Search

Fan coil units (FCUs) are decentralized air-conditioning devices to locally condition zone air. In the U.S. and Europe, FCUs are widely deployed in diverse types of buildings such as offices, hotels, schools, and residential apartments because of their low cost and easy installation. The abnormal operation of FCUs due to faults or malfunctioning components may cause significant energy waste and degrading thermal comforts. However, faults occurring in FCUs have been seldom investigated. A systematic analysis of fault impacts of FCUs would enable a better understanding of fault impacts, an efficient development of fault diagnostics approaches, and an improvement of FCUs monitoring system design. In this paper, we used a FCU simulation model, which was developed in the HVACSIM+ environment from a previous study to evaluate FCU fault impacts. Five common faults with different intensities were simulated within a one-year time window to generate fault inclusive operation data. We employed a bottom-up fault impact analysis framework. Fault effects on multiple measurements were firstly evaluated to obtain fault symptom occurrence probability distributions which quantify measurements' sensitivities. Secondly, fault thermal comfort impact and fan power energy consumption impact were assessed. Lastly, the result from fault thermal comfort impacts and energy penalties was used to rank FCU faults. [ABSTRACT FROM AUTHOR]

Aligning with the global movements towards mitigating CO2 emissions and regulations to phase-down HFC refrigerants, many low-Global Warming Potential (GWP) refrigerants are being tested and proposed as fourth-generation refrigerants. R1234yf (HFO-1234yf) is a refrigerant with GWP <1 (0.31) and has replaced R134a (HFC-134a), which has GWP 1300, in automobile air conditioning systems and has a high potential to replace it in domestic refrigerators. In this paper, an energy performance evaluation and a life cycle climate performance assessment for R1234yf were conducted and compared to R134a. The study involved two identical domestic refrigerators with the same refrigerant charge that is recommended by the manufacturer. R1234yf showed resulted in similar cabinets air and refrigerant temperatures. However, the discharge temperature for the R1234yf refrigerator was relatively higher temperature than that for R134a. Also, R1234yf demonstrated higher daily energy consumption and more extended compressor run-time than of R134a. On the other hand, R1234yf proved significantly lower direct emissions and higher indirect emissions than those caused by R134a. Overall, R1234yf resulted in 3% reduction in the Lifecycle Climate Performance (LCCP) CO2 emissions compared to R134a. [ABSTRACT FROM AUTHOR]

Delhi Metro is India's first modern public transportation system and the world’s 8th longest metro system with network length of 347.6 kilometers (215.9 miles) and 253 stations. The total energy consumption for running of trains and auxiliary systems was 1117 million kWh in the year 2018-19. The electrical and mechanical equipment at stations consumes about 40% of the total energy consumption of the entire network. An underground station consumes about 8 to 10 times of energy than an elevated station because of air conditioning and lighting requirements. The Environment Control System (ECS) or Ventilation, and Air-Conditioning (VAC) systems consumes approximately 70% of total energy consumption at an underground station. The Air Handling Units (AHUs) and Trackway Exhaust Fans (TEFs) which consumes about 50% of total energy consumption of VAC systems are selected on the basis of Open Mode, Close Mode and Emergency Mode operations which requires different pressure rating of the fans in different modes. During implementation of Phase-I and Phase-II of Delhi MRTS, the AHUs and TEFs were fixed speed type and consumes more power because of selection of fans at higher pressure rating. In Phase-III, all the 34 underground stations are provided with Variable Frequency Drives (VFDs) for AHUs and TEFs which resulted in the huge amount of energy savings at the underground stations as the fans can be operated with required pressure rating as per the mode. Further, Ministry of Housing & Urban Affairs, Government of India, in their publication titled ‘Best Practices & Innovations in Metro Rail Systems’ have acknowledged this endeavour of Delhi Metro and suggested all metros in India to provide their systems with VFDs. The actual energy savings to the tune of 35% or more are realized with the use of VFDs. This paper presents a detailed comparative study between VFD system and fixed speed system based on actual energy consumption at underground stations of Delhi Metro. The control algorithms designed to vary the speed along with the other intelligent features implemented in the station’s Building Management Systems for energy savings are also presented. The paper also discusses the design basis for selection of the various equipment used in VAC systems at underground stations. [ABSTRACT FROM AUTHOR]

Heating, Ventilation and Air conditioning (HVAC) systems account for approximately 40% of the total energy used by buildings in the USA. To reduce this consumption States enforce minimum energy codes that currently range from strict (ASHRAE 90.1-2016) to relaxed (ASHRAE 90.1- 2007) with some states following no particular standard. To reach as close as possible to net zero carbon and energy, each statewide energy code requires different levels of interventions for each code minimum building. This paper presents a collection of potential HVAC retrofits to transition each State’s current code minimum buildings towards the goal of net zero to achieve a carbon free future by 2050. The study shall use a large array of code minimum criteria and climate zones covering the 48 contiguous United States to determine the most successful interventions at reducing the energy use of buildings meeting today's energy codes. Office use type has been selected for the study as they account for 18% of total buildings and close to 19% of the total commercial floorspace. A number of interventions will be applied to this use type that will vary based on current code and climate zone; however, a common theme will be electrification through the use of heat pump technology. Each intervention will be scored based on energy and carbon savings, along with level of difficulty and cost. The study not only provides a comprehensive transition guideline toward the net zero energy and carbon but also predicts the future project opportunities. [ABSTRACT FROM AUTHOR]

Dehumidifiers (DHUs) are the second most-selected equipment, after air conditioning (AC), used to manage indoor relative humidity (RH) in homes. They can offer the lowest first-cost, are well-established in the market, and are often easier to install than other supplemental dehumidification alternatives. However, DHUs have the potential to use significant amounts energy and may impact the performance of the central ducted cooling system under certain conditions. Dehumidifiers may be designed to be ducted or un-ducted. Dehumidifiers with ducts are sometimes referred to as whole-house or ducted dehumidifiers. Manufacturer manuals offer several different options for ducting DHUs, but they do not provide adequate information about potential performance impacts. Also sorely missing are expanded DHU performance metrics to help professionals and consumers determine the appropriate DHU capacity and to help predict operational efficiency for specific realistic applications. The Florida Building Commission initiated a research project to determine if some common ducted DHU configurations had significant energy and moisture impacts and whether any configurations should be not allowed in Florida Building Code. The research evaluated measured energy use and latent heat removal rates of AC and DHU for four different common ducted DHU duct configurations. Testing occurred during variable weather and interior latent loads common in a warm moist climate. A highly-instrumented building lab was used to evaluate AC and DHU performance based upon how a DHU was ducted to a central AC ductwork and compared these to a DHU ducted to and from an open central room. There was less than 1% difference in annual space conditioning energy (DHU + AC) among two different methods of DHU ducted to the central supply duct and the DHU ducted directly to indoors. However, steady-state and longer-term test findings showed that a DHU ducted to and from a central cooling system return upstream of the central cooling evaporator coil resulted in the annual predicted space conditioning energy use of 308 kWh/year (4%) more than the DHU ducted directly to indoors. It also resulted in decreased central AC latent performance by 28% when the DHU and AC ran simultaneously. This DHU duct configuration further degraded dehumidification performance by causing moisture to be evaporated off of the central cooling coil at a rate as high as 2-3 pounds of water per hour when the AC was cycled off and DHU operated. This paper discusses the experimental method, results and recommended practice of ducting DHU for optimum performance. [ABSTRACT FROM AUTHOR]

Building air distribution terminal system designers and system installers require accurate quantitative information on the diffuser throw and pressure loss performance of the installed system to achieve optimum efficiency and levels of human comfort. This research project, covered in three papers, establishes the diffuser baseline performance and then determines the field installation adjustment values. The first paper covers baseline performance. This paper documents the field conditions difference in throw and pressure loss from ideal conditions of six types of ceiling diffusers, each with three different inlet sizes at three different inlet velocities. The third paper covers differences in sound generation from ideal conditions. Full scale laboratory testing of typical field installation variations was completed with variations in damper installation, duct approach angle, duct type, duct vertical height above the diffuser, and close coupling duct installation. A predictive model was developed and used to create a set of look-up tables that can be used to easily predict how the installation configuration would affect diffuser performance compared to published data. The results in this report can be used to determine the corrections for throw and pressure loss for field conditions from baseline results. [ABSTRACT FROM AUTHOR]

Building air distribution terminal system designers and system installers require accurate quantitative information on the noise performance of the installed system to achieve optimum system efficiency while maintaining preferred levels of human comfort. This research project, covered in three papers, establishes the diffuser baseline performance and then determines the field installation adjustment values. The first paper covers baseline performance. The second paper documents the field conditions difference in throw and pressure loss from ideal conditions of six types of ceiling diffusers, each with three different inlet sizes at three different inlet velocities. This paper documents the field conditions difference in sound performance from ideal conditions of the same variety of diffusers and inlet velocities. Full-scale laboratory testing of typical field installation variations was completed with variations in damper installation, duct approach angle, duct type, duct vertical height above the diffuser and close coupling duct installation. A predictive model for sound generation was developed and used to create a set of look-up tables that can be used to easily predict how the installation configuration would affect room sound levels compared to published data. [ABSTRACT FROM AUTHOR]

This paper reviews the previous attempts to evaluate the Indoor Air Quality (IAQ), investigates previously proposed IAQ factors and analyses the evaluation methods of these factors. The present work introduces, also, a new hypothesis of the optimum HVAC airside system design of the surgical operating theatres to achieve the comfort and hygiene levels. The present work is devoted to propose and formulate a new scale capable of adequately evaluating the airflow pattern in the surgical operating theatres. The proposed new scale is proposed to cover the local and overall air quality evaluations. A new Neuro fuzzy technique was applied to derive measures for indoor air quality indices. Indoor Air Quality (IAQ) is more critical in healthcare facilities due to the dangerous microbial and chemical agents present and the increased susceptibility of the patients. Hospitals and other healthcare facilities are complex environments that require ventilation for comfort and to control hazardous emissions. Surgical operating theatre is the most important and complex zone in the hospital, and requires more careful control of the aseptic conditions of the environment. Most of the previous researches aiming at evaluating the IAQ were based on the evaluation of the air distribution depending on the residence and leaving age of the air supplied to the enclosure. Other attempts were also reported to indicate the effectiveness of contaminant removal by the entire airflow pattern as an indication to the IAQ. This paper recommends some designs of the supply air outlets to provide the vertically downward airflow as a practical solution. The near ceiling and near floor extract ports are to be used instead of the hypothetical complete floor extract as a practical solution. [ABSTRACT FROM AUTHOR]

Heat pumps provide an efficient heating method; however they suffer from sever capacity and performance degradation at low ambient conditions. This has deterred market penetration in cold climates. There is a continuing effort to find an efficient air source cold climate heat pump that maintains acceptable capacity and performance at low ambient conditions. Systematic optimization techniques provide a reliable approach for the design of such systems. This paper presents a step-bystep approach for the design optimization of cold climate heat pumps. We first start by describing the optimization problem: objective function, constraints, and design space. Then we illustrate how to perform this design optimization using an open source publicly available optimization toolbox. The response of the heat pump design was evaluated using a validated component based vapor compression model. This model was treated as a black box model within the optimization framework. Optimum designs for different system configurations are presented. These optimum results were further analyzed to understand the performance tradeoff and selection criteria. The paper ends with a discussion on the use of systematic optimization for the cold climate heat pump design. [ABSTRACT FROM AUTHOR]

This paper provides a new implementation model of the BACnet objects on high-level functionality for variable refrigerant flow (VRF) air-conditioning systems for commercial buildings. First, the paper discusses a model of the air-conditioner cell that consists of a group of BACnet standard type objects using the Unified Modeling Language (UML). In addition, this paper provides a new concept of a virtual wattmeter using the BACnet Accumulator object type for power consumption allocation to each tenant of the building. Examples of computer simulation and field testing show the effectiveness of our approach to expedite communication access and to provide more accurate allocation of power consumption for VRF air-conditioning systems. [ABSTRACT FROM AUTHOR]

This paper addresses the field cooling performance of a natural gas-engine-driven heat pump (GHP) system for space cooling and heating applications. Performance data were collected from six 10-ton GHP units installed at six military installations in the southwest United States. Note that the test sites in the southwest United States offer challenging operating conditions to air-cooled space cooling systems. Theoretical analysis showed significantly higher energy efficiency in space heating and cooling by GHP units compared to a conventional gas furnace for heating and electric direct expansion (DX) system for space cooling. In this paper, field measured cooling performance of the GHP units was compared to the theoretical efficiency during the 3 months of the 2007 cooling season. An independent laboratory reported testing GHP system performance in a laboratory environment (Zaltash et al. 2007). The test results are presented in the same symposium session featuring GHP technology, and will be published in the same ASHRAE Transactions volume. GHP performance under field conditions and laboratory conditions were compared. This paper also presents the GHP system's energy conservation and cost savings potential in space air conditioning. [ABSTRACT FROM AUTHOR]

This paper proposes a new index of the seasonal energy efficiency for chillers. The new index, the CSE (chiller seasonal efficiency) index, can be used by building designers for specifying the required chiller performance to manufacturers. This index has an advantage in that it is adaptable to multiple-chiller systems by setting six rating points to consider the difference in the COP due to the entering condenser water temperature as well as the part load. In addition, the use of the weighted harmonic mean equation improves the accuracy in predicting the seasonal COP In this paper, the rating condition for the CSE index is determined from the cooling load profile of office buildings in Japan. Using the CSE index, the advantage ofa variable-speed compressor chiller is presented. In the final part of the paper, the effect of the difference in chiller sequence control is discussed. [ABSTRACT FROM AUTHOR]

This paper presents a new methodology for screening measured data from buildings where heating, cooling, and electricity consumption are separately recorded. It defines energy balance load (EBL) as the difference between the heating requirements plus the electric gains in the building and the cooling coil loads. It then applies first law energy balance in conjunction with the concepts of analytical redundancy, trend checking, sensitivity, and uncertainty analysis to develop a methodology using measured values of EBL to identify bad data. This paper is the first part of a two-part series; it presents the theoretical basis for the methodology and illustrates its use on samples of measured building data. In part two, a program that was created to automatically pre-screen the measured building energy consumption data by utilizing EBL methodology and case studies will be introduced. [ABSTRACT FROM AUTHOR]

Testing energy wheels to determine their effectiveness under steady-state operating conditions has proved to be difficult, time consuming, and costly if accurate results are to be obtained. This paper investigates the theoretical feasibility of using transient response tests on a stationary energy wheel to determine the effectiveness of the same energy wheel rotating at a specified rate. In this paper mathematical models for predicting first the characteristic time constants and, second, the effectiveness of an energy wheel are developed using only the expected transient response functions for the wheel. These time constants for sensible and latent (phase change) energy transient response are directly related to the corresponding sensible and latent effectiveness of an energy wheel operating at steady state at a specified rotor speed. It is concluded that it is feasible to use a simple transient parallel flow test on a stationary energy wheel and use these data to predict the sensible and latent effectiveness of the same energy wheel operating at a known speed. Furthermore, the energy wheel and HVAC designer can use the equations developed for the time constants and the effectiveness to provide guidance toward better performance. [ABSTRACT FROM AUTHOR]

Floor heating has been the most basic version of panel heating and cooling systems since ancient times. Recently newer applications are becoming widely used, especially in Europe. For all panel applications, whether the most basic or the most innovative, their attributes are mainly focused on energy efficiency and better comfort. So far, little attention has been paid to their exergy efficiency, which in fact is a more insightful means of analyzing and comparing HVAC systems to optimally resolve the quadrilemma of human comfort, environment, energy, and economy. This paper shows that panel systems, especially when coupled with a convective component in a hybrid HVAC panel, are more exergy-efficient when they are tied into low-exergy energy sources. A typical analysis for a residential home indicates that the exergy efficiency of a hybrid panel utilizing a low-enthalpy energy resource and a heat pump is almost tenfold higher than a forced-air system utilizing natural gas and grid electricity. This paper draws an energy-based roadmap for the next-generation HVAC systems. [ABSTRACT FROM AUTHOR]

Today's modern enterprise data center must be capable of efficiently operating at current average power densities of 30 to 50 W/ft² (∼320 to 540 W/m²) and, based upon industry trends, support growth in the foreseeable future toward 150 W/ft² (∼1,610 W/m²) and also incorporate provision to possibly support significantly higher power densities in local areas. This paper summarizes the industry trends toward greater power consumption and higher processing speed servers and gives an overview of current and expected techniques for cooling high power consuming cabinets and mainframes. The potential impact of these trends and new techniques on the design of the raised floor cooling system will also be discussed. Additionally, during the installation of new equipment and the migration of equipment from other data centers to the new center, the new data center at start-up is often required to operate with almost no computing equipment load. The start-up conditions can be an operational problem for equipment sized to operate at maximum load. In response to the potentially large range of power density operation and the high costs of data center construction, the majority of owner/operators plan to accommodate this expected power density growth in phases. This paper summarizes the planning to accommodate the various load conditions of the mechanical systems for one recently designed data center including raised floor cooling, central plants, and pipe distribution. [ABSTRACT FROM AUTHOR]

Building operations account for approximately 40% of US energy use and carbon emissions, and vapor compression cycles are the primary method by which refrigeration and airconditioning systems operate. Representing a significant portion of commercial and residential building energy consumption, vapor compression cycles are a target for improvement in efficiency and savings. This paper presents a data-driven approach to find the optimal operating conditions of single- and multievaporator systems to minimize energy consumption while meeting operational requirements such as constant cooling or constant evaporator outlet temperatures. The problem lies in the development of a control architecture that will minimize the energy consumed without requiring any models of the system or expensive mass flow sensors. The application of the presented approach improves efficiency and is demonstrated in simulation and on an experimental system. [ABSTRACT FROM AUTHOR]

With the advent of high efficiency air-conditioning and heat pump systems, achieving even higher seasonal efficiency is becoming more complex and incremental in nature. For this reason, component modifications that provide improvements of even a few percent can become very attractive. If these component level improvements can also provide secondary benefits, such as a reduced bill of materials or more compact packaging, the likelihood of acceptance and market penetration becomes high. One example of such a component level improvement is the novel integration of a stepper motor controlled electronic expansion valve with the distributor for a multi-circuited round tube plate fin heat exchanger. This paper describes the experimental validation of the potential improvements in seasonal performance achieved by implementing this novel electronic expansion valve design into a high efficiency reversible 3-ton air-conditioning/heat pump system. The implementation of this technology led to increases of nearly 5% and 3% in SEER and HSPF, respectively. [ABSTRACT FROM AUTHOR]

Variable Refrigerant Flow (VRF) heat pumps are often regarded as energy efficient air-conditioning systems which offer electricity savings as well as reduction in peak electric demand while providing improved individual zone setpoint control. One of the key advantages of VRF systems is minimal duct losses which provide significant reduction in energy use and duct space. However, there is limited data available to show their actual performance in the field. Since VRF systems are increasingly gaining market share in the US, it is highly desirable to have more actual field performance data of these systems. An effort was made in this direction to monitor VRF system performance over an extended period of time in a US national lab test facility. Due to increasing demand by the energy modeling community, an empirical model to simulate VRF systems was implemented in the building simulation program EnergyPlus. This paper presents the comparison of energy consumption as measured in the national lab and as predicted by the program. For increased accuracy in the comparison, a customized weather file was created by using measured outdoor temperature and relative humidity at the test facility. Other inputs to the model included building construction, VRF system model based on lab measured performance, occupancy of the building, lighting/plug loads, and thermostat set-points etc. Infiltration model inputs were adjusted in the beginning to tune the computer model and then subsequent field measurements were compared to the simulation results. Differences between the computer model results and actual field measurements are discussed. The computer generated VRF performance closely resembled the field measurements. [ABSTRACT FROM AUTHOR]

Indirect evaporative cooling (IEC) is a water-based cooling technology that is attractive for space cooling in dry and hot climates due to its lower energy consumption (compared to vapor compression air conditioners) and lack of humidification (compared to direct evaporative cooling). The key component of advanced IEC or hybrid IEC/DX (Direct eXpansion vapor compression) systems (Elberling 2006)(Elberling 2006)(Elberling 2006) is the IEHX (indirect evaporative heat exchanger). A practical accurate model of an IEHX is needed to characterize the thermal behavior of these coolers and to support their implementation by HVAC designers. This paper presents a methodology for the thermal modeling of IEHXs that is analogous to the effectiveness-NTU method for sensible heat exchangers. The governing differential equations that describe IEHX behavior are transformed to a set of analytical equations that can be solved stably within short computation times. The model can be applied without any performance data for simple cases, or using measurements at two different air flow rates (often available in manufacturers' catalogues). The model's performance was investigated utilizing experimental data from the literature. As an implementation example, the method was used to analyzing the sizing of a plate regenerative-type IEHX under constraints of fixed HX volume and space cooling load. It produced an optimal channel height of 2-3 mm to best satisfy specified trade-offs between wet bulb effectiveness, coefficient of performance, and cooling produced per unit area. [ABSTRACT FROM AUTHOR]

Single-duct variable-air-volume systems often use series- and parallel-fan-powered terminal units to control the airflow in conditioned spaces. A laboratory-verified model of single-duct variable-air-volume systems was developed to simulate both series and parallel fan terminal units where the terminal unit fans are controlled by either silicon-controlled rectifiers or electronically commutated motors. The paper provides the equation needed to simulate the performance of a fan-powered terminal unit. The simulation model developed here includes a five-zone office building whose performance was simulated in five cities in the United States: Houston, Phoenix, Chicago, New York, and San Francisco. The model includes total plant energy, total cooling plant energy, primary fan energy, terminal unit fan energy, and heat energy added. The single-duct variable-air-volume simulation results showed that the reduction in the annual energy used by the office building with series-fan-powered terminal units having electronically commutated motors compared to series units having silicon-controlled rectifier-controlled motors varied by location. The largest energy savings for the building was in Phoenix (8.4%), while the smallest was in Chicago (5.9%). In all cases, the reduction in electricity used by the terminal unit fans with electronically commutated motors was near 65%. These results indicate that using fan-powered terminal units with electronically commutated motors offers the potential for sizable savings in energy compared to units with silicon-controlled rectifier-controlled motors. [ABSTRACT FROM AUTHOR]

This paper will discuss treatment of large thermal storage systems in district cooling, particularly with respect to maintaining proper biological control. Covered topics include proper biocide selection and the implementation of side-stream filtration to control microbiological growth within the systems while mitigating corrosion and other effects. [ABSTRACT FROM AUTHOR]

Task-ambient conditioning (TAC) systems have proven success in reducing power consumption, improving thermal comfort and enhancing air quality. However, the adoption of TAC has, however, been generally slow. We propose an improvement to TAC systems by disconnecting them from the central air-handler, effectively making them ductless. The Ductless Task Air- Conditioner (DTAC) utilises thermoelectric modules and phase change materials for heat exchange and heat sink respectively. Prototypes of DTAC have been developed concurrently with test regimes for the proof of concept. The paper also presents the technical studies performed on the prototypes to show its capability and limitations. Whilst still in its early stages, DTAC shows promise for delivering supplementary air-conditioning to office occupants, conserving overall air-conditioning by allowing the central air-conditioner to have a higher temperature set-point and increasing occupant thermal comfort by allowing them to have direct control over their immediate thermal environment. [ABSTRACT FROM AUTHOR]

According to DOE's Commercial Buildings Energy Consumption Survey (CBECS), the average energy use for all existing U.S. buildings has essentially remained flat since the early 1980s at about 88,000 Btu/ft² (277.4 kW/m²) despite public and private initiatives that resulted in increased standards and improved components. Furthermore, 98% of all buildings are less than 100,000 ft² (9,290 m²) with the distribution heavily weighted to buildings between 25,000 and 50,000 ft² (2,323 and 4,645 m²). The Greater Philadelphia Innovation Cluster (GPIC) for Energy Efficient Buildings, a Department of Energy Hub, has examined existing buildings, regulations, policies, and current retrofit practices in the ten counties including and surrounding Philadelphia. This paper will provide details of barriers to energy efficiency retrofits of small and medium sized buildings and suggest market and technology pathways forward. [ABSTRACT FROM AUTHOR]

An article published in the December 2009 ASHRAE Journal suggested that a detailed modeling analysis, in lieu of a single-number such as IPLV per AHRI Standard 550/590-2003, should be used to make purchasing decisions for chillers, especially in multi-chiller applications. Detractors claim that an hourly modeling analysis is too cumbersome, whereas IPLV is easy. In this paper, a consulting engineer presents examples of an easy-to-use modeling method that is more true-to-life than IPLV for multi-chiller plant energy evaluations based on life cycle cost, for comparison of chiller purchasing options. [ABSTRACT FROM AUTHOR]

Ongoing commissioning is important for improving the energy efficiency of large scale air conditioning systems. It should be an essential part of building operation and maintenance. However, normal ongoing commissioning is time-consuming and needs expert experience. This paper therefore presents a quick, streamlined ongoing commissioning method. Based on operation data logs stored by building management systems (BMS), this method can give primary evaluations on system performance and supply suggestions for operation optimization and equipment retrofit. This method has been applied in a shopping center in Hong Kong. The applications have been introduced in detail as examples to illustrate the method. [ABSTRACT FROM AUTHOR]

In this paper Artificial Neural Networks (ANN) are used to predict the energy consumption in an air conditioned administrative building. The model is constructed by a simulation package called Design Builder where EnergyPlus is the core program which is provided with the weather data for Cairo and simulated to produce the system performance hourly data (Total energy consumption of the Building, Chiller energy consumption, etc). Different experiments and cases are done to evaluate the performance of the prediction at different types of inputs introduced to the ANN. Different combinations of Input parameters and different structures of ANN are used. A feed forward backpropagation structure is used for modeling which is trained by Levenberg Marquardt algorithm. It was found that changing the input data which is introduced to the ANN has a great effect on its predicting ability. Different performance parameters are defined for assessment of the ability of the trained neural network such as Root Mean Square Error and coefficient of variation where at the best case they became 4.014KW and 0.042. This will introduce the ANN capability and will show the effect of different parameters and conditions on its predictability. This model can also be potentially used for optimization of building control systems. [ABSTRACT FROM AUTHOR]

This paper aims to study the impact of introducing the return air concept into rooms conditioned by chilled ceiling displacement ventilation (CC/DV) system to save energy while limiting a time-dependent return fraction based on room load in order to maintain an acceptable air quality in the breathing zone. A transient coupled thermal and contaminant transport model is needed to assess the indoor air quality based on predicted levels of carbon dioxide concentrations in the radiant-cooled space under varying load conditions. For that reason, the Kanaan et al. (2010) contaminant transport model in CC/DV conditioned spaces is extended to transient applications that have substantial wall plumes induced by external loads. Experiments are performed to validate the extended model predictions of air quality expressed in the level of CO2 concentration in spaces conditioned by CC /DV system. Experiments are conducted in a chamber with two external walls in Kuwait Climate. Measurements are recorded in time of the air temperature and carbon dioxide concentration at selected location in the room and are compared with values predicted by the model. The experimental results agreed well with extended contaminant transport model predictions. The maximum errors in predicted CO2 concentrations are less than ± 25ppm in presence of external load. It was also found that the mixing fraction reaching up to 60% resulted in 37% less energy consumption of the system when compared with 100% fresh air CC/DV system. [ABSTRACT FROM AUTHOR]

This paper evaluates the central chilled water system of the Southern Illinois University Carbondale (SIUC) campus using exergy-based cost accounting to quantify the magnitudes and cost impacts of internal losses with the goals of maximizing chiller capacity utilization and minimizing the unit cost of delivered chilled water. Two independent systems, each comprised of a primary-secondary-tertiary distribution network and cooled by a 12,300 kW (3,500 RT) steam-turbinedriven centrifugal chiller, were modeled as control volume networks using steady-state rate balances for energy, exergy, and cost. An extensive set of measurements, collected over the 2006 cooling season, was used as the input data for the models. Results show that while the steam turbines are the largest source of exergy destruction, mixing in the distribution loops is the dominant source of exergy unit cost at low cooling loads, and refrigeration cycle losses dominate costs at high loads. Recommendations include: (1) Convert the chilled water distribution to an all-variable-speed, direct-coupled configuration; (2) During low cooling loads use only one chiller; (3) During high cooling loads, increase the flow rate of water through the evaporators; (4) Favor speed control over inlet guide vanes for capacity modulation; (5) Better insulate steam piping; and (6) Consider replacing the steam turbines with variable speed motors. [ABSTRACT FROM AUTHOR]

A substantial reduction in analysis time would greatly aid the proliferation of CFD-based modeling tools which, in turn, would reduce IT equipment operating temperatures and energy consumption. As solution time is dominated by total grid count, an obvious question is: how coarse can the grid be made while retaining meaningful accuracy? This paper exams the effect of grid size on solution time and accuracy. Ten data center layouts, based on actual facilities, are analyzed over a range of approximately-uniform grid sizes with a commercially available CFD package. Accuracy improves significantly as average grid size is reduced to about six inches. As grid size is further reduced from six to two inches, results improve only marginally while solution time increases by about a factor of 50. Finally, an example in which the local grid size near IT racks is varied independently from the global (room) grid suggests that substantially coarser grids may be used for much of the data center so long as the grid is more refined in key areas of interest. [ABSTRACT FROM AUTHOR]

Clear associations are being established between ventilation rates, indoor air quality (IAQ), and the productivity of the workforce in various types of buildings, most significant of which is the commercial and office building sector. While source control is commonly advocated as the fundamental approach to eliminating or containing the contaminant levels inside the building, a more practical and often necessary approach is likely to be exposure control. Thus, ventilation plays an important role in providing a good quality built environment. However climatic conditions pose considerable challenges in the design of air-conditioning systems, and, in a hot and humid climate, this can translate to significant energy penalty. Two considerations are highlighted in order to achieve ‘good’ IAQ and energy efficiency—the enhanced dehumidifying performance of cooling coils and the effectiveness of air distribution strategies. This paper reviews some of the current and future technologies for air conditioning and air distribution that can collectively contribute to the design of energy-efficient healthy buildings. The air-conditioning technologies reviewed include outside air pretreatment systems, single-coil twin-fan (SCTF) systems employing a compartmented cooling coil, desiccant dehumidification systems, and heat pipes. The air distribution systems reviewed include an SCTF system with independent ‘ventilation’ and ‘thermal cooling’ on zone-based demand, a personalized ventilation system coupled with secondary ambient air distribution system, a displacement ventilation system, an underfloor air distribution system, and a dedicated outdoor air system coupled with radiant chilled ceiling. Applications of some of these technologies, such as the SCTF air-conditioning and air distribution systems and personalized ventilation systems, in Singapore are presented. [ABSTRACT FROM AUTHOR]

This paper shows the results of a characterization of an 11,490 ft2 (1067 m2) high-density data center with focus on a zone with heat dissipation greater than 8 kW and up to 26 kW per frame. To gain insight into the operational health, a data center survey is conducted. The purpose of the survey is to measure and collect data on power consumption, airflow, and temperature throughout the data center. The results are used to profile and validate the data center via a computational fluid dynamics (CFD) model for detailed analysis. The methodology used in the study is similar to that of the National Center for Environmental Prediction (NCEP) data center case study (Schmidt 2004). [ABSTRACT FROM AUTHOR]

Because of their ability to improve building air quality and their potential to reduce energy usage in some climates by allowing more conditioned air recirculation, use of gas contaminant filters in buildings is increasingly considered. Air cleaning is an option under ASHRAE Standard 62 and is required if the outdoor air is poor. New media and processes are becoming available, and their performance needs to be evaluated. Further, evaluation of existing technologies needs to be standardized. Both small-scale and full-scale testing is required, and there is not a standard method for systematic evaluation of commercial full-scale gas-phase air cleaners in a duct. A number of laboratory tests of full-scale gas-phase air filtration equipment (GPAFE) have been conducted at RTI over several years. The methods were developed during ASHRAE and EPA research and refined on later commercial projects. The full scale test method uses a modified ASHRAE Standard 52.2 test rig. This paper presents an overview of fullscale GPAFE testing and discussion of the considerations that go into design of a full-scale test. Selected results of full scale tests are presented. [ABSTRACT FROM AUTHOR]

This paper provides a method for verifying the accuracy of computer models that simulate the performance of the airhandling components of four types of heating, ventilating, and air-conditioning systems: the dual fan VAV dual-duct system, the single-zone system, the four-pipe fan coil system, and the four-pipe induction system. To accomplish this, a detailed description of each system and its operating parameters was developed and a set of eight test conditions was generated, consisting of carefully chosen space loads and weather conditions. Each of the systems was simulated at each of the defined conditions. The thermodynamic properties at each point in the system, as well as the heating and cooling coil loads, were calculated. The calculations were then repeated by a second analyst using an independently developed program. The maximum deviation in the total coil loads was 1.8%, and the average of the absolute deviations was 0.4%. These validated results can be used by program developers or users to test the performance of the air-side simulations contained in most building energy analysis computer programs. [ABSTRACT FROM AUTHOR]

Variable primary flow chilled water pumping systems allow flow through chiller evaporators to vary in response to changes in load. Variable primary flow proponents claim that this approach uses less energy and is more economical than other pumping schemes, in particular, the well-established primary/secondary system. This paper investigates these claims via a parametric modeling study. Parameters varied included plant cooling load profile and climate, number of chillers in the plant, chilled water temperature difference vs. load, and others. Construction cost and operating cost differences were calculated and systems were compared on a lifecycle cost basis. Variable flow, primary-only systems reduced total annual plant energy use by 2%-5%, first cost by 4%-8%, and life-cycle cost by 3%-5% relative to equivalent primary/secondary systems for the assumptions and range of parameters considered. [ABSTRACT FROM AUTHOR]

In line with the mission of the National Park Service, the Zion National Park Visitor Center was designed to use 70% less energy than a comparable visitor center built to Federal Energy Code 10 CFR 435 (DOE 1995). The authors and NPS staff used an integrated design process, including extensive simulations, to minimize the energy consumption. The result was a passive solar commercial building that has a good thermal envelope, daylighting, and natural ventilation. Passive downdraft cooltowers provide all the cooling. Two Trombe walls provide a significant amount of the heating. After two years of metering, the results show a net energy use intensity of 24.7 kBtu/ft² (280.5 MJ/m²) and a 67% energy cost saving. Low energy use and aggressive demand management result in an energy cost intensity of $0.43/ft² ($4.63/m²). The paper discusses lessons learned related to the design process, daylighting, PV system, and HVAC system. [ABSTRACT FROM AUTHOR]

An independent dehumidification air-conditioning system has been built in Beijing, China. The dehumidificaiton is done by a hot water-driven liquid desiccant dehumidification subsystem. This paper reports results of field measurement of the system, which shows that the system can produce a comfortable indoor environment even in very humid weather. On dry days, the dehumidification system bears around 40% of the total load, while on humid days, it bears around 50%. Economic comparison of the independent dehumidification system and a conventional system indicates that the two systems have equivalent distribution power consumption, but the former one may save about 30% cooling source cost when the price ratio of electricity to heat is reasonably set. [ABSTRACT FROM AUTHOR]

This paper introduces the modeling of single-split coil room air-conditioning systems governed by modulating control action for use in building energy simulation. The model calculates energy consumption, sensible and latent cooling capacities of the split coil system at part-load operation, matching the sensible and latent cooling zone loads. As a result, the zone air states can be exactly determined. The model of the split system under two-position control has previously been developed and verified (Neymark and Judkoff 1998, 2000; Knabe and Le 2000a). Results of the simulation show a significant impact of the controller type on both room comfort (temperature and humidity) and energy consumption. [ABSTRACT FROM AUTHOR]

Many studies have highlighted that American supermarkets are energy-intensive commercial users of energy with approximately 54.5 billion kWh of electricity consumed annually. Refrigeration and HVAC systems account for about 50% and 10% of the electrical load, respectively, and refrigeration compressors alone constitute about 30%. There is a direct and strong interaction between the refrigerated display cases and .space conditioning .systems and the store air conditions. The conditioned store air exchanges heat and moisture with the refrigerated cases. Most refrigerated cases are designed to operate in an environment of 55% RH and 75 °F (24 °C). However, removing additional moisture with HVAC systems to lower store RH levels at 7.5 °F(24 °C) could yield overall HVAC and refrigeration energy cost savings. Drier store air will reduce the latent load on the refrigeration compressors by reducing the moisture entering the display cases. This will lead to less condensation and frost formation, reductions in defrost cycles, decreases in anti-sweat heater energy requirements, and improvements in temperature stability of products. It has been over a decade since Howell and Adams (1991) surveyed the "Effects of Indoor Space Conditions on Refrigerated Display Case Performance " under ASHRAE Research Project 596. At that time they cited the "limited amount of experimental or measured data available." Since then, laboratory and field work in this area has generated significant additional findings, although not always extensive or consistent in their results. This paper will provide an updated review of currently available databases, from computer simulations, laboratory tests, and field evaluations, that address the effect of supermarket humidity on refrigerated case energy performance. The findings from this database review will he tabulated by case type (if individual case data are available), humidity range (from 55% down to 35% RH. when provided), and case energy performance impact (separately for compressor energy, defrost energy, and anti-sweat energy, whenever possible). Inconsistencies in this group of findings will be highlighted, potential sources for differences in these findings will be explored, and conclusions regarding any consensus in these findings will be offered. A comparison will then be made to data published in the ASHRAE Handbooks along with recommendations for any revisions. Finally, recent guidance from ASHRAE has encouraged the incorporation of "rules of thumb" in the Handbooks, so a generic nomograph is presented that could provide the basis for estimating refrigerated case energy consumption and demand reductions at lowered humidity levels. [ABSTRACT FROM AUTHOR]

Fan energy use in variable-air-volume (VAV) systems can be reduced by resetting the supply duct pressure. The standard way to reset duct pressure is by controlling the most open terminal damper to a nearly open position. This strategy is rarely used because of a variety of issues including sensing limitations, network bandwidth, and stability. This paper describes the development of a new method of determining the critical supply duct pressure for VAV systems. The method relies on a short, simple functional test and a data processing technique that is based on a simple model of the system behavior The method can be implemented during normal system operation, and it could be automated. The system model includes the effect of duct leakage, which offers the potential for dual use as a duct leakage diagnostic. Results from experiments on a laboratory-scale system demonstrate good accuracy for determining critical pressure and moderate accuracy for determining duct leakage. Results from experiments on two commercial air-handling units demonstrate that the method is practical and that it offers the potential for large energy saving. [ABSTRACT FROM AUTHOR]

Air-to-air energy recovery can be used to reduce ventilation loads for small commercial buildings. Enthalpy exchangers are one approach to energy recovery that is commonly employed. An alternative technology involves the use of a heat pump that operates between the ventilation and exhaust streams. In this paper, the performance of a ventilation heat pump heat recovery unit was studied through simulation. A model of the heat pump was developed and validated using manufacturers' and laboratory test data. This component model was then incorporated within a system simulation to investigate operating cost savings for the heat pump relative to a base case that does not employ energy recovery but utilizes fixed minimum ventilation rates with an enthalpy economizer. The operating costs were found to be greater than the base case in moderate climates with relatively small savings in more extreme climates (hot or cold). The performance is not competitive with the performance of enthalpy exchangers or demand-controlled ventilation. The breakeven ambient conditions for positive savings utilizing a ventilation heat pump were also investigated. The primary performance penalties associated with the use of a heat pump are added fan and compressor power consumption, along with lost economizer savings. [ABSTRACT FROM AUTHOR]

The ventilation airstream required to maintain acceptable indoor air quality is typically a .significant contributor to the total heating and cooling load in commercial buildings. Demand-controlled ventilation (DCV) and enthalpy exchangers are two technologies that can be used to reduce ventilation loads and overall operating costs. This paper evaluates the operating cost savings and overall economics associated with these two different ventilation load reduction technologies for a variety of small commercial building types and climates. A specialized simulation tool was developed and utilized to perform the evaluations. Both demand-controlled ventilation and enthalpy exchangers were shown to result in significant operational cost savings as compared with fixed ventilation and no energy recovery in a number of small commercial buildings and locations. For both technologies, the savings potential and economic payback are better in more extreme climates. The opportunities are particularly great in cold climates because the ventilation load is a larger portion of the overall toad. For retrofit applications, demand-controlled ventilation (DCV) with an economizer was found to give the greatest savings in utility costs for all the buildings and climates considered. Air-conditioning utility cost savings for DCV of up to 52% were found for offices and restaurants. Payback ranged from about one to six years for most locations. Although utility cost savings were found to be less for enthalpy exchangers, they have the advantages of allowing smaller primary cooling and heating equipment for new applications and providing better indoor air quality. The operating cost savings for both DCV and enthalpy exchangers are dependent on assumptions concerning occupancy. The impact of occupancy schedules on cost savings for DCV and enthalpy exchanger systems should be considered in more detail in future studies. [ABSTRACT FROM AUTHOR]

This paper reports the relative energy consumption of prototype VAV and CAV air-conditioning systems under various load conditions simulating those of a typical office building in humid tropical climates such as Singapore's. Tests were conducted inside two adjoining environmental chambers where space loading was varied from 0.217 to 0.295 kW/m² (68.81 to 93.54 Btu/h ft²) with corresponding sensible heat ratio (SHR) ranging from 0.65 to 0.9. The VAV system consistently consumed less energy compared to the CAV system under constant as well as variable load conditions. The percentage energy saving ranged from 21.97% at 0.217 kW/m² (68.81 Btu/h ft²) to 12.42% at 0.295 kW/m² (93.54 Btu/h ft²) under constant loading, and it decreased with increased space loading. The experiments measured moderate energy savings under the experimental conditions that are assumed to be the typical load condition in Singapore. Because the implementation costs are significant, it appears that a VAV system has marginal economic benefit in Singapore. [ABSTRACT FROM AUTHOR]

This paper summarizes key results of ASHRAE Research Project RP-1137, which sought to quantify the benefits and longevity of the recommissioning process on variable air volume (VAV) systems that incorporate direct digital control (DDC). Field testing was completed in three diverse facilities over a period of up to two years, generating three data trends. General performance indicators were compared using the data collected prior to commissioning, immediately after commissioning, and long after commissioning was completed (a minimum of six months later). Key performance indicators included: improved DDC system accuracy, indoor air quality (IAQ), and energy efficiency/savings. It is important to note that RP-1137 did not seek to determine all possible recommissioning benefits, only to quantify some of the benefits using field testing and laboratory experiments. This research indicates that commissioning is beneficial and that system recommissioning is typically justified within a time period similar to the capital payback period. Conclusions are limited to the time period specified: thus, the longevity of recommissioning is at least equal to the payback period but cannot be predicted beyond this within RP-1137. [ABSTRACT FROM AUTHOR]

Within rating procedures established by the U.S. Department of Energy, benchmarks have been established for the comparative performance of heat pumps and air conditioners. The heating seasonal performance factor (HSPF) and seasonal energy efficiency ratio (SEER) index heating and cooling season performance, respectively. Although the procedures result in a highly desirable standard metric, the climate-related limitations of the published values must be understood--particularly when attempting to extend performance prediction across regions. This paper describes evaluation of climate-related variation of heat pump and air-conditioner performance. Operating seasonal efficiencies are statistically related to location-specific winter and summer design temperatures and manufacturers' equipment ratings. Implications are discussed. [ABSTRACT FROM AUTHOR]

The life-cycle assessment (LCA) methodology is used in this paper to assess the environmental effects of air-handling units (AIIU) over a 20-year life cycle. This assessment is based on quantifying the consumption of resources (energy and materials,), the harmful emissions into the environment (`air; water, and soil), and the potential changes in the environment (climate change, acidification, and ozone production,). A normal AIIU, with a face velocity of 3 m/s (600 fpm), and a small AIIU, with a face velocity of 4 m/s (800 fpm), are investigated with and without two types of air-to-air energy exchangers (plate and rotating wheel). The research demonstrates the following benefits of air-to-air energy exchangers: reduced energy consumption, reduced emissions to the environment, and reduced potential harmful changes in the environment. For both of the AIIUs' studied, these benefits are several times greater than the burdens arising from the production and operation of the AIIU, where the function of the AIIU is to provide 2000 L/s (4200 cfm) of outdoor air to the building space for 2500 h/year, but not to condition this air A larger AIIU with an air-to-air energy exchanger of higher efficiency has the smallest harmful effect on the environment. [ABSTRACT FROM AUTHOR]

A representative "worst-case" office environment, which defines the size and volume of the office space, the amount and type of office furniture surface area, and the outdoor, clean airflow rate is necessary to estimate the impact of office furniture emissions on indoor VOC concentrations based on the emission rates measured from chamber tests. In this study, 31 randomly selected floor plans from North American office buildings were analyzed in detail. The floor plans were from projects in late 2004 and early 2005 and were provided by an industry cross section of seven major office furniture manufacturers. The analysis included documenting the potential emitting surface area for each workstation and a determination of how much common office space (aisles, etc.) was present and shared between workstations and other adjoining spaces. The 90th percentile conditions for total furniture surface area within the 50th percentile workstation footprint sizes were identified from the more than 5000 workstations analyzed to provide a representative "worst-case" office environment model (i.e., occupant exposure scenario). Based on the analysis, the representative "worst-case" standard open plan office environment for a single workstation system is defined as 5.94 m2 (64 ft2) floor area by 2.74 m (9 ft) high (576 ft3 or 16.3 m3), accounting for a standard 1.83 m × 1.83 m (6 ft × 6 ft) open plan workstation system, traffic area, and support space for shared copiers, files, storage, etc. The space is assumed to be occupied by a single occupant and has an outdoor or clean air ventilation rate of 4.17 L/s (8.84 cfm), in accordance with ASHRAE Standard 62.1-2004. The representative "worst-case" standard private office environment for a single workstation system is defined as 23.78 m2 (256 ft2) floor area by 2.74 m (9 ft) high (2304 ft3 or 65.2 m3), accounting for a standard 13.38 m2 (144 ft2) private office workstation system, traffic area, and support space for shared copiers, files, storage, etc. The space is assumed to be occupied by a single occupant and has an outdoor or clean air ventilation rate of 9.63 L/s (20.4 cfm) in accordance with ASHRAE Standard 62.1-2004. A comparison to historical office environment models is included. [ABSTRACT FROM AUTHOR]