Heating Ventilation Air Conditioning Research Articles

Cost-sensitive and sequential feature selection for chiller fault detection and diagnosis

Fault detection and diagnosis (FDD) plays an essential role of maintaining large-scale heating ventilation air conditioning (HVAC) systems for industrial usage. The process of selecting important features is a crucial step for FDD methods of HVAC components, such as chillers. A suitable feature selection method selects the minimum number of features to save the number of installing sensors, and simultaneously maximizes the FDD accuracy. According to the surveyed related works, it is found that most existing works only focus on maximizing the classification accuracy, and miss two important points. First, the misclassification costs of false positive and false negative are different for chiller FDD. Second, the selected feature subsets must be sequential for real-world applications. In this study, a cost-sensitive and sequential feature selection algorithm for chiller FDD is proposed to select the most important features using a back-tracing sequential forward feature selection (BT-SFS) algorithm. The ASHRAE dataset collected by project number 1043-RP is utilized. Support vector machine (SVM), which is proved to be one of the most effective FDD classification method for chillers in existing works, is employed for accuracy measurement. This work fills in the gap between theoretical HVAC FDD methods and real-world HVAC FDD applications.

Geothermal heat pumps for sustainable farm climatization and field irrigation

In intensive breeding farms, maintaining an adequate indoor thermal environment and air quality is crucial in order to establish healthy conditions and increase productivity. In the EU, fossil fuels and electricity are the main energy sources adopted for this purpose, yet introducing renewable energy sources and efficient Heating Ventilating Air Conditioning systems would reduce energy consumption and improve sustainability.Another environmental concern in agricultural production is related to the intensive use of fertilizers, causing nitrate contamination in surface water and groundwater. Therefore, innovative strategies to reduce fertilizers and simultaneously reduce primary energy consumption are worthy of investigation.This paper addresses both issues, studying the application of geothermal heat pumps in the agro-zootechnical sector, where they are rarely applied and thus their potential needs to be verified. The study considers systems based on the closed loop configuration, i.e. Ground Source Heat Pumps (GSHP), and on the open loop configuration, i.e. Groundwater Heat Pumps (GWHP).Firstly, a pilot GSHP system for a piglet stable in Northern Italy is presented. Thanks to the use of both ground source and thermal recovery of air ventilation, the system achieves an appreciable reduction in both primary energy consumption and running costs, compared with a more traditional system typically adopted in this kind of farm.Secondly, the feasibility of an innovative concept of a GWHP combined with the irrigation system is studied through numerical modelling. The area of the piglet stable is represented in a flow and heat transport model; groundwater used by the heat pump is re-injected up-gradient during the cold season, while it is used for irrigation during the warm season. The system would provide energy-efficient climatization to the farm stables and, at the same time, promote the reuse of nitrogen in cultivated fields as a result of groundwater recirculation through irrigation.

Parametric Investigation Using Computational Fluid Dynamics of the HVAC Air Distribution in a Railway Vehicle for Representative Weather and Operating Conditions

A computational fluid dynamics (CFD) analysis of air distribution in a representative railway vehicle equipped with a heating, ventilation, air conditioning (HVAC) system is presented in this paper. Air distribution in the passenger’s compartment is a very important factor to regulate temperature and air velocity in order to achieve thermal comfort. A complete CFD model, including the car’s geometry in detail, the passengers, the luminaires, and other the important features related to the HVAC system (air supply inlets, exhaust outlets, convectors, etc.) are developed to investigate eight different typical scenarios for Northern Europe climate conditions. The results, analyzed and discussed in terms of temperature and velocity fields in different sections of the tram, and also in terms of volumetric parameters representative of the whole tram volume, show an adequate behavior from the passengers’ comfort point of view, especially for summer climate conditions.

Nearly Zero Energy Buildings: An Overview of the Main Construction Features across Europe

Nearly Zero Energy Buildings (nZEBs) represent the backbone to achieve ambitious European goals in terms of energy efficiency and CO2 emissions reduction. As defined in the EPBD, by 31 December 2020, all of the new buildings will have to reach a target of nearly zero energy. This target encourages the adoption of innovative business models as well as the technology development in the building sector, aimed at reducing energy demand and exploiting local renewable energy sources (RES). Assessing the share of implementation and the performance of technologies in new or renovated nZEBs is strategic to identify the market trends and to define design guidelines with the most effective solutions according to the context. In this regard, this paper analyses the construction features of a set of nZEBs, collected in 17 European countries within the EU IEE ZEBRA2020 project, with a special focus on the influence of the boundary conditions on the technologies adopted. The results show a general high insulation level of the envelope and recurrent specific technologies in the Heating Ventilation Air Conditioning (HVAC) system (i.e., heat pumps and mechanical ventilation), while the climatic conditions do not drive significantly the design approach and the nZEB features.

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO2) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO2 levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm3, although CO2 levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO2 levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm3. We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO2 concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO2 levels during 100% recirculation. For various fan speeds, recirculation fractions of 50–75% maintained lower CO2 levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants’ exposures to particulate matter and CO2 in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO2 exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO2 accumulation.

Comparative Study of Cost and Power Consumption of HVAC System Using Phase Change Material

Phase change materials (PCM) are materials which absorb the latent heat of the surrounding air. They usually have characteristics such as near to constant temperature operating range with high energy density of melting from solidified state. Nowadays, heating ventilation & air conditioning (HVAC) of commercial & domestic buildings, green rooms in pharmaceutical companies is necessary for maintaining desired atmospheric condition inside the building compound for optimum working environment. For doing so, lot of energy is consumed in this process. Therefore, there is a need of reduction in power consumption where PCM finds a huge market. These materials store the latent heat of the net heat available as latent heat thermal energy without increase in its temperature. Thus, there is a large scope for its usage for reducing the heat load for refrigerating effect for a specified area. This paper intends to compare the variation in heat load calculation of air refrigerated areas like that in commercial buildings, domestic purposes, industrial applications etc. with and without the use of PCM materials.

Draught Comfort in a Slot-ventilated Room at various Inlet Aspect Ratios

Slot-ventilated rooms are widely used in comfort type HVAC (Heating, Ventilation, Air Conditioning) systems, where the air inlet is usually a simple slot-diffuser. The geometry of the slot is often expressed by the aspect ratio (AR), which is an important designing parameter of the room air distribution in ventilation systems. Aspect ratio of the slot-diffuser is the non-dimensional ratio of the slot's length and width. This AR value can influence room airflow characteristics, including draught comfort. Previously, the effect of inlet aspect ratio on a slot-ventilated room's draught environment was not investigated. In this article, the influence of various aspect ratios was investigated on a slot-ventilated model room's draught comfort, using Fanger's DR model. The investigations included air velocity and temperature measurements in a full-scale single (or cellular) office model room and the measured data were evaluated with statistical methods.

Alternative Air-Conditioning Options for Developing Countries

This study assesses the potential selection of efficient air-conditioning (AC) and cooling systems in order to avoid excess power consumption, mitigation of harmful refrigerants generated by the existing AC systems. Several varieties of active and passive air-conditioning systems i.e. heating ventilating air-conditioning (HVAC), vapor compression air-conditioning (VCAC) conventional direct evaporative cooling (DEC) and indirect evaporative cooling (IEC) and desiccant air-conditioning (DAC) systems are under practice for the cooling and dehumidification. The storage of agricultural products mainly based on product individual characteristics i.e. respiration rate, transpiration rate and moisture content of that product. Variant ambient air conditions and the type of application are the main parameters for the choice of air-conditioning system to get optimum performance. The DAC system subsidize the coefficient of performance (COP) in humid regions, coastal ranges of developing countries e.g. Karachi and Gawadar (Pakistan) with hot humid climatic conditions. In similar way, hottest regions of the country such as Sibbi, Jacobabad and Multan perform better results when incorporates with M-cycle evaporative cooling system. Variation in ambient air conditions directly affect the cooling load and the choice of sustainable air-conditioning system

Alternative Air-Conditioning Options for Developing Countries

This study assesses the potential selection of efficient air-conditioning (AC) and cooling systems in order to avoid excess power consumption, mitigation of harmful refrigerants generated by the existing AC systems. Several varieties of active and passive air-conditioning systems i.e. heating ventilating air-conditioning (HVAC), vapor compression air-conditioning (VCAC) conventional direct evaporative cooling (DEC) and indirect evaporative cooling (IEC) and desiccant air-conditioning (DAC) systems are under practice for the cooling and dehumidification. The storage of agricultural products mainly based on product individual characteristics i.e. respiration rate, transpiration rate and moisture content of that product. Variant ambient air conditions and the type of application are the main parameters for the choice of air-conditioning system to get optimum performance. The DAC system subsidize the coefficient of performance (COP) in humid regions, coastal ranges of developing countries e.g. Karachi and Gawadar (Pakistan) with hot humid climatic conditions. In similar way, hottest regions of the country such as Sibbi, Jacobabad and Multan perform better results when incorporates with M-cycle evaporative cooling system. Variation in ambient air conditions directly affect the cooling load and the choice of sustainable air-conditioning system

Ancillary Services Through Demand Scheduling and Control of Commercial Buildings

Prior work showed building Heating, Ventilation, Air Conditioning (HVAC) systems can provide ancillary services to the power grid without sacrificing occupant comfort if the reference power variation is of high frequency (seconds to a few minutes). This paper addresses the question of how to do that when the reference power variation is of lower frequency, e.g., periods of a few minutes to an hour. The proposed control system to do so uses a two-layer architecture. An optimizer schedules the baseline cooling and heating power of a building based on load forecasts. A lower level controller is then used to track the scheduled baseline plus ancillary service reference signal. The schedule is periodically updated based on indoor measurements to ensure quality of service in spite of load forecasting error. The algorithm is tested in simulation. Results show that ancillary services in the frequency range of $f \in {[1/(1\; \text{hour}),1/(10\; \text{minutes})]}$ can be extracted from commercial building HVAC systems while still maintaining a comfortable indoor climate.

The Application of Coconut Fiber as Dissipative Silencer

Heat ventilation air conditioning system (HVAC) is one of the ducting systems that broadly applied in the building. There are HVAC silencers in the market, however the sound absorptive material commonly used is mineral wool. In this research study, a sound absorptive material made of coconut fiber was tested to identify its performance as a potential replacement of green material for ducting silencer. The experiment was carried out in a testing apparatus that follows the BS EN ISO 11691:2009 standard. Different configurations of sound absorptive material and contents of coconut fiber were investigated in the study. The trend of insertion loss at 1/3 octave frequency was identified where at frequency below 3000Hz, the insertion loss of dissipative silencer is observed high at certain frequency with a very narrow range. At 3000Hz, the insertion loss of 4dB to 6dB is constant until 4000Hz and drops until 5000Hz before it increases again steadily up to 13dB at 10000Hz. A similar trend was observed for different configuration of sound absorptive material. Despite the configuration different, the outcome shows that the insertion loss is increasing with higher content of coconut fiber.

Investigation of heat load calculation for air carrying energy radiant air-conditioning system

Radiant heating and cooling has been widely acknowledged as an important energy-saving technique for building air-conditioning. This paper put forward the concept of Air Carrying Energy Radiant-air-conditioning System (ACERS) to solve some of the limitations of existing radiant air-conditioning systems. Since the orifice plate of ACERS would enable radiant and convective heat transfer with indoor surfaces, using the traditional load calculation method could result in inaccuracy. Therefore, a correction coefficient method for load calculation for ACERS was developed. Based on experiments conducted in summer and winter, in a room installed with ACERS, the cooling and heating loads of the test room were calculated by traditional and newly developed Computational Fluid Dynamics (CFD) simulation method. Then the cooling and heating load calculation results of two methods were compared as the approximate correction coefficient of ACERS, which was validated as about 0.75 in summer cooling and 0.8 in winter heating. Furthermore, the components of air-conditioning load calculation are unrelated with room type, so this simplified load calculation method can be extended to other rooms with ACERS. The load calculation is the foundation of ACERS design and application, and should also contribute to energy conservation in usage of Heating, Ventilating, Air-conditioning (HVAC).

Online fault detection methods for chillers combining extended kalman filter and recursive one-class SVM

Automatic, accurate and online fault detection of heating ventilation air conditioning (HVAC) subsystems, such as chillers, is highly demanded in building management system (BMS) to prevent energy waste and high maintenance cost. However, most fault detection techniques require rich faulty training data which is usually unavailable. In this study, a novel hybrid method is proposed to detect faults for chiller subsystems without any faulty training data available, i.e. by training the normal data only. A hybrid feature selection algorithm is applied to the chiller dataset collected by ASHRAE project 1043-RP to select the most significant feature variables. An online classification framework is introduced by combining an Extended Kalman Filter (EKF) model and a recursive one-class support vector machine (ROSVM). Experiment results show that the proposing algorithm detects typical chiller faults with high accuracy rates and requires less feature variables compared to existing works.

Study on the Energy Efficiency Optimization of Solar Power System

In this paper, we design solar power controller based on the model in which the HVAC(Heating, Ventilation, Air Conditioning) fan driving type and hybrid charging type are combined to optimize the energy efficiency of eco-friendly solar cell-based vehicle HVAC system. Because the system characteristics of the traditional MPPT method have many limitations to be applied in vehicle with relation to driving the HVAC blower motor, the limitations and efficiency of such pre-existing system was improved through designing the MPPT load variation method that is able to be used with the MCU(Micro Controller Unit) and is altered from the MPPT P&O(Perturbation and Observation). The DC step down converter(Buck) was used, which allowed for the efficiency to be increased by at least 10% when applied in the HVAC blower motor. And the system was designed to allow the battery to be charged by using the DC-DC step up converter(Boost). In order to confirm the efficiency of the proposed controller system, the results from conducting the operating experiment and vehicle performance evaluation verified the system efficiency.

A newly composed paraffin encapsulated prototype roof structure for efficient thermal management in hot climate

For efficient thermal management in the building under hot weather condition a new paraffin composition as suitable PCM is needed. Several notable attributes of paraffin wax including thermo-physical properties, open air atmospheric condition, economy, and environmental amiability make them suitable PCM for incorporation in the building. Thus, new PCM with massive storage of heat or cold in a specific volume is demanded. Iraqi local paraffin waxes as PCM are proven to be highly prospective due to their high-vitality thickness and isothermal conduct. However, thermal performance optimization of new PCM is pre-requisite to determine its effectiveness in hot climate location. We prepare three new PCM compositions with different oil to wax ratios from the crude petrochemical feed stock waste using fractionation followed by de-waxing and crystallization. The melting temperatures and flash points of these paraffin waxes are ranged between 19 and 44 °C and 177–256 °C, respectively, which upon encapsulation in the prototype roof construction are demonstrated to produce thermal comfort in rooms under hot climate (Iraq). Furthermore, these indigenous PCMs (local paraffin) are abundant, environmental friendly, economic and save electricity cost and HVAC (heating-ventilating air conditioning) systems. Experimental results displayed much reduced temperature fluctuation and internal heat flux of the prototype room than the commercial PCMs. Temperature profiles and solar irradiances inside the room on hot summer days in Bagdad showed remarkable electricity saving. This newly extracted PCM being non-flammable and thermally comfortable are truly secure for buildings construction worldwide.

Model Predictive Control for Energy and Climate Management of a Subway Station Thermo-electrical Microgrid

Electricity consumption in urban railway stations accounts for almost one third of the total energy consumption of a subway network of a city like Paris. The overall systemʼs efficiency can be optimized by taking advantage of available sources of energy such as regenerative braking of trains or local renewable energy resources. This can be achieved by handling the intermittent nature of the various sources and consumption points and by redesigning the station energy grid in a global approach.Microgrids have been an actively researched subject since a few years with the growing interests in smart electricity networks as a mean to decentralize the global power supply facilities. We present hereby a methodology for the optimal management of a microgrid connecting regenerative braking energy sources, eventual distributed energy resources, heating, ventilation, air conditioning (HVAC) systems, specific electricity consumptions and electricity storage systems (ESS) for energy management in subway stations. The overall energy cost is minimized adjusting in real-time electricity demand and availability using demand-response strategies while ensuring an optimal thermal comfort and a safe indoor air quality environment.

Solar Thermal Systems for Low Energy Hotel Buildings: State of The Art, Perspectives and Challenges

The implementation of energy efficiency measures, as well as the integration of renewable energy systems, are challenging tasks on the road towards the Low or Zero Energy Buildings (ZEB). This is even more the case, when considering intensively energy consuming buildings, amongst them hotels and touristic lodgings, especially when they operate in intensively seasonally visited regions, such as the Mediterranean. Even when applying the fundamentals of energy efficient design of buildings to a hotel, like the implementation of sound sun-protection schemes, the use of thermal insulation, and the use of efficient Heating Ventilating Air Conditioning (HVAC) systems, there is a significant demand for sanitary hot water, as well as for warm water for purposes like swimming pools that has to be covered. This can be ideally done by means of Renewable Energy Sources (RES) with solar thermal systems being a primary candidate, as they meet the range of temperature requirements and feature a proven efficiency, reliability and durability. For over thirty years now, solar thermal systems have been applied in hotel buildings in Greece, mostly with success, although failures were also part of the learning procedure. It is therefore of interest to present the current situation of solar thermal systems applications in the hotel sector and to review the state of the art of large scale solar thermal systems, in order to be able to determine future challenges.

A simplified mathematical model for transient simulation of thermal performance and energy assessment for active facades

The extended use of double skin façade (DSF) in different kinds of buildings imposes HVAC (Heating Ventilation Air Conditioning) designers to use quick and accurate software to help in taking the right decisions related to energy consumption and thermal comfort. The lack of such methods was the motive to present this paper. Validation of a simplified mathematical model for dynamic simulation of the thermal performance of DSF was presented by comparing results with another detailed simulation model DIGITHON, for a complete year. Moreover the mathematical model was developed to calculate thermal energy due to convection losses from outer facade layer, solar gains and internal loads. A more detailed comparison of energy consumption at different climatic conditions of four cities in Europe has been shown. Implementation of the simplified model in thermo-active-building-system-(TABS) also was illustrated, and how such a model could be useful in one of four methods mentioned in standard ISO-11885-4 to predict heat transfer on TABS. This particular method needs the solar gains and losses due to transmission determined with a constant room temperature by another software which the mathematical model could be implemented in.

Operational planning for multi-building portfolio in an uncertain energy market

In this study, we propose an optimization framework for day-ahead operational planning of a multi-building portfolio under market uncertainty. The portfolio of interest consists of two groups of buildings: controllable and uncontrollable. In the proposed framework, first, physics-based and statistical models are developed for estimation and prediction of end-use consumptions including Heating, Ventilation Air Conditioning (HVAC), lighting, and equipment in controllable buildings. In addition, calculation of hourly load distributions in uncontrollable buildings is developed using a non-parametric bootstrapping method. Then a multi-objective mathematical programming is formulated to minimize the energy expenditure given utility price signals while satisfying the occupants’ comfort. The proposed pricing scheme considers the differences between the day-ahead and real-time prices to reflect the trend of energy market uncertainty. It is demonstrated that this pricing scheme results in better performance, in terms of achieving to demand management goals, than the current scheme. Current pricing scheme is solely based upon the day-ahead forecasted price. The performance of the proposed framework is explored using real energy market data.

Dilute Hydrogen Peroxide Technology for Reduction of Microbial Colonization in the Hospital Setting

It is estimated that hospital-acquired infections (HAIs) cost US hospitals over $30 billion annually. Dilute hydrogen peroxide (DHP) technology is a new patented technology that utilizes ambient air to produce hydrogen peroxide as a near-ideal gas, creating concentrations of peroxide that are well below the Environmental Protection Agency safety thresholds. In laboratory testing, DHP has demonstrated potent disinfective activity against a variety of bacteria, fungi, and viruses. DHP technology has never been studied in the healthcare environment. In this study, DHP was incorporated into a community hospital’s 34-bed Cardiovascular/Telemetry (CV-Tele) unit's existing heating-ventilation-air-conditioning (HVAC) system. The study was designed to answer the question: Does DHP reduce microbial contamination in the hospital unit? In phase one of the study, culture samples were taken from functioning hospital rooms and common work areas before and after standard disinfection to establish a baseline of microbial colonization before the application of DHP technology. In phase two, samples were taken from the same rooms and work areas daily for one week after the institution of DHP technology. A significant reduction in microbial colonization was observed over seven days after instituting DHP technology as shown in Figure One. Complete eradication of S. aureus, Candida parapsilosis, Pseudomonas putida, Flavobacterium meningosepticum, Pseudomonas picketti, and Citrobacter was seen at seven days. In addition, a reduction in Alcalagines (68%), Pseudomonas aeruginosa (95%), and Enterobacter (50%) was seen from time of terminal cleaning to seven days. Conversely, an increase in mold species was observed from post-cleaning to seven days. DHP technology demonstrates activity against a variety of pathogenic microbes. The data strongly suggest that DHP effectively reduces microbial counts in the hospital setting which may help reduce hospital-acquired infection rates. Further study into the effects of DHP on HAIs is indicated.