Solar Greenhouse Dryer Research Articles

Internet of things based smart system in the modified greenhouse solar dryer for agricultural products

The objective of this study is to develop a smart monitoring and control system for a modified greenhouse dryer for agricultural products utilizing Internet of Things (IoT) technologies and wireless sensor networks. This system enables real-time monitoring of air temperature and humidity, activation of the exhaust fan, adjustment of the heater, and determination of the optimal heating time. The investigation focused on the implementation of a microcontroller in the modified greenhouse system. The system possesses the capability to issue commands for the initiation of the heater and exhaust fan while also facilitating real-time monitoring. The system is equipped with an emergency command that can temporarily halt activities. The system utilizes two different temperature ranges, namely 45°C–50°C and 35°C–65°C, to analyse variations in heater usage across different temperature levels. Both software tools (Telegram and Google Excel spreadsheet) possess the functionality to monitor and regulate the temperature within a greenhouse by utilizing the chat network Telegram. Furthermore, the users possess the capability to store and access data related to the greenhouse system within an Excel spreadsheet.

Studies on semi-cylindrical solar tunnel dryer for drying wastewater sludge

Drying plays an important process for wastewater sludge management, as it can minimise the volume of wastewater sludge before disposal, and consequently the cost of storage, handling and transport. In this study, the wastewater sludge was dried by using a solar tunnel greenhouse drying system. The performance of the dryer for drying wastewater sludge has been analyzed through no load and full load test. The three full load drying tests recorded that the temperature inside the tunnel dryer fluctuated around 55±5°C; while the no load drying test, the temperature of the drying tunnel maintained within 60±5°C; as compared to the ambient temperature of 30±5°C. The average moisture content of solar dried sludge decreased from 88.69 - 90.84% to 7.78 – 13.30% in the mixing conditions and 14.78 – 19.52% in the non-mixing conditions, in 5 days. The study suggests that the semi-cylindrical solar tunnel dryer of wastewater sludge has given satisfactory results within five days.

Comprehensive analysis of the greenhouse solar tunnel dryer (GSTD) using Tomato, snake Gourd, and Cucumber: Insights into energy Efficiency, exergy Performance, economic Viability, and environmental impact

With the goal of sustainability, an innovative walk-in type Greenhouse Solar Tunnel Dryer (GSTD) with GI pipe and MS plate foundation, polycarbonate walls and roof, and cudappah stone flooring was developed and investigated. A comparison of GSTD and open sun drying was performed with tomato, snake gourd, and cucumber. The greenhouse drier drastically reduced the moisture content of the products, decreasing it from roughly 90 % to 2 % or less in 24 h. The developed GSTD was subjected to extensive energy, exergy, economic, and environmental assessments in order to examine its thermodynamic performance, economic viability, and environmental impact under forced convection by drying the three products chosen. The average efficiency of energy and exergy is 30.86 % and 14.76 %, respectively. The cost of utilizing GSTD to dry 1 kg of tomato, snack gourd, and cucumber was computed using the annualised cost technique to be 0.41, 0.1075 and 0.1232 USD, respectively. The lifetime savings range from 18,497 to 38,296 USD relying on the type of dried goods. The payback period for tomato is 1.34 years, snake gourd is 2.73 years and cucumber is 1.63 years. The lifetime carbon mitigation for tomato, snake gourd, and cucumber is 61.72 tonnes, 726.92 tonnes, and 175.74 tonnes, respectively, while the carbon credit earned is 1234.4 USD, 14538.4 USD, and 3514.8 USD.

Development and enhancement in drying performance of a novel portable greenhouse solar dryer

The increasing demand for drying technology for agriculture and food products has gained significant attention due to population explosion and inadequate resources available. The present study focuses on the concept of enhancing the drying performance of portable greenhouse solar dryer. The experimental investigations for evaluating the dryer performance were carried out while drying out onion slices. The experimentation was carried out in 4 different modes to demonstrate the effect of various modifications implemented to improve the dryer performance. The active greenhouse solar dryer (AGHSD) is the first working mode which comprises of the conventional drying system with active mode of removing moisture. The second working mode uses recirculating fans along with exhaust fans (AGHSD@circulating fans). In the third working mode an Evacuated Tube-type solar Air Heater was added to along with previous modification (AGHSD@circulating fans + ETAH). The last working mode adds an air flow distribution system to the incoming pre heated air from the Evacuated Tube-type solar Air Heater (AGHSD@circulating fans + ETAH + air flow system). Various performance characteristics like moisture ratio, heat utilization factor, coefficient of energy, heat gain and thermal efficiency of the dryer are used to analyze the changes in the drying performance. AGHSD@circulating fans + ETAH + air flow system reduced the moisture ratio in the onion slices to 5.32% from 95% in one day, compared to 19.99% for AGHSD and 46% for open sun drying. The heat utilization factor and coefficient of energy for AGHSD@circulating fans + ETAH + air flow system and AGHSD@circulating fans + ETAH improve by 10% and 15% respectively as compared to AGHSD. AGHSD@circulating fans + ETAH + air flow system shows improved heat gain of 29.53% and shows the best drying rate for the developed drying system. The thermal efficiency of AGHSD@circulating fans + ETAH + air flow system is around 60% while for AGHSD is around 41% which is higher than the thermal efficiency of 20% for sundried samples.

Thermal performance enhancement in an indirect solar greenhouse dryer using helical fin under variable solar irradiation

In this study, the effect of helical fins on the thermal performance of the greenhouse solar dryer with solar air heater under non-uniform thermal radiation has been analyzed. This article is written with the aim of investigating various parameters, including the type of helical fin (CASE A to CASE D), pitch of the helical fin (170 mm to 320 mm), mass flow rate (0.01, 0.013, 0.015 kg/s) and variable solar irradiation (10:00 AM to 14:20 PM). The 3D simulation was performed using the finite volume method (FVM) in ANSYS-Fluent software under k-ε RNG turbulent modeling. The results demonstrate that using four helical fins inside the tube increases the outlet temperature by 5.22 % at 10:00 AM. Compared to the simple model. Increasing the flow rate cause less opportunity for heat transfer rate from the solid surface to the airflow, so the outlet temperature decline by 19 % when the air flow rate rise to 0.015 kg/s. In the flow rate of 0.01 kg/s, by decreasing the pitch of the helical fin from 320 mm to 170 mm, the greenhouse outlet temperature rises by 3.01 %. Unexpectedly, changes in solar irradiation at different flow rates do not exhibit a linear correlation with thermal efficiency. Nevertheless, the highest achievable thermal efficiency of 61.30 % occurs at 13:00 with an airflow rate of 0.015 kg/s.

Kinetic analysis, mathematical modeling and quality evaluation of mint drying in greenhouse solar dryer

The goal of this study is to evaluate the potential of the Greenhouse Solar Dryer (GSD) for drying the mint leaves and compare it with other traditional drying methods. The top 10 mathematical models introduced by literatures were selected to describe the drying kinetics of mint leaves. The results showed that the average drying time in the GSD is 32 % and 50 % less than the open sun and shade place drying, respectively. Wang and Singh model with R2 = 0.9944, RMSE = 0.02021 and χ2 = 0.00052, logarithmic model with R2 = 0.9918, RMSE = 0.02556 and χ2 = 0.00078, and Henderson-Dabbie with model with R2 = 0.9774, RMSE = 0.04189 and χ2 = 0.00175 were determined as the best models for GSD, sun and shade place drying, respectively. The amount of changes in the color of the dried mint according to the index of total changes (ΔE) was recorded as 0.53 in the shade place, 0.60 in the GSD, and 0.89 in the open sun drying, respectively. The average of dried mint essential oil that was extracted by hydro-distillation method was 0.0254, 0.0237 and 0.0101 for shade place, GSD and open sun drying, respectively. Comparison of the average amount of extracted dried mint essential oil using ANOVA test, two LSD and Tukey HSD (Honestly Significant Difference) tests showed that there is no significant difference between the two treatments of drying in the shade place and GSD, while both of them have a significant difference with the open sun.

Optimum scheduling of shared greenhouse solar dryer in Thai community

Drying agricultural products is crucial in improving product quality and reducing post-harvest losses, ultimately increasing income for farmers. Greenhouse solar dryers (GSD) amplify these benefits by enhancing quality, preserving nutrients, and extending shelf life, thus elevating the economic worth of agricultural products. However, optimizing GSD utilization faces challenges from seasonal crop patterns, limited variety, and uncertain yields, curbing their full economic potential. Therefore, GSDs must be shared among farmers to address the underutilization of the infrastructure and increase the community’s overall profit. In addition, prioritizing higher value-added goods further maximizes gains from the shared infrastructure. Considering these factors, this research aims to demonstrate the financial benefits of sharing GSDs within a community. To determine the optimal sharing schedule, a mixed-integer linear programming (MILP) model is formulated that considers the monthly production of fresh and dried products, with their corresponding prices and value-added. We tested the model’s performance under three different sharing schemes using the data of a typical Thai agricultural community. It is clearly shown that by sharing the GSDs and importing products to fill empty days, the utilization rate of the GSD can be increased from 23% to 62% by following the optimal schedule. Besides, this approach can boost the overall profit of the community by 1.6 times compared to individual GSD utilization practices. The proposed concept provides a robust schedule for dependable and profitable sharing, even amid unpredictable conditions. However, realizing these benefits entails managing additional challenges, highlighting the need for intelligent unit support for successful community-sharing GSD implementation.

Annual Performance Evaluation of a Novel Industrial-scale Solar Dryer for Phosphogypsum Waste

Introduction: Solar drying is considered one of the most promising technologies for drying the phosphogypsum “Calcium Sulfate Dehydrate” material as a clean source of energy and saving the environment from its negative impact if it is dried in an open landfill. Method: The dried phosphogypsum (PG) may be recycled and utilized in many useful applications. The presented design of the trapezoidal-shaped greenhouse solar dryer is the preferable solution to perform the drying process in the daytime with solar energy. It may be usable at night, during cloudy and rainy periods, using evacuated tube solar collectors via sensible heat solar thermal energy storage. The system can be operated for 24 hours by solar energy. From theoretical calculations, it was found that the drying time decreased as the gypsum layer in the drying trays decreased due to the improvement of the heat transfer mechanism. The designed solar dryer was studied at various loading capacities depending on the gypsum thickness on the dryer trays. Capacities were 8280 kg, 6624 kg, 4968 kg, 3312 kg, and 1656 kg, corresponding to gypsum thickness of 5 cm, 4 cm, 3 cm, 2 cm, and 1 cm, respectively. The daily collected amount of water and the daily moisture content were estimated with different gypsum thicknesses during all months of the year. Result: It was found that the solar dryer with a capacity of 1,656 kg weight was technically and economically feasible. It was also found that the maximum reduction of moisture content occurred during the summer season, while the minimum values were achieved during winter. Conclusion: With a mass of gypsum equal to 1,656 kg weight, the moisture content of gypsum started to decrease from its initial value (35%) until it reached the final value (10%) in 4 scenarios: the first one, 2 days from April to September, 3 days from March to November, more than 3 days in other months while the minimum moisture content, i.e., 20%, was reported in the first day in June.

Experimental testing of mixed-mode double pass solar air heater integrated with aluminium cans for red pepper drying

A solar air heater that operates in the mixed-mode double pass and an absorber plate has aluminum cans at the top and bottom of the absorber for red pepper drying experiments was conducted in Bahir Dar, Ethiopia climatic conditions. A total dying period of red pepper in a mixed-mode solar greenhouse dryer takes less time than an open solar drying system. From the experiment, the average daily dryer chamber temperature ranges between 39.93 0C and 47.02 0C and the average daily ambient temperature ranges between 24.890C and 27.530C. Solar insolation reached 973 W/m2 when the sun was at mid-day and minimum solar insolation was 220 W/m2 and 0.0383 kg per second of air are expelled. A newly designed mixed-mode double pass, integrated with an Aluminum can dryer and the traditional open sun dryer, achieves an efficiency of 46% and 28%, respectively. In the open sun dryer system and the mixed-mode solar dryer, the drying rates are 0.0003395 kg/s and 0.0000365 kg/s respectively. On eleven mathematical models, Microsoft Excel was used to perform the statistical analysis. Logarithmic models were found to be the best explanation of red pepper behavior in both mixed-mode and open-sun solar dryer systems. These models were tested by comparing the maximum value of the coefficient of determination R2 and the minimum value of reduced chi-square X2 and root mean square error RMSE between experimental and predicted moisture ratios.

Performance of a solar greenhouse-biogas hybrid dryer for dehydration of water hyacinth (Eichhornia crassipes)

The development of a solar greenhouse dryer combined with an anaerobic digester for biogas production can reduce carbon emissions and create zero waste. This paper presents the performance of a solar greenhouse biogas dryer (SGBD) that burns biogas to supplement the drying of water hyacinth. The SGBD has an overall efficiency of 87% for 100 kg of fresh water hyacinth. The auxiliary heating system enabled the SGBD to achieve drying temperatures of 24.5 to 45.0 degrees during cloudy and rainy days and produce high quality dried products. There was a fivefold increase in drying capacity and a reduction in drying time of six hours (38%) using the SGBD. End users of the dried product judged it to have improved consistency in color and shape. The SGBD cost less than US$3800 to build with a payback period of five months. This design demonstrates a low-cost and simple technology for small businesses.

Heat and Mass Transfer, Quality, Performance Analysis, and Modeling of Thin Layer Drying Kinetics of Banana Slices

Abstract In this study, experimental works were carried out in three different drying methods named heat exchanger-evacuated tube-assisted drying system (HE-ETADS), greenhouse solar dryer (GHSD), and open sun drying (OSD) to compare thin-layer drying kinetics, concept of mass transfer, and quality assessment of banana slices. Initial moisture content (MC) of banana slices was obtained as 78 ± 2.0% (wb), which decreased to 23.2 ± 2.0% (wb), 25.6 ± 2.0% (wb), and 28.8 ± 2.0% (wb) in all three drying systems, respectively, in 9 h of drying time. Average drying rate was evaluated as 7.89, 7.65, and 7.25 g water/g solid h in HE-ETADS, GHSD, and OSD, respectively. Weibull model (WM) defines thin-layer drying kinetics of banana slices in all three drying processes. Maximum hardness and shrinkage factor of dried banana slices were obtained as 373.6 g and 75%, respectively, in HE-ETADS. Effective moisture diffusivity, activation energy, and mass transfer coefficient were computed as 1.11–2.48 × 10−07 m2 s−1, 30.25 kJ/mole, and 3.21–1.0 × 10−04 m/s, in HE-ETADS. Similarly, in GHSD and OSD, these factors were observed as 1.21–2.34 × 10−07 m2 s−1, 41.25 kJ/mole, 3.15–1.0 × 10−04 m/s and 1.3–2.21 × 10−07 m2 s−1, 56.89 kJ/mole, 3.01–1.0 × 10−04 m/s. Maximum total color changes were noted in OSD. Hence, HE-ETADS can potentially dry high moisture content crops effectively within a minimum drying period.

A New Mode of a Natural Convection Solar Greenhouse Dryer for Domestic Usage: Performance Assessment for Grape Drying

It is known that the natural convection (NC) solar drying process is a simple and cheap method for drying foodstuffs, but it is not preferable for common users in the case of drying high-moisture content agro-products due to the slow rate of drying. Meanwhile, the forced convection (FC) drying process is most appropriate for such products, but its economic feasibility may be affected due to high initial and maintenance costs. Therefore, the present study proposed a controlled natural convection (CNC) drying mode using a solar greenhouse dryer (SGD) for drying grapes with two types of cover materials, glass and Plexiglas, through intermittent operation with a PV system to save energy as a simple and inexpensive domestic dryer instead of the common forced convection SGD and the conventional natural convection SGD. The obtained results of the new CNC drying mode using a Plexiglas SGD showed a higher drying rate than the NC drying mode and are close to the FC drying mode using the same cover material. The initial moisture content of the grapes was reduced from 5.91 g water/g dry matter to the final moisture content of 0.15 g water/g dry matter within 12 h and 15 h for the CNC and NC drying modes, respectively, using the Plexiglas SGD. Moreover, the thermal drying efficiency for the two mentioned drying modes was 12.5 and 9.7%, respectively. The Page model was found to be the most appropriate model to predict the kinetics of the SGD in all drying modes, regardless of the cover type. The new CNC drying mode using the Plexiglas SGD achieved the lowest cost per kg of dried grapes (1.26 USD/kg), the highest total saved costs over the lifespan of the dryer (USD 245.46) and the shortest payback period (1.08 years) compared to the other two dryers, NC-SGD and FC-SGD. Generally, the CNC-SGD had good performance over the NC-SGD because it is not affected by the fluctuation in the volume, velocity and direction of the inlet ambient air/wind during drying grapes as a high-moisture content product without external heating sources or complicated parts. Thus, the proposed drying system has the advantage in terms of simplicity, cheapness and saving energy compared to FC-SGD.

Experimental evaluation and modeling the mass and temperature of dried mint in greenhouse solar dryer; Application of machine learning method

This study is aimed to model the temperature and mass of dried mint in a Quonset type of Greenhouse Solar Dryer (GSD). The inputs including ambient air temperature (◦C), ambient air humidity (%) and solar radiation (Wm-2) and output data including temperature (◦C) and mass (gr) of dried mint were collected from a Quonset GSD. Artificial Neural Network (ANN) models including Multilayer Perceptron (MLP) and Radial Bias Function (RBF) and also, Gaussian Process Regression (GPR) by k-fold cross validation method were used for modeling. Levenberg-Marquardt (LM) learning algorithm with Sigmoid-Tangent transfer function by different combinations of neurons in the hidden layer were assessed for ANN models. The results showed that MLP and GPR have higher error than RBF model for predicting the temperature and mass of dried mint. The results of RBF optimization indicated that 3-15-1 and 3-18-1 topologies with using 60 and 50% of total dataset for training steps and having 0.4 and 0.3 spread factor values can predict the temperature and mass of dried mint with Mean Absolute Percentage Error (MAPE) of 1.4 and 1.82%, respectively. The results of t, F, and Kolmogorov–Smirnov tests indicated that there is no significant difference between actual and RBF output values.

Performance Evaluation of Natural Convection Small Scale Greenhouse Solar Dryer for Drying Grapes

Performance Evaluation of Natural Convection Small Scale Greenhouse Solar Dryer for Drying Grapes

Impact of the greenhouse drying modes of two-phase olive pomace on the energy, exergy, economic and environmental (4E) performance indicators

This research aims to valorize olive pomace waste as bio-combustible. Therefore, the drying of two-phase olive pomace in a solar greenhouse dryer was studied under the weather conditions of Marrakech, Morocco. The experimental results of natural, hybrid, and forced hybrid drying modes of two-phase olive pomace were used to determine the energy and exergy efficiencies of the greenhouse dryer and to analyze the kinetics of drying. Moreover, the economic viability and environmental suitability of the three drying modes were also investigated. The results indicated that the humidity level of the product dropped from 54% to 4% (wt%) in 28, 19 and 14 h for the natural, hybrid, and hybrid forced drying modes, respectively. The effective moisture diffusivity varied significantly between the drying modes with a lowest average value of 1.28 × 10−09 m2/s and a highest average value of 2.71 × 10−09 m2/s associated to the natural and hybrid forced drying modes, respectively. The drying and exergy efficiency of the hybrid forced greenhouse dryer was improved by 31.61%, 51.95%, and 36.91%, 21.05% compared to the natural and hybrid greenhouse drying modes, respectively. The environmental analysis showed that the carbon emissions, and carbon mitigation depend strongly on the greenhouse drying mode, and the material used for the construction of the drying system. The hybrid forced greenhouse dryer ensured the mitigation of 1.29 and 1.15 times more CO2, compared to the natural, and hybrid greenhouse dryers. The economic analysis revealed a payback period of 1.27 years, 1.03 years, and 0.67 for the natural, hybrid, and hybrid forced modes for a selling price of 3 (MAD), which are very small compared to the lifespan of the greenhouse dryer (35 years).

Design, Development and Evaluation of Photovoltaic Integrated Solar Greenhouse Dryer for Paddy

The present study was conducted at College of Agricultural Engineering, Bapatla, Andhra Pradesh, India during the month of January, 2021 to develop photovoltaic power assisted forced circulation solar greenhouse dryer and to evaluate its performance for drying of paddy. A free standing greenhouse structure with arch roof was selected to have high light transmission and low cost of construction. To get adequate and uniform light inside the greenhouse east-west orientation was selected. A frame of solar greenhouse dryer having 4.467 m length, 2.134 m width and 2.591 m height was constructed and was covered with twin wall polycarbonate sheet of 6 mm thickness. Freshly harvested paddy was filled in perforated tray with size 142.5×80×12.5 cm up to 10 cm height the trays were placed in drying chamber consists of three tires and two columns. Forced ventilation was provided with four 40 W DC fans which were powered with two 150 W photovoltaic panels. During drying, the green house and ambient air temperature, relative humidity data was collected at every 1 h interval using data logger, the moisture content of the paddy was determined at every 2 h interval. The paddy was dried till getting 12% (w.b.) final moisture content. The highest greenhouse dryer temperature of 48.1°C was recorded as compared with highest ambient temperature of34.2°C. Moreover, the air flow rate achieved was varied between 75.52‒34.25 m3m-1.In this dryer the paddy was dried from 25.3‒12.0% (w.b.) moisture content in 21 h whereas open sun drying took 28 h of drying time.

Development of IoT based smart monitor and control system using MQTT protocol and Node-RED for parabolic greenhouse solar drying

Development of IoT based smart monitor and control system using MQTT protocol and Node-RED for parabolic greenhouse solar drying

Experimental investigations on drying kinetics and modeling of two-phase olive pomace dried in a hybrid solar greenhouse dryer

Experimental investigations on drying kinetics and modeling of two-phase olive pomace dried in a hybrid solar greenhouse dryer

A Novel Method Using Two-stage Anaerobic Digestion Integrated with Greenhouse Solar Dryer for Increased Biogas Production

Solar energy is infinite and environmental-friendly energy that is widely used in many fields such as solar cells, solar roofs, solar dryers and so on. However, solar energy has never been used in anaerobic digestion processes for biogas production. The use of solar energy may accelerate the biogas reaction to achieve higher gas production rates. Hence, the purpose of this research was to study a two-stage anaerobic digestion system in combination with a greenhouse solar dryer to increase the rate of biogas production. The study consisted of two parts: the first was to study the temperature variations in greenhouse solar dryers using computational fluid dynamic techniques, and the second was to conduct two-stage anaerobic digestion integrated with the greenhouse solar dryer system for biogas production. The results showed that the average temperature and biogas production rate in the integrated two-stage anaerobic digestion system compared to a conventional system increased by 16.2% and 19.69 %, respectively

Energy analysis of drying basil (Ocimum basilicum) leaves in an active greenhouse solar dryer

AbstractThe need for better utilization of solar greenhouses during summer in the hot climate conditions of Mexico led to the development of the concept of active greenhouse solar dryers. The objective of this research was energy analysis of an active greenhouse solar dryer for basil leaves drying. The effect of variable solar irradiation on drying was accounted for by monitoring instantaneous effective diffusivity. Our experiments showed that the effective diffusivity of basil leaves increased with solar irradiation 100 times from 0.08 × 10−10 m2/s in the morning to 8.11 × 10−10 m2/s at the solar noon. The air temperature in the solar dryer was ranging from 42 to 48°C at the solar noon with solar irradiance of 806 W/m2. The energy required for moisture evaporation of basil leaves depended on the air temperature, reaching 337.6 kJ/mol just before solar noon. The amount of energy available in the solar dryer at noon was 124.14 MJ, much exceeding the energy required for basil leaves drying (16.94 MJ). The results of our study showed the feasibility of basil solar drying. The predictive model of basil drying in an active greenhouse solar dryer was developed.Practical ApplicationsThe feasibility of adaptation of an active greenhouse solar dryer to variable solar irradiance to ensure energy‐saving drying is a contribution in the field DSG's. For this purpose, we propose to evaluate the energy transferred to the solar greenhouse, the instantaneous effective diffusivity of basil leaves accounting for air thermophysical properties Cp(Ta,x), k(Ta,x), as well as material thermophysical [Cp(Ti,x), k(Ti,x)] and mass transport properties Deff, (t) as time‐dependent values. These, leads to monitoring the drying process under uncertain weather conditions, which allows to minimize risks of product quality loss and introduce advanced energy‐saving control of active greenhouse dryers. Furthermore, the greenhouse driers can be uses as a cheap technology, with low energetic cost.