Passive Solar Dryer Research Articles

Performance analysis of an improved solar dryer integrated with multiple metallic solar concentrators for drying fruits

Reducing postharvest losses (PHL) of fresh perishable agro-produce is a key strategic pathway to increasing incomes, food and nutrition security in East Africa. In response, an improved Hybrid Indirect Passive (HIP) solar dryer with a modified solar collector plate and drying cabinet, has been developed and presented as a better food drying alternative against the traditional open sun drying (OSD) method. A conventional active-mode Solar Photovoltaic and Electric (SPE) dryer with an auxiliary thermal-backup system was also fabricated. The fruit drying performance of the HIP and SPE dryers was evaluated using pineapples and mangoes, and compared against the traditional open sun drying (OSD) method. The food drying duration for the SPE, HIP and OSD methods were 10 h, 18 and 30 h; respectively. Drying efficiency of the improved HIP dryer was comparable to the SPE dryer and was 18% higher than the OSD method. Therefore, modifying the solar collector plate with multiple metallic solar concentrators coupled with an improved greenhouse cabinet significantly improves the drying performance of the HIP dryer. The HIP dryer is, therefore recommended for mass adoption against the OSD method.

Thermal performance analysis of natural convection solar dryers under no load condition: experimental investigation and numerical simulation

ABSTRACTThe present work evaluates the thermal performance of direct, indirect, and mixed mode passive solar dryers under no load condition in terms of efficiency and convective heat transfer coefficient between absorber plate and moving air (hc,p-a). The temperature measurements of various components of the collector and drying chamber of solar dryers were monitored at regular time intervals throughout the experimental period. Based on the energy balance equations of different parts of the dryer and experimentally observed temperatures, the hc,p-a was determined. The no load efficiency was found to be 31.40%, 27.55%, and 41.43% in direct, indirect, and mixed mode solar dryers, respectively. The efficiency was observed to be a function of temperature difference between absorber plate and air and the radiation intensity. The average values of hc,p-a was found to be 16.31, 14.92, and 23.81 W/m2°C in direct, indirect, and mixed mode solar dryers, respectively. Finite element (FE) model was developed using COMSOL Multiphysics software to study the temperature distribution of air inside the solar dryers. The lower values of statistical errors indicated a close agreement between the experimental and predicted air temperature inside the dryers.

Energy and Exergy Analysis on Drying of Banana Using Indirect Type Natural Convection Solar Dryer

Energy and exergy analysis, in the thermodynamics, is an important tool used to predict the performance of drying system. In this work, energy and exergy analyses are made during the drying process of banana using an indirect type passive solar dryer. Solar flat plate air collector is used to heat the air. Banana gets sufficiently dried at temperatures between 28 and 82 °C. Solar radiation is measured and it is ranged from 335 to 1210 W/m2. Using the first law of thermodynamics, energy analysis was carried out to estimate the amounts of energy gained from solar air heater. Also, applying the second law of thermodynamics, exergy analysis was carried out to determine exergy losses during the drying process. The exergy losses varied from 3.36 to 25.21 kJ/kg. In particular, the exergy efficiency values vary from 7.4 to 45.32%.

Design, Construction, and Analysis of a Passive Indirect Solar Dryer With Chimney

The growing demand for alternative technologies, of clean and sustainable nature, has fostered the development and improvement of equipment that uses solar energy for the dehydration of seeds and fruits. Such equipment has been used worldwide for hundreds of years; however, it remains uncommon in Serra Gaúcha, a region of great production of grapes and apples for natura consumption in the state of Rio Grande do Sul—Brazil. In order to investigate the economic and technical viability of solar dryers in the Serra Gaúcha, this work has as target the design, simulation, construction, and experimental analysis of an Indirect Passive Solar Dryer with Chimney. The prototype, divided into three parts: solar collector, dehydration chamber, and chimney, was built prioritizing materials of low cost, but that did not compromise its performance. The device was submitted to experiments, which observed: solar collector behavior very close to the simulated one; obtaining a coefficient of performance of 87% in the equipment; satisfactory rise in temperature at the collector outlet comparing to its inlet; and dehydration of apples with a reduction of 89% in mass with 32.78 MJ of energy delivered to the system. The prototype payback period was estimated in two years.

Design, Fabrication and Performance Analysis of Economical, Passive Solar Dryer Integrated with Heat Storage Material for Agricultural Products

Design, Fabrication and Performance Analysis of Economical, Passive Solar Dryer Integrated with Heat Storage Material for Agricultural Products

Design and Fabrication of a Passive Solar Dryer for Meat Preservation in the Cordillera Region of Northern Philippines

The production of “etag” or smoked meat in the Cordillera Region of the Philippines is very common and is part of the Igorot culture. However, this is associated with an unsanitary product and even with carcinogenic contents. To provide an alternative and more sanitized setup for the production of “etag,” a passive solar dryer was initially designed in this study. The designed capacity is 5 kg of meat. The design utilizes solar as energy input to dry the products. It is comprised of four major parts: the solar heat collector, combustion chamber, drying chamber, and exhaust/air vent chimney. Dry air will enter through the cylindrical tubes of the solar heat collector where it is basically heated. The air thus contains energy to absorb the moisture from the meat and makes its way to the environment through the air vent.

Design and fabrication of a direct passive solar dryer for tilapia fish filets

Design and fabrication of a direct passive solar dryer for tilapia fish filets

Performance of a desiccant assisted packed bed passive solar dryer for copra processing

In this paper, the performance of a novel desiccant assisted packed bed passive solar dryer was evaluated for copra processing and compared with conventional passive solar dryer. This novel solar dryer consists of a desiccant assisted packed bed solar air heater attached with a dryer cabin. The desiccant and phase change materials packed in the solar air heater has control the humidity and retains the heat for longer duration, respectively. The performance of the dryer was evaluated (in terms of drying time to attain the final equilibrium moisture content, drying rate, specific moisture extraction rate, pick-up efficiency, and dryer efficiency) under the meteorological conditions of Coimbatore city in India during March and April 2016. The copra was dried from initial moisture content (wet basis) of about 52% to the final moisture content (wet basis) of about 8% in 62 hours with specific moisture extraction rate of 0.82 kg/kWh. The drying time was reduced by about 44 hours when compared to the conventional passive solar dryer. The dryer pick-up efficiency was varied between about 10% and 65%. The average dryer thermal efficiency was calculated to be about 32%. The quality of final dried product was found to be good.

Performance evaluation of solar dryer with a biomass stove to meet Indonesian National Standard of ginger simplisia

In Indonesia, ginger simplisia's (dried form) quality standards is regulated in SNI 01-7087-2005. The conventional drying method, direct open sun drying, has several weaknesses. It could reduce the quality of products that do not meet standards. Relating with these problems, one of the improvement efforts that can be done is by using the solar dryer technology. In this study, design and prototype of the mixed passive solar dryer has been made. Then, the solar dryer was tested to evaluate its performance. Tests were done through simulation and direct (prototype) tests. Based on the results of simulation and prototype tests, the performance of solar dryer designed was quite satisfactory (temperature ranges between 40-60°C). ANOVA and t-tests showed that there were no differences in temperature between each racks in each heat sources. In addition, based on the validation test there were no significant differences between the measurement results of the simulation and prototype tests.

Simulation of a passive solar dryer to charqui production using temperature and pressure networks

This paper presents a passive solar dryer that includes a chimney and a wind turbine to improve the airflow rate. The prototype of 2m2 of drying chamber area was tested to obtain charqui (dried beef). In relation to the traditional charqui, the final quality was greatly improved and drying time was reduced to less than two sunny days. A simulation method of the passive solar dryer is also presented. In this, pressure and thermal coupled network are used to represent the dryer, and they are solved by electrical analogy. Simulation and experimental results were analyzed, showing a good fit to the measured data, especially with trends. In all cases, the fits between measured and simulated data have coefficients of determination r2 higher than 0.93. The simulation method is suitable to be used in the design of passive solar dryers to find the optimum mass air flow.

Design and Construction of a Passive Solar Power Clothing Dryer

This manuscript presents the design and construction of the energy efficient, time saving, cost effective of passive solar powered clothes dryer. This manuscript begins with a derivation of mathematical model represents of solar dryer followed with an analysis of the elements necessary for successfully designing the various components of a solar dryer. The solar drying performance achieved an average drying rate of 0.35 kg/h and drying time of 3 h in a typical day, even under local low ambient humidity of around 35% and at moderate outdoor wind speed. Also, the computational fluid dynamic CFD of transient thermal behavior based on Navier-Stokes equations was used to demonstrate the prevailing temperature rises in the solar natural-ventilation system associated with the internal heat flux due to solar radiation and moisture removal. The efficiency of solar dryer was improved using Nano coating technology. The result showed good agreement between the computational solid simulation and the experimental measurements obtained from this system.

Performance study of different solar dryers: A review

Crop drying is essential for preservation in agricultural applications. It is performed either using fossil fuels in an artificial mechanical drying process or by placing the crop under the open sun. The first method is costly and has a negative impact on the environment, while the second method is totally dependent on the weather. By contrast, using a solar dryer is comparatively cheaper and more efficient. Some solar dryers run without electrical grid power or fossil fuels. This paper presents the state of various kinds of solar dryers that are widely used today. The indirect, direct, and mixed mode dryers that have shown potential in drying agricultural products in the tropical and subtropical countries are discussed. Aside from identifying the active and passive mode solar dryers, we also highlight the environmental influence on solar energy (harnessing) that plays a vital role in the solar drying sector. This paper also presents the related technologies that can help improve existing solar dryers.

Modeling of Thin Layer Drying Kinetics of Salted Fish Fillets (Tilapia Zilli) in a Direct Passive Solar Dryer.

An empirical thin layer drying model for modeling the salted fish filets in a direct passive solar dryer was developed. The experiment was conducted in a factorial form arranged in a completely randomized design (CRD) with three treatments replicated five times. The model got evolved from Wang and Singh model. The statistical analysis was done with a non linear regression analysis program (NLRP). From the result it is evident that the new model was found best to describe the drying process of salted fish filets over the conditions tested (temperature 20 to35.1 0 C, Relative Humidity54 to100% ). Results also showed that the new model in this work was the best in terms of explaining the drying kinetics of the fish fillets with χ 2 , SE R 2 , and P values ranging from, 2.22x10 -6 to 0.001176 ,0.008171 to 0.010844 ,0.9978 to 0.9981 and 0.0226 to 0.2151 respectively.

Studies on drying rates of brined and spiced Clarias gariepinus (Catfish) using solar dryer

The objective of this study was to determine the effect of brining and spicing with ginger or garlic on the drying rate of cat fish in a passive solar dryer. Samples of cat fish were solar dried under three different conditions: brine only, spiced with garlic and spiced with ginger. Their respective weight losses were used to determine the reduction in moisture contents. Graphs of drying rate versus time were plotted in each case and used to obtain the drying rate constant, k for the three drying conditions. This procedure is useful when a given level of moisture content must be linked to time of drying under similar conditions. The results obtained showed that cat fish dried using brine solution only is the best since its drying rate constant has the highest value of 0.375 units per day followed by ginger (0.273 units per day) and then garlic (0.254 units per day) is the least. The results also show that spicing with ginger and garlic reduce the drying rate of cat fish when dried in a passive solar dryer. Key words: Comparative, drying, solar, rate, brine, ginger, garlic, fish.

Drying Characteristic of Apple Slices Undertaken the Effect of Passive Shelf Solar Dryer and Open Sun Drying

Apple Varity (Golden Delicious) is widely cultivated in Syria and is consumed either fresh or in the form processed products such as juice, marmalade, jam and less as dried product. The present study was conducted to investigate the drying characteristics of apple slices and the quality parameter of apple slices (color, Rehydration ratio) undertaken the slice thickness (5, 10 mm) pre-treatment and the drying method by using a Passive Shelf Solar Dryer (PSSD) and in the Open Sun Drying (OSD). Results showed that there is a significant effect of the drying method and slices thickness on the moisture content and the drying time. The drying time decreased by 40% for 5 mm thickness of slices in the (PSSD) drying system comparison to the (OSD) system and the drying time decreased by 22% for 10mm thickness of slices in the (PSSD) drying system comparison to the (OSD) system. The slices thickness has a significant effect on the drying time where, the drying time for 5 mm thickness was less by 80% comparing to 10 mm in the passive solar dryer and less by 57% in the open sun drying. Rehydration ration also affected by the slices thickness and the slices treating by ascorbic acid, where the rehydration ratio values at the drying air temperature of 40°C increased by 41.7% and by 33.3% for treated and untreated slices when the slices thickness increased from 5 mm to 10 mm respectively.

Drying rates of some fruits and vegetables with passive solar dryers

Two passive solar dryers were designed and constructed with available local materials. The passive solar dryers which were direct and indirect types were tested with pepper (Capsicum annum L.), okro (Abelmoschus esculentus L.) and vegetables (Amaranthus hybridus L.) in order to evaluate the drying rate of these produces. The moisture content of 78.9% (w.b.) for 180 g freshly harvested peppers was reduced to 24.0% (w.b.). The drying rate in the direct passive solar dryer was found to be higher than the indirect passive solar dryer. The initial moisture content of 92% (w.b.) for 1000 g okro was reduced to 20% (w.b.). The drying rate in the direct passive solar dryer was also found to be higher than in the indirect passive solar dryer. The initial moisture content of 90% (w.b.) for 400 g vegetable was reduced to 20% (w.b.). The drying rate with the direct passive solar dryer was found to be higher than that with indirect passive solar dryer. During the course of drying, after each crop was kept inside the drying system, the temperature of the drying was monitored at an-hour interval; the moisture content was also monitored at a three-hour interval until there was no more change in the weight of the crop. The crops dried faster with the direct passive solar dryer than with the indirect passive solar dryer. As a result of the highest temperature attained in the direct passive solar dryer, the rate of moisture removal was the highest in this dryer.

Studies on the effect of different solar dryers on the vitamin content of tomato (Solanum lycopersicon)

Samples of tomato fruit were dried under four different conditions: open-air sun drying method and by using three different models of integral passive solar dryers which include green house solar dryer, sun-tracking solar dryer, and latitudinal box solar dryer. The fresh tomato samples and the dried samples were analysed for vitamins A, C, and E. The results showed a significant difference in the concentrations of vitamins A, C, and E between the fresh samples and the dried samples for all drying systems. While vitamin C is reduced in concentration for all dried samples, vitamins A and E are increased significantly with open-air system having the highest value in vitamin C concentration while latitudinal box dryer gives the best result in terms of vitamins A and E retention. All year round, availability of tomato could be enhanced by chipping and drying. Packaging and marketing of dried chips in small quantities could be a lucrative entrepreneurial endeavour for the business minded.

Studies on the Effect of Different Solar Dryers on the Vitamin Content of Tomato (Solanum lycopersicon)

Samples of tomato fruits were dried under four different conditions: open-air sun drying method and by using three different models of integral passive solar dryers which include Green house solar dryer, Sun-tracking solar dryer and Latitudinal box solar dryer. The fresh tomato samples and the dried samples were analysed for vitamins A, C and E. The results showed a significant difference in the concentrations of Vitamins A, C and E between the fresh and the dried samples for all drying systems. While Vitamins C reduced in concentration for all dried samples, Vitamins A and E increased significantly with open-air system having the highest value in vitamin C concentration while latitudinal box dryer gave the best result in terms of vitamins A and E retention. All year round availability of tomato could be enhanced by chipping and drying. Packaging and marketing of dried chips in small quantities could be a lucrative entrepreneurial endeavour for the business minded.

An Indirect Passive Solar Dryer for Drying

A solar drying system designed on the principles of convective heat flow, constructed from local materials was employed in drying yam (Dioscorea Alata). A glass collector having an efficiency of about 0.63 was used along with an absorber for absorbing the heat energy. The drying chamber consisted of drying trays. A chimney fitted at the top centre of the drying chamber enhanced airflow. Air passing through the collector heated up and dried the foodstuff in the drying chamber. The latitude of Ilorin is 8.26oN and the collector angle could be varied . 56o C, 41o C and 71o C were obtained as the maximum attainable temperatures for the drying chamber, ambient and collector respectively. Two samples of yam chips, each weighing 1560g and having an average size of 1cm thick, were dried both inside the dryer and outside the dryer within its surrounding. The initial moisture content of the yam was 70.3% (wet basis) and its final moisture content was 9% (wet basis).The result was compared to natural sun drying. It was observed that the drying time was reduced from 52 hours for sun drying to 45 hours for solar drying. The total cost of the construction was 6, 105 Naira.

Drying sage (Salvia officinalis L.) in passive solar dryers

Sage plants (Salvia officinalis L.) were dried in the passive dryers in different times of the year. Different passive solar dryers were used to achieve the socio-economical benefits from drying the medicinal plants growing in Sinai area. Drying sage plants might be a source to increase the Bedouin income instead of cannabis or marijuana, especially if it is exported abroad. Four drying methods were used in this investigation to dry sage in two seasons, namely August 2009 and March 2010 before flowering stage. Plants were dried in an Unglazed transpired passive solar dryer with 100% exposure to direct sun-rays, in a greenhouse dryer covered with shading cloth with 50% exposure to direct sun-rays, and with 0% sun-rays while the medicinal plants were protected from sun i.e. in shaded barn. Investigations were carried out under the environmental weather conditions of Ismailia, Egypt. The study revealed that sage can be dried at different times of the year even before the flowering stage of the plants.