Climate Control Strategies Research Articles

Emulation environment for automobile automatic climate control

This study presents the development of a simulation platform for evaluating climate control strategies for automobiles. Unified modeling language-based use-case diagrams and statechart diagrams are employed to model the functionalities and dynamic behaviors, respectively, of a typical automatic air-conditioning system. With these two modeling diagrams as blueprints of the simulation target, a general simulation platform is implemented on Matlab/Simulink. Given a tested climate control algorithm and environment conditions, simulation results in terms of temperature and relative humidity in the car compartment can be visually presented on an implemented graphic user interface of a psychrometric chart. With its flexibility to replace control algorithms and to change testing parameters, the implemented platform has been utilized to test the control results of an enthalpy-based control algorithm, robustness of the same control algorithm at different initial conditions, and comparison of two different control algorithms.

Improving Sustainability of Housing in Ghana through Energy Efficient Climate Control Strategies

This paper aims at explaining testing procedures used to evaluate the potential of natural ventilation and daylighting applications to passive design of housing in Ghana. The objectives of research were to reduce energy costs and increase the sustainability of housing. From the results of these experiments actual and potential designs are illustrated and discussed. Mass housing results in multi-storey buildings which require substantial artificial lighting and ventilation. Also, with the increasing usage of glass for windows and doors in Ghana, even the shaded depths of buildings require additional daylight usually resulting in more energy consumption. By supplementing the internal lighting levels with daylight, reducing the internal heat load by shading windows to direct radiation and the utilization of natural ventilation over air conditioning where possible, significant energy savings are could be achieved. The research proposes mass housing design changes such as: delivering daylight above the suspended ceiling into the depths of the building by horizontal light pipes and natural ventilation, utilizing stack effect and wind siphonage, etc.

Optimization of an envelope retrofit strategy for an existing office building

Energy-efficient retrofits include improvement of building envelope via insulation, employment of building integrated renewable energy technologies, and climate control strategies. Building envelope improvements with insulation is a common approach, yet decision-making plays an important role in determining the most appropriate envelope retrofit strategy. In this study, main objective is to evaluate and optimize envelope retrofit strategies through a calibrated simulation approach. Based on an energy performance audit and monitoring, an existing building is evaluated on performance levels and improvement potentials with basic energy conservation measures (ECMs). The existing building is monitored for a full year and monitoring data is used in calibrating the simulation model. In order to obtain a better-performing building envelope three retrofit strategies including several ECMs are proposed. Retrofit strategies are simulated through calibrated base-case model, and results are evaluated according to changes in indoor environmental parameters and annual energy consumption measures. The analysis of results indicated that pre-assessed strategies yield close results. Therefore, a more comprehensive evaluation based on different decisive criteria is used in optimization of the final retrofit strategy, with the intention to evaluate the effect of individual ECMs on annual end-use energy consumption and investment.

NEW GREENHOUSE CONCEPT WITH HIGH INSULATING DOUBLE GLASS AND NEW CLIMATE CONTROL STRATEGIES - MODELLING AND FIRST RESULTS FROM A CUCUMBER EXPERIMENT

ISHS International Symposium on Advanced Technologies and Management Towards Sustainable Greenhouse Ecosystems: Greensys2011 NEW GREENHOUSE CONCEPT WITH HIGH INSULATING DOUBLE GLASS AND NEW CLIMATE CONTROL STRATEGIES - MODELLING AND FIRST RESULTS FROM A CUCUMBER EXPERIMENT

ZINEG - THE LOW ENERGY GREENHOUSE: AN INNOVATIVE GREENHOUSE WITH NEW CLIMATE CONTROL STRATEGIES SUPPORTED BY PHYTOMONITORING DATA

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Greenhouse 2010 and Soilless Cultivation ZINEG - THE LOW ENERGY GREENHOUSE: AN INNOVATIVE GREENHOUSE WITH NEW CLIMATE CONTROL STRATEGIES SUPPORTED BY PHYTOMONITORING DATA

DEPENDENCE OF THRIPS INFESTATION ON SPATIAL CLIMATE DISTRIBUTION IN A ROSE GREENHOUSE CROP

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Greenhouse 2010 and Soilless Cultivation DEPENDENCE OF THRIPS INFESTATION ON SPATIAL CLIMATE DISTRIBUTION IN A ROSE GREENHOUSE CROP

Comparison of three evapotranspiration models for a greenhouse cooling strategy with natural ventilation and variable high pressure fogging

Even though several models to predict evapotranspiration (ET) of greenhouse crops have been developed, previous studies have evaluated them under fixed greenhouse conditions. It is still not clear which model is more appropriate, accurate, and best suited for applications such as inclusion in greenhouse cooling strategies for different crops, climatic conditions and greenhouse cooling settings. This study evaluated three theoretical models (Stanghellini, Penman–Monteith and Takakura) to simulate the ET of two crops (bell pepper and tomato), under two greenhouse cooling settings (natural ventilation with fog cooling and mechanical ventilation with pad and fan), and for three growing seasons (spring, summer, fall). Predictions of ET from the models were compared to measured values obtained from sap flow gauges. Inputs of internal and external crop resistances for Stanghellini and Penman–Monteith models were calibrated separately by crop and by model. Even though Stanghellini model produced the smallest deviations of the predicted ET from the measured ET, having the best overall performance under all conditions evaluated, an analysis of variance of the daily mean square errors did not show significant differences ( α = 0.05) between the three models. This suggested that any of the three models could be used for inclusion in a greenhouse cooling climate control strategy. However, parameter adjustments such as stomatal and aerodynamic resistances, and the need of leaf area index (LAI) in the models of Penman–Monteith and Stanghellini represent a limitation for this application. The Takakura model was found to be easier to implement; however as the crop grows, careful adjustments on the height of the solarimeter used for this approach are required. Such adjustments determine the field of view of the solarimeter and play a significant role on the determination of radiation balances and the average apparent temperature of the evaporative surface.

Nonlinear MPC based on a Volterra series model for greenhouse temperature control using natural ventilation

Suitable environmental conditions are a fundamental issue in greenhouse crop growth and can be achieved by advanced climate control strategies. In different climatic zones, natural ventilation is used to regulate both the greenhouse temperature and humidity. In mild climates, the greatest problem faced by far in greenhouse climate control is cooling, which, for dynamical reasons, leads to natural ventilation as a standard tool. This work addresses the design of a nonlinear model predictive control (NMPC) strategy for greenhouse temperature control using natural ventilation. The NMPC strategy is based on a second-order Volterra series model identified from experimental input/output data of a greenhouse. These models, representing the simple and logical extension of convolution models, can be used to approximate the nonlinear dynamic effect of the ventilation and other environmental conditions on the greenhouse temperature. The developed NMPC is applied to a greenhouse and the control performance of the proposed strategy will be illustrated by means of experimental results.

Response of Greenhouse Tomato to Varied Low Pre-night Temperatures at the Same Daily Integrated Temperature

Early production and high energy efficiency are important in greenhouse vegetable production in cold regions. A dynamic temperature integration strategy with low pre-night temperature (PNT) has been developed to reduce energy consumption and to improve early fruit yield and energy use efficiency. However, the application of this temperature control strategy is feasible only if there is no crop yield and quality loss. To determine the low PNT tolerance threshold and explore the mechanism of this temperature control strategy on plant growth and development, the effects of four PNT temperature integration treatments (PNT9, PNT11, PNT13, and PNT15, with an actual PNT of 9.4, 11.3, 13.3, and 15.1 °C, respectively) on greenhouse tomatoes (Solanum lycopersicum) were investigated. The PNT was applied at the beginning of the night for 3 h, whereas temperatures in other periods during a day (24 h) were adjusted accordingly to ensure the same 24-h average temperature (19.4 °C) for all PNT treatments. Four cultivars (Bigdena, Clarance, Quest, and Conchita), representing all three types (beefsteak, cluster, and cherry) of greenhouse tomatoes, were used in the study. The optimum PNT for fruit yield was 13.8 and 14.9 °C for ‘Bigdena’ and ‘Conchita’, respectively. Low PNT down to 11 °C did not compromise fruit yield and plant development in ‘Clarance’, and thus a PNT lower than 13 °C can be used for ‘Clarance’ if it does not have a negative effect on fruit quality. In ‘Bigdena’ and ‘Conchita’, the above-ground biomass increased with increasing PNT at the low range of PNT, peaked at ≈13 °C PNT (13.7 and 13 °C for ‘Bigdena’ and ‘Conchita’, respectively), then declined at high PNT. Leaf photosynthesis rates were increased by the highest PNT (PNT15), whereas respiration rates were reduced by the lowest PNT (PNT9). Therefore, PNT at ≈13 °C might have allowed for the proper balance between the high photosynthesis for photoassimilate generation and the low respiration for photoassimilate conservation and thus accumulated the highest photoassimilate and the highest fruit yield in ‘Bigdena’. Flower development rate in ‘Conchita’ decreased linearly with low PNT, which might have limited the response of its fruit yield to low PNT and raised the optimum PNT for fruit yield to 14.9 °C. Temperature integration with proper low PNT can be an effective climate control strategy for increasing early fruit yield and energy use efficiency in greenhouse tomato production.

Canopy Photosynthesis and Time-of-day Application of Supplemental Light

There is increasing use of electricity for supplemental lighting in the northern European greenhouse industry. One reason for this may be to secure a high growth rate during low-light periods by an attempt to increase net photosynthesis. We wanted to clarify which period of the day resulted in the best use of a 5-h supplemental light period for photosynthesis and growth. The periods tested were supplemental light during the night, day, morning, and evening. The experiments were carried out in daylight climate chambers measuring canopy gas exchange. The air temperature was 25 °C and the CO2 level ≈900 ppm. Vegetative chrysanthemum was used, because this species responds quickly to change in light level. The leaf areas of the plant canopies were nondestructively measured each week during the 4-week experimental period. The fact that the quantum yield of photosynthesis is greater at low than at high light intensities favors the use of supplemental light during the dark period, but growth measured as dry weight of the treated plants at the end of the experiments was not significantly different given identical light integrals of the treatments. However, one experiment indicated that increased time with dark hours during day and night (24 h) might decrease net photosynthesis. The assimilation per unit leaf area was approximately the same during times of sunlight through a diffusing screen at 100 μmol·m−2·s−1 of photosynthetic photon flux (PPF) as during times of supplemental (direct) light application at PPF of 200 μmol·m−2·s−1 by high-pressure sodium lamps. We conclude that during the winter and periods of low light intensities, the daily carbon gain does not depend on the time of supplemental light application, but is linked to the total light integral. However, extended time with dark hours during day and night (24 h) might be a disadvantage because of longer periods with dark respiration and subsequent loss of carbon. Our results indicate that during times of low light conditions, it is not necessary to include factors such as the timing of supplemental lighting application to achieve higher net photosynthesis in climate control strategies.

OPTIMAL GREENHOUSE DESIGN SHOULD TAKE INTO ACCOUNT OPTIMAL CLIMATE MANAGEMENT

The objective of this paper is to demonstrate that optimal greenhouse design must account for (and be combined to) optimal climate management. We prove this by showing that different strategies and set-points to control the greenhouse ventilators result in different ?optimal sets? of design parameters. We determined these optimal sets for a passive greenhouse in Almeria, Spain where tomatoes were grown. The greenhouse design parameters investigated in this research were: 1) the transmission of the cover for photosynthetically active radiation (PAR), 2) the transmission of near infrared (NIR) radiation and 3) the emission coefficient for longwave radiation of the cover. Six optimal sets of design parameters were determined by maximising the marginal revenues (crop yield minus costs of design parameters), under given climate conditions, and for different ventilation control strategies. Each ventilation control strategy had different set-points for the air temperature and carbon dioxide concen¬tration to control the greenhouse ventilators. To solve this optimization problem we used a dynamic crop-greenhouse model and an optimization algorithm. The model described the combined influence of the relevant design parameters, outdoor climate and ventilation control upon economic crop yield, through their effect on indoor climate. The yearly costs of the design parameters were empirically derived from prices, physical properties and lifespan of a number of greenhouse cover materials. Results showed that indeed for different strategies and set-points to control the green¬house ventilators different ?optimal sets? of design parameters and marginal revenues were obtained. For example, the difference between the highest optimal NIR trans¬mission 1.00 and the lowest optimal NIR transmission 0.40 was 60%, while the highest marginal revenues 16.94 ?m-2 differed 18,7% with the lowest marginal revenues of 13.77 ? m-2. Additionally, it was found that the cover design parameters were time dependent. In conclusion, only a combined optimal control and design approach that takes into account the best climate control strategy and the time dependency of the design parameters will ensure optimal design parameters and maximum marginal revenues.

CLIMATE CONTROL BASED ON STOMATAL BEHAVIOR IN A SEMI-CLOSED GREENHOUSE SYSTEM 'AIRCOKAS'

Climate control in a greenhouse is usually based on maintaining a specific air temperature, sometimes adjusted to the available light level or the cost of energy. According to theoretical physiological knowledge optimal photosynthesis depends on the behavior of the stomata. No existing climate control strategy is based on measurement or modeling of the stomatal opening. A soft-sensor based on a crop energy-balance equation was developed. The validation of this sensor was started, but the method using a porometer and a silicone rubber impression proved to be inappropriate. A climate control strategy for stomatal opening based on the use of a high pressure misting system, an energy-balance equation and adjusted ventilation window control was developed. This system with the name `Aircokas? was introduced in commercial greenhouse operations and used for various crops. A new approach for the representation of stomatal conductance is suggested

Assessing the Effects of Climate Change on Aquatic Invasive Species

Different components of global environmental change are typically studied and managed independently, although there is a growing recognition that multiple drivers often interact in complex and nonadditive ways. We present a conceptual framework and empirical review of the interactive effects of climate change and invasive species in freshwater ecosystems. Climate change is expected to result in warmer water temperatures, shorter duration of ice cover, altered streamflow patterns, increased salinization, and increased demand for water storage and conveyance structures. These changes will alter the pathways by which non-native species enter aquatic systems by expanding fish-culture facilities and water gardens to new areas and by facilitating the spread of species during floods. Climate change will influence the likelihood of new species becoming established by eliminating cold temperatures or winter hypoxia that currently prevent survival and by increasing the construction of reservoirs that serve as hotspots for invasive species. Climate change will modify the ecological impacts of invasive species by enhancing their competitive and predatory effects on native species and by increasing the virulence of some diseases. As a result of climate change, new prevention and control strategies such as barrier construction or removal efforts may be needed to control invasive species that currently have only moderate effects or that are limited by seasonally unfavorable conditions. Although most researchers focus on how climate change will increase the number and severity of invasions, some invasive coldwater species may be unable to persist under the new climate conditions. Our findings highlight the complex interactions between climate change and invasive species that will influence how aquatic ecosystems and their biota will respond to novel environmental conditions.

Decision support for dynamic greenhouse climate control strategies

Earlier, different dynamic greenhouse climate regimes were designed with various aims as energy saving, biocide reduction or reduction of chemical growth retardants that are used for quality improvement. The aim of this research was to create a decision support tool in order to decide at which week of the year to use which climate control regime for the optimal gain of sustainability and plant quality. A combined greenhouse climate and control model was used to analyse separate and combined effects of six different regimes with increasing degrees of freedom for various climate variables. In this simulation study the model crop cut chrysanthemum was used. Temperature integration, dynamic humidity control, and negative DIF regimes were adapted from earlier papers (DIF=difference between average day and average night temperature, reduces the use of chemical growth regulators). Temperature integration with a regular 24-h averaging period (TI24) and with two nested temperature averaging periods 24h and 6 days (TIn, subscript 'n' for nested), and combinations of TI24 and TIn with the DIF concept (TI24,DIF^x and TIn,DIF^x, respectively) to control stem elongation were simulated. TI24 and TIn were also combined with a dynamic humidity control. All strategies were compared to a standard climate regime (BP, blueprint). The best choice of regimes regarding energy saving, plant quality and reductions of the use of chemicals was targeted for different seasons. In winter absolute energy saving compared to BP was highest when a DIF regime was applied, and the energy saving increased with decreasing DIF set point. In relative sense the largest energy saving can be obtained with TIn (51% in a 4-week period), in spring or autumn (and then with TI24 and the DIF regimes). In these seasons, however, TI24,DIF^x or TIn,DIF^x should be used to reduce chemical growth regulators. The decision whether to use TIn, TI24, or a DIF regime was therefore a decision between energy saving or saving of chemicals. The tool developed in this paper can be used to quantify the costs in energy or chemicals when using the one or other strategy.

Development of Peronospora parasitica epidemics on radish as modelled by the effects of water vapour saturation deficit and temperature

Epidemics of Peronospora parasitica are strongly affected by temperature and air moisture, and the interaction of these factors. Because a significant percentage of radish plants are grown in greenhouses, it may be possible to influence epidemics by altering the greenhouse climate. The objective of this study was to test the hypothesis that epidemics of P. parasitica can be modelled by the effects of air temperature and moisture in the greenhouse. Such a model could then be used to analyse greenhouse climate control strategies with regard to managing downy mildew. Five radish crops were grown under greenhouse conditions with set-points for heating and ventilation intended to obtain favourable conditions for disease development during the first part of the growing cycle. Subsequent to this first phase, unfavourable conditions were set until harvest. Disease incidence was measured once a week until the radishes reached marketable size. In addition, experiments were carried out in growth chambers in which inoculated plants were subjected to air temperatures between 8 and 27°C, and disease incidence and sporulation intensity were measured. Data from these two experiments were then used to estimate model parameters. In this model, the interactions of air temperature (T) and water vapour saturation deficit (SD) were adequately described by a multiplicative relationship. The simulated epidemics by the fitted model were highly correlated with the observed epidemics (r = 0.91, R2 = 0.83, n = 29). Parameter estimates indicated that T of ca. 20°C and SD 2.0 hPa. Both experimental data and simulations showed that epidemics of P. parasitica can be effectively controlled by managing the greenhouse climate.

Climate Change and Air Quality—Measures with Co-Benefits in China

This article examines the links between climate change and air quality and the health and environmental benefits associated with alternative measures and policies for carbon dioxide mitigation in China. The methods used to estimate the costs and benefits of policies to reduce emissions are outlined. A case study is presented for the co-control of carbon dioxide and air pollution in Shanxi province focusing on its capital Taiyuan. Clean Development Mechanism (CDM) projects, where industrial countries can invest in projects in developing countries that will reduce greenhouse gases, are shown to potentially benefit China. Indoor pollution due to dirty household fuels is likely to be responsible for some deaths in China. Details are given of emissions related to coal use. The prospects for future greenhouse gas abatement in China are considered. It is argued that the potential to cut greenhouse gas emissions whilst simultaneously reducing air pollution should make cooperation on climate control strategies more attractive to China.

A Daylight Climate Chamber for Testing Greenhouse Climate Control Strategies and Calculating Canopy Carbon Dioxide Exchange

A daylight climate chamber was designed with the aim of testing new greenhouse climate control strategies on a small scale. Precise control and measure ment of the chamber climate and long-term measurement of canopy carbon dioxide (CO2) exchan ge was possible. The software was capable of simulating a climate computer used in a full-scale greenhouse. The parameters controlled were air temperature, CO2 concentration, irradiance, air flow, and irrigation. The chamber was equipped with a range of sensors measuring the climate in the air of the chamber and in the plant canopy. A chamber perfor mance experiment with chrysanthemum (Chrysanthemum grandiflorum `Coral Charm') plants grown in perlite was carried out over the course of 3 weeks. Five air temperature treatments at a day length of 13 hours were carried out, all with the same 24-hour mean temperature of 20 °C, but different day temperatures (18.0 to 25.1 °C) and night temperatures (14.0 to 22.4 °C). Rate of canopy CO2 exchange in the chambers was calculated. In the range of day temperatures used, rates of canopy photosynthesis were almost equal. The results showed that leaf area and plant dry weight after 3 weeks were not significantly different among temperature treatments, which is promising for further investigations of how climate control can be used to decrease energy consumption in greenhouse production.

A VIRTUAL CHICKEN FOR CLIMATE CONTROL DESIGN: STATIC AND DYNAMIC SIMULATIONS OF HEAT LOSSES

The simulation of the effects of different control strategies on the interior climate in animal houses has been a frequent focus of research work for the last 30 years. Only in a few cases have realistic computer simulations of animal occupants been used in the development of new climate control strategies. The aim of this research was to develop a virtual chicken (VirChick) for computer-aided design and engineering of climate controllers for poultry houses. The objective was to develop a dynamic simulation model of the energy and mass transfer between the chicken and its thermal environment as a first step in the making of a VirChick. A static as well as dynamic model of heat loss for VirChick was developed. Two experiments were performed to generate data for the evaluation of the static heat loss model. It was demonstrated that the modeling results for the heat loss components were in agreement with data found in the literature. Furthermore, on the basis of three dynamic experiments, it was demonstrated that dynamic responses of total heat loss to step variations in temperature (ranging from 18°C to 35°C) could be modeled with a correlation coefficient between measured and simulated total heat loss of 0.83 to 0.96. In the future, such a virtual chicken can be equipped with many more properties, such as realistic locomotion, thermoregulatory and other behaviors, artificial intelligence, etc.

SE—Structures and Environment: A Single-bladed Ventilation Damper: Mixing Ratio Models and Measurement

Fresh air control in a mushroom tunnel is by adjustment of the ventilation damper in the air handling unit, and this has a major impact on the climate of the tunnel. Damper angle affects the proportion of fresh to recirculated air, i.e. the mixing ratio. The primary objective of this study was to determine the mixing ratio as a function of the damper angle, thus facilitating predictive climate control strategies. Measurement of mixing ratio was achieved by psychrometric measurement of the fresh, recirculated and mixed airflows. A full range of damper angles, from horizontal to vertical, i.e. 0–90°, at 9° intervals were used. Compared to mixing ratio models from the literature, results showed that the effect of damper angle on mixing ratio can be better modelled by an exponential relation, but a much better model is a sigmoid. The benefit obtained for an exponential model was a fit improvement of 37%, but a sigmoid model gave a 583% fit improvement. In practice, model parameterization could be by low-cost automatic calibration during periods when the tunnel is unoccupied, subject to the constraint that a minimum psychrometric distance between the fresh and recirculated airflows is maintained during data collection.

TEMPERATURE INTEGRATION ON A 24-HOUR BASE: A MORE EFFICIENT CLIMATE CONTROL STRATEGY

TEMPERATURE INTEGRATION ON A 24-HOUR BASE: A MORE EFFICIENT CLIMATE CONTROL STRATEGY