analysis assesses the geometrical factors, which influence the drying parameters. The objective of this work is to propose recommendations for a wide use of solar dryers and to study the feasibility and the exploitation of these clean systems, especially in the Maghreb region.

Performance of hybrid solar-biomass dryer

Drying of agriculture product is energy intensive and traditional open sun drying is associate with many problems. Use of solar dryer is one of the alternative options. However, it is problematic in rainy and cloudy days. In order to measure the efficiency of solar/biomass hybrid dryer was proposed. A solar/biomass hybrid dryer was fabricated in RECAST Lab. Wood blocks were used as fuel for the gasifier stove. Biomass burning gasifier stove was integrated with solar dryer as an auxiliary heat source through a heat exchanger. The hybrid system of biomass with solar dryer ensures to provide continuous heat when needed. Due to the intermittent nature of sun, especially in rainy or cloudy season, food materials being processed get spoiled. A hybrid solar/biomass drying system solve such problems. Experiments were conducted to test performance of hybrid solar dryers by drying chili and banana. During the load test, conducted for chili, 16 kg of ripen chili with initial moisture content 72.58% (w. b.) was dried to moisture content of 7.13% (w. b.) in 20 hours. The result indicated that drying of chili was faster, within 20 hours (2 days), in natural sunny weather, against 48 hours (5 days) in open sun drying during April, in Kathmandu. Overall efficiency of drying system was found to be 4.29%.

Effects of Blanching and Natural Convection Solar Drying on Quality Characteristics of Red Pepper (Capsicum annuum L.).

The objective of this work was to determine the effects of blanching and two drying methods, open-sun drying and natural convection solar drying, on the quality characteristics of red pepper. A 2 × 3 factorial design with experimental factors as 2 drying methods (open-sun drying and use of solar dryer) and 3 levels of pepper blanching (unblanched, blanched in plain water, and blanched in 2% NaCl) was conducted. Dried pepper samples were analysed for chemical composition, microbial load, and consumer sensory acceptability. Blanching of pepper in 2% NaCl solution followed by drying in a natural convection solar dryer reduced drying time by 15 hours. Similarly, a combination of blanching and drying in the solar dryer improved microbial quality of dried pepper. However, blanching and drying processes resulted in reduction in nutrients such as vitamin C and minerals content of pepper. Blanching followed by drying in natural convection solar dryer had the highest consumer acceptability scores for colour and overall acceptability, while texture and aroma were not significantly (p > 0.05) affected by the different treatments. Therefore, natural convection solar dryer can be used to dry pepper with acceptable microbial and sensory qualities, as an alternative to open-sun drying.

Study of the Drying Behavior and Performance Evaluation of Gas Fired Hybrid Solar Dryer

AbstractThe conventional drying methods are energy intensive and are not cost competitive. The severe energy crises in Pakistan during the last decade has decreased the interest in drying of farm produce which is resulting huge postharvest losses due to product spoilage and nonavailability of storage facilities. This study has been carried out for the performance evaluation of newly developed hybrid solar dryer for the drying of onion, ginger and cabbage under local climatic conditions. The hybrid solar dryer has a total cross‐sectional area of 0.122 m2 out of which 34% is the collector while 64% is drying section. The dryer uses solar energy for drying during daytime while assisted with backup source during night for continuous product drying. The average initial moisture content of ginger, onion and cabbage batches was measured to be 88.45, 55.76 and 72.51%, respectively, while the final moisture content after drying was 10.27, 15.69 and 15.02%, respectively. The result also shows that the initial high moisture content of the products was removed in early hours of sunshine without any expense of primary energy cost. However, the remaining small amount of hygroscopic moisture was removed using backup energy source but with lower costs as compared with conventional drying. The final moisture content was achieved between 10 and 16 h for all batches of the onion, ginger and cabbage. On an average, greater than 70% moisture of the products was removed on the expense of solar energy. The overall average efficiency of the dryer was found to be 42.79%.Practical ApplicationsThe agro‐climatic conditions of Pakistan are ranging from tropical to temperate, thus, allowing to grow 40 different kind of vegetables and 21 type of fruits. Due to lack of processing facilities, the farmers have to sell their products at very low prices. Moreover, nearly 40–50% amount of perishable products are spoiled all over the world due to lack of farm gate processing facilities. In this research, the experiments have been conducted on onion, ginger and cabbage and successful results were obtained for all the products. In the conventional solar dryer, the major problem faced was to maintain the drying rate at uniform level but these types of dryer gave unsatisfactory results during the adverse weather conditions when the solar radiation are not in the limit to dry the products. Additionally, in winter, when the day time duration is comparatively shorter and solar dryer were not capable to dry the product in a single day. The objective of the hybrid solar dryer was to use the solar energy as a primary heat source during the favorable environmental conditions and the backup system is only taken into circuit when the solar system is not capable to maintain the desired drying rate. So, this type of dryer, not only maintain the drying rate but also vanishes the inversion rate of the perishables and hence ensures the quality of the dried products. So this hybrid feature built in the dryer is more attractive option for the farming community to dry their products without any harmful effects on the products. The hybrid solar dryer is demand base technology and will find a place in the manufacturing circle to transfer this technology to the end users, stakeholders and farming community for on‐farm processing of variety of perishable products for value addition. Furthermore, using hybrid solar dryer does not cause any kind of environmental pollution. On the contrary, solar dryers can help the rural and farming community to improve their living standard by earning profit through drying their on‐farm perishable and agro‐products while, at the same time, protecting their environment. At the same time the use of solar dryers on a large scale could be beneficial to reduce carbon emissions and the associated global warming issues.

A Comparison between the Effects of Solar and Sun (Traditional) Drying Methods on the Quality and the Quantity of Lemon in Jahrom City

In the food industry, there is an increasing tendency to develop economic ways to prepare food with high nutritional values and sensory qualities. One of the most widely used methods for preserving fruits and vegetables is drying. Citrus are among the most important tropical and subtropical fruits of the world which are highly putrescible and due to the fact that they are not available in all seasons, the main purpose of the present study is to study and compare traditional and solar drying methods of the product. After identifying one of the lemon groves in Jahrom, 80 lemon fruits perfectly uniform in the color and perfectly healthy in the lack of fungal infection were selected. In the solar drying method, 5 packs and 10 fruits in each pack and in the traditional drying method, 3 packs and 10 fruits in each pack were used. After the study of the treatment, fruit shrinkage rate, fruit moisture loss and fruit color index were measured. The results show that in both methods of drying, water absorption decreases with increasing temperature. In solar method, drying time is 17-45 percent less than that of the traditional method. In the solar technique, the fruit color is brighter than that of the traditional method. The results showed that the solar drying method is better than the traditional method. But on the other hand, the use of solar dryers because of the unavailability of equipment is not cost-effective and needs more detailed studies but in terms of the product quality is costeffective.

The Drying Characteristics of Amaranth Leaves under Greenhouse Type Solar Dryer and Open Sun

The dehydrated leafy vegetables have the potential to become an important product because of relatively inexpensive, easily and quickly cookable and rich in several nutrients which are essential for human health. The proper drying techniques are the most important aspect of leafy vegetable preservation. The use of solar dryer helps to reduce the losses and improves the quality of product. A Greenhouse type solar dryer was used and the experiments were conducted to develop dehydrated amaranth leaves so as to enhance the availability of amaranth leaves during off season. In the present study, fresh amaranth leaves were pretreated in two ways viz; (i) dipping in a solution (leaves to water 1:5 (w/w)) containing 0.1% Mgcl 2 + 0.1% NaHCO 3 + 2% KMS in distilled water for 15 minute and (ii) blanching in boiling water containing 3% sodium bisulphate for 2 min. The leaves were dried at 1.5, 2.0 and 2.5 kg/m 2 loading density, under greenhouse type solar dryer and in open sun. Untreated amaranth leaves were also