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Applied Sciences
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Renewable Energy in Agriculture Ⅱ
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Renewable Energy in Agriculture Ⅱ

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy Science and Technology".

Deadline for manuscript submissions: closed (10 December 2021) | Viewed by 17763
Related Special Issue: Renewable Energy in Agriculture

Special Issue Editors

Prof. Dr. Joachim Müller

E-Mail Website
Guest Editor
Institute of Agricultural Engineering, University of Hohenheim, 70593 Stuttgart, Germany
Interests: solar energy; bioenergy application in agriculture; postharvest processing; irrigation technology; efficient water and energy use; renewable energy; expertise covers systematic design (VDI 2221); computer-aided engineering (CATIA); computational fluid dynamics (ANSYS); transient systems simulation (TRNSYS); machine vision; hyperspectral imaging
Special Issues, Collections and Topics in MDPI journals
Dr. Hans Oechsner

E-Mail Website
Guest Editor
State Institute of Agricultural Engineering and Bioenergy, University of Hohenheim, D-70599 Stuttgart, Germany
Interests: bioenergy; biogas process; trace elements for biogas; pretreatment of substrates; drying of digestate; efficiency of biogas processes; BMP test methods; energy crops; AD of organic waste; platform chemicals
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Against the background of the discussion on climate change, renewable energies have experienced an enormous increase in public interest. In this context, agriculture plays a doubly important role: both as a consumer and as a provider of renewable energy. Rural areas in many regions are only sparsely supplied with energy networks, and the agricultural sector can benefit from easy access to (micro)hydropower; wind energy; solar energy; and, of course, bioenergy. In addition to meeting its own energy needs, agriculture can act as an energy supplier by producing biomass, biodiesel, bioethanol, and biogas. Public and private research funding has led to a considerable increase in research and development activities in this field. This Special Issue is intended to bring together the latest findings of researchers in order to initiate new research based on the state-of-the-art. We invite you to submit your recent research addressing one of the following topics:

  • Production and processing of energy crops;
  • Provision of solid biofuel, biodiesel, bioethanol, and biogas;
  • Processing and use of biogas digestate;
  • Combustion and pyrolysis of biomass;
  • Engines and stoves for vegetable oil;
  • Solar heating in agriculture;
  • Solar drying of agricultural products;
  • Solar cooling of agricultural products;
  • Solar desalination of irrigation water;
  • Agrophotovoltaics;
  • Photovoltaic pumping of irrigation water;
  • Wind and water driven pumps in agriculture;
  • Renewable energy in greenhouse applications;
  • Modelling and simulation;
  • Life cycle assessment.

Prof. Dr. Joachim Müller
Dr. Hans Oechsner
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • energy crops
  • solid biofuels
  • biodiesel
  • bioethanol
  • biogas
  • solar heating
  • solar drying
  • solar cooling
  • solar desalination
  • agrophotovoltaics
  • photovoltaic pumping
  • microhydropower
  • wind energy
  • modelling
  • life cycle assessment

Published Papers (6 papers)

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Research

27 pages, 7215 KiB  
Article
Experimental Evaluation and Theoretical Optimization of an Indirect Solar Dryer with Forced Ventilation under Tropical Climate by an Inverse Artificial Neural Network
by M. Moheno-Barrueta, O. May Tzuc, G. Martínez-Pereyra, V. Cardoso-Fernández, L. Rojas-Blanco, E. Ramírez-Morales, G. Pérez-Hernández and A. Bassam
Appl. Sci. 2021, 11(16), 7616; https://doi.org/10.3390/app11167616 - 19 Aug 2021
Cited by 7 | Viewed by 2832
Abstract
In this theoretical–experimental study is presented a hybridization strategy based on the application of an inverse artificial neural network model (ANNi) coupled with metaheuristic optimization algorithms to optimize the drying velocity (vd) of an active indirect solar dryer for plantain [...] Read more.
In this theoretical–experimental study is presented a hybridization strategy based on the application of an inverse artificial neural network model (ANNi) coupled with metaheuristic optimization algorithms to optimize the drying velocity (vd) of an active indirect solar dryer for plantain and taro (Colocasia antiquorum). In the experimental stage, both fruits were evaluated in periods from 9:00 a.m. to 5:00 p.m. under a humid tropical climate region, varying the voltage of the air extractor fan (at 6 V, 9 V, and 12 V) to control the fan velocity. The experimental results showed that the maximum drying velocities were reached at 9 V, achieving a drying velocity of 1.5, 0.9, and 0.55 g/min, with a total drying time of 465 min for the taro, and 1.46, 1.46, and 0.36 g/min, with a total drying time of 495 min, for the plantain. As a result of the drying curves, it was observed that the drying velocity is higher in taro than in plantain. Subsequently, an artificial neural network (ANN) architecture was trained using the database generated from the solar dryer’s experimental stage. Six environmental variables and one operational variable were considered as the model’s inputs, feeding the ANN to estimate the drying velocity (vd), obtaining a linear regression coefficient R = 0.9822 between the experimental and simulated data. A sensitivity analysis was performed to determine the impact of all the input variables. A hybrid strategy based on ANNi was developed and evaluated with three metaheuristic optimization algorithms; the best result was obtained by genetic algorithms (ANNi-GA) with an error percentage of 0.83% and an average computational time of 4.3 s. The scope of this optimization strategy was to obtain a theoretical result that allows predicting the behavior of the dryer and improving its performance for its practical application in future work through the implementation in development boards. Lastly, the optimization strategy presented is not limited to indirect solar dryers and opens a research window for evaluating other solar drying technologies. Full article
(This article belongs to the Special Issue Renewable Energy in Agriculture Ⅱ)
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14 pages, 1726 KiB  
Article
Performance Evaluation of an Inflatable Solar Dryer for Maize and the Effect on Product Quality Compared with Direct Sun Drying
by Janvier Ntwali, Steffen Schock, Sebastian Romuli, Christine G. Kiria Chege, Noble Banadda, Gloria Aseru and Joachim Müller
Appl. Sci. 2021, 11(15), 7074; https://doi.org/10.3390/app11157074 - 30 Jul 2021
Cited by 6 | Viewed by 3290
Abstract
Maize is an important staple in Africa, which necessitates immediate drying to preserve the postharvest quality. The traditional drying of maize in the open sun is prone to adverse weather and extraneous contamination. In this study, the drying performance of an inflatable solar [...] Read more.
Maize is an important staple in Africa, which necessitates immediate drying to preserve the postharvest quality. The traditional drying of maize in the open sun is prone to adverse weather and extraneous contamination. In this study, the drying performance of an inflatable solar dryer (ISD) was compared to direct sun drying (DSD) in Gombe Town, Wakiso District (Uganda) by analysing the moisture content, yeasts, moulds, aflatoxin, and colour. The maximum temperature inside the ISD reached 63.7 °C and averaged 7 °C higher than the ambient temperature. Maize was dried using both methods to a moisture content below 14% after two days. In one of the received maize lots that was already heavily contaminated after harvest, drying with DSD and ISD reduced the aflatoxin content from 569.6 µg kg−1 to 345.5 µg kg−1 and 299.2 µg kg−1, respectively. Although the drying performance in terms of drying time and product quality regarding colour, yeast, and mould was similar for both drying methods, the advantage of ISD in reducing the risk of spoilage due to sudden rain is obvious. A strategy for the early detection of aflatoxins in maize is recommended to avoid contaminated maize in the food chain. Full article
(This article belongs to the Special Issue Renewable Energy in Agriculture Ⅱ)
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16 pages, 18945 KiB  
Article
Small Heat Source Used for Combustion of Wheat-Straw Pellets
by Marian Pafcuga, Michal Holubcik, Peter Durcansky, Andrej Kapjor and Milan Malcho
Appl. Sci. 2021, 11(11), 5239; https://doi.org/10.3390/app11115239 - 04 Jun 2021
Cited by 8 | Viewed by 1829
Abstract
Wheat straw, as a secondary waste agricultural product, presents a potential renewable source of energy. It is necessary to design simple heat sources to achieve better usage. As part of an analysis of heat sources, a tubular type of heat exchanger was reviewed. [...] Read more.
Wheat straw, as a secondary waste agricultural product, presents a potential renewable source of energy. It is necessary to design simple heat sources to achieve better usage. As part of an analysis of heat sources, a tubular type of heat exchanger was reviewed. The design of the exchanger was focused on the smallest possible dimensional requirements, low costs, high reliability and easy maintenance. We chose a tubular type of heat exchanger. In our case, flue gas flows through the tubes, and water flows outside of the tubes. This type of exchanger allows for continuous cleaning, but also simple maintenance, even in case of equipment failure. It is possible to replace individual parts (pipes) of equipment that are exposed to the adverse corrosive effects of biomass flue gases. A mathematical model was composed to compute the construction of a heat source. The model was verified by CFD simulation. The main idea of this design is modularity. The composed model can be used to design a series of similar heat sources with different levels of power, and which, as it is of maximal availability for this type of construction, increase use of waste straw as fuel by small farms. Full article
(This article belongs to the Special Issue Renewable Energy in Agriculture Ⅱ)
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22 pages, 6797 KiB  
Article
CFD-Simulink Modeling of the Inflatable Solar Dryer for Drying Paddy Rice
by Ana Salvatierra-Rojas, Iris Ramaj, Sebastian Romuli and Joachim Müller
Appl. Sci. 2021, 11(7), 3118; https://doi.org/10.3390/app11073118 - 01 Apr 2021
Cited by 5 | Viewed by 3494
Abstract
Small-scale farmers in developing Asian countries have minimal agricultural mechanisms available to them. In the Philippines, postharvest losses in rice production can reach about 36% in the drying process alone. Thus, the inflatable solar dryer (ISD) was developed through the collaboration of the [...] Read more.
Small-scale farmers in developing Asian countries have minimal agricultural mechanisms available to them. In the Philippines, postharvest losses in rice production can reach about 36% in the drying process alone. Thus, the inflatable solar dryer (ISD) was developed through the collaboration of the University of Hohenheim, the International Rice Research Institute, and GrainPro Philippines Inc. Although the ISD was successfully tested with different agricultural products, further characterization of the ISD design is required for predicting the drying performance. To this end, the airflow behavior in the ISD was simulated using computational fluid dynamics (CFD) via ANSYS Fluent. Moreover, a thermal model was developed in MATLAB/Simulink by taking into account heat transfer in the heating area and coupled heat and mass transfer within the drying area. Three batches of drying experiments were performed and airflow measurements were taken inside the dryer to validate the models. The MATLAB/Simulink model was further used to predict the drying performance under various weather conditions spanning 10 years. The simulated temperatures and moisture content in the ISD showed high accuracy (mean absolute percentage error (MAPE) < 10%) with the experimental data. The proposed dynamic model provides an efficient computational tool that can be applied to predict the drying performance and to optimize the ISD design. Full article
(This article belongs to the Special Issue Renewable Energy in Agriculture Ⅱ)
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20 pages, 5140 KiB  
Article
Influence of Roof Installation of PV Modules on the Microclimate Conditions of Cattle Breeding Objects
by Matúš Bilčík, Monika Božiková and Ján Čimo
Appl. Sci. 2021, 11(5), 2140; https://doi.org/10.3390/app11052140 - 28 Feb 2021
Cited by 9 | Viewed by 2046
Abstract
This paper is focused on the temperature measurements which can detected the influence of temperature changes on the microclimate in animal production building after the installation of photovoltaic (PV) modules. The first series of experiments were performed on a specially designed model cowshed. [...] Read more.
This paper is focused on the temperature measurements which can detected the influence of temperature changes on the microclimate in animal production building after the installation of photovoltaic (PV) modules. The first series of experiments were performed on a specially designed model cowshed. For the data comparison and verification, the same measurements were realized in real conditions of the animal production object. The temperature balance was identified by measurements of the temperatures in the different parts of roof, PV modules, and the most important were measurements of the ambient temperature and temperatures in three levels of the cowshed interior. For the confirmation of results, measurements were done in two cowsheds, which had the same azimuth orientation and roof slope. The first cowshed was without installation of the PV modules on the roof and the second building had installed PV modules. By the data analyzed from experimentally obtained time-temperature dependencies, it was found that the installation of PV modules on the cowshed roof had a positive influence on the interior temperature balance. The installation of PV also had a positive effect on the cowshed microclimate, which was declared by calculation of the Temperature—Humidity—Index. Full article
(This article belongs to the Special Issue Renewable Energy in Agriculture Ⅱ)
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17 pages, 3085 KiB  
Article
Operating Performance of Full-Scale Agricultural Biogas Plants in Germany and China: Results of a Year-Round Monitoring Program
by Lijun Zhou, Benedikt Hülsemann, Zhiyang Cui, Wolfgang Merkle, Christian Sponagel, Yuguang Zhou, Jianbin Guo, Renjie Dong, Joachim Müller and Hans Oechsner
Appl. Sci. 2021, 11(3), 1271; https://doi.org/10.3390/app11031271 - 30 Jan 2021
Cited by 6 | Viewed by 3291
Abstract
Germany (DE) and China (CN) have different political approaches in supporting the biogas sector. Three German and three Chinese large-scale biogas plants (BGPs) were evaluated as part of a year-round monitoring program. Laboratory methods were utilized to analyze the chemical indicators. Results showed [...] Read more.
Germany (DE) and China (CN) have different political approaches in supporting the biogas sector. Three German and three Chinese large-scale biogas plants (BGPs) were evaluated as part of a year-round monitoring program. Laboratory methods were utilized to analyze the chemical indicators. Results showed a stable anaerobic digestion process without system failures in all BGPs. The methane yield had a range of 0.23–0.35 m3CH4/kgODM for DE BGPs and 0.11–0.22 m3CH4/kgODM for CN BGPs, due to different substrates and working temperatures. Financial analyses indicated that DE BGPs are viable under their current feed-in tariffs contracts. Their financial internal rate of return (IRR) ranged between 8 and 22%. However, all CN BGPs had negative IRRs, indicating that they are financially unfeasible. Risk analyses illustrated that DE BGPs will face financial nonviability if benefits decrease by 9–33% or costs increase by 10–49%, or if a combined worse case (benefit decrease and cost increase) of 5–20% occurs. Incentives to BGP operations are particularly important in China, where the government should consider switching the construction-based subsidy to a performance-based subsidy system to motivate the operators. BGP monitoring is necessary to understand the performance, in addition to briefing policymakers in case a policy reform is needed. Full article
(This article belongs to the Special Issue Renewable Energy in Agriculture Ⅱ)
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