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Indian jujube (Ziziphus mauritiana) and Date palm (Phoenix dactylifera L.) the most important fruit crops that can grow in India's hot arid regions. The perishable nature of Indian jujube and date fruits leads to post-harvest loss. Both of these fruits are highly perishable, containing more than 80% moisture. Moisture needs to be reduced to less than 20% for storing it for a longer period of time. A phase change material (PCM) based hybrid solar dryer was developed, which consisted of the collector of area 1.06 m2 and two drying trays made of SS (0.50 m2) and that two half trays (0.24 m2). The performance of the developed PCM dryer was evaluated by drying fresh Indian jujube and date palm fruits having an initial moisture content of 65–80% (wet basis) and compared with the developed dryer without PCM. The drying system works so that phase-change material stores the thermal energy during sunshine hours and releases it at night. Therefore, the dryer is effectively operative for the next 5–6 h. The temperature of the drying chamber was observed as 6 °C higher than the ambient temperature in July 2020 during date palm drying after sunshine hours till midnight and it falls gradually, and temperature in the drying chamber was observed as 5°Celsius higher than the ambient temperature in January 2021 during Indian jujube drying. The variations in moisture content (wet basis) of the Indian jujube fruit are reduced from 80% to 22% within seven days by using the dryer with PCM and in 9 days dryer without PCM. In date palm fruit, MC reduced from 65 to 20% in 6 days in the dryer with PCM and eight days without PCM. The thermal efficiency (η) of PCM based hybrid photovoltaic thermal (PV/T) solar dryer (η = 18.0%) was found better than that of natural convection mode without PCM based hybrid solar dryer (η = 15.8%). The developed solar dryer provides a promising alternative for drying other arid food produced after sunshine hours with a real-time data acquisition system. It is also found to be superior in retaining quality.

The objective of the research was to determine the amount of moist extractable matter from the precooked potato dough with the cut in the shape of sticks and the acceleration of the subtraction of moisture from the matter to be dried inside the solar dryer, controlling the flow of dry air entering the collector through six fans. The temperature and relative humidity in the dryer vary with the flow of air that enters the interior of the dryer and by the heat of the brass generated by the exposure of the extraction chamber to radiation from the Sun from 9:00 am. to 5:00 pm. The temperature and relative humidity values detected by the DHT 22 sensor were processed by the Arduino based microcontroller that has embedded the PID control program, whose outputs acted on the fans and heaters, fed with conventional energy, with respect to the setpoints of temperature 36.5 °C and relative humidity 33%. 26 temperature and relative humidity samples were taken during the day, inside the solar dryer chamber with electronic PID controller. As a result, an average controlled temperature of 36.36 °C and relative humidity of 33.115% were obtained in the dryer chamber, allowing the extraction of 73.16% of the weight of the wet matter from the precooked potato. Achieving, dry potato weighing 26.84% of the initial mass, in a drying time of 8 hours.

Photovoltaic-thermal (PVT) collectors can be applied in order to concurrently generation of electrical and thermal energy. In the present study, a vertical hybrid PVT solar dryer has been developed and analyzed by utilizing numerical and experimental approaches. ANSYS Fluent software has been employed to visualize both flow and thermal behavior inside the vertical PVTs. The main aim of using vertical structure of PVT dryer is its space-saving potential. For enhancing heat transfer, fins have been integrated over the absorber plate and PV panel. The obtained experimental findings showed that thermal efficiency values of the finless and finned vertical PVT collectors were in the ranges of 47.46-54.86% and 50.25-58.16%, respectively. Moreover, sustainability index values of finless and finned drying systems were achieved between 2.16-2.75 and 2.38-3.25, respectively. The obtained results showed that applying high air flow rate in finned vertical dryer notably improved the drying performance. In addition, the deviation between numerical and experimental findings obtained in the range of 4.2-8.7%. (c) 2021 Elsevier Ltd. All rights reserved.

Due to continuous growth in population and sharp increase in energy and food demand, research on alternative energy sources independent of fossil fuels has increased over the last decade. Moreover, limitations on greenhouse gas emissions by developed and developing countries are imposing much pressure on the energy sector worldwide to use renewable energy sources such as solar, wind, biomass, hydro, and geothermal. Food production is one of the biggest industries in the world, and it consumes a large amount of energy in the form of heat and electricity. In this work, agro-product drying technologies powered by solar energy are presented and discussed. Different types of solar dryers based on direct, indirect and mixed modes are described. Moreover, energy, exergy, economic, and environmental analyses for these technologies are presented to determine the main parameters affecting the dryer performance. The results indicate that the air mass flow rate, temperature, moisture content, and drying time are the most important parameters in solar dryer performance. Finally, a comparative assessment of the performance of different existing solar dryer has been highlighted with a detail scope of future works.

Solar dryers utilise solar radiation for producing hot air to dry various food and agricultural products. The limitation of solar dryers is their inability to achieve continuous drying during off sunshine hours. Thus, solar dryers are integrated with thermal energy storage units to achieve continuous drying operation. The thermal energy storage unit employed in solar dryer consists of either sensible, latent heat storage systems or the combination of these two. The article provides an extensive review on the various sensible and latent storage units and materials used in different solar dryers viz., direct type, indirect and mixed-mode type dryers operated in both natural and forced convection. A detailed discussion on different dryer types, product dried, operating parameters, sensible and latent heat storage materials used, and their outcomes are reported and tabulated. Further, the article also provides a detailed summary on the implementation of thermal storage units in solar dryers. The future challenges and recommendations on the selection, implementation and testing of the thermal storage unit for different solar dryers are also reported.

Solar energy is a widely used green energy resource that is used for drying processes. Through this assessment, the performance of an Indirect Solar Dryer (ISD) with three different cases, namely solar collector - without Thermal Energy Storage (TES), with TES unit having Phase Change Material (PCM) and with TES having fins inserted PCM have been experimentally analyzed during spring and summer seasons for drying Momordica charantia. Totally six experiments were undertaken to compare temperature, drying kinetics, and energy analyses. The initial moisture level of 2 kg of specimen decreased from 1.84 kg of water (92% w. b) to 0.24 kg of water (12% w. b) in 10.5 h utilizing ISD with TES having fins inserted PCM (Test 6). The maximum thermal efficiency achieved about 19.41% on Test 6. Exergy efficiency increased from 8.66% to 79.02% at Test 6. Environmental impacts assessment has revealed that the Energy Payback Time for the ISD was 1.42 years. The CO2 emission, mitigation, and carbon credit gained (Test 6) are 23.88 kg/year, 20.13 tons, and $100.642 to $402.569 for the 35 years’ intended lifespan. The assessment report showed that the device established was a potentially effective commercial drying technique, both in energy utilization and environmental sustainability.

The aim of the present study is to investigate the experimental performance of a solar dryer by using a novel type of a drying chamber for increasing the drying performance and ensuring homogeneous...

Solar drying has received great interest as a viable alternative solution to fossil fuel dryers. However, due to the intermittency of the solar resource, solar dryers suffer from discontinued drying and thus, long drying time. In this paper, the use of sorption materials to enhance the performance of solar dryers is reviewed. The main aspects regarding their use as thermal energy storage or dehumidification materials are highlighted. The paper shows that solid adsorbents, especially silica gel, are the most used materials. The use of composite materials, for instance the mixture of bentonite, CaCl2, vermiculite, and cement proved to be promising. The incorporation of a sorption dehumidifier in a solar dryer, usually at the solar collector inlet, generally leads to a reduction of the drying time of 15–30%, although values up to 50% and even 64% have been reported. On the other hand, introducing sorption materials as thermal storage in a solar dryer, mostly integrated at the top in the drying chamber, usually leads to a reduction of the drying time in a range of 30–45%. There are still various aspects to be investigated in depth before a large-scale utilization of these techniques in solar drying technology.

OBJECTIVE: The primary objective of this study was to minimize post-harvest damages and improve the handling of agricultural commodities. The secondary objective was to assess the performance of the dryer by varying inlet velocity of air on temperature, final moisture of the product, drying period, and drying rate METHODS: The present research was carried out for the development, fabrication, and testing of a multi-portioned type solar dryer. The multi-portioned dryer consisted of a collector unit, air storage chamber, drying cabins, and a chimney. A fan assembly was also attached at the inlet of the collector and at the outlet of the drying compartment to control the air velocity and to remove the moist air. RESULTS: The data obtained from the experiments revealed that the maximum temperature elevation of 36.5oC was attained during a no-load test. The results obtained after carrying out load tests revealed that the maximum drying rate of 47 g/hr was achieved at the air inlet velocity of 3.2 m/s. The initial moisture content of 80.50% was brought down to 3.31% in five sunshine hours of 150 gram sliced potatoes. Each portion received air at varying speeds, and it was observed that the portion receiving air at the lowest speed had the maximum temperature. CONCLUSION: The lowest temperature elevation was recorded for the portion receiving air at the highest speed. The dryer was also found to be suitable for the on-field practical application for the drying of perishable commodities.

Drying foods and medicinal plants is a process with high energy consumption because high amount of energy is needed for evaporating the water from the surface of the fresh materials. Therefore, developing cost-effective and simple-structured drying systems with low energy demand is a crucial matter. In the present study, compact type solar dryers have been designed, manufactured and tested experimentally. Within this context, thermal and flow behavior of compact dryers with and without baffles have been analyzed using CFD method. Then, fabricated compact dryers have been experimented at different conditions to determine their performance. Experimental and numerical findings of this study illustrated the effective design of the developed compact solar dryers. However, compact solar dryer with baffles exhibited better performance than the solar dryer without baffles. According to the experimental results, mean specific moisture extraction rate in compact dryers with and without baffles obtained between the ranges of 0.55–0.69 and 0.47–0.62 kg/kWh, respectively. In addition, average exergy efficiency of drying chambers was attained over the range of 44.91–55.28%. Overall findings of this study indicated successfulness of a compact solar dryer which developed using simple and lightweight materials.

Solar energy as a clean energy source is widely investigated to find out the effective mechanisms to meet a large part of energy demand in the near future. In the present research, a square-spiral finned quadruple-flow solar collector assisted dryer has been designed, and numerically compared with finless collector. Main aim of the current work is to develop and analyze a sustainable solar drying system. In this study, different from similar works, heat transfer surface area has been enhanced by using square spiral geometry which is an unconventional fin type. According to the numerical findings, a finned quadruple-flow collector which found more efficient has been manufactured, integrated with a drying chamber and performance experiments have been conducted. In the manufactured solar dryer, a PV panel has been used to run utilized fan. CFD simulation and empirical outcomes of this research exhibited the successful design of finned quadruple-flow collector. Experimentally obtained average efficiency of quadruple-flow collector varied in the range of 73.27-78.19%. Also, mean exergy efficiency of drying chamber was found between 44.16 and 58.38%. Sustainability index and waste exergy ratio values as important factors were attained between the ranges of 1.93-2.73 and 0.52-0.56, respectively. (c) 2021 Elsevier Ltd. All rights reserved.

Research on solar dryer technology proliferates since it reduces the drying period while keeping nutritional values in the agricultural products. This paper presented a review of recent advances in the solar drying system. This review is composed of working principles and classifications of solar dryers. They were classified into two main elements: airflow modes, either passive or active, and the way heat is transferred: direct, indirect, mixed-mode, and hybrid. The hybrid system used several types of elements to supply additional heat in the drying system, as elaborated in this paper, such as the electrical heater, biomass, and photovoltaic system. The advantages and disadvantages of the solar dryer also being discussed in this paper

For low temperature agricultural crop and meat drying, dryers utilizing the renewable energy source (solar energy) appear to be an efficient technique as it is ecofriendly, energy efficient, and available in free of cost. This work presents the experimental investigation on a solar food dryer equipped with external reflectors to enhance the rate of drying efficiency by removing the moisture content available in the anchovy fish. A comparison of conventional open solar drying is carried out to assess the parameters such as drying efficiency, moisture removal rate, and heat energy required for drying the anchovy fish using the modified solar dryer using the natural convection technique. From the experimental results it is observed that the relative humidity greatly influence the rate of drying. The average relative humidity during the experiments using open solar drying is found as 50–65% whereas, the using solar dryer the average relative humidity inside the chamber is found as 20–35%. The relative humidity of the fish using open solar drying is higher as compared to solar dryer drying as the drying products are kept in open atmosphere. The physical examination results on the dried products proved that using a modified solar dryers, the dried product is free from insects, and dust. Also, it is found that the loss of color from the product is a minimum while compared to conventional open solar drying. The results showed that the thermal efficiency of top tray (dryer 1) and bottom tray (dryer 2) is comparatively higher as compared to that of conventional open solar drying and found as 16.73 and 19.34 %, respectively. Results also showed that nearly 20.05% of the energy could be saved using the modified solar dryer as compared to the open solar drying technique.

This research study presents the experimental assessment of two sensible heat materials originating from the State of Yucatan, Mexico, which were incorporated into three compartments within an indirect type solar dryer with a storage system (ITSD-TSS). The experimental tests were carried out under different environmental conditions and were compared with the results obtained from a conventional solar dryer without thermal storage. Temperature and humidity were measured during the different tests and various indicators were used to compare both drying systems. The results revealed that the solar dryer that used limestone as storage material indicated better performance than the dryer that utilized beach sand, since the drying efficiency with limestone was higher by 1.55% and allowed to extract 0.0257 kg more water per unit kWh. Similarly, beach sand stored 1.5 times more energy than limestone, however, this material is very susceptible to variations of solar radiation, so it is not recommended to implement it in areas with high cloudiness. Finally, the implementation of the three storage compartments in the ITSD-TSS allowed an increase between 3 and 4% of the drying efficiency as compared to the conventional solar dryer. The findings of the work can contribute to sustainable development in the agricultural drying process in rural communities.

This Paper attempts to study the variation of simulation and fabricated jet impingement dryer to define how to increase efficiency, temperature and best quality of the dryer. The jet impingement is helps to increase the overall temperature of the exhaust air. where increasing the temperature slightly and velocity ranges of drying time as been reduced. The experimental process has been carried in the copra.From the CFD analysis end results establish the flow jet impingement processing on the absorber where a strong function of heat transfer enhancement. The present process concludes that the mass flow ranges of air as been influence the heat transfer rates. At solar radiation 500-1000 (W/M2), 348K ambient temperature and 0.048(Kg/S) mass flow ranges has been get at the end analysis.Now a day the new model innovations are needed in solar dryer to fulfil the requirements of drying industrial and agricultural products. The new design process analysis and assumptions are very necessary to design any system. By comparison solar drying fulfil the requirements than sun drying processing. Under the such process and conditions Effect of mass flow ranges of air, solar radiation on exit air temperature, and efficiency has been analyzed.

A sensor based solar dryer was designed to control the drying environment for precision drying of agricultural produce. The system entirely used solar energy utilizing both thermal and electrical effect. Paraffin wax (PCM) was used for storage of thermal energy whereas solar battery was used to store the electrical energy. Hot air blower was also provided to supply heat when there is less or no solar radiation. Temperature sensors were provided to control the environment of drying chamber. The exhaust fan started operating depending on the set temperature and thus control the drying environment. Load cells were provided below each tray to measure the dry weight. The drying chamber was made of mild steel with glass wool insulation. The capacity of the designed dryer was 10-15 kg with 6 trays. The designed dryer has target temperature of 55-60oC.

The work is devoted to the issue of the rational use of the solar energy in the technological process of fruit drying based on the use of solar drying devices, which are applied in various sections of the agro-industrial centers of Ukraine. The aim of this research was intensification of the fruits drying process using the solar energy by combining an air collector and drying chamber into a single power unit. To achieve the aim the heat exchange diagnostic techniques with alternative potentials of diffusion and moisture transfer was developed. This technique differs from those existing for the heat exchange research in that it allows the intensity of the moisture evaporation from a unit of the material surface to be calculated, based on the synthesis of the moisture content and the irreversible major laws of processes of the heat exchange characteristics of the fruits drying using the solar dryer. The above model makes it possible to diagnose the heat exchange processes and analyze the mathematical model of the heat exchange processes. It also allows modeling the changeable diffusion and moisture transfer potentials based on the dependences obtained and for the purpose of a further application in the methods and devices development to control the strain-deformed state of the fruits during the drying process. The method is offered for the calculation of diffusion and moisture transfer during drying fruits in the solar dryer.

Global energy demand continues to increase with the expansion of the economy activities and sustainable development. Meanwhile, the world is suffering from pollution and harmful greenhouse gases originated from burning of fossil fuels where the consequences of climate changes are also alarming. Solar energy is an alternative energy source that is abundant, safer and cleaner. This article provides a comprehensive review of works pertaining to solar thermal energy utilization in the drying process. In this article, the classification of solar dryers, the main components which includes solar collector, drying chamber and auxiliary systems, prospects, challenges, recent advancement and performance are discussed. The existing literature reported that solar dryer and solar collector maximum efficiency of 54% and 81% respectively, with superior products quality than the open solar drying. Solar drying is economical method with the payback period of 0.54–4.69 years. Solar dryer can also reduce 34% of CO2 emission to the atmosphere with less consumption of fossil fuel. Improvements such as in the design of solar collector, drying chamber, new auxiliary system, and material are essential to elevate the solar drying system performance. A review of the technologies can provide a base for the next generation of sustainable solar drying systems and helps policymakers to frame strategies aiming for clean technology and sustainable development.

In this study, the manufacturing and testing of an infrared dryer equipped with a PV/T solar collector were investigated. The total energy for the drying process is provided by solar energy. This study sought to compare the experimental results of glazed and unglazed modes and observe the effect of volume flow rate variations on the drying process of the products to determine the dryer’s energy and exergy efficiency and analyze the drying kinetic of potato slices. The amount of inlet airflow to the PV/T was controlled during the experiment. The power of the fan is supplied directly from two photovoltaic panels and the surplus amount of electrical energy is assigned to an infrared radiation source to enhance the process. Despite the low energy consumption of the current system, the products’ drying time was significantly reduced compared to similar systems. As a result, in glazed experiments, the drying time is prolonged in a range of 12–25% for 3 mm thicknesses and between 5 and 25% for 7 mm thicknesses compared to unglazed experiments. The maximum system energy efficiency and system exergy efficiency were 9% and 0.5%, respectively, calculated for 7 mm slices in unglazed tests.

Improper handling of fruits and vegetables causes a significant postharvest loss. Among the postharvest preservation mechanisms, solar dryers are reported as sustainable and suitable preservation systems for fruit and vegetable products. This paper summarizes the recent advances, opportunities, and challenges in solar drying of fruit and vegetable products. Besides, the review discusses the commonly used mathematical models for the evaluation, design, and optimization of solar dryers. The review discusses the factors that affect the performance of solar drying systems concerning drying time, drying rate, and product quality attributes. Short drying time, uniform drying air velocity, temperature, and product moisture distribution in the drying chamber are the critical parameters that are required for an efficient operation of a solar dryer. There is a good prospect in the application of mathematical modeling techniques such as computational fluid dynamics (CFD) in identifying the optimum solar drying conditions and dryer design that can maintain the required quality of the product. CFD has been used extensively in studying the airflow, heat, and mass transfer processes for optimizing the design and operation of different drying systems, similarly different quality models have been applied to evaluate the quality of dried products. However, most CFD studies did not include the quality aspect for dryer performance evaluation or optimization studies. To get the best result, CFD based performance evaluation or optimization studies of the solar dryers should have the capacity to predict the product quality in addition to the airflow, heat, and moisture transfer characteristics.

Solar air heaters (SAHs) are commonly utilized in different applications due to their simple structure and low setup cost. Optimizing operating parameters of the SAH is highly linked to the desired application. The aim of this study is to determine the optimal geometric and operational parameters of finned SAH for food drying. In order to achieve this goal, response surface methodology was combined with an experimentally validated thermal model of the SAH system. Multi-objective optimization is carried out according to energy-exergy analysis, improvement potential (IP) and outlet temperature suitable for food drying (40–70 °C). Length/width ratio (L/W) (1–5), height of air duct (0.02–0.2), and number of fins (0-60) were the operating variables. The experimental tests were carried out on the indirect type solar dryer composed of SAH and the drying chamber. The developed code led to consistent numerical results that have been confirmed by experimental tests. The optimal parameters were defined as 1.28 L/W, 0.067 m air duct height and 49 fins. In these optimal conditions, the outlet temperature, thermal efficiency, and IP were 52 °C, 51.78% and 1397.34W, respectively. The optimal design improved the thermal efficiency by 15.76% and IP by 19.33%.

This article performed various analysis on Red chilli by hybrid collector with solar dryer (HCSD). This study was carried out forced convection solar dryer which performed better in all aspects such as drying time, moisture removal rate, electrical efficiency, electrical thermal efficiency, thermal efficiency and overall thermal efficiency. In general, solar radiation was provided a sources of generating energy to drive a solar dryer. Hybrid collector has been provided the electrical and thermal energy to run a solar dryer. The solar dryer was tested by drying 12 kg of red chilli in the drying air temperature in the range of 32 0C – 56 0C. The initial moisture content of the red chilli was 71.5 % (weight basis) and was reduced to the final moisture content of 16.2 % (weight basis) in 6 consistent days with clear sunny days. The HCSD was operated between 9 hrs to 16 hrs. Finally, comparative study was also handled for better understanding in HCSD, in which solar dryer drying made better outcome than open sun drying.

Present work is focused on the assessment of energy and exergy flow in a mixed-mode solar dryer during the drying of pineapple slices by utilizing first and second law of thermodynamics. Moreover, drying kinetics and effective moisture diffusivity with shrinkage correction were also investigated at natural convection (NC) and forced convection (FC) conditions. The initial moisture of pineapple slices (90%, wb) was reduced to 29.66, 23.06, 24.05 and 19.68% (wb) in 6.5 h under NC, air mass flow rates of 0.006, 0.01 and 0.015 kg/s, respectively. Results revealed that diffusivity determined by assuming negligible shrinkage demonstrated 3.5–5.3 times overestimation than shrinkage consideration. Energy analysis exhibited that about 55–78% of total input solar energy constituted thermal losses from the absorber plate. Remarkably, an increase of air mass flow rate caused an augmentation in useful heat gain by air and a simultaneous reduction in thermal losses from collector along with its efficiency improvement. Exergetic investigation of dryer identified that the exergy efficiency of the solar collector and drying chamber was positively influenced by increasing air velocity. Furthermore, exergy efficiency of the dryer for NC and drying air mass flow rate of 0.006, 0.01 kg/s was 85.45%, 46.15%, and 18.88% lesser than 0.015 kg/s, respectively.

In this paper, a concentrated photovoltaic-thermal solar dryer (CPV/TSD) using nano-enhanced PCM (Al2O3Paraffin wax) is experimentally studied. A comprehensive thermodynamic analysis of the system according to the first and second laws is discussed. Besides, the drying parameters (moisture content and moisture ratio) are predicted using the two machine learning algorithms (ANN and SVM) and compared the prediction success with four evaluation metrics (R2, rRMSE, MBE, and rMAE). The overall thermal energy efficiency and exergy efficiency of the CPV/TSD system are found to be 20% and 8%, respectively. Although solar radiation to the environment has decreased a lot, it has been found that the thermal energy transferred to the nano-enhanced PCM prevents the decrease in greenhouse temperature for the first 100 min. In the system, mushrooms are dried from the initial moisture content of 17.45 g water/g dry matter to the final moisture content of 0.0515 g water/g dry matter. Then the drying rate value for CPV/TSD system is calculated to be 0.436 g matter/g dry matter.min. On the other hand, even if both ANN and SVM algorithms have exhibited very satisfying results, ANN is coming to the fore in the prediction of the drying parameters considering all evaluation metrics together. WOS:000637191800006 2-s2.0-85102023951

An experimental investigation was conducted to study the performance of a novel indirect type free convection solar dryer. The novel and a conventional indirect passive solar dryer were built. Solar irradiation and temperature of different locations were recorded. The air at the drying chamber entrance, lower space, and upper space temperatures besides the thermal efficiency of the novel dryer were 68, 39, 49 and 85%, respectively, higher than the conventional one.

This study describe the design features and performance of the unglazed transpired solar dryer for large and medium scale drying of Dates in the Dates growing area of Pakistan. The dryer has the designed capacity to dry 500 Kg of Dates from Khalaal (70% humidity) to Tamar (25% humidity), at 55 C ± 5 C in 72 continuous hours using biomass furnace as an auxiliary heat source and it covers approximately 256 m2 areas. This is the ideal humidity condition to store Dates for one year without any further degradation. In traditional open sunshine the huge quantity of Dates are dried in over 150 h hours and requires hectare of area to spread the Dates. Moreover, the quality of Dates in the open sunshine is affected badly due to two main reasons. Firstly, the heavy dust in the area that sticks the Dates during the drying process makes them unable to eat. Secondly, the Monsoon rains in the months of July and August also destroys Dates placed in the open areas for drying. Dera Ismail (D.I.) Khan, a remote district of Khyber Pakhtoon Khawa province of Pakistan, was selected to study the performance of Dates dryer, where solar insolation is 700-750 W/m2 in the months of July and August. The Dates were dried continuously and during off sunshine hours biomass auxiliary source was used. This solar dryer, containing eight trolleys and each trolley is loaded with twelve trays, is the first in Pakistan to dry a large amount of Dates. Moreover, the unglazed transpired dryer is designed in such a way that it can withstand the dusty atmosphere of D.I. Khan and also protect the Dates from dust and rainy water during the drying period. The design does not have any adverse effect on the quality of dried Dates. In D.I. Khan around 350 days are sunny per year and solar thermal technology is economically feasible compared to other conventional energy resources with a payback period of 3 and 7.5 years compared to un-subsided and subsided cost of Natural Gas respectively. The Natural Gas is the cheapest conventional energy source in Pakistan. But solar thermal technology is yet not popular source of energy in the area due to lack of information, fear of initial capital cost and weak government policies for renewable energies. This study also incorporates the recommendations to overcome these issues regarding Solar Thermal Technology, PACS Number: 44.40.+a, 89.30.Cc, 84.60.- h, 89.30.-g.

Food storage is a widely known practice performed since ancient times at the domestic and industrial levels, and the vital process of food storage is food drying. The dried food has a longer shelf life than fresh food. To obtain the dried product with good taste and quality as the original food crop, this must be dried in a controlled environment. Solar food drying is the process through which the better quality of dried food crop can be obtained with low investment and minimal deterioration chances. Among the categories of solar food dryers, an indirect type solar dryer is most advantageous. It provides better quality of dried food crop in a shorter duration, and it can be embedded with the phase change materials (PCM) to achieve maximum efficiency during utilisation. PCM material helps to make the food dryer works during off sunshine hours. This work focuses on the advancement of PCM-based indirect type solar dryers during recent years. Paraffin wax emerged as a widely used PCM material for drying applications. The PCM-based indirect solar dryer developed by Atalay and Cankurtaran showed the highest thermal efficiency and CO2 mitigation among the various discussed drying systems.

The solar energy is very plenty which is used to remove the moisture level in the food material and to preserve the food material. The aim of this experiment is to evaluate the performance of greenhouse solar dryer using North Wall insulation. When the food products are placed inside the dryer, due to the high temperature inside the dryer when compared to the atmospheric temperature will lose the moisture content in them quickly and gets dried within a short span of time. The dryer is covered with PVC sheet and the construction of the dryer is made up of Wood. The dimensions of the dryer are 1 m length and 0.75 m height are constructed. Inside the dryer stainless steel tray is placed in which the food materials are kept for drying. Below the tray a black sheet is kept at certain distance for absorbing the maximum heat from sun which helps to increase the temperature inside the dryer. Through drying in solar dryers the food material temperature can be observed till 61 °C as a result the moisture inside the food material can be dried more quickly, also there will be a steady decrease in the moisture inside the solar dryer from 60% to 32%. By these observations and results the food material placed in the parabolic dryer with insulation has given the best drying performance which took 5 days to complete the drying process followed by the triangular dryer with insulation took 5 and half days to complete the drying process. The parabolic dryer without insulation took 6 days and triangular dryer without insulation took 6 and half days to complete the drying process and the open drying process has taken 8 days to complete the entire drying process.

The drying process is generally carried out by burning wood and fossil fuels. However, this method is expensive and may damage the environment which has an adverse impact on climate. The world is facing the problem of shortage of fossil fuels. Some researchers did historical work on design and development of solar technology which is faster, more efficient, and hygienic and better quality of the product. Several solar dryers reviewed and enlisted the performance of dryers as per application. This paper gives an idea about the recent development in solar dryers. Some solar dryers are equipped with thermal storage to enhance the efficiency and drying rate in off-sunshine hours. To overcome the sunshine irregularity, some solar dryers have come up with solar thermal reservoirs. A comprehensive review on different dryers according to the product has been carried out, which helps in development and redesign of the solar dryer. From this paper, an idea regarding products drying likes chili, turmeric, peanut, grapes, copra and fish are presented. Which type of dryer is suitable and what kind of improvement could be possible in the future is obtained. For performance evaluation of the solar dryer, researchers used parameters like moisture reduction, moisture removal rate and different efficiencies. Solar dryer did not receive commercial utility because of high initial investment, long payback period and intermittent application. The study shows that the solar dryer not only saves fossil fuel for drying but also adds great worth to improve the product quality in terms of taste and color. It also doesn’t have any harmful effect on the environment. Solar dryer is therefore ideal to use for preservation of food in rural areas. This study may help farmers and new researchers for the design new type of solar dryer for products.

One of the important global concerns is to reduce the spoiling of agricultural products for avoiding food demand. The solar drying techniques play a vital role to avoid post harvest losses. Mixed mode type, passive solar dryer is the most efficient dryer compared to other passive dryers. The performance of the solar dryer is mainly depends on its construction and material. Presenting the various studies in mixed mode passive solar dryer and its details of construction is the main objective of this paper. This paper focuses on recent development in passive type mixed mode solar dryer. This study will help the researchers find the new direction of research to improve the performance of mixed mode passive solar dryers. The basic idea is providing to the former for constructing and modifying their solar dryer.

Solar drying has emerged as a potential drying solution for agricultural products in many developing nations. The drying behavior of the product to be dried depends on many parameters of the dryer. A box-type natural convective solar dryer was developed to analyze the drying performance of Wood chips. Experiments revealed promising drying results with drying efficiency. The design of the dryer could further be enhanced by hybridization with an external heat source.

Solid biofuels such as woodchips have always been a significant source of fuel in the field of renewable energy. However, the drying of wood chips has been a challenge in preparing biofuels and other applications. The moisture content of below 25% in the wood chips of grade EN 14961 is considered the premium wood chip material. Solar drying emerged as a leading solution for the drying of wood chips. The paper investigates the comparison of moisture removal rate using a natural convective solar dryer compared to open sun drying developed at Miskolc, Hungary (48°06'15.0"N 20°47'30.0"E).

A solar dryer assisted by biomass back-up heater was designed and manufactured from locally available materials to dry maize, and the drying model is selected, which better fits the dryer test results. This study tried to address the problem associated with the fact that solar dryers are efficiently operational only when there is sufficient solar energy. The dyer comprises a solar air heater, drying chamber, biomass back-up heater, and airflow systems. The solar heater has a length and width of 2 m × 1 m respectively and is enclosed with a transparent glass that allows the solar energy into the collector. The measurement taken to evaluate this dryer's performance is temperature, moisture content, solar irradiation, and airspeed. The average temperature difference between the ambient and the collector outlet was recorded as 9.6 °C, and 12.8 °C in the solar and biomass assisted dryer. The daily average solar insolation for the test periods of October and December at the site was 673 W/m2. When the system is loaded with 50 kg of wet maize grain at an initial moisture content of 21.3% and dried to 14.4% moisture content in 45 h drying time in the solar dryer, 4.03 kg of moisture is removed. A 50 kg of wet maize grain at an initial moisture content of 22.9% and dried to 14.2% moisture content in 27 h in solar dryer assisted by biomass back-up heater, 5.06 kg of moisture is removed. Solar dryer collector efficiency was estimated as 64.2% with an average drying rate of 0.0746 kg/hr. The solar dryer system efficiency was 20.8%, and solar assisted dryer efficiency was 4.3%.

This paper presents a hybrid solar dryer with baffles disposed of on the solar collector. When the levels of solar radiation are low, an electrical heater is used to increase the drying air temperature. A photovoltaic system feeds the electrical heater and the fans, and it is also used to preheat the drying air, increasing the temperature at the inlet of the solar collector. Experimental results of corn drying indicated that the baffles augmented the energy efficiency of the system (from 23.5 to 24.9%) and the temperature rise in the solar collector (from 13.5 to 20.2 ℃), reducing the time required for the corn to reach the final desired moisture content.

The abundant and unpredictable use of fossil fuel accelerate the continuous search in that field of an alternative source. Most of the researchers are attracted to the solar power, that is one of therenewable and sustainable energy sources. Based on the current scenario, in futurethe energy requirement will be tremendously high. The effectiveuse of solar energy can be reduced the problem of huge energy demand in all agricultural, industrial, domestic and power production sectors. In agricultural sector, one of the areas is drying technology. The drying technique is one of the applications of the solar energy. Drying is the process of removing moisture from the agricultural produce. From our ancestor to modern humanbeing, various improvement occurs in the solar drying system. The indirect solar drying with integrated flat plate collector is most popular, simple in design, cost effective, maintenance free and easy to operatevegetable drying system. The flow of air movement, thermal leak proof cabinet structure, flat plate collector’s (FPC) absorber plate design, optimum thickness of selective coating materials, etc. directly affect the efficiency and moisture removing rate of the solar drying system. Here, the 15 kg green chili has been taken for drying in solar drying system. The dryer is integrated with phase change materials (PCM) in drying trays, flat plate collector’s absorbing plate coated with activated charcoal and black board paint, the variable air mass flow rate of the blower. It has been found that, at 0.008 kg/s air mass flow rate the outlet temperature of the FPC is 96 °C and efficiency is 33%. The drying time was 16 h as compared with open sundrying time 28 h for the 15 kg chili. It was compared with indirect solar dryer without thermal energy storage and found that the time required for drying chili with thermal energy storage is 4 h less than the without thermal enrgy storage solar dryer.

The article outlines the relevance of production of dried products using a mobile solar dryer plant with mobile shelving. For intensification of the drying process, the convection of the drying agent flow in the proposed design of drying chamber was studied via numerical solution of the Navier–Stokes equations. As a result, a graphical interpretation of isolines of moving stream of drying agent in a chamber was obtained. Varying dimensionless parameters of the drying agent enabled complete coverage of all zones of the dryer chamber. The motion of shelves due to gravitational forces allowed uniform drying of materials. Through multivariate experiments, the influence of the temperature-time regimes of the dryer chamber on the particle size was investigated. The optimal drying conditions for cut fruit are presented.

In the present study, a low-cost solar fruit and vegetable dryer was designed, constructed, and tested for small-scale production, especially in households. An optimizing procedure was performed to convert a typical widely-used direct cabinet dryer into a new indirect dryer using experimental data and numerical simulations. Several well-designed experiments accompanied by CFD simulations using finite volume method were carried out. It was concluded that the proposed conversion procedure could be achieved utilizing a blackened absorber plate, an air circulating unit, and a honeycomb air manifold. The drying capacity of the dryer could be increased by more than 50% in comparison with the direct type by adding a new tray to the optimized dryer. The thermal efficiency of the proposed solar dryer was estimated 16.4%, indicating that the desirable energy performance of the dryer was superior to some available designs of solar dryers. Besides, it was observed that the proposed numerical approach was able to produce a reliable qualitative and quantitative insight into both the thermal and fluid mechanical behavior of the dryer. Finally, it was claimed that not only was the developed apparatus suitable and efficient for the household usage, but also the optimized version of the dryer could be inspiring for those who are currently using typical direct cabinet dryers to convert their dryers into indirect ones.

It is an essential and most abundant energy resource on earth. Solar energy can be caught and utilized in a few different ways and as a sustainable energy source is a significant part of our virtuous energy future. Its technology can be passive solar or active solar depending on how it can store excess energy and converting into solar power the storage of solar energy require a storage medium or accumulator. It can help to store excess solar energy for future use. One of the best methods to store heat energy from the sun is by making use of phase change material (PCMs) due to a huge ton of captured latent heat and isothermal kind of PCM during heat expansion and dismissal during phase change. PCM becomes an ideal candidate for a thermal energy storage medium in building applications. Now a day PCM gained special attention in building applications like water and air heating application, building-integrated system (ceilings, walls, and floor), H.V.A.C/solar absorption system for building, and other useful applications PCM concrete, PCM shutters, solar cooker, and solar dryer. In this paper, an attempt has been made to provide an overview of the progress and application of PCM in solar thermal energy.

The agricultural and food products may be enhanced by reducing their moisture contents, by means of a drying process. The aim of the work is to evaluate a mathematical modelling based on the experimental analysis of forced circulation of mixed mode solar dryer. From previous literature four different models (Newton, Page, Henderson & Pabis and Wang & Singh) are chosen for testing the performance of solar dryer. Selected models are evaluated by using EMD, ERMS, R2 and χ2 and it is concluded that Page model is more suitable for the fabricated mixed mode solar dryer at air flow rate 0.009 Kg/s based on the experimental analysis.

Building cooling is achieved by the extensive use of air conditioners. These mechanically driven devices provide thermal comfort by deteriorating the environment with increased energy consumption. To alleviate environmental degradation, the need for energy-efficient and eco-friendly systems for building cooling becomes essential. Evaporative cooling, a typical passive cooling technique, could meet the energy demand and global climatic issues. In conventional direct evaporative cooling, the sensible cooling of air is achieved by continuous water circulation over the cooling pad. Despite its simple operation, the problem of the pad material and water stagnation in the sump limits its usage. Moreover, the continuous pump operation increases the electrical energy consumption. In the present work, a porous material is used as the water storage medium eliminating the pump and sump. An experimental investigation is performed on the developed setup, and experiments are conducted for three different RH conditions (low, medium, and high) to assess the porous material’s ability as a cooling medium. Cooling capacity, effectiveness, and water evaporation rate are determined to evaluate the direct evaporative cooling system’s performance. The material that replaces the pump and sump is vermicompost due to its excellent water retention characteristics. There is no necessity to change material each time. However, the vermicompost is regenerated at the end of the experiment using a solar dryer. The passing of hot air over the vermicompost also avoids mould spores’ transmission, if any, present through the air. The results show that vermicompost produces an average temperature drop of 9.5°C during low RH conditions. Besides, vermicompost helps with the energy savings of 21.7% by eliminating the pump. Hence, vermicompost could be an alternate energy-efficient material to replace the pad-pump-sump of the conventional evaporative cooling system. Further, if this direct evaporative cooling system is integrated with solar-assisted drying of vermicompost, it is possible to provide a clean and sustainable indoor environment. This system could pave the way for year-round thermal management of building cooling applications with environmental safety.

The most noteworthy advantage of solar power as compared to other forms of energy is that it is clean and might be supplied with no contamination to the environment. Over the past centuries, it is believed that energy from fossil fuels is less expensive and more helpful than energy from other sources. This research thus results to the successful fabrication of a solar dryer with tests distributed for various performance comparisons like No-load and load performance of the dryer. Direct sun-drying comparisons depicted discernable contrasts within the final moisture content specified. The utmost temperature recorded within the drying chamber and solar dish for No-load are 44.5 and 52 respectively. Whereas when the cupboard is loaded, the highest temperature of 34.5 and least temperature of 23 are recorded. An average temperature of 27 was obtained, thereby giving the solar dryer an exegetic efficiency between 70% and 80%. Performances of the tests were done from 9am to 5pm. The solar store that was designed to heat to the drying chamber within the night was found to possess its most elevated temperature at 43 . These performance results were achievable due to daily precipitation, and in some cases, cloudy days when the sun was not shining at its peak. The load outcome was done with red-sweet pepper and yam food items.

This paper presents the energy and exergy-based environmental sustainability analyses of a developed solar dryer equipped with electric heater as supplementary heat. The experimental study was applied for drying a local variety of red pepper (Shombo) near a coastal region of eastern Nigeria. The objectives of the study were to assess the suitability and overall performances of the hybrid solar dryer in this area. Results obtained indicate that the solar collector contributed about 39.4 to 48.5% of the total drying air temperature required for drying operation. The energy efficiency of the hybrid solar dryer ranged between 13.2 to 35.6%, whereas the specific energy requirements varied between 7.24 kJkg− 1 to 63.5 kJkg− 1. The percent solar energy contribution to the total energy requirement ranged between 28.8–52.68% at varying air temperatures (50, 60, and 70oC) and air velocities (1.14, 2.29, and 3.43 ms− 1). The drying time varied between 75 ± 5 to 180 ± 24 min. The energy and exergy efficiencies varied between 13.2–35.6% and 35.8 to 92.3%, respectively. The exergy-based sustainability indicators which take into account the ratio of waste exergy, sustainability index, and improvement capacity of the hybrid heat source dryer were found to be 0.11–0.167, 1.14–6.12, and 0.099–0.289 kJs− 1, respectively. Comparison between a CI-engine powered dryer reveals that the use of a hybrid solar-electric dryer can prevent emission of 398.86 to 3872.7 tons of CO2 into the environment per annum. Recommendation for future studies was suggested.

Drying characteristics of stevia leaves were investigated in an infrared (IR)‐assisted continuous‐flow hybrid solar dryer. Drying experiments were conducted at the inlet air temperatures of 30, 40, and 50°C, air inlet velocities of 7, 8, and 9 m/s, and IR lamp input powers of 0, 150, and 300 W. The results indicated that inlet air temperature and IR lamp input power had significant effect on drying time (p, A comparative study was performed among mathematical, artificial neural networks (ANNs), and Adaptive Neuro‐Fuzzy System (ANFIS) models for predicting the experimental moisture ratio (MR) of stevia leaves during the drying in an infrared (IR)‐assisted continuous‐flow hybrid solar dryer. The drying time was decreased significantly by increasing the inlet air temperature and increasing IR lamp input power (p

The world is acting towards the reduction of use of fossil fuels. Therefore, a big number of innovations are utilized that adopt sources of renewable energy such as wind, solar, tidal etc. Solar radiation is used for different applications, one of them is drying different products from thousands of years. Thus, solar energy was the only used energy until the discovery of fossil fuel sources, especially utilized for solar dryers. These dryers are not very commercialized, and their designs are based on empirical and semi-empirical systems. Therefore, theoretical studies will be of high importance in this field. The majority designs of solar dryer available in the market, are used mainly for drying of various crops either for family use or for small-scale industrial production. In this article a simulation of the Lebanese ambient temperature and the relative humidity will be conducted then compared to the meteorological experimental data. After that, a modeling of a direct solar dryer system is developed based on the heat transfers phenomena inside and outside the dryer. This model is simulated using five different products that helps us to determine the instant temperatures of the product, of the internal air of the dryer and of its cover, in addition to the instant water content of the product dried. Finally, a linear relation between the thermal capacity of the product dried with a range going from 1100 to 2300 J/kg.K and a defined drying characteristic time will be concluded from this work.

The simplicity of solar flat plate air collector and free availability of solar energy sources attract attention to the optimization of the collector. This study aims to assess the effect of double pass air flow on the performance of flat plate air collectors. The analysis of the performance characteristics of the indirect solar dryer was carried out by CFD simulation with three different smooth, rough and V-grooved surfaces, keeping the lower and lateral collector well insulated and the drying chamber acting as a vertical chimney. The average thermal efficiency of the V-grooved surface, smooth surface, and rough surface is 90%, 78%, and 62% respectively. The total area of the collector is 1.20 × 2.0 = 2.40 m2 with the dimension of drying cabinet width, depth, and height 1200 × 650 × 1000 mm respectively. The pressure drop observed at the entrance to the drying chamber is high in the case of a smooth surface, medium in a rough surface and low in a V-grooved plate which will allow sufficient gas pressure to pass through completely.The air mass flow rate is the most important and effective factor during drying. The humidity of the air, as well as air velocity, is also an important factor in improving the drying rate. ©2020. CBIORE-IJRED. All rights reserved

In this study, an energy and exergy analysis of the drying process of corn was developed for a hybrid dryer coupled with a PV system. The differential of the dryer is the fact that the PV system was used to feed an electrical heater and fans and also to preheat the drying air through the use of the PV panel rear side as heat exchanger, increasing the air temperature before the inlet of the solar collector. The performance of solar drying processes is extensively investigated in the literature, but usually the drying chamber is used as control volume in the analysis. The main contribution of this work is the assessment and comparison of the performance of the dryer using three different control volumes in the thermodynamic analysis: only the drying chamber, the drying chamber and the solar collector, referred to as solar dryer and the complete drying set, corresponding to the drying chamber, the solar collector and the PV module. The results indicated that the efficiency values found are greatly affected by the control volume used, with variations of the exergy efficiency ranging from 22.2% to 45.0%, depending on the control volume used. It was found that the higher efficiencies were found selecting the drying chamber as control volume (as usually chosen by most works from literature). For the complete drying set, the individual contributions of the exergy rates were evaluated. It was concluded that the main contribution to the input and output exergy are the heat transfer and the outflow exergy rates, respectively.

Hybrid solar drying technology for food products is a clean and cost-effective replacement of highly energy intensive thermal dryers employed in agri-food processing chain. This involves the amalgamation of “only solar dryer” with various other energy harvesting systems like, biogas, heat pump, and thermal storage materials. This paper reviews the significance of hybrid solar dryers in terms of withstanding varied climatic and uncontrolled environmental conditions and their impact on drying characteristics of food products. From the appraisal, heat pump hybrid solar dryers proved to be more efficient, having wide range of drying temperature, and is suitable for heat-sensitive products. On the other hand, the advantages of biomass hybrid solar dryer lies in its ability to utilize cheap local resources for assisting the energy requirements and have low constructional cost. However, the state of art indicated that sanitary aspects of solar drying have not been explored much and should be encouraged. The presented review also explores the research scenario of relevant virtual platforms, applicable for simulating the dryer design and drying parameters. The important findings on modeling aspects of dryer design and thick layer drying of food products in solar dryer are also discussed. The economic assessment of presently available hybrid solar dryers showed competitive profitability metrics and equipment cost. Moreover, it is suggested for the promotion of energy-efficient hybrid solar dryers and its environmental benefits in the future to provide a benchmark for drying applications in food processing industries.