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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).

East Java Province is one of main producers of cabya (Piper retrofractum Vahl) fruit in Indonesia. The fruit has huge utilizations and economic potential, but lack in postharvest process investigation. Traditional open sun drying by farmers has deficiency, e.g. unpredictable weather and longer process. In the present study, the indirect forced convection solar dryer was used to dehydrate the cabya fruit as affected by hot water blanching. The drying behavior, drying kinetics model and shrinkage of the fruit were evaluated. One kilogram of cabya fruit at the red edible maturity stage with 70.29 ± 2.89% (wb) of average moisture content was used as raw material for each with and without hot water blanching. Two units of forced convective solar dryers with identical specification consisting of solar air collector and drying cabinet were employed in parallel for 18 h in 3 days. The obtained drying data were fitted to 12 mathematical drying kinetics models. The moisture content of cabya fruit with and without hot water blanching was reduced to the final moisture content of 6% (wb) and 9% (wb), respectively. Among examined models, The Page model satisfactorily described cabya fruit drying kinetics. The results also indicated that hot water blanching affected significantly the drying behavior of cabya fruit. Significant shrinkage was also found in the final dried product of cabya fruit.

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.

Environment and Economy are the two important pillars of sustainability. In this paper, the economic viability and environmental impact of the novel greenhouse dryer with an evacuated solar collector are calculated. For this analysis, tomato is dried inside the dryer as it is a high moisture crop that requires a faster drying rate otherwise it starts giving a bad odor and gets contaminated. The hybrid active greenhouse dryer is developed especially for drying high moisture agro and non-agro-based produce. Evacuated tube solar collector is integrated with the dryer that supplies the hot water to the heat exchanger kept inside the dryer. The hot water flowing inside the copper tubes of the heat exchanger transfers its heat to room air through convection and to crop through conduction. Hence the higher room temperature and faster moisture removal rate are obtained. Tomato slices have been dried from 94.6% (wb) to 10% (wb) moisture content in 10 h. The developed dryer can produce 261 kg of dried tomato annually and its payback time is only 1.73 years which is very less as compared to its life of 30 years. In its entire lifetime, the dryer will mitigate 169.10 tonnes of CO2 that prove its suitability from a sustainable point of view., Graphical abstract Image 1, Highlights • A Novel hybrid greenhouse Solar dryer is developed for drying high moisture crops. • Dryer is totally dependent on renewable energy source with an increased drying period per day even after sunset. • The economic analysis shows that the capital cost of hybrid dryer is not too high as compared to other hybrid dryer.

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.

Seaweed is one of the marine commodities that has high economic value and benefits for humans, because seaweed can be processed into basic food ingredients and various types of products such as seaweed lunkhead, gelatin, cosmetic medicines and so on. The post-harvest handling process for the Papuan community, Kec. Taliwang, West Sumbawa Regency (NTB) is still done traditionally so natural drying usually takes a long time because the temperature and energy depend on sunlight. This will lead to a decline in the quality of seaweed products because temperature and energy depend on sunlight. One of the efforts to improve the quality of seaweed production is to reduce the water content, the maximum water content limit, which meets SNI 25% - 50%. In this study, four forms of cover were used, namely the cover form of a single oblique solar dryer, the cover form of the taper solar dryer, the cover form of the double slanted solar dryer, the cover form of the rectangular prism solar dryer. The peak drying rate lies on a double sloping cover of 0.40 g / minute, a taper cover of 0.37 g / minute, a rectangular prism cover of 0.34 g / minute and a single sloping cover of 0.30 g / minute. The hot peaks that are useful are located on a double sloping cover of 3.82 Watt, a taper cover of 2.80 Watt, a rectangular prism cover of 2.09 Watt and a single cover of 0.46 Watt. The peak of efficiency lies in the double sloping cover of 8.57%, taper cover of 6.28%, rectangular prism cover of 4.69% and single sloping cover of 2.28%. The peak of seaweed residual water content lies on a double sloping cover of 13.21%, a taper cover of 19.61%, a rectangular prism cover of 25.73 and a double sloping cover of 27.75%. This shows that drying using double sloping covers is more effective and efficient, so it can accelerate the drying rate and can increase the selling price of seaweed for seaweed farmers in Kertasari Village, Taliwang District, West Sumbawa (NTB).

Herein, a forced convection solar fish dryer is designed, constructed and characterized to yield a better main of drying fish. The designed dryer incorporated a heat storage unit which complimented the drying rate of the product during off sunshine hours. The device was characterized during raining and dry seasons and results clearly indicated the influence of seasonal variation on the performance of the device. Average hourly variation of the dryer and ambient temperatures measured on the selected days of the different months of measurement during the two seasons, clearly indicated that temperatures were significantly enhanced by the device. This was due to the high ability of the designed solar collector to trap large amount of long waves. Maximum dryer and ambient temperatures during raining season were measured to be (58.9±2) oC and (40±2) oC whereas, (73.5±1.3) oC and (45±1.8) oC respectively, were measured during the dry season. Average daily moisture loss from the drying fish was notably high, especially during dry season which was due to the high dryer temperatures and decrease in atmospheric humidity. The efficiency of the solar dryer was estimated to be 76 %. The fishes with initial moisture content of 87 % was dried to 13 %. This moisture content is in range with the United Nations Economic Commission for Europe (UNECE) Standard DDP-19 concerning the marketing and commercial quality control of dried fish.

Tomato (Solanum lycopersicum) and brinjal (Solanum melongena) are food products that are frequently wasted in Indian markets as their shelf lives are only a few days. An indirect type solar dryer (ITSD) has been developed. It’s performance and drying kinetics of brinjal and tomato slices have been analyzed. The moisture content of tomato decreased from 15.667 to 0.803 kg/kg of dry basis (db) and that of brinjal reduced from 10.111 to 0.498 kg/kg of db. The drying curve was fitted with the different models of existing studies. The average effective moisture diffusivity is estimated and it is 3.60 × 10−9 and 4.00× 10−9 m2/s for tomato and brinjal, respectively. Mass transfer coefficient was in the range of 0.82 × 10−4 to 2.85 × 10−3 m/s for tomato and 1.11 × 10−4 to 3.32 × 10−3 m/s for brinjal. The heat transfer coefficient was in the range of 0.089 to 2.888 W/m2 K and 0.1066 to 3.3564 W/m2 K for tomato and brinjal, respectively. The activation energy for tomato and brinjal was 21.19 and 19.46 kJ/mol, respectively. The average thermal efficiency of the collector and dryer was 59.05% and 31.4% during tomato drying and 58.42% and 25.16% for brinjal drying, respectively.

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.

Objectives: This study aims to develop better solar dryer for paddy drying. Methods and Analysis:The design and fabrication of a parabolic cylinder type collector-drying unit has been developed. Paddy is dried by the variation which took place into four batches starting from batch 1 (08:30 - 09:20), batch 2 (09:30- 10:10), batch 3 (10:20 - 11:10) and batch 4 (11:40 - 12:20) Western Indonesia Time (GMT +7), with a capacity of 5 kg of paddy/batch and solar radiation is in the range of 408.5 - 547.2 Watt/m2. The highest irradiation takes place in batch 2 with the maximum temperature inside the dryer reaching 74◦C. Findings: Overall the experiments achieved that paddy temperature are in the range of 43 – 45◦C, with the shortest drying time achieved in batches 2 and batch 4 i.e. 40 minutes. Thermal efficiency are in the range of 37.91% - 50.35%, SEC of 5.318 - 7.042 MJ/kg H2O evaporated and drying rate of 1.06 - 1.38 kg/hrs. Thus, this solar dryer is more effective than industrial inclined bed dryer or theindustrial horizontal rotary dryer. Novelty: The solar dryer using a parabolic cylinder type solar collector with a screw conveyor has been designed which can reduce drying time and moisture content better. Keywords: Solar dryer; parabolic collector; paddy; efficiency

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.

Cyclic drying has been reported as an innovative drying technique for the drying of food materials in terms of drying time, energy cost and product quality. In this study, drying characteristics and product quality of continuous and cyclic drying of Mytilus galloprovincialis in a convective solar dryer were investigated. A two-stage increasing–decreasing drying air temperature (sinusoidal pattern) of the solar dryer was used to obtain the desired cyclical variation of the drying temperature while keeping other drying air parameters constants. The advantages of employing cyclic heating on the drying kinetics, energy consumption are demonstrated. Analytical results illustrated an effective drying time of mussels by a reduction of 1.5% and optimum energy consumption does not exceed 23 kWh of drying process by applying cyclic drying technique compared to continuous drying of air temperature. Furthermore, According to the proximate composition of AOAC method and following Total viable count (TPC) of the dried mussels, it was observed that cyclic air temperature allows to yield higher retention of protein, glycogen, reduce significantly the effect of stresses compared to the constant conditions of drying, and it is possible the reduce the overall color change as well as an accepted texture. Several empirical and semi-empirical models were used to fitting drying curves of experimental data. It was found that the Page model seems to be most suitable to describe the drying curves of Mytilus galloprovincialis. The second law of Fick’s was used to determine the effective moisture diffusivity at different conditions of drying. As results, the values of effective diffusivity obtained by applying cyclic drying were in the margin with the drying at constant conditions that was reached 2.84 × 10−9 m2/s.

An innovative design of front loaded multi-rack tray (MRT) solar cabinet dryer is presented having optimally inclined reflective north wall (RNW) which utilizes reflected component of the solar radiation in addition to the beam radiation for efficient drying particularly in winter when conventional dryer does not perform well at higher latitudes (>30°N). A modified global solar radiation capture model coupled with RNW is presented to determine the effect of RNW on its performance. A thermal model is also developed for chamber air temperature (Tch) and crop surface temperature (Tc) with experimental validation and solved using Modified Euler’s method using FREEMAT software with experimental validation at Ludhiana climate (30.56°N) India. Use of RNW enhances the radiation capture by 37.58%, 31.57% and 23.24% at 30°, 40° and 50°N latitude respectively in winter. Daily average efficiency η(avg) with RNW was 5% and 4.35% higher under natural and forced convection modes respectively as compared to without using RNW. By using RNW, 4–7 °C and 2–5 °C higher Tch was observed as compared to when RNW was not used under natural and forced convection modes respectively. Total reduction in drying time for carrot drying was observed to be 20% and 15% under natural and forced convection modes respectively. Predicted and experimental values for Tch were successfully validated with root mean square error (RMSE) ranging between 2.6 and 4.9. Uncertainty was found to be 20.5 out of which 19.3 was internal and 1.2 external which indicates the accuracy of observed data to determine the performance of solar dryer.

Horticulture produce have very high-water content, sometimes more than 90% by volume. Several of them are oily and hard. These horticulture produce have very high count of free radicals and are medicinal in nature. Usually, these are grown in scattered places in rural areas on sidelines of regular agriculture, far from the market place. Their price slumps during seasons and increase exponentially after it, due to short lifetime and absence of good transportation network, cost-effective proper preservation technology as well as specialized transportation vehicles. In this paper, Small state of the art family size solar dryer of 5 kg per day is designed to dry these produces in a single day and validated in real time experiments. The dryer is capable of maintaining desired temperature range to extended period even after sunshine, with the help of High Heat Capacity Material and Phase Change Material. Humidity removal mechanism is also introduced to reduce drying time by at least two hours.

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

Triangular duct cross-section is introduced for solar air heater (SAH) of an indirect type of solar dryer (ITSD). Using computational study, the thermo-hydraulic performance of triangular duct SAH with inclined ribs for varying rib inclination (30°

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.

In the north-eastern geographical setting of India, lies Tripura, the second largest state of India in terms of natural rubber cultivation. Often, the unpredictable weather and lack of appropriate drying methodology deteriorates the quality of the dried natural rubber fetching less income to the unorganized small scale farmers. Installation of modular solar thermal dryers in this region can resolve this problem. In this study, a 6 kg/batch mixed-mode solar thermal dryer was developed and installed at Agartala for performance investigation. Moisture content of the natural rubber sheets dried in the solar thermal dryer was reduced from 40% to 4% vis-a-vis 11% in open sun drying condition in 3 days’ time on wet basis. Six drying models were studied and validated against the experimental data. The average energy and exergy efficiencies of the system for natural rubber sheet drying were 9.09% and 2.48% respectively. Quality of the solar dryer dried sheets were found to be superior to the open sun dried ones. Techno-economic analysis showed a payback period of 2.2 y. Innovative features of the developed solar thermal dryer include (a) recirculation of spent dehumidified air to minimize thermal energy loss (b) 90% UV cutoff in the drying chamber leading to better colour retention of the product (c) solar photovoltaic operated dehumidifier for use during night to prevent reabsorption of moisture. The higher throughput, better quality and ease of operation can make this mode of natural rubber sheet drying an attractive option among akin communities.

In this paper, the hybrid PVT double pass system with a mixed-mode solar dryer type under forced convection has been designed, fabricated and installed for drying crops. The dryer was tried by drying 300 grams of banana slices in the air temperature of dryer range from 43.2 to 60.2°C. The initial moisture rate of banana was about 78% and the most dropped in moisture content was from 78% to 33% after 8 hours of the drying process. The banana slices are distributed in two identical trays and it was noticed that the most and least decreasing in weight of banana samples was from 150 to 48 gram and from 150 to 55 gram in lower and upper tray respectively, when the mass flow rate as 0.031 and 0.017 kg/s, which means that the high reduction was 68% of weight banana at a high mass flow rate of airflow. The critical parameter such as temperature distribution of the PVT with dryer room, useful heat gain, and thermal efficiency are computed by using the MATLAB 2015b program built for this purpose. The optimum useful heat gain and thermal efficiency were reached 423.7 and 52.98% respectively when the solar radiation 1190 and the mass flow rate of 0.031 kg/s.

Zero hunger is one of the goals out of 17 sustainable development goal set by United Nations for 2030. As the population is growing at a rapid rate so the demand of food will also increase. Solar dryers are considered as the sustainable solutions for conserving the food for longer duration. The enviro-economic analysis becomes necessary to check the impact of developed dryer on environment and its economic viability. This review article focuses on the environmental and economic analysis of hybrid greenhouse solar dryers. The dryers although operates using the solar energy but still in case of hybrid dryers some other devices are also used which emits CO2 and other non-environmental friendly gases during their use or disposal. The impact of a solar dryer on the environment is very low but still, it is necessary to check the impact. The economy is another factor that is kept in mind while developing the dryers. It is observed that the cost of dryer and its impact on environment increases with the increase in floor area of dryer. The hybrid dryers are usually costly due to use of various additional devices but gives better performance than passive and active dryers. The payback time of hybrid dryers are almost same as active dryers that is about 1-2 years, thus hybrid dryers can be developed commercially to get more profit. The parameters which are considered during environmental and economic analysis are discussed in the paper. The paper presents a way to carry out the environmental and economic analysis of hybrid dryers.

In this study, mixed mode solar dryer of forced convection type, integrated with a CuO nanoparticle coated flat plate solar collector was developed and its effectiveness of drying maize under the meteorological conditions of Coimbatore, India was evaluated. The aforementioned setup entails a solar collector (flat plate type) with 3 drying trays and a centrifugal blower. The conventional solar absorber plate was made up of aluminium, which was coated with black paint. Another modified solar absorber plate was made up of aluminium with a coating of black paint with two different vol% of CuO nanoparticles (0.02% and 0.04%), for improving the heat transfer rate. Performance tests on the modified dryer were carried out at constant air flow rate (1.5 m3/min) and the results were compared with the conventional type. The efficiency of the collector got improved by 4% while using black paint with 0.04 vol% of CuO nanoparticle coated absorber. Also the drying time got reduced by 6%, when compared to conventional type dryer. Also the collector temperature recorded in the black paint with 0.04 vol% CuO nano-particle coated collector was higher compared to black paint coated and black paint with 0.02 vol% CuO nanoparticle coated collector.

The traditional vegetable drying (open-air/sun drying) method of harvesting of tomato, potato and onion in the Fogera District in Amhara regional state, Ethiopia, leads to loss of product, reduction in the quality of product and economic loss for the poor farmers. So, this experiment aimed to show the effectiveness of solar dryer technology by increasing the quality of the product in tomato, potato, and onion in Fogera district Northwest Ethiopia, 2018. A simple solar vegetable dryer is experimentally analyzed to alleviate the problem associated with vegetable processing in Woreta city. The first law of thermodynamics energy analysis was carried out to estimate the amount of useful energy gained from solar air dryer and energy utilization ratio of the drying chamber and the energy through drying box. The magnitude of the exergy inflow, outflow and exergy losses in the drying chamber during the drying process was determined by applying the second law of thermodynamics. The average solar drying efficiency was found to be 75.01% to 86.70% for tomato, 75.70% to 87.90% for potato and 58.7% to 85.5% for onion. Regrading the drying period, it took 33 h for tomato, 27 h for potato and 44 h for onion during the experimental test.

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.

Thermo-chemical degradations of five paraffin waxes were investigated, during 750 accelerated thermal cycles to determine their suitability as phase change material in solar dryer. Discharge time w...

In present communication, a solar dryer having semi-transparent photovoltaic thermal (SPVT) roof has been used to dry bitter gourd. Experimentation has been done and results were validated with linear regression method through mathematical modelling as well as for non-linear Artificial Neural Network (ANN) modelling has been used. The experimental data namely, ambient air temperature, moisture evaporated, bitter gourd surface temperatures, solar intensity on different surfaces of dryer, room temperature and relative humidity have been recorded for the climatic condition of Varanasi, UP, India. The numerical value of convective heat transfer coefficients for bitter gourd found to be between 0.69–14.45 W/m2 K. The results for mass transfer (moisture evaporated) during drying of bitter gourd from theoretical model (linear regression method and ANN) and experiments showed good agreement. Further, net electrical energy, thermal energy and overall thermal energy were found to be 0.62, 3.77 and 5.41 kWh/m2/day respectively. The payback period at 10% interest rate and 4% inflation rate with ₹ 50 ($0.77) and ₹ 100 ($1.54) saving rate per kg were found to be 1.47 and 0.72 years respectively.

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.

This study is aimed to find the quality and appropriate thin layer mathematical model suitable for drying kinetics of turmeric which has the least impact of weather conditions. A user-friendly indirect natural convection solar dryer (INCSD) working on compound parabolic concentrator (CPC) was developed and fabricated for this purpose. It is observed that there is a dominant impact of the environmental conditions on the efficiency of solar drying. Adverse weather conditions hinder the collection of solar radiation. It was observed that the moisture content reduces from 77 to 18% in the solar dryer in 24 h as compared to open sun-drying, which requires 40 h. Six thin layer mathematical models reported in the literature have been tried for INCSD and open sun-drying. Thin layer mathematical modeling at different temperatures is presented with quality analysis. Maximum curcumin percentage 3.73% in the turmeric is found at 55°C drying air temperature. Minimum ash content is found to be 6.5% at 60°C. Experimental results reveal that the page model fits best for INCSD as well as for open sun-drying (OSD).

The world as a whole more than 25-30 % food grains and 30-50 % vegetables, fruits etc. is damaged before they reach to the consumers. For disabling issues of vegetables, grains and natural product; different protecting strategies are utilized and renewable sources are best for this reason by which we are able spare vitality for conservation and keeping the item in their characteristic flavor, as conservation of commodities items are exceptionally imperative. The major concern with drying utilizing sun battery-powered appliance is that it's vitality seriously so in spite of the actual fact that drying time is shorter as compared to the conventional strategy of drying. In order to preserve and protect the fruits from bacterial growth, solar dryer is to be designed. System consists of solar air heater, drying chamber, blower and recirculation tube. In a solar drying system the solar energy are used for heating air and to dry any fruit substance which is loaded for drying purpose. Which is not only expedient but also it reduces wastage and makes transportation easy and it also helps in preservation of any fruit substance. This review paper is focused on preservation of dry fruits through different solar drying technology. Also attempt has been given to improve the efficiency of these dryers, various enhancement techniques and design modifications need to be applied to them such as desiccant materials, heat storage units, etc.

Drying of agriculture food products is the need and most of the cost effective application of solar energy. This review paper presents the various types of solar dryer namely direct solar dryer, indirect solar dryer and hybrid solar dryer, etc. and their applications are also represents. Result View Original This paper deals with a comprehensive review of the varied designs, constructions and operational principles of the big variety practically. Also the performance evaluation of solar dryers has also been reviewed. Solar Drying is not only a technology but it is process which gives us the product with better color, flavor and best nutrition value than traditional drying. This review paper focused here on different drying technologies with new innovations and new design of convection by considering specific local climate for development of perfectly marketable product to improve income. This paper is also focus on commercialization aspect of solar dryer for micro-enterprises, formers to improve the income in the rural areas.

Large-scale greenhouse solar dryers have been used for drying various products and this type of dryer is usually equipped with LPG burner as auxiliary heater, which creates more operating cost. To ...

Grain drying is a process to reduce grain moisture content to certain conditions, so the grain can last longer in storage. The grain dryer model used in this research was Indirect Type Solar Dryer (ITSD). In order to make this dryer can work at night, heating element that used electrical energy from solar panels was added. This energy is a renewable and environmentally friendly energy. This dryer was equipped with a temperature monitoring system and control of the photovoltaic heater. The results of temperature monitoring and voltage sensors to controlling photovoltaic heaters based on validation are categorized as work measurement tools, because they have an error of 0.5% – 2%. Whereas the relay works when the battery voltage is 11 - 10.9 V. This dryer can dry grain to reach a moisture content of 14.90% from initial moisture content of 48.46%. The drying process lasts for 11 hours, which is 7 hours using solar energy and 4 hours using photovoltaic heaters. The average temperature produced by dryer system during the drying process is 35.28 °C with a drying efficiency of 60.14%.

This research work presents the detailed explanation of the design, construction and performance evaluation of mixed-mode solar agricultural products dryer. The experimental set up used for testing the performance of the mixed-mode solar agricultural products dryer and determining the influence of various drying methods on the drying behaviour of agricultural products. Evaluation of the dryer was centered on the moisture content reduction, temperatures and relative humidities variations. 1680 g of freshly potato slides were used for evaluation. The test results gave that the temperatures inside the dryer cabinet and the solar collector were much higher than the ambient temperature during most hours of the daylight. The temperature inside the solar collector was up to 27 o C approximately higher than the ambient temperature. The temperature inside the drying cabinet was up to 22 o C approximately higher than the ambient temperature for about three hours immediately after 12.00 h (noon). The relative humidity in the solar collector and drying cabinet were lower than the ambient air relative humidity, with the ambient air recording the highest relative humidity at each reading followed by the drying cabinet and finally by the solar collector. Because of the decreased relative humidity inside the dryer, all the time, the temperature inside the dryer was high which is sufficient enough to dry the potato at an early time. Based on the results obtained during the test, temperature above 65 o C was recorded inside the drying cabinet. This high temperature in the drying cabinet causes 419 g of moisture to be removed on the first day, 257 g on the second day, 191 g on the third day, 136 g on the fourth day and finally 108 g on the fifth day. At the end of the five days of drying process, the mass of 1680 g of potato was reduced to 569 g. Total amount of moisture removed was 1111 g and total moisture loss was 66.1 %, which is the required amount of moisture to be removed for safe drying of freshly potato slides. The moisture content of the freshly potato slides was 24.9 % at the end of drying for the first day at about 5:00 pm, 20.4 % at the end of drying for the second day, 19 % at the end of drying for the third day, 16.7 % at the end of drying for the fourth day and finally 15.9% at the end of drying for the fifth day. It was observed that the drying rate increased from the end of one day to another, which shows the earlier and faster removal of moisture from the dried item.

Free water contained in porous structure of food plays a fundamental role in proliferation of microorganisms and bacteria that can damage the product materials. This work presents a thermo-kinetic study carried out in a natural and forced convection solar dryer; the objective was to establish the optimal conditions for drying and storing Herniaria hirsuta by testing the impact of different aerothermal conditions (air temperature, air velocity) on water loss of fresh Herniaria hirsuta. The kinetics of drying is studied for three temperatures (50, 60 and 70 °C) in two-air velocities (0.09 and 0.18 m/s). The optimal water activity which is related to conservation is 0.28. The LESPAM model was found to be the most appropriate for describing the sorption curves. The air drying temperature is a principal factor influencing the drying kinetics; the drying rate decreases in low air drying temperature, the air velocity had a small impact on the drying kinetics of Herniaria hirsuta. The Midilli-Kuck model was found to be the best fitted drying curves in thin layers for Herniaria hirsuta. The effective diffusivity of moisture water values changed from 2.5312 10−9 to 18.0511 10−9 m2·s−1, and increased simultaneously with the increase of temperature. The average activation energy of the diffusion process is obtained to be 2938.46 kJ/kg; it expresses the temperature effect on the diffusion coefficient. Dried Herniaria hirsuta under the maximum drying parameters showed highest retention of antioxidant activity, while the total phenolics and flavonoids were decreased by 10 and 46%, respectively.

This paper was aimed to evaluate the effect of fluid type on thermal performance of parabolic trough solar collector (PTSC). The simulation process was performed to predict thermal variations in receiver tube and storage tank by CFD. The experiments were conducted with 0.025 kg/s as air flow rate. Four fluid types including Nano-fluid (Al2O3, 4%), engine oil (10W40), glycerin and water and were considered for the performance analysis. Moreover, the drying process of the solar dryer was considered during the drying of apple slices with 5 mm thickness. The results showed that overall input thermal energy for dryer was about 17.36 MJ, 18.46 MJ, 17.76 MJ and 16.80 MJ for Nano-fluid, oil, glycerin and water, respectively. It also implied that using Nanofluid, oil and glycerin improved the overall efficiency of the dryer about 9.7%, 20.2% and 12.4%, related to water. The comparison of simulated and predicted results it is implied that CFD method can predict the performance of PTSC with different working fluids with good accuracy. Using different working fluids assisted with PCM did not have undesired effect on the quality of dried apples.

After treatment of municipal wastewater sludge in treatment plants is not removed for several decades. This has led to the accumulation of huge amounts of sludge on sludge sites, which is a threat to the environment. The purpose of this study is to accumulate statistical data on the process of drying sludge and to study the effect of the amount of product mixing on the specific productivity relative to the moisture removed from the material. The experiments were performed using a reduced model of a solar industrial dryer. The model was located with the orientation of the elongated horizontal axis in the east-west direction and was extended outside the building into the environment using a special system. Evacuation of steam coming from the material to be dried was performed by molecular diffusion through a window, which was located on the north wall of the model and closed by a louver. The experiments changed: season, weather conditions, layer thickness and initial moisture content of the material, the amount of mixing. Both ambient conditions were determined: temperature and relative humidity, "clarity-cloudiness", and conditions in the drying chamber: temperature and relative humidity in the chamber volume and in the material layer, material humidity, specific productivity of the dryer model, in relation to the moisture removed from the material during the day. It is determined that the most noticeable changes in the specific productivity of the laboratory dryer are caused by changes in ambient temperature, "clarity-cloudiness"; relative humidity of the outside air and the amount of mixing. The layer thickness and the initial humidity of the material do not significantly affect the specific productivity of the dryer. Key words : waste water, sludge sediment, solar dryer