Climate Control System Research Articles

Composite Thermal Model for Design of Climate Control System

Composite Thermal Model for Design of Climate Control System

A Review of Greenhouse Climate Control and Automation Systems in Tropical Regions

Design and development of automation system for a tropical greenhouse involves different phases, including studying of environmental factors and crop responses, control algorithm, instrumentation and software/hardware interface. In contrast to cold arid climates, a tropical greenhouse is not to provide a warm and humid environment for crop, but to create an ideal condition in which plants can be protected against heavy rainfalls, direct sun radiation, disease, insects and birds. High relative humidity and ambient temperature climate in a tropical greenhouse creates a complicated dynamic system that is influenced by changes of external conditions, making it a challenging environmental control task. This paper reviews and addresses issues involved in the design procedure of automation control system in tropical greenhouses.

Energy transfer through single- and double-pane windows subject to wintertime environmental radiation

This work applies a new model that treats solar and longwave radiative transfer, thermal conduction, and sensible heat transport to quantify the flow of energy across single- and double-pane windows. A set of radiometers based in Chicago, Illinois, observed solar and longwave irradiances incident on and emerging from a window on a low-rise building. The incoming radiation fields, averaged over a 10-day period in January, drive the energy budget calculations, while a comparison of measured and computed outgoing irradiances validates the results. The indoor–outdoor temperature contrast creates a gradient in longwave radiative heating across the glass. This drives a heat flux that increases sensible heat flow to the exterior atmosphere by approximately a factor of 3 over what would exist without thermal radiation. Absorption of sunlight by the glass also increases energy lost to the atmosphere. For the conditions analyzed, approximately 40% of the solar energy absorbed by the window-plus-interior system is returned to the exterior as sensible heat and longwave radiation. The remaining absorbed solar energy offsets the demand for heating from the climate-control system.

Feasibility study of a green energy powered thermoelectric chip based air conditioner for electric vehicles

Traditional compressed-refrigerant air conditioning systems consume substantial energy that may reduce the driving performance and cruising mileage of electric vehicles considerably. It is crucial to design a new climate control system, using a direct energy conversion principle, to further aid in the commercialization of modern electric vehicles. A solid state air conditioner model consisting on TECs (thermoelectric chips) as the load, DSSCs (dye sensitized solar cells) as the renewable energy source and high power LiBs (lithium-ion batteries) as an energy storage device are considered for a personal mobility vehicle. The power management between the main power net and the solid state air conditioner interface is designed with an outer proportional-integral controller and an inner passivity based current controller with a loss included model for perfect tracking. This model is intended to comprise thermal and electrical elements which can be tunable for performance benchmarking and optimization of a solid state air conditioning system. Dynamic performance simulations of the solid-state air conditioner are performed, alongside guidelines for feasibility.

Development and Evaluation of A Comprehensive Greenhouse Climate Control System Using Artificial Neural Network

Development of controlled environment in greenhouse is of prim importance for out of season production, increasing yield and enhancing the quality of produce. Due to high cost and impossibility of continuous human attendance in greenhouse, it is desirable to control the greenhouse environment by employing automatic control devices. In This study, the greenhouse conditions were controlled by using artificial neural network (ANN). First, an experimental greenhouse was built and equipped with control instruments. Then by using electronic sensors, some climatic parameter data (temperature, humidity, carbon dioxide and light index) were measured and saved during five minute periods. In the next stage, three types of ANN including feed forward neural networks with multiple delays in the input, two-layer neural network with a feedback from hidden layer and input delay and three-layer neural network with two feedbacks from hidden layers and input delay were trained by 66% of the recorded data, and were evaluated by using the remaining data. The three-layer neural network with two feedbacks from hidden layers and input delay was able to better predict humidity and light index of the greenhouse with MSE,s of 0.025 and 0.032, respectively. Temperature and infrared index were better predicted by using the feed forward neural networks with multiple delays in the input with MSE,s of 0.016 and 0.017, respectively. In all cases, training time was less than 14 minutes and simulation time being always less than 0.2 second, makes using neural network feasible for automatic control of greenhouse.

Application Plan for an Intelligent Façade and Interactive Design of Environment-Friendly Buildings

This study presents the application method of the intelligent facade and interactive design of environment-friendly buildings. The planning elements of the environment-friendly and intelligent skin design include (1) energy power generation system, (2) solar ray control system, (3) indoor climate control system, and environment-friendly buildings. An introduction for technologies relevant to these planning elements is yet to be explored in this early stage of the study. An introduction is presented for the new skin design method in response to the critical aspect and present era of facilitating high-tech equipment.

Plug-and-Play Control—Modifying Control Systems Online

Often, when new sensor or actuator hardware becomes available for use in a control system, it is desirable to retain the existing control system and apply the new control capabilities in a gradual fashion rather than decommissioning the entire existing system and replacing it with an altogether new control system. However, this requires that the existing controller remains in action, and the new control law component is added to the existing system. This paper formally introduces the concept of Plug-and-Play control and proposes two different methods of introducing new control components in a smooth manner, providing stability guarantees during the transition phase as well as retaining the original control structure. The applicability of the methods is illustrated on two different practical example systems, a livestock stable climate control system and a laboratory-scale model of a district heating system.

Review. Advantages and disadvantages of control theories applied in greenhouse climate control systems

Today agriculture is changing in response to the requirements of modern society, where ensuring food supply through practices such as water conservation, reduction of agrochemicals and the required planted surface, which guarantees high quality crops are in demand. Greenhouses have proven to be a reliable solution to achieve these goals; however, a greenhouse as a means for protected agriculture has the potential to lead to serious problems. The most of these are related to the inside greenhouse climate conditions where controlling the temperature and relative humidity (RH) are the main objectives of engineering. Achieving appropriate climate conditions to ensure high yield and quality crops reducing energy consumption have been the objective of investigations for some time. Different schemes in control theories have been applied in this field to solve the aforementioned problems. Therefore, the objective of this paper is to present a review of different control techniques applied in protected agriculture to manage greenhouse climate conditions, presenting advantages and disadvantages of developed control platforms in order to suggest a design methodology according to results obtained from different investigations.

Automated leaf temperature monitoring of glasshouse tomato plants by using a leaf energy balance model

In order to detect biotic and abiotic stress at leaf level thermal indices based on leaf temperature measurements have been commonly used. The application of these indices within glasshouse crops is, however, restricted due to the specific humid conditions and the large spatial variability of irradiance and air temperature inside a glasshouse. In this study, a novel diagnostic algorithm is proposed as an alternative method to automatically monitor the leaf temperature of a glasshouse tomato crop based on the ecophysiological interactions between a leaf and its surrounding microclimate. Given that this algorithm is intended to be implemented as a software tool in glasshouse climate control systems, a critical overview of all relevant equations found in literature was first given. Next, the most appropriate equations were selected by using two objective criteria, i.e. the commonly used R2 and the less conventional Young Information Criterion, which also takes into account the complexity of an algorithm, so that the most feasible algorithm for automated monitoring purposes was built. Our results also showed that an in situ calibration of the selected algorithm was needed, for which a novel procedure was proposed. Once calibrated, this algorithm successfully simulated the leaf temperature of a well-watered tomato plant during several days given that the environmental conditions in its microclimate were accurately measured. Finally, the 95% confidence limits on the leaf temperature simulations provided the requested dynamic thresholds necessary for an effective automated monitoring tool. It was demonstrated that by using this novel diagnostic algorithm unexpected and likely harmful stomatal closure can be detected before visual signs of turgidity loss are observed.

GREENHOUSE DESIGN: CONCEPTS AND TRENDS

Greenhouses provide fresh vegetables and ornamentals year-round, worldwide; the type and equipment used in any region generally suit the local weather, construction materials availability, and type of crop. In each region, elements such as structure, cover materials, climate-control systems, and irrigation and fertilization equipment are routinely evaluated by growers, designers and researchers, to improve their efficiency, reduce inputs, and minimize undesired environmental effects. The term includes too many aspects to be covered in one paper, therefore, this paper mainly addresses developments related to possible effects of manipulations of structure and cover materials on microclimate; it also emphasizes the main concepts and trends in greenhouse horticulture that emerged during the last decade. The major driving forces toward improving greenhouse design have sprung from the desire to achieve a sustainable greenhouse that is energy neutral, consumes only the essential amount of water, and has minimal negative environmental impact - all while maximizing net financial return. Consequently, recent years have witnessed the development and expansion of tall and large structures, innovative cover materials, and closed and semiclosed greenhouses, and progress in solar greenhouses that harvest solar energy for heating. Most recently the incorporation of arrays of photovoltaic cells for power generation in protected cultivation became popular: a trend that still has to be carefully evaluated. In warm climates we have witnessed the expansion of screenhouses and innovative insect-proof screens that provide a reasonable environment for various crops, with much lower capital investment than fully equipped greenhouses. Progress was also made in development of tools for better and faster design of structures for protected cultivation. For example, CFD (computational fluid dynamics) simulations were extensively used to investigate the effects of structure shape, and ventilator size and arrangement (with or without insect-proof screens) on microclimate. These studies indicated that there is still scope for improving the currently prevailing designs of structures and their components.

Nonlinear adaptive PID control for greenhouse environment based on RBF network.

This paper presents a hybrid control strategy, combining Radial Basis Function (RBF) network with conventional proportional, integral, and derivative (PID) controllers, for the greenhouse climate control. A model of nonlinear conservation laws of enthalpy and matter between numerous system variables affecting the greenhouse climate is formulated. RBF network is used to tune and identify all PID gain parameters online and adaptively. The presented Neuro-PID control scheme is validated through simulations of set-point tracking and disturbance rejection. We compare the proposed adaptive online tuning method with the offline tuning scheme that employs Genetic Algorithm (GA) to search the optimal gain parameters. The results show that the proposed strategy has good adaptability, strong robustness and real-time performance while achieving satisfactory control performance for the complex and nonlinear greenhouse climate control system, and it may provide a valuable reference to formulate environmental control strategies for actual application in greenhouse production.

MECHANICAL INSULATION CASE STUDY— TIMELY OPPORTUNITY FOR RETROFITS AND NEW CONSTRUCTION

INTRODUCTION “You won't find any issues in our newly constructed and retrofitted buildings,” was the response that Lyndon Johnson, representative of the BC Insulators, got from the campus facility manager when explaining the poor state of practice of mechanical insulation, “let me show you one of our showcase buildings.” The building in question had just undergone $80 million in upgrades and was designed to achieve LEED® Silver equivalent rating. The upgrades included a high-performance climate control system that allows for precise control of temperature and humidity in different rooms. “We toured the building and found many problems with the mechanical insulation,” explained Mr. Johnson afterwards, “including substandard finish, adhesive tape lifting, and most disturbing, 20 feet of missing insulation on each floor of the building along the dividing line of the two phases of the project. One or both sets of contractors that worked on the job had completely left off the insulation. The saddest part is, t...

Experimental investigation of thermal comfort and air quality in an automobile cabin during the cooling period

The air quality and thermal comfort strongly influenced by the heat and mass transfer take place together in an automobile cabin. In this study, it is aimed to investigate and assess the effects of air intake settings (recirculation and fresh air) on the thermal comfort, air quality satisfaction and energy usage during the cooling period of an automobile cabin. For this purpose, measurements (temperature, air velocity, CO2) were performed at various locations inside the cabin. Furthermore, whole body and local responses of the human subjects were noted while skin temperatures were measured. A mathematical model was arranged in order to estimate CO2 concentration and energy usage inside the vehicle cabin and verified with experimental data. It is shown that CO2 level inside of the cabin can be greater than the threshold value recommended for the driving safety if two and more occupants exist in the car. It is also shown that an advanced climate control system may satisfy the requirements for the air quality and thermal comfort as well as to reduce the energy usage for the cooling of a vehicle cabin.

ENVIRONMENTAL IMPACT ASSESSMENT OF DUTCH TOMATO CROP PRODUCTION IN A VENLO GLASSHOUSE

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Greenhouse 2010 and Soilless Cultivation ENVIRONMENTAL IMPACT ASSESSMENT OF DUTCH TOMATO CROP PRODUCTION IN A VENLO GLASSHOUSE

Investigating the impacts of climate change on slopes: field measurements

Abstract Climate change has the potential to have significant effects on the stability and serviceability of earthworks slopes, impacting on the performance of transport infrastructures. This paper describes how a unique facility for engineering and biological research was established in NE England through the BIONICS Project (Biological and Engineering Impacts of Climate Change on Slopes). It describes the building and monitoring of a full-scale embankment representative of road/rail embankments in the UK. The paper presents the results of monitoring of pore water pressure carried out between 2007 and 2009. The pore water pressures within the upper 3 m of the embankment have been largely positive, in some case approaching hydrostatic conditions after wetter periods. This is largely due to the wet nature of the summers in both 2007 and 2008 since monitoring began, as well as the application of artificial inundation using a climate control system. Negative pore water pressures (suctions) of the order of −30 kPa were recorded at greater depths below 3 m. The experimental facility provides essential field measurements that can be used to calibrate numerical models of soil responses to climatic changes and gain a better understanding of the response of engineered UK fills to climate events.

Analysis of control system for industrial air-conditioner with desuperheater

The industrial air-conditioner is a complex device, which can not operate in manual mode. The existing approaches to automation assume the decomposition of conditioning technology at intermediate portions with their subsequent automation. In this case, the control system does not take into account the mutual influence of the equipment. The article analyzes the artificial climate system as technological complex with an integrated control system. This approach permits to take into account the effect of external perturbations and technological interaction of the equipment in the control system. Applying the methods of structural analysis of the theory of control we obtained the parametric scheme of the industrial air-conditioner with desuperheater. To improve the quality of control it is recommended to apply the program-parameter setting of temperature and humidity regulators of the air-conditioner, depending on the season. The suggested parametric scheme can be used by specialists occupied with the design of industrial computer-integrated technological complex of air conditioning. This will bring the control system of the air conditioner to a higher level and will ensure the efficient consumption of energy for the artificial climate control system

Finding Balance between Human Need and Global Stewardship

Finding Balance between Human Need and Global Stewardship

RBF Network Based Nonlinear Model Reference Adaptive PD Controller Design for Greenhouse Climate*

This paper presents a model reference adaptive PD control scheme based on RBF neural network for the greenhouse climate control problem. A model of nonlinear conservation laws of enthalpy and matter between numerous system variables affecting the greenhouse climate is used to validate the proposed control scheme. Compared with the conventional adaptive PD control scheme based on RBF neural network, the proposed scheme has better adaptability, stronger robustness and set-point tracking performance for the complex and nonlinear time-varying greenhouse climate control system, and it may provide a valuable reference to formulate environmental control strategies for actual application in greenhouse production.

Robust climate control of a greenhouse equipped with variable-speed fans and a variable-pressure fogging system

A climate control system for a small greenhouse equipped with a variable-pressure fogging system and variable-speed extracting fans was developed and validated. The controllers were designed using the robust control method quantitative feedback theory (QFT) that guarantees adequate performance of the controlled system despite large modelling uncertainties and disturbances. In order to simplify the design of the controllers and achieve better performances, partial decoupling between the two control loops was achieved by describing the greenhouse climate in terms of air enthalpy and humidity ratio. This led to using ventilation for achieving the desired air enthalpy, and fogging for achieving the desired humidity ratio, assuming that the ventilation rate was approximately known. The implementation results demonstrated the good performance of the controllers, with mean tracking errors of ∼100 J kg−1 [dry air] and ∼0.1 g [water] kg−1 [dry air] for enthalpy and humidity ratio, respectively. For practical applications, the desired climate was expressed in terms of air temperature and relative humidity, which were converted into enthalpy and humidity ratio using the psychrometric relationships. In this case, the mean tracking errors were ∼0.2 °C air temperature and less than 1% relative humidity, and the maximum mean deviations over a 10-min period with constant setpoints were 2.5 °C air temperature and 5% relative humidity.

The Environmental Performance of Air Conditioning Systems in Heritage Buildings in Tropical Climates

This paper examines the performance of retrofitting climate control systems focusing on air conditioning systems in refurbished old buildings in tropical climates. Data was gathered by means of investigation in the sequential steps of condition survey, space audit, ventilation systems, indoor/outdoor temperature reading and relative humidity (RH) measurement. The study raises several important issues relating to indoor environmental quality. Beyond the obvious aesthetical issues that are addressed here, the installation of air conditioning systems tends to create thermal instabilities and indoor environment imbalances in refurbished buildings. Furthermore, there is also a gap between the necessities of conserving the precious features of old buildings and the demand for better thermal comfort by the occupants. This study outlines the risks as well as making recommendations for future strategies.Keywords: Climate control, indoor environment, heritage buildings, Malaysia