Solar Food Drying Research Articles

Optimized solar food dryer with varied air heater designs

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

An experimental case study of solar food dryer with thermal storage using phase change material

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

Design of a Friendly Solar Food Dryer for Domestic Over-Production

Solar drying is one of the many ways of efficiently making use of solar energy to meet the human demand for improved sustainability. In this study, we describe the construction and testing of two indirect solar dryer prototypes, especially designed for vegetables and fruits. The dryers had two compartments: a solar panel and a drying chamber. The dryers were mainly made of wood (Prototype 1) and styrofoam (Prototype 2) and both used recycled aluminum cans. The calculated yield of solar panels was 82% and 77% for Prototype 1 and 2, respectively. The drying tests performed with different fresh products showed that it was possible to dry all of them until less than 10% of their initial weight, at different times, depending on the type of product. As regards the apple slices, the solar dryers were able to remove 95.7% and 95.0% of initial moisture on a wet basis for Prototype 1 and 2, respectively. Comparative tests were conducted with an electric commercial dryer using the same product to explore the drying dynamics and costs. The cost of the final dry product, excluding the purchase of fresh goods, was 6.83 €/kg for the electric dryer, 1.78 €/kg for Prototype 1 and 1.72 €/kg for Prototype 2. Dehydrated apple slices are currently available on the market for around 34.50 €/kg. Our solar dryers can dry quality products at a very low cost for their entire life span, which allows them to compete with electric systems to prevent food waste in a cheaper and environmentally friendly way.

Solar drying Technologies: A review and future research directions with a focus on agroindustrial applications in medium and large scale

• Design, integration schemes, and economic analysis of Solar Dryer were discussed. • The most important works about industrial Solar Dryer were classified and tabulated. • The current state of the art and future development of Solar Dryers were presented. • Loads greater than 90 kg of fresh food or solar collection areas greater than 30 m 2 was analyzed. • Industrial drying literature was reviewed to identify opportunities for integrating solar thermal technologies. The food industry accounts for approximately 30% of global energy consumption. In addition, food-processing activities contribute almost 26% of total greenhouse gas emissions. Dehydration is an energy-intensive unit operation, and most foods require drying, at least partially, at some stage of processing. Solar food drying can help sustainable energy supply and contributes to the solution of environmental degradation problems. This review focuses on medium and large-capacity solar drying systems, some challenges for their implementation in the agro-industrial sector, and the analysis of the integration schemes of solar thermal systems to the most common drying processes in the agroindustry. A systematic information search was carried out by analyzing four reviews on industrial solar drying and more than 50 articles on medium to large scale solar food drying (i.e., fresh product load greater than 90 kg or solar collection area greater than 30 m 2 ); from 1991 to date. The solar technology with thermal convection systems is mature for industrial food drying on an industrial and semi-industrial scale. There is a niche opportunity to produce industrial size systems for small and medium producers, which can incorporate added value to their production.

Detailed analysis of mass transfer in solar food dryer with different methods

In this study, the mass transfer, effective diffusion coefficient (Deff), activation energy (Ea), and drying efficiency values of the product dried in the solar food drying system were experimentally investigated. It was determined that Deff values, Ea values, and drying efficiency values calculated with experimental data varied between 0.15 × 10−10 - 0.1 × 10−10 m2/s, between 21.6 and 15.9 kJ/mol, and between 51.8% and 15.9%, respectively. Mass transfer values in the drying system are modeled in detail with four different methods such as numerical analysis method (CFD), machine learning algorithms (ANN, SVM) and drying kinetics mathematical models (Newton, Page, Midilli and Küçük, Thompson). The root means square error (RMSE) error analysis method was used to determine the validation of the models. For mass transfer studies, the moisture content (MR) values of the 10 mm thick product were taken into account. The novelty of this study is that mass transfer, which is an important parameter for drying system design and product selection, is expressed by mathematical empirical equations, artificial intelligence methods, and numerical analysis methods. The mass transfer of the product is shown by numerical analysis simulation with moisture contours. The method that models the MR values with the least error (0.01 RMSE) is the SVM algorithm.

Experimental studies on natural convection open and closed solar drying using external reflector

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.

Bioactive compounds conservation and energy-mass analysis in the solar greenhouse drying of blackberry pulps

Recently, the quality of food solar dried has been associated to solar irradiance, irradiation and UV-light. Different materials used as covering materials in direct solar dryers had different optical properties, thus, different quality should be expected in solar food drying. The objective of this study was to compare two direct solar dryers builder with different covering materials: Direct Solar Drying with Poly (methyl methacrylate) (DSD), and Greenhouse Solar Drying with polyethylene (SGD), based on their three aspects: chemical composition, heat-mass transference, economic-environmental effect. Chemical composition was evaluated as the total phenolic compounds (TPC), flavonoids (TF) anthocyanins (TA) and antioxidant activity (AA) of blackberry pulp (Rubus spp). Dehydrated blackberry pulp contains lower TA than raw samples because TA is sensitive to solar irradiation and UV solar irradiation. TPC, TF and AA averages do not show significant differences among all the drying processes. Evaluation of energy and heat transfer in the evaporative and diffusive periods of the drying technologies led to an assessment of the return of investment period for DSD and SGD technologies for different power sources. The results suggest payback periods between 39 and 121 months, considering only the 6 months of harvest duration without using the solar dryers the rest of the year.

Application of wavy absorber plate in solar dryer for higher drying speed in solar food dryer

Conventional food drying by using ambient air is the oldest and widely applied method to preserve agriculture product. This method, however, shows several challenges, e.g. contamination problem, inhomogeneous drying process, difficulty in control of water content which may lead to product degradation. Contamination during this method could be due to many factors, e.g. dirty air, insect, wind which may carry out garbage and animals’ sewage and rain. An alternative solution to overcome these challenges is by developing solar dryer method. This method is widely applied particularly in the area with abundant supply of solar energy. In this research, solar dryer is equipped with wavy plate consisting of two ducting. Two ducting design is expected to result in higher drying temperature compared than one ducting. The research was worked out through experimental method. Data of solar radiation, temperature of ambient air and drying room collected in this research was then synchronized with speed of drying process. The prototype developed in this research showed that drying speed could achieve 8.51% per hour.

Recent advancements of PCM based indirect type solar drying systems: A state of art

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.

Numerical and experimental analysis of heat and mass transfer in the drying process of the solar drying system

Design in a solar food drying system is crucial for food drying performance. In order to make effective use of the sun, the use of air-heated solar collectors is gradually increasing in drying systems. Dryer room temperature and pressure distribution modelling is a very important factor for system design and product selection. In this study, the drying air speed, drying temperature, and product moisture content values of a solar drying system were numerically modelled in a time dependent manner. In numerical analysis, temperature and drying air velocity were defined as variable under initial and boundary conditions. Polynomial equations based on time obtained from drying room inlet temperature and drying air velocity data were used. The R2 values of these equations were calculated as 0.96 and 0.91, respectively. COMSOL multiphysics program was used for temperature values, drying air velocity, product moisture content values and drying chamber pressure values modelling. Depending on the position of the sun and the time, the drying chamber inlet temperature values and air velocity values have been change. During the drying process of the product, moisture content values, heat and mass transfer values, drying efficiency values, diffusion coefficient and activation energy values were examined. Experimental data and computed fluid dynamics analysis (CFD) data were compared. Using the CFD numerical analysis program, the drying room temperature, moisture content and air velocity values were modelled with mean absolute percent error (MAPE) of 5.34%, 3.74% and 6.30%, respectively.

Effect of Boosting Solar Radiation Intensity on Thermal and Hydraulic Performance and Characteristics of Forced Circulation Food Dryer Provided with Roughened Solar Air Heater

This paper focus on effects of boosting solar intensity on the thermal performance of solar food dryer coupled with roughened solar heater. Boosting of solar intensity increases the temperature of air entering into the food dryer without changing the specific humidity. The methods which have been used to increase the intensity of incidence radiation on the collector of food dryer are plane mirrors with tracking, parabolic reflectors and compound parabolic concentrator. It has been observed experimentally that boosting intensity improves performance characteristics of solar air heater and food dryer. It increases collector efficiency, dryer efficiency, loss of moisture content and diminishes the moisture content in the product at any time.

HYBRID SYSTEM SIMULATION TO SUPPLY HEATED AIR TO A SOLAR FOOD DRYER

The intermittence of solar radiation, due to continuous rainy or cloudy days, is a limitation of simple and small solar dryers. These conditions often make them impossible to use. By including storage systems (thermal accumulation) and/or auxiliary energy sources, drying processes or dehydration can be conducted continuously, even during periods of low insolation. Therefore, the present work simulates and evaluates the thermal and energetic behavior of a hybrid system for heating the air that is directed to the dehydration chamber of a solar food dryer. The software selected for the simulation was TRNSYS. The simulated hybrid system consists of a flat plate solar collector and an arrangement of electrical resistors that guarantee the entry of air, at a constant temperature, into the dehydration chamber. The target temperature selected is 70 oC, and the absence of food products in the chamber is assumed. An arrangement with four electric resistors totaling 1900 W, with three different powers of 1000 W, 500 W, and 200 W proved adequate to guarantee the entrance of air at a constant temperature when considering the climatic conditions of a city in the South of Brazil.

Energy and Performance Analysis of a new Solar Dryer

The discrepancies of using open-air sun drying method for drying agricultural produce and to preserve other variety of food items still exists. In the present time, to get rid of all the disadvantages associated with it, many comprehensive design structures of solar food dryer and their modification has been presented and investigated This research paper highlights the energy analysis performed on a latest design of a solar food dryer in which impinging jet mechanism and fins are clubbed together. The enhancement in heat transfer under preferred range of important parameters investigated namely mass flow rate (ṁ), Reynolds’s number, Flow-wise pitch ratio, Fin-spacing ratio etc. It has been observed that this new design of solar food dryer is more efficient and user friendly. The result has been plotted for Reynolds’s number (Re), mass flow rate (ṁ). The findings for this new design of solar food dryer reflect that temperature range of air coming out from outlet section is in the range of (45˚C-55˚C) which is undoubtedly good.

On the comparison between computational fluid dynamics (CFD) and lumped capacitance modeling for the simulation of transient heat transfer in solar dryers

In this paper transient heat transfer in a solar food drier is modeled by using both computational fluid dynamics (CFD) and lumped capacitance modeling techniques. The CFD model is used to simulate the air flow and transient heat transfer within the dryer. A lumped capacitance model, developed from energy exchanges between various components of the drying chamber, is extensively compared with the results of the CFD model. The two models predict both a 40 °C rise in steady-state temperature within the drying chamber. Before reaching this temperature, there is about 8 °C RMS deviation between the transient temperature prediction of the two models. This deviation is mainly caused by the heat transfer coefficient around the food rack shelfs. Fitting these coefficients give rise to a minimal RMS deviation between the two models of 1.8 °C and 0.9 °C on the lower and upper rack shelfs respectively. The transient heat transfer phenomenon from CFD modeling also showed that the spatial distribution of temperature after 30 min is uniform thus validating the very assumption of lumped capacitance modeling. This demonstrates that the lumped capacitance model can supplant the computationally demanding CFD modeling technique in predicting transient heat transfer phenomenon in solar food dryers.

Design, development and CFD modeling of indirect solar food dryer

Abstract In this study, a solar powered indirect food dryer is designed and developed. The dryer design consists of a solar collector unit, drying chamber with two columns of four rack shelves, chimney for the exhaust air, and a solar powered fan. The outlet of the dryer is designed in a truncated pyramid geometry so that precipitation of condensed water would be minimized and additional heating of the drying air is possible at the exit. The dryer is developed and manufactured in Mekelle, Ethiopia. Computational Fluid Dynamics, CFD is employed for predicting a transient three dimensional flow field and temperature distribution within the drying chamber using a symmetric flow domain. The predicted air flow distribution in the vicinity of the rack shelves showed that the mean flow velocity is 0.14 m/sec for the lowest shelf and 0.12 m/sec for the other shelves due to cooling of the air. A significantly uniform airflow distribution is observed on the top three shelves compared to the bottom shelf. The inside of the drying chamber evolves towards a steady operating temperature of 315K. The temporal temperature distribution reveals that the food to be dried will evolve to this temperature in about 35 minutes. For validating the model, the temperature distribution on each rack shelf is measured along with the global solar irradiation. The maximum average temperature difference between the measurement and the CFD simulation is found to be 4.3 °C. Hence, the CFD model is able to produce a good qualitative and quantitative insight into the temperature distribution within the drying chamber, rack shelves, and symmetry plane.

Computational fluid dynamics simulation and energy analysis of domestic direct-type multi-shelf solar dryer

Solar food drying is a well-established food-conserving process in India. Various researchers had developed solar dryer models which were usually validated using experimental observations and numerical simulation processes that are time-consuming and money-consuming. Computational fluid dynamics (CFD) simulation software facilitates the simulation of the models and gives same results in a comparatively small frame of time. This research paper is focused on CFD simulation, validation of design, energy analysis and numerical computation for domestic direct-type solar dryer for which experimental observations were performed at Ludhiana in November 2006. The design and simulation of the domestic direct-type multi-shelf dryer at no load condition are performed using ANSYS Fluent 14.0 software. The temperature of the air inside the dryer is found to be 326 K, which validates the design and purpose of the domestic direct-type multi-shelf dryer. The embodied energy of the constituents used in the construction of dryer is obtained as 339.015 kWh, and the energy payback time and carbon credit are found to be 7.57 years and INR 2055, respectively. The convective heat transfer coefficient for the dryer varies from 2.4 to 2.8 W m−2 °C−1. Coefficient of determination is estimated to be 0.98 under no load condition which shows the fare agreement between predicted and experimental value.

Performance Evaluation of an Adjustable and Collapsible Natural Convection Solar Food Dryer

The performance evaluation of an adjustable and collapsible natural convection solar food dryer, capable of taking 14,688 pieces equivalent to 16.52kg of fresh groundnut with maximum moisture content of 35%, at maximum capacity of 3.39m 2 , and 3,672 pieces equivalent to 4.06kg of groundnut at minimum capacity of 0.8475m 2 , was carried out. The solar food dryer with air vents gap diameter of 10cm was tested at Sokoto Energy Research Centre from 29 th September 2012 to 1 st October 2012. It was used to dry 6kg of groundnut per day for three consecutive days. After drying for about 8 hours each day, it was found that the mass of the groundnut reduced to 4.5kg in the first day, 4.0kg in the second day and 3.5kg in the third day. At the end of the study, the collector's efficiency was 28.3% , dryer's efficiency was 23.0% and the system efficiency was 81.3%, while the drying rate of groundnut was 0.25kg/hr

Road to Kamaka: the struggles of poverty and desertification

Subject area Sustainable development (in under-developed rural communities). Study level/applicability Bachelor's degree. Case overview The case follows six young adults from Quebec, who are mandated with a three-month agro-environmental project in the fight against desertification and poverty, in Kamaka, a village in the Sahel region of Mali. The project's central element is the development of a community garden that would ensure the diversification of the community's nutritional diet, and the rehabilitation of the environment. The mandate also consists of various environmental awareness workshops pertaining to efficient energy consumption, composting, and solar food drying techniques. The project, in its fourth year of collaboration between the Quebec organization and their local Malian partner, does not seem to have been yielding the desired results. The team is faced with the challenges of understanding the opportunities and limitations of the project so that they can try to succeed where previous teams have failed; while overcoming the organizational and logistical shortfalls that they faced prior to the start of their work, as they simultaneously struggled to adapt to their totally new context. Expected learning outcomes How to prepare for, approach, and carry out local community development projects – environmental and/or social – in under-developed regions such as Mali. Mainly, how to create a shared vision with the concerned community; build an effective multi-stakeholder network; and ultimately co-create sustainable value (as per the proposed Senge model). Supplementary materials Teaching notes and short documentary online link.

Optimization of a Convective Air Flow Solar Food Dryer

A solar food dryer, previously developed for personal and small community use, was the object of this optimization study. Based on previous research of convective solar food dehydrators, several dryer parameters were identified for this study. Chimney height and dryer product load were two factors tested in a central composite experimental design. Dryer product load was found to produce a maximum efficiency of the dryer when fifteen product-filled trays were inserted in the dryer. Maximum efficiency was observed at the maximum chimney height tested. Post-optimization configuration compared with pre-optimization configuration resulted in a 40% increase in final dry product production per hour of dehydration time.

A comprehensive procedure for performance evaluation of solar food dryers : Augustus Leon, M. et al. Renewable and Sustainable Energy Reviews, 2002, 6, (4), 367–393

A comprehensive procedure for performance evaluation of solar food dryers : Augustus Leon, M. et al. Renewable and Sustainable Energy Reviews, 2002, 6, (4), 367–393