Contribution to the sustainability of agricultural production in greenhouses built on slope soils: a numerical study of the microclimatic behavior of a typical Colombian structure

This is the final version. Available from MDPI via the DOI in this record. The use of covered structures is an alternative increasingly used by farmers to increase crop yields per unit area compared to open field production. In Latin American countries such as Colombia, productive areas are located in with predominantly hillside soil conditions. In the last two decades, farmers have introduced cover structures adapted to these soil conditions, structures for which the behavior of factors that directly affect plant growth and development, such as microclimate, are still unknown. Therefore, in this research work, a CFD-3D model successfully validated with experimental data of temperature and air velocity was implemented. The numerical model was used to determine the behavior of air flow patterns and temperature distribution inside a Colombian passive greenhouse during daytime hours. The results showed that the slope of the terrain affects the behavior of the air flow patterns, generating thermal gradients inside the greenhouse with values between 1.26 and 16.93 ◦C for the hours evaluated. It was also found that the highest indoor temperature values at the same time were located in the highest region of the terrain. Based on the results of this study, future researches on how to optimize the microclimatic conditions of this type of sustainable productive system can be carried out

陝西省南部の伝統的集落におけるコールドアレイのメカニズムとその省エネルギー効果

This study found a solver suitable for simulating the wind environment of a village with a complex architectural layout. A new passive cooling and energy saving system for traditional Chinese buildings has been established. This system is based on cold lanes. Above all, the conclusions of this research can be summarized as following: Three research methods of this research are introduced. The steady-state simulation accuracy of the CFD software was verified, and the most suitable simulator for simulating the settlement wind environment with complex building distribution was selected. Introduced the ventilation characteristics of traditional settlements, the passive energy-saving mode of traditional houses, and the application of traditional energy-saving methods in modern buildings. A new passive cooling and energy saving mode based on cold lanes is proposed, and the total energy saving of this new system in one year and the time suitable for use are calculated.北九州市立大

Full Proceedings, 2018

Full conference proceedings for the 2018 International Building Physics Association Conference hosted at Syracuse University

THERMAL ENVIRONMENT MODELING AND OPTIMIZATION OF GREENHOUSE IN COLD REGIONS

Thermal simulation models for the time-dependent heating requirement of greenhouses are very important for the evaluation of various energy-saving technologies, and energy-efficient design of greenhouses based on local climates. A quasi-steady state thermal model “GREENHEAT” was developed using the programing language MATLAB for simulation heating requirement in conventional greenhouses. The model could predict the hourly heating requirement based on the input of hourly weather data, indoor environmental parameters, and physical and thermal properties of greenhouse building materials. The model was validated with measured data from a commercial greenhouse located in Saskatoon, Canada, and the monthly average error in prediction was found to be less than 5.0%. This study also reviewed various energy-saving technologies used in greenhouses in cold climate, and the GREENHEAT model allowed selections of commonly used ones in the simulation. The GREENHEAT model was used for evaluating the impact of various geometrical parameters on the heating requirement of the single span and multiple-span conventional greenhouses located in Saskatoon. Results showed that the east-west oriented gable roof greenhouse could be more energy-efficient for the multi-span gutter connected greenhouse whereas quonset shape as a free-standing single span greenhouse. The large span width could be beneficial for the single-span greenhouses, but the impact of increased span width could be negligible on the heating demand of multi-span greenhouses. The model was also used for an economic feasibility analysis of year-round vegetable production (tomato, cucumber, and pepper) in northern Saskatchewan, and tomato was found to be the most economical vegetable as compared to the cucumber and pepper. Another heating simulation model CSGHEAT was developed to estimate of the supplemental heating requirement of mono-slope Chinese-style solar greenhouses (CSGs). This model is also a quasi-steady state thermal model using the programming language MATLAB, and it can simulates the hourly heating requirement of CSGs. The model was validated with experimental data from a CSG located in Winnipeg, Manitoba. The average error for prediction of the hourly heating requirement was found to be less than 8.7%. The model sensitivities to various geometrical and thermal parameters were studied. The results indicated that the thermal properties of cover, thermal blanket, and parameter insulation were the most important design parameters in CSGs. Finally, the heating requirement in CSGs was modeled using TRNSYS simulation tool, and the predictions were compared with that of CSGHEAT. The result indicated that TRNSYS had serious limitations for modeling of greenhouse thermal environment, thereby high uncertainties could occur, thus was not suitable for greenhouse simulation

Thermal Comfort Analysis Inside of a Recreational Vehicle

The focus of the current study is on the numerical investigation of airflow and temperature distribution in a representative Class B Recreational Vehicle (RV) with the objective of optimizing the inlet and exhaust vent configurations to enhance thermal comfort levels. The Computational Fluid Dynamics (CFD) simulations are carried out using ANSYS FLUENT. The CFD model of a representative RV is described in detail. First, a reference case that is based on the existing RV model is presented. For further optimizations with respect to this reference case, a parametric study is performed. This parametric study focuses on evaluating the impact of inlet and outlet vent locations, supply airflow direction, and varying the number of exhaust vents on temperature and airflow distributions. Seven test cases are simulated in total. The simulation results are evaluated based on their temperatures, velocity magnitudes, PMV (Predicted Mean Vote), and PPD (Predicted Percentage of Dissatisfied) values

Energy Efficiency and Indoor Environment Quality

This Special Issue addresses a topic of great relevance. In developed countries, there is a higher prevalence of people choosing to spend time indoors. Data show that the time a person spends at home ranges from 60% to 90% of the day, and 30% of that time is spent sleeping, though this varies depending on the individual. Taking into account these data, indoor residential environments have a direct influence on human health. Furthermore, in developing countries, significant levels of indoor pollution make housing unsafe, impacting the health of its inhabitants. Housing is therefore a key health factor for people all over the world: various parameters such as air quality, ventilation, hygrothermal comfort, lighting, physical environment, and building efficiency can contribute to healthy architecture; poor application of these parameters can result in conditions that negatively impact health

The impact of air well geometry in a Malaysian single storey terraced house

In Malaysia, terraced housing hardly provides thermal comfort to the occupants. More often than not, mechanical cooling, which is an energy consuming component, contributes to outdoor heat dissipation that leads to an urban heat island effect. Alternatively, encouraging natural ventilation can eliminate heat from the indoor environment. Unfortunately, with static outdoor air conditioning and lack of windows in terraced houses, the conventional ventilation technique does not work well, even for houses with an air well. Hence, this research investigated ways to maximize natural ventilation in terraced housing by exploring the air well configurations. By adopting an existing single storey terraced house with an air well, located in Kuching, Sarawak, the existing indoor environmental conditions and thermal performance were investigated and monitored using scientific equipment, namely HOBO U12 air temperature and air humidity, the HOBO U12 anemometer and the Delta Ohm HD32.3Wet Bulb Globe Temperature meter. For this parametric study, the DesignBuilder software was utilized. The field study illustrated that there is a need to improve indoor thermal comfort. Thus, the study further proposes improvement strategies to the existing case study house. The proposition was to turn the existing air well into a solar chimney taking into account advantages of constant and available solar radiation for stack ventilation. The results suggest that the enhanced air well was able to improve the indoor room air velocity and reduce air temperature. The enhanced air well with 3.5 m height, 1.0 m air gap width, 2.0 m length was able to induce higher air velocity. During the highest air temperature hour, the indoor air velocity in existing test room increased from 0.02 m/s in the existing condition to 0.29 m/s in the hottest day with 2.06 °C air temperature reduction. The findings revealed that the proposed air well could enhance the thermal and ventilation performance under the Malaysia tropical climate

Energy Systems and Applications in Agriculture

Agriculture, as a production-oriented sector, entails energy as a substantial input by which global food security is ensured. Agricultural systems require energy for farm machinery and equipment; lighting; heating, ventilation, and air-conditioning (HVAC); food processing and preservation; fertilizer and chemical production; and water/wastewater treatment/application. Increasing agriculture mechanization mitigates conventional energy reserves that escalate greenhouse gas emissions and climate change.This book aims to offer energy-efficient and/or environment-friendly ways for the agriculture sector to achieve the 2030 UN Sustainable Development Goals. The book provides cutting-edge research on next-generation agricultural technologies and applications to develop a sustainable solution for modern greenhouses, temperature/humidity control in agriculture, farm storage and drying, crop water requirements, agricultural built environment, and wastewater treatment