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Heating Degree Days at 65°F (HDD65) is still utilized by ASHRAE Standard 169 for determining Climate Zones and in other fundamental HVAC resources, such as Air Conditioning Contractors of America's (ACCA's) Manual J and S calculations. The U.S. Energy Information Administration (EIA) also uses HDD65 and it even occurs within the Passive House Institute US (PHIUS) where heating is not in demand until Outdoor Air Temperatures (OAT) reach 45°F. This paper explores and supports utilization of Heating Degree Days at 55°F (HDD55) for building energy analysis in heating dominant climates. This is supported by EnergyPlus modeling results for a sample of building types. A degree days overview on Energycap states that "The 65-degree balance point standard was developed 75 years ago to help the gas industry predict heating loads in residences. Studies back then showed that when the average daily temperature fell below 65°F, residences began turning on the heat." Today, HDD65 doesn't reflect structures built to modern energy codes, because internal loads are offsetting thermal envelope losses and when combined with the continued tightening of ventilation energy recovery requirements, heating is not necessary until much cooler than 65°F. According to a Regional Technical Forum (RTF) presentation titled "Overview of Updated Commercial EnergyPlus Building Models and Alignment with CBSA Data" dated August 31, 2021, the 'apparent balance point range between 50-60°F' was the reasonable OAT before heating was utilized by occupants. When energy modeling to HDD65, decisions are being made relative to temperature ranges that have minimal impact on building energy use. For example, when the OAT is in the 50-65°F range, this may mean more economizer hours are available without having to reheat the outdoor air or heat exterior spaces/operating zones. This would decrease the amount of energy the building utilizes, allowing for more accurately sized equipment. Similarly, utilizing Cooling Degree Day's at 50°F (CDD50), as ASHRAE Standard 169 does to determine Climate Zones, to predict cooling loads isn't appropriate as most building types don't need cooling starting at 50°F. Economizers are essentially mandatory for larger buildings which might need cooling at 50oF OAT, but smaller buildings will possibly be in heating mode when the OAT is 50oF. Utilizing CDD in the range of 60-70°F would give a more accurate representation of required cooling loads and will also be a minor focus of this technical paper. New HDD and CDD figures should be produced for ASHRAE Standard 169, Technical Resource Manuals (TRM's), and other publications that utilize degree days. With this information, end users can better analyze the weather's impact on actual building energy usage and better determine equipment sizing and other impacts. [ABSTRACT FROM AUTHOR]

This paper, concerned with the low and ultra-low-temperature district heating goals of several countries for decarbonization, reveals the temperature mismatch between existing heating and cooling equipment and the thermal supply. The industry and the energy sector aim to resolve this conflict by total electrification with renewables and heat pumps for temperature peaking and, or equipment oversizing. This study shows that both measures defeat the purposes of decarbonization and quantify the carbon dioxide responsibility in embodiments and during operation according to exergy destructions. It has been concluded that widely available but with low exergy waste and solar energy resources can be mobilized for decarbonization in the building sector only with temperature-compatible heating and cooling terminal units minimizing the temperature mismatches. In this respect, a new panel radiator with heat pipe technology, which can satisfy indoor thermal loads with supply temperatures as low as 35oC (95oF) and sensible cooling loads as high as 19oC (292 K, 66.4oF) with little oversizing, is introduced. Test results from the ASHRAE Standard 138 are discussed. [ABSTRACT FROM AUTHOR]

This paper analyzes the performance uncertainty of heat pump(s) of three different design cases that employ the different number (one unit, two units, three units) and sizing of heat pumps in an office building. Because the thermal behavior of a building is highly stochastic due to uncertain factors such as infiltration/ventilation, heat generation from people, lights and equipment, indoor setpoint temperature, the authors assumed three use scenarios (low/medium/high). Then, the authors used EnergyPlus simulation runs developed by US DOE and evaluated the performance uncertainty in terms of heat removal, energy consumption, PLR, and COP. It was found that the PLR and COP of the heat pump(s) are more influenced by the design cases than the use scenarios. In addition, the ranking of the design cases also varies under different cooling loads. This study suggests that for rational design making of heat pumps for a building, stochastic analysis of the system performance is necessary. [ABSTRACT FROM AUTHOR]

Due to air conditioner (AC)/heat pump unit fault, cooling capacity degradation usually exists in residential buildings. This sometimes makes the heating, ventilation, and air-conditioning (HVAC) system struggle in maintaining thermal comfort when the cooling load is getting higher, especially in extreme weather events (e.g., heat waves). A potential solution to tackle these issues is to pre-cool the house to deal with the limitation of house thermal mass or the HVAC capacity. Adaptive model-predictive control (AMPC) is a promising control strategy that can help mitigate those over-heating risks. It predicts the future system state and makes appropriate actions through optimizations ahead of time, and thus effectively responds to disturbance variations (e.g., weather). Optimization is essential to AMPC, but matrix multiplication and inversion cannot be executed online in most existing building controllers. Therefore, AMPC informed rule extraction is proposed to extract simple operation rules from the results of a large-scale AMPC offline implementation. Then, those computationally efficient simple rules will be online executed in the residential HVAC controller. The goal of rule extraction is to select the minimum sets of inputs and feed them to the rule-based controls (RBC) and maintain the same or close levels of energy consumption and thermal comfort with the AMP simultaneously. The AMPC-informed RBC avoids the online execution of computationally expensive optimization, thus alleviating computation load in building HVAC controllers. It is anticipated that if rules are extracted with large sets of data covering different operation scenarios and climate zone, these heuristic rules can be used by practitioners and homeowners, even without a learning model-based adaptive control framework. This paper implements an AMPC in a virtual testbed of a DOE prototype EnergyPlus residential building model. Classification and Regression Tree (CART) are adopted as the rule extraction algorithm to extract operation rules from the AMPC results. The test case is for RBC with an AC unit cooling capacity degradation under an extreme weather event of heatwaves. A preliminary comparison of the performance of ad-hoc RBC, AMPC, and AMPC-informed RBC strategies will be presented. [ABSTRACT FROM AUTHOR]

In 2016, Kujak presented a current state of how to apply hydrocarbon safely per standards consideration and methodologies for direct expansion air conditioning applications. Refrigerant charge limits at the time were very restrictive and did not allow for larger capacity direct refrigerant expansion systems. In recent years, the HVACR industry has been actively investigating the safety of flammable refrigerants by determining their risks, potential occurrences and severity of events and hydrocarbon refrigerant charges have increased significantly. This paper will provide an updated view of the selection challenges faced by air conditioning product designers and compare the various flammability characteristics of R290 compared to R454B. It will give an updated overview of standards methodology to determine the refrigerant charge and resulting cooling load to compare various flammable refrigerants for ASHRAE 34 Standard Class 2L, 2 and 3 refrigerants. In addition, the authors investigated the optimization of blends using R290, R1270 and RE170 to understand if there are possible optimization of properties and flammability limits to increase refrigerant charges. [ABSTRACT FROM AUTHOR]

Recently, thermal comfort in newly built stadiums is having increased attention. For example, in the last five years 8 air-conditioned stadiums were built in Qatar as they prepare for the next FIFA world cup. Moreover, stadiums in both Saudi Arabia and UAE are being designed to be air-conditioned as well. The main effect on the cooling load calculation comes from the hot ambient infiltrated air. This paper investigates the effect of stadium oculus size, height and shape on the amount of infiltrated air into the cooled space. Computational Fluid Dynamics (CFD) is utilized to simulate the wind air flow around and inside the 3D model of a typical stadium shape. The numerical model adapts both mass, momentum and energy conservation equations. The turbulence is modeled using RNG k-∊ model, as it is the most applicable and economic model for industrial applications. Parametric study is made to investigate the effect of changing the canopy height and oculus size on the amount of infiltrated air. Each geometrical configuration is tested against different wind speeds blowing parallel to the oculus long side. The effect of the infiltrated air is depicted by the effect of wind on the inner air velocity near the FoP. The results show that decreasing the oculus area from (129 X 92) m2 (630 X 300) ft2 to (105 X 68) m2 (345 X 223) ft2 can reduce the effect of infiltrated air by 50%. However, while keeping the oculus area unchanged, the oculus with oval shape showed almost the same air velocity pattern and averge velocity of the rectangular one with lower speeds at the FoP upstream part. Also, increasing the canopy height between the oculus and the field of play from 15 to 22 m (50 to 72 ft) can decrease the effect of the infiltrated air by 25%. However, increasing the canopy height beyond 22m (72 ft) resulted in a negative impact on limiting the infiltrated outside air amount. Three different canopy profiles were simulated in order to depict the effect on infiltrated air. Sharp edged canopy resulted in an average inside air velocity of about 0.7 m/s (1.56 mph), while changing the profile into a smoother one resulted in decreasing the average velocity to 0.35 m/s (0.78 mph) Making the canopy profile even more smoother with an aerofoiled shape has resulted in lowering the average velocity to 0.25 m/s (0.56 mph). This paper gives a general guideline for architects while designing a semi-open air-conditioned stadium in order to minimize the required cooling load for acceptable thermal conditions. [ABSTRACT FROM AUTHOR]

Zone minimum airflow set point in a single-duct VAV terminal unit with reheat has a great impact on zone reheat requirement and ventilation efficiency. Lowering the set point reduces the zone reheat requirements but drops the ventilation efficiency and thereby increases the ventilation load. When the economizer is enabled, a large amount of fresh air is introduced into the system, and then the set point can be lowered to reduce reheat requirements without any effect on ventilation load. Thus, this paper introduces a control strategy to reset the minimum airflow set point during partial or full free cooling mode and measure its performance under various conditions through simulations and experiments done in fully instrumented VAV systems located in the HVAC lab at the University of Cincinnati. The experiments were conducted on chilled-water VAV system that serves three controlled zones with hot-water reheat VAV boxes controlled by a typical commercial BACnet web-based building automation system BAS. The simulation studies were conducted using the building energy simulation software EnergyPlus to evaluate the strategy in different locations. The results show that, depending on locations, the minimum airflow rate resetting strategy can reduce the reheat requirement by 12 -32%, fan energy use by 1.5 -6%, and the cooling load by 0.5% to 1%. [ABSTRACT FROM AUTHOR]

As more buildings are connected to cloud-based large data systems, there is an opportunity to learn from the data. Predictive load and energy modeling calculations, which have long been performed based on assumptions, can be validated, or adjusted based on accrued data from in-service buildings. This paper publishes zone sensible cooling loads, based on historical data. The results should serve as a guideline to cooling load and energy modeling calculations in future designs. The data assessed includes room temperature, supply temperature, and airflow, collected on 5-minute intervals for one year of operation. Data assessed is limited to the cooling hours between 8 AM to 6 PM, May through October. Sensible load was calculated for each hour using the difference in temperature, multiplied by the airflow. Zones are classified into Zone Type, based on the room name where the thermostat resides. Loads are normalized to zone area. The results include (1) cooling loads for the 75%, 50%, 25%, 2%, and 0.4% exceedance values, and (2) diversity factors indicating the maximum simultaneously occurring load in multiple zones of the same type. [ABSTRACT FROM AUTHOR]

District Cooling is an energy-efficient technology that can satisfy the cooling demands of regions with extremely hot climates such as the middle east. Designing and operating these plants requires accurate modeling of the existing cooling load created by the building stock connected to the central plant. During the design stage, building archetype models can be used for sizing district cooling load, whereas both the input and output uncertainties of these models have not been well addressed. This paper conducts a comparative analysis of two methodologies of building archetype development, develops an importance ranking for the input parameters of these models, and tries to quantify the uncertainty of the cooling energy output due to input value uncertainty. It develops a region-specific highrise residential archetype and compares it to the US DOE Prototype models. It also develops the parameter ranking using a global sensitivity analysis methodology. It is found that the most practical approach towards the development of building archetypes for a specific region is the development of region-specific models adapted to local practices rather than converting standard models for accuracy and computational cost considerations. It was also concluded that a set number of parameters are responsible for most of the model's output variability. Finally, this study demonstrated the usability of the building archetype models for the hot and arid climate. [ABSTRACT FROM AUTHOR]

The requisite amount of ventilation air of the HVAC system depends on heating/cooling load. The load on HVAC system varies with the condition of outdoor ventilation air that may requires additional heating, cooling and humidification or dehumidification. In most of the cases, outdoor air is more economical to use than recycled return air. The heat transfer in an exterior rectangular duct is a function of solar irradiation, air gap width, mass flow rate and pressure, wall and air temperatures. The significance of analysis of an outdoor HVAC rectangular duct is important, for example, in modeling photovoltaic solar wall structures. The complete duct design is based on complete information for the given design conditions and limitations of operation results. The design of an outdoor duct is either based on a velocity method, an equal friction method or a static pressure recovery method. The design of mass flow rate through the duct is based on heating/cooling load on the ventilation system. The aim of the paper is to present an improved method for design, ventilation and noise assessment of an outdoor duct for pre-heating of fresh air through an example of an outdoor duct [2.5 mm aluminum rectangular duct with a size of (0.25 m (H) X 1.0 m (W) X 3.0 m (L))]. The given outdoor duct is exposed to a steady solar heat flux and is installed on a well insulated building façade. The sensitivity analysis for an outdoor duct is conducted for critical design of ventilation requirements and materials with supply of varying outdoor mass flow rate to a single building zone. The improved method is useful for accurately predicting ventilation air requirements through an outdoor duct. Noise, defined as 'a sensation of unwanted intensity of a wave', is perception of a pollutant and a type of environmental stressor. An environmental stressor such as noise may have detrimental effects on various aspects of health. The unwanted intensity of a wave is a propagation of noise due to transmission of waves (viz. physical agents) such as sun, light, sound, heat, electricity, fluid and fire. The noise scales/charts are calculated from the newly devised noise measurement equations and their units by the author. Furthermore, based on these newly devised noise measurement equations, noise assessment calculations of an outdoor HVAC duct exposed to solar radiation are also presented. [ABSTRACT FROM AUTHOR]

Although EnergyPlus is widely used by researchers and engineers for whole building energy simulations, it is not capable of modeling variable airflow fanpowered terminal units (FPTUs) using build-in modules. Energy Management System (EMS) and user-defined modules in EnergyPlus provide flexibility in modeling customized equipment and systems. In this paper, the performance model of variable airflow series FPTUs was implemented using EMS and user-defined modules. The performance model was also integrated with the rest of HVAC system to investigate the impact of terminal unit fan operation on system energy consumption. A single story, five-zone office building model was created in EnergyPlus as the testbed. Simulations were performed with four different climates and two terminal unit fan operation modes. Compared with the constant airflow series FPTUs, simulation results revealed that the variable airflow series FPTUs can save up to 85% of terminal unit fan energy consumption. It is also shown that the variable airflow series FPTUs can save central supply fan and cooling coil energy consumption by 4% and 6%, respectively, due to decreases in motor heat gains from terminal unit fans and primary air reduction at a given zone cooling load. Although the heating energy is increased due to the reduced heat gain from terminal unit fan motors, the use of variable airflow series FPTUs can lead to 15-35% savings in the annual energy consumption of HVAC system. [ABSTRACT FROM AUTHOR]

Grid-interactive efficient buildings (GEBs) require quick and accurate manipulation of flexible electrical loads. Heating, ventilating, and air conditioning (HVAC) loads are particularly well suited for demand flexibility control by utilizing thermal mass in building structures. The HVAC load and its responding zone temperature (ZT) can be optimized by model predictive control (MPC) to minimize the operation cost with the indoor comfort constraint. However, due to the lack of reliable and affordable energy meters, the current HVAC demand control is implemented using ZT feedback control with the responding ZT optimized by MPC as the setpoint and the HVAC load as the response. Unfortunately, the building thermal mass makes the actual HVAC load significantly different than the optimized HVAC load, which is the on-demand setpoint, with potential demand penalty. Low-cost virtual flow meter technology makes the cooling load measurement at air handling units (AHUs) available, thus energy feedback control can be applied to actively control the cooling load of AHUs at its on-demand setpoint. The objective of the paper is to preliminarily investigate the demand flexibility control performance of the energy feedback control at AHUs. First, the energy feedback control at AHUs is introduced. Then, the performance of a single zone AHU is simulated and compared between the ZT feedback control and energy feedback control. Finally, a field experiment is conducted on a 7-ton single duct variable air volume AHU with these two different controls. Experimental results show that the cooling load with the current ZT feedback control drops to the on-demand setpoint after 25 minutes. On the other hand, the energy feedback control can reduce the cooling load to the on-demand setpoint in less than 3 minutes. Therefore, the active energy feedback control can significantly advance the current ZT feedback control by quickly and accurately controlling the cooling load at AHUs to avoid the demand penalty. [ABSTRACT FROM AUTHOR]

Single-duct variable-air-volume (VAV) systems are widely used to condition buildings in the United States. When such a system serves multiple zones with different load profiles, simultaneous cooling and heating frequently occur. To avoid this inefficient scenario, dual VAV systems, where one VAV system provides cooling and the other provides heating, could be used. This paper proposes a new configuration for dual VAV systems to improve their operation to reduce the loads on cooling and heating equipment and thereby total energy use. The proposed configuration and its sequence of operation can reduce cooling and heating loads by eliminating simultaneous heating and cooling and maximizing the use of outdoor air (OA) for cooling and return air for heating. The performances of both single and dual VAV systems are simulated for given buildings and for different locations to estimate load reductions and fan energy savings achieved by the proposed dual VAV system configuration and control strategies. The simulation results that show significant heating load reductions of up to 89%, great fan savings up to 15%, and minor cooling load reductions of around 1% can be obtained, depending mainly on load variations and locations. [ABSTRACT FROM AUTHOR]

In Canada, builders and energy advisors use HOT2000 for simulation of new housing and retrofits for various labelling, energy rating and incentive programs as well as code compliance. HOT2000 is a monthly building energy simulation tool, specifically made for low-rise residential buildings. It calculates monthly loads from a combination of first principles, and various simple mathematical models developed from hourly simulation tools. As a consequence of the methodology, many state-of-the-art Energy Conservation Measures (ECM) can not be simulated accurately in HOT2000. A Housing Technology Assessment Platform (HTAP) software was previously developed, using HOT2000 as the simulation engine. HOT2000 was chosen as the simulation engine, because of its wide adoption and acceptance by builders and professionals in Canada. HTAP can run parametric runs, and provide energy demand and costing for a variety of ECMs. However many ECMs require hourly simulations to provide accurate energy demand estimates. In order to be able to evaluate these ECMs in HTAP, a methodology has been developed to estimate hourly heating, cooling, domestic hot water, and plug load profiles using monthly loads, and hourly climate data. This paper presents the approach and its limitations, as well as some validation results. [ABSTRACT FROM AUTHOR]

Optimal sequencing of chillers and boilers based on short-term energy demand forecasts represents an untapped opportunity to improve the energy efficiency of central heating and cooling plants. This paper presents a case study conducted in a heating and cooling plant with four boilers and five chillers. Time-series modeling methods are examined to forecast hourly heating and cooling loads 24 hours in advance. The results indicate that a hybrid of autoregressive moving average and change-point models can parsimoniously predict the heating and cooling loads. A boiler and chiller sequencing scheme that uses the day-ahead load forecasts is determined by using a nonlinear programming solver. The implementation of this sequencing scheme is estimated to result in a 4% reduction in heating and 25% reduction in cooling energy use. [ABSTRACT FROM AUTHOR]

In commercial buildings with high glazing fractions, the transmission of solar radiation to perimeter spaces represents an important source of thermal influx, and is typically controlled with shading devices such as interior venetian blinds. The influence of interior blinds on cooling and heating loads is not straightforward or obvious: they may actually cause increases in cooling loads if they prevent solar influx from reaching room surfaces with thermal mass, while rapidly transferring the solar energy to the room air via convection. This paper presents the results of experiments conducted in an outdoor office-scale façade performance testing laboratory, designed to measure the effect of slat-type blinds on cooling energy. A number blind positions, slat angles, and slat colors were tested. A simulation model of the lab was developed in parallel to check the agreement with the blind modeling algorithms of EnergyPlus, by comparing daily energy consumption and the magnitude of peak cooling load. While an exterior blind was found to greatly reduce energy consumption and peak cooling load as compared to un-shaded glazing, all cases with indoor blinds showed minimal reductions in both energy consumption and magnitude of the peak. For both dark and light-colored interior blinds, the cases with slat angles at 45º resulted in higher energy consumption than the open slat cases, and the dark blind also exhibited a greater peak load. The model closely matched experimental results for bare glazing, but tended to overestimate the reduction in energy consumption and cooling load in the presence of blinds. In addition to the presentation of experimental results, this paper will present a critical a discussion of some key considerations for modeling a space with interior blinds. [ABSTRACT FROM AUTHOR]

The first part of this paper (Revising ASHRAE Climatic Data for Design and Standards--Part 1: Overview and Data [1613-RP]) provided a summary of the changes made to the tables of climatic design conditions in the 2013 ASHRAE Handbook--Fundamentals. This second part describes changes that are made to the clear-sky solar radiation model. The model provides a simple way to calculate solar irradiance components from a pair of location-specific parameters for any location in the world, and is used in particular to evaluate cooling loads in buildings. The model was first introduced in the 2009 Handbook but frequently exhibited an apparent bias (direct normal irradiance too low, diffuse irradiance too high), which presumably resulted from a high bias in the aerosol data sets used for its derivation. This paper explains how the bias was corrected for the 2013 Handbook. Various sources of gridded aerosol data, derived from satellite observations, were combined and calibrated with sun photometric data from 652 ground stations. A statistical analysis was performed to determine the most appropriate statistical estimator of aerosol optical depth to use. It was found that because of the log-normal distribution of aerosol optical depth over monthly periods, using its median (rather than its mean) translates into irradiance values that are more representative of average conditions. A simple linear correlation was established to correlate the median aerosol optical depth to its mean. Finally, the derivation of a condensed set of equations, which constitutes the clear-sky model as it appears in the Handbook, was revised to cover a larger set of aerosol and surface albedo conditions. The clear-sky model has been validated against clear-sky solar irradiance data from a number of research-class stations, including Darwin, Australia; Golden, Colorado; and Xianghe, China. Based on the analysis summarized here, the clear-sky model is found to be in reasonable agreement with measured values for these stations, even under very hazy conditions. [ABSTRACT FROM AUTHOR]

This paper presents a practical and useful engineering method for the design and control of optimum efficiency water cooled chiller plants. The proposed design approach uses the chiller load normalized efficiency characteristics of chillers, cooling towers, and condenser water pumps to optimize design and control based on the concept of derivative efficiency, a term which is applied to the operation of chillers, condenser water pumps and cooling tower fans. One of the significant recommendations in the paper is that after the chiller plant is fully designed the chiller plant sequence of control can be based primarily on just two parameters, chiller lift and chiller load. [ABSTRACT FROM AUTHOR]

Historically, detailed building energy simulation programs have been used to either perform heating and cooling load calculat ions for HVAC equipment sizing purposes or to predict the whole building annual energy usage for evaluating a particular design. Based on user inputs that describe the building and imported weather data, these software programs simulate the hourly building performance over the course of a year, and provide outputs such as energy consumption by end use, demand, utility costs, etc. In this conventional approach, the building design parameters are essentially fixed by the user before the simulation is performed. Therefore, the standard practice is to use these programs for design analysis rather than design synthesis. The intent of the automated design methodology concept proposed in this paper is to use detailed building energy simulation programs in a different manner. Due to design constraints, aesthetic issues, program restrictions, or specific owner requirements, the optimal design may not be always desired. More valuable to the designer than determining the optimum is knowing the "latitude" s/he has in changing certain design variables while maintaining pre-selected desired performance criteria. The goal of the automated design methodology is thus to provide designers with a decision support tool rather than an optimization tool, i.e., a manner of generating numerous (in the hundreds) design alternatives which meet pre-stipulated performance criteria from which the designer can make the final selection for a particular project. Implementing such a methodology early in the design process will provide building professionals with a much larger solution set of possible designs options (which may not have been selected from intuition and experience alone). This paper describes the concept of automated design, lays the foundation for building such a methodology, and provides an illustrative example which begins to explore one possible approach of practically implementing the automated design approach. [ABSTRACT FROM AUTHOR]

This paper reports the application of a hybrid ventilation system to a high-rise building, especially on the indoor environment in the building and the effects of the system on the variation of thermal load. The hybrid ventilation system executes natural ventilation while operating air-conditioning systems. The number of the system applications has been increasing, but the change of thermal load by the operation method is not estimated precisely, which leads to less reliability in energy conservation effect. By the hybrid ventilation system, the thermal environment may become worse with the draft caused by natural ventilation. It is especially important to consider indoor thermal environment when ventilation openings are located in occupied zone of the building. In this paper, hybrid ventilation system applied to a super high-rise building in Tokyo, Japan is presented. The evaluation on indoor environment by measurement is discussed, which shows little problem on thermal environment. The effect of thermal mass is important for thermal load estimation, especially when utilizing "night purge" of natural ventilation. The change of thermal load is estimated by the simulation validated by the reproduction of the shift in slab temperature with estimated indoor heat generation and outdoor condition. The annual cooling load reduction is evaluated to be about 21%. [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]

A public middle school located in the Massachusetts town of Westborough is the first fully heated and cooled public school in New England using standing column geothermal wells. This successful geothermal retrofit has been functional since 1996. This paper details the performance of the geothermal system, including the performance of the standing column wells, their maintenance, and their overall heating and cooling costs. The 200 ton installation utilizes six standing column wells for earth coupling. Twenty 10 ton water-to water geo heat pump modules supply existing unit ventilators (after modification) and large air handlers. The in-place unit ventilators were refitted with new hydronic coils. This paper describes the installation, its costs, and its performance for the period from 1996 to late 2005 and illustrates the long-term thermal stability of a standing column well system. Management of the project was fully integrated. The design engineers and architects were also the construction managers. [ABSTRACT FROM AUTHOR]

High-performance glazing systems incorporate low-emissivity coating on glass, heavy gas fill in the glazing cavity, and thermally improved spacer bars instead of the conventional metal bars. The improved design and proper selection of material for spacer bars provide means to improve the overall thermal characteristics and condensation resistance of windows, particularly in the edge-of-glass region. Experimental results showed that there is an interaction between the spacer bar and sash/frame material of the window assembly that affects the overall performance of the fenestration products. In an effort to investigate the interaction between the spacer bar design and frame/sash material on the thermal performance of windows, a series of tests were performed on a number of windows in a controlled environment (e.g., laboratory testing). In an earlier study, a summary of the experimental setup and the results of testing small insulating glass (IG) units was presented to report the surface temperature distribution and condensation resistance of a set of IG units in the absence of framing material. Ten spacer bars, including conventional metal spacer, hybrid system, silicon foam, and thermally broken bars, were included in that set of IG units. The later spacer bars, were referred to as warm edge technology (WET) bars. The full documentation of that part of the study was published in Elmahdy (2002). In this paper, the results of investigating the thermal coupling effects and the interaction between the spacer bar and the window sash/frame material of a number of different spacer bar designs and frame material are summarized. The same spacer bars reported in the earlier study are included in this paper. Framing materials (wood, vinyl, aluminum, and glass fiber) were used to study the combined effect of spacer bar design and frame material on the overall window performance. The test results showed that the use of WET spacer bars demonstrated higher glass surface temperature in the edge-of-glass region, improving the condensation resistance and the overall R-value of the fenestration products relative to windows made with conventional metal spacers. There exist some combinations of certain spacer bar designs and frame material that produce favorable performance. However, it is important not to generalize the reported results due to the many varieties in frame designs and profiles that would have greater impact on the final results. On the other hand, these results provide clear indications of the interaction between spacer bar design and the frame material on the overall thermal performance of windows. As an added benefit, window designers have options to produce windows of a wide range of performance factors to meet the demands for different applications and consumers' preferences. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the conduction transfer function (CTF) and periodic response factor (PRF) methods of calculating conductive heat transfer. Different forms of the equations used in cooling load calculations are compared and contrasted. Particular attention is given to the methods included in the ASHRAE Loads Toolkit. The toolkit contains the source code for ASHRAE's new load calculation methods, the heat balance method (HBM) and the radiant time series method (RTSM). Each method uses a similar, but different, conduction calculation technique. The HBM uses CTFs and the RTSM uses PRFs. Since there are limited numbers of CTFs and PRFs in the literature, the toolkit algorithms provide a means of calculating CTFs and PRFs for stand-alone computer programs or for generating CTF and PRF libraries. This paper describes the CTF and PRF algorithms in the toolkit and demonstrates implementation of the toolkit modules in a program that calculates CTFs and PRFs. [ABSTRACT FROM AUTHOR]

This paper provides an overview of methods reported in the literature for generating typical load shapes required for the simulation of energy use and peak cooling loads in commercial buildings. It also includes a survey of available databases of monitored commercial end-use electricity data and a review of classification schemes of the commercial building stock. This study was conducted as part of ASHRAE RP- 1093, whose objective was to identify and utilize the most appropriate methods for developing diversity factors on relevant monitored sets of lighting and equipment data. The paper also provides a discussion of four methods in the literature that were adapted and combined in RP-1093 to develop a library of diversity factors and schedules for use in building energy and cooling load simulation programs. [ABSTRACT FROM AUTHOR]

The objective of this paper is to develop a simple empirical modeling approach that uses laboratory data from standard testing to represent the performance of variable air variable water (VAVW) fan coil units (FCUs) over a wide operating range. As the first step, ten horizontal high-capacity FCUs from three manufacturers were tested in a psychrometric facility with each unit being tested under 27 operating conditions at various combinations of airflow rate, entering air condition, water flow rate, entering water temperature, and water temperature rise. Then, regression analysis was conducted on the experimental data to derive performance curves that characterize the impact of varying flow and temperature on cooling capacities. A modeling approach utilizing the performance curves was developed to estimate the air and water flows responding to zone cooling load with modulation control. The developed empirical modeling approach can be easily implemented in spreadsheet-based building energy calculation to quantify the energy consumption of VAVW FCUs. [ABSTRACT FROM AUTHOR]

Many governments worldwide are setting more stringent targets for reductions in energy use in government/public buildings. Buildings constructed more than 10 years ago account for a major share of energy used by the building stock. However, the funding and "know-how " (applied knowledge) available for owner-directed energy retrofit projects has not kept pace with new requirements. With typical retrofit projects, reduction of energy use varies between 10% and 20%, while experience from executed projects around the globe shows that energy-use reduction can exceed 50%, and renovated buildings can cost-effectively achieve the passive-house standard or even approach net zero energy status (Hermelink and Muller, 2010; NBI 2014; RICS 2013; GreenBuildingAdvisor.com 2013; Shonder and Nasseri 2015; Miller and Higgins 2015; Emmerich et al. 2011). Previous research conducted under the International Energy Agency's Energy in Buildings and Communities Program (IEA EBC) Annex 46 identified and analyzed more than 400 energy-efficiency measures that can be used when buildings are retrofitted. Measures include those related to the building envelope, mechanical and lighting systems, energy generation and distribution, and internal processes. Implementation of some individual measures (such as building envelope insulation, improved airtightness, and cogeneration) can significantly reduce building heating and cooling loads or minimize of energy waste, but require significant investments with long paybacks. However, when a limited number of core technologies are implemented together, or bundled, they can significantly reduce energy use for a smaller investment, thereby providing a faster payback. In some countries, energy savings performance contracts (ESPC) have proven to be an effective tool for implementing energy retrofit projects. Nevertheless, in many countries the number of projects funded by ESPCs still do not form a significant part of the total investment budgeted by public institutions for energy retrofits. This paper presents the concept and several case studies that illustrate mechanisms that will increase the acceptance of deep energy retrofit (DER) and broaden acceptance of its implementation using ESPCs for a comprehensive refurbishment of existing buildings. [ABSTRACT FROM AUTHOR]

Saudi Arabia has been subsidizing residential energy prices for decades, drawing on its vast oil reserves. Meanwhile, electricity consumption has been steadily increasing by nearly 8% annually in the past 10 years with energy consumption per capita 3.6 times higher than the world's average. As a result, and without a mandatory energy building code, 70% of Saudi Arabian homes are today not insulated, consuming nearly 52% of electrical power generated. A critical factor in determining the overall energy consumption of residential Saudi homes is the envelope dominated cooling load. Constructing building envelope assemblies -- to optimize thermal insulating properties -- is challenging in Saudi Arabia as most small to mid-size local design firms do not have access to a database library of certified building materials. Determining a building envelope's energy performance requires energy modeling skills and tools not readily available to these firms. This has resulted in squandering significant amounts of electrical energy. An energy modeling software program is developed that is a KSA-specific, user-friendly, online and free graphical user interface (GUI) for the U.S. Department of Energy's (DOE's) EnergyPlus software, with an integrated database library of local building materials. The software enables local practitioners to evaluate alternative building envelope assemblies and the relative energy efficiency between them. Encouraging the use of energy modeling for envelopes will encourage local manufacturing and sourcing of high-end materials. This paper will present the details of the methodologies used for the software's development and design, along with result validation using real-life examples. [ABSTRACT FROM AUTHOR]

This paper compares load and energy calculations with measured building loads. Both load and energy calculations are performed by using the energy simulation software, EnergyPlus. The ASHRAE Headquarters Building Renovation Project acts as a live lab and its database can be used to validate the simulation results. The ASHRAE building, located in Atlanta, comprises more than 1600 sensors to check and record the performance with the help of the Building Automation System (BAS). The energy model involves the coupling of a Dedicated Outdoor Air System (DOAS), an ideal air loads system, and a dedicated building model. Different cases were created by using the ASHRAE standard 90.1 and by changing key parameters like plug loads, lighting loads, room temperatures, DOAS supply and temperature, etc. The predicted and measured results were used to estimate the uncertainty in calculated cooling loads due to the difficulty in accurately specifying inputs to the cooling load calculation procedures. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the variable refrigerant flow heat pump computer model included with the Department of Energy's EnergyPlus™ whole-building energy simulation software. The mathematical model for a variable refrigerant flow heat pump operating in cooling or heating mode, and a detailed model for the variable refrigerant flow direct-expansion (DX) cooling coil are described in detail. [ABSTRACT FROM AUTHOR]

Ice thermal storage is a promising technology to reduce energy costs by shifting the cooling cost from on-peak to off-peak periods. The paper discusses the application of ice thermal storage and its impact on energy consumption, demand, and total energy cost. Energy simulation software along with a chiller model is used to simulate the energy consumption and demand for the existing office building located in central Florida. Furthermore, the study presents a case study to demonstrate through real monthly utility bills the cost saving achieved by the ice storage applications. The results show that although the energy consumption may increase by using ice thermal storage, the energy cost drops significantly, mainly depending on the local utility rate structure. It found that for the investigated system the annual energy consumption increases by about 12% but the annual energy cost drops by about 36%. [ABSTRACT FROM AUTHOR]

This paper describes a study done in cooperation with the local Habitat for Humanity chapter to ensure that the houses that are built have low energy consumption to ease the burden of utility expense on the low-income clients that Habitat services. Two of the most popular house designs were modeled with energy simulation program to determine how much energy is required for heating and cooling. Both designs were single story houses, three bedrooms, about equal total window areas, and both approximately 1100 square feet (100 m²), but there were some significant differences in their energy usage, resulting from the shading of the windows. Modifications to the models were made including: orientation of the house, R-values of insulation in the walls, crawlspace and attic, U-values of the windows, conditioning and un-conditioning of the crawlspace and attic, and the set point of the thermostat; the effect of energy usage from each of these modifications is reported. An economic impact of each of the modifications was calculated, using present-day costs for the construction improvements and present-day, local utility rates for natural gas and electricity. It was found that the houses are well designed for the current rates and local climate. A 3 cent per kilowatt-hour increase in the electrical rate would make extra insulation in the attic cost effective (with a 4.5 year simple payback), and higher rate increases would make more of the modifications cost-effective. The conclusion is that the current design of the Habitat homes is optimized for the present economic conditions, but an increase in electrical rates would change that. [ABSTRACT FROM AUTHOR]

Phase-change materials (PCMs) are substances with a high heat of fusion that, melting and solidifying at a certain temperature range, are capable of storing and releasing large amounts of energy. In PCMs, energy is absorbed or released when the material changes from solid to liquid and vice versa. Different types of PCMs have been tested as dynamic components in buildings during the last four decades. Most historical studies have found that PCMs may notably improve building energy performance. Experimental results that are reported for both laboratory-scale and full-size building elements were tested in the field. Some PCM-enhanced building materials, such as PCM-gypsum boards, PCM-impregnated concretes, or PCM-enhanced fiber insulations have already found their limited applications in different countries. Today, continued improvements in building envelope technologies suggest that throughout southern and central U.S. climates, residences may soon be routinely constructed with PCMs in order to maximize insulation effectiveness and maintain low heating and cooling loads. However, PCM applications, in order to be fully effective, need to be well engineered, taking into account optimum functional temperature for the PCM, its location, and its concentration. This paper presents a short overview of basic material characteristics and energy performance data necessary for future applications of simple PCM systems in residential and commercial buildings. [ABSTRACT FROM AUTHOR]

The introduction of air, preconditioned with a renewable low exergy source, into a building envelope has the potential of reducing its energy use. Structures incorporating dual-wall construction in order to accomplish this have been shown to be effective under certain conditions, but have not been proven to be economically practical in most situations. This paper re-examines the technology and describes a practical method in which it might be applied economically. A dual envelope is created with the addition of an inexpensive, light-weight skin over a standard wood-frame construction. Air preheated through the ground and passed between the skin and the wall will provide a temperature buffer within the wall, effectively decreasing the temperature differential across it. A portion of energy lost through the exterior façade is now supplied from the ground rather than from the interior heating source. A geosolar storage reservoir provides enhanced conditioning of the interstitial air. The addition of the sheathing that forms the exterior skin increases the total R-value and thus the energy efficiency of the building. Another benefit is that of the positive pressure in the air passage: any infiltration into the room is at ground rather than at outdoor temperature, reducing convective heat losses. The geothermal component of this air introduction to the wall may be enhanced by increasing the ambient temperature of the earth with unwanted heat absorbed by the roof of the structure during the summer months. The roof of the structure is fitted with narrowly spaced runs of PEX (cross-linked poly-ethylene) pipe just below the roof surface. Water circulating between these coils and the ground serve to transfer summer heat into the ground while cooling the building. A horizontal blanket of insulation, buried around the perimeter of the building allows heat removed from the roof to be retained for winter use. In addition, cool air from the ground can also be circulated between the walls and the exterior skin during the summer to keep the structure cool. In order to establish a proof of concept of integrating this annualized geosolar exergy storage technology with the ground-coupled dynamic wall, a prototype structure has been constructed in central New York. Preliminary results are encouraging. [ABSTRACT FROM AUTHOR]

This paper deals with prediction methods for evaluating the thermal performance of various window systems, such as single glazed with blinds and exhaust system, low-e double glazed with blinds, and airflow windows (AFW), and double-skin facades. Calculation models to evaluate both loads and the thermal environment near the window were developed for each window system by solving the heat balance equation for each window element. The precision of these models was evaluated by comparing the calculated predictions with the results of tests or measurements. These models (window models)were shown to reproduce the test and measurement results reasonably well. Case studies were also conducted using annual simulations for various window systems by evaluating both thermal loads and the thermal environment near windows. It was confirmed that double-skin facades and AFW have better performance compared with other window systems when transparent glazing is used, that the low-e double glazed with blinds results in a relatively high annual cumulative cooling load due to the low heat release through the windows in the spring and autumn, and that it is possible to reduce the cooling loads and improve the thermal environment by using glazing with low solar transmittance. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of field testing to evaluate the performance of simplified and optimal control strategies for shifting peak cooling loads and reducing building energy costs through the utilization of both the passive and active thermal energy storage systems for an elementary school in Colorado. In particular, the performance of precooling of building thermal mass as well as real-time model-based predictive optimal controls is evaluated. The results indicate that the school is saving roughly 47% on its annual electricity costs by utilizing the TES operated using their optimal control strategy. [ABSTRACT FROM AUTHOR]

Data center facilities that house computer equipment represent a high capital investment and are typically designed to function for at least a few years, often without any down time. The computer equipment is usually designed with the assumption of rack air inlet temperatures in the 20-30° C range. Although there are many different perspectives for optimizing such a computing facility, ensuring device reliability by delivering uninterruptible power and cool air to the inlet of the electronics remains the most important goal. The objective of this paper is to compare two dominant airflow designs, namely, under floor supply (raised floor) and overhead supply, with specific focus on the rack air inlet temperature. Numerical models of two data center sections, representing under floor air supply and overhead air supply designs, were constructed utilizing commercial software, and the data generated from a parametric study were analyzed. The model constitutes a half-symmetry section of a 40-rack data center that is arranged in a cold aisle/hot aisle fashion. Temperature data were collected at several locations at the inlet to the racks. The effects of two different airflow designs (raised floor versus non-raised floor), supply airflow fraction, location of rack, and height of measurement were studied. [ABSTRACT FROM AUTHOR]

This paper presents the preliminary measurements performed in an indoor ice rink. The results include the cooling load, the air temperature variation at several locations, the ice temperature, and the brine temperature. The measured data will be used for the verification and calibration of a new numerical model that was developed for ASHRAE Research Project RP-1289. [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]

This paper investigates the ability of intermediate models such as zonal models to predict environmental conditions in a room. The first part compares experimental data to zonal and conventional k-ϵ computational fluid dynamics model predictions in a mixed-ventilation room. Then, in order to investigate the impact of building material moisture adsorption and desorption processes on indoor air humidity and predict humidity distribution in a room, a zonal model was integrated with a building material moisture transfer model, based on the conservation of energy and dry air and water vapor mass. The model is applied to a room conditioned by a fan-coil unit. Our results suggest that this model is able to give a satisfactory prediction of transient humidity distribution in the room as well as to provide meaningful information on cooling loads. [ABSTRACT FROM AUTHOR]

Window solar gain can strongly influence building energy consumption and peak cooling load. Shading devices such as venetian blinds, roller blinds, and drapes are routinely used to control solar gain. There is a strong need for models that allow shading layers to be included in glazing system analysis. This paper presents methods by which existing solar optical models for systems of specular glazing layers can be extended to include the effect of layers that create scattered, specifically diffuse, radiation in reflection and/or transmission. Spatially averaged optical properties (i.e., ‘effective’ optical properties) can be used to characterize shading layers, including their beam-diffuse split. Solution techniques can be formulated on the basis of matrix reduction. However, an alternative technique has been developed with the goal of computational simplicity and speed. These attributes are important in the context of hour-by-hour building energy analysis. Sample calculations are presented. [ABSTRACT FROM AUTHOR]

Buildings account for approximately 40% of the nation's total energy demand1. About 39% of total primary building energy consumption can be attributed to losses through building envelope. Therefore, building envelope load reduction plays a key role to minimize building heating and cooling load, and building electricity consumption. Phase change material (PCM)-based thermal energy storages have re-gained increased attention in recent years, in particular, for a peak load shifting of grid-interactive efficient buildings (GEBs). To simulate PCMs and facilitate the performance studies of PCM-based system using the whole building simulation program, EnergyPlus, two PCM modules have been added to EnergyPlus: the single curve model and the dual curve hysteresis model. Different from the single curve model, the dual curve model allows the melting/freezing process to follow different curves. The proposed dual curve model is useful to represent the hysteresis effect better compared with the existing EnergyPlus model. Our study found that the current hysteresis model in EnergyPlus has problems modeling the partial transition process. A static two-phase model is used to replace the current hysteresis model, and this is implemented by modifying EnergyPlus source code. Validation simulations has confirmed that our new model could successfully model the partial transition process. [ABSTRACT FROM AUTHOR]

People spend about 87 - 92% of their overall time of day in some form of indoor environment. It is also well established that buildings consume about 40% of the total electricity generated. Studies have shown that operating windows during HVAC use can increase the heating and cooling load. Until now, fixed window opening and closing schedules have been used in Building Energy Simulation engines (BES) like Energy Plus. We studied the window opening behavior of students living in a residential dorm at Syracuse University for over a year. The window opening behavior changed depending on the location of the window and the time of the year. During summer, the bedroom windows were opened substantially for a longer time and living room windows were opened briefly. During transition seasons, all windows were opened very briefly. We created a specific set of neural network models that could predict the state of the window and the duration of the window opening. We modeled the open/close state change for all three windows in three different zones using Artificial Neural Network (ANN) machine learning architecture. The three model, when trained on individual datasets generated a True Positive Rate (TPR) of 0.97, 0.99, and 0.97. The newly released Python API incorporated the models into Energy Plus. The sensible heating/cooling energy for the living room, north-facing bedroom, and south-facing bedroom were calculated based on the window schedule predicted by the ANN model. Compared to the baseline model of complete mechanical ventilation, the heating energy was reduced by 3.96% and 24.78% for north and south-facing bedrooms, respectively, for October. [ABSTRACT FROM AUTHOR]

As renewable energy resources, such as wind and solar, continue to be added to the US electric grid, the available energy produced will become more variable. Wind and solar energy resources are highly dependent on wind and solar radiation availability, which are highly varied compared to traditional electricity generation sources. With an increase in variable generation, it is beneficial for grid reliability to modulate grid loads to match available generation. This can be accomplished through building load participation in flexibility services (FS). The various primary end-uses such as heating, ventilation, and air conditioning (HVAC) and lighting in commercial buildings can provide Demand Response (DR) services such as regulation, contingency, and ramping. Overall, in the US, HVAC loads, specifically cooling in commercial buildings, account for around 15% of electricity consumption. However, these loads further vary based on the climate zone in which the building is located. To provide load flexibility, HVAC loads can be switched off for a limited time be such that the thermal comfort criterion of predicted mean vote (PMV) remains under 0.5. Overall, this study aims to estimate the amount and duration for HVAC cooling loads that can provide demand flexibility using US Department of Energy (DOE) commercial Reference and Prototype building models for small office buildings. [ABSTRACT FROM AUTHOR]

Measurement of the heat loss from equipment in buildings is necessary in order to make accurate assessments of its impact on cooling loads. Advances in the design of buildings and improvement of the thermal characteristics of insulation materials and building envelope systems have significantly reduced the cooling load from external sources; however, the addition of various types of office equipment to buildings has become a major source of internal cooling load. Some equipment includes a nameplate rating showing total power consumption, while other equipment does not. Some manufacturers measure the equipment's maximum electric power consumption and list that as a power rating on the nameplate or in the equipment literature, while others list the equipment's maximum power capacity. Since the manufacturers' power ratings, if reported, are usually based on instantaneous measurement while the equipment is working at maximum capacity, use of equipment nameplate values for cooling load calculations may lead to oversizing of air-conditioning equipment, resulting in an extra initial cost as well as higher operating costs. On the other hand, underestimating the cooling load may result in insufficient cooling capacity. Another factor affecting calculation of cooling load is the split between the radiant and convective heat loads from the equipment. The convection portion of the heat transferred from the equipment to the surroundings is an instantaneous load, since it is added to room air by natural or forced convection without time delay, whereas the radiation portion is absorbed by the surfaces of the room and then dissipated over time. Accurate determination of cooling load is important in gauging the proper size of air-conditioning equipment. This article presents experimental results for the total heat gain and radiant/convective split from a sampling of the different types of equipment used in offices. The nameplate vs. measured values, operational vs. idle values, and radiant vs. convective values are compared and discussed. [ABSTRACT FROM AUTHOR]

Building cooling load consumption is heavily influenced by two factors, i.e., spatial correlations such as outside air conditions and temporal relations, which factors the occupancy influence into account. Moreover, the anomalies in cooling consumption patterns are mainly caused by the abnormal behavior of the time-dependency of such temporal networks. A novel framework for building cooling load prediction is proposed to explore these dependencies separately using regression and recurrent neural networks for spatial and temporal relations, respectively, and then combine their outputs using an ensemble approach. The proposed forecasting model provides a 3-4% higher R2 value and 2-3% better CVRMSE accuracy when compared with the traditional machine learning model. [ABSTRACT FROM AUTHOR]

Implementing various control strategies on the chilled water temperature setpoint will increase waterside economizer run hours and ease the transitions between chiller and economizer modes. Controlling the chilled water temperature setpoint far lower than normal operation improves chiller operation while the condenser water sump cools enough to maintain the temperature setpoint and cooling load. Controlling the chilled water temperature setpoint based on what the chiller is doing currently versus what it needs to do eliminates the risk of peaking the machine or pulling too many amps trying to recover a building that does not need recovering. The warmer the chilled water temperature setpoint can be the more efficiently chillers operate, the more economizer hours are available, and the easier the transition between mechanical and economizer cooling is. [ABSTRACT FROM AUTHOR]

Absorption refrigeration (ABR) processes are affected in real operating environments by exogenous disturbances (e.g., ambient conditions) and by switching between different operating conditions (e.g., partial cooling load operation). The ABR operational performance is highly dependent on the selection of the working fluid with current selection approaches considering only steady-state ABR behavior. Working fluids that exhibit good steady-state performance, may be highly sensitive to disturbances and fluctuating operating conditions. In such a case, the implemented control system would require intense utilization of resources and possibly fail to reach the satisfaction of the desired load specifications. In this respect, it is imperative to evaluate ABR performance with different working fluids under variability in addition to their steady-state performance. In this work, the dynamic performance of a model-predictive controller (MPC) implemented on a single effect ABR utilizing different organic working fluids is investigated aiming at the selection of the most suitable working fluid. The dynamic performance of the closed-loop system is then evaluated in terms of resource utilization, speed of response and deviation from the desired setpoints under a specific disturbance scenario that involves load demand changes. Two comprehensive indices are utilized to evaluate and select the optimal working fluid; one describing the setpoint tracking ability and another describing the resource utilization. It is observed that Acetaldehyde/DMF (dimethylformamide) exhibits the best performance in terms of setpoint tracking resource utilization under variability, followed by NH3/H2O. The latter further ranks second in terms of COP under steady-state operation. This indicates that dynamic performance is equally important to steady-state operation as a criterion for working fluid selection. [ABSTRACT FROM AUTHOR]

Co-working space has been growing significantly in the past few years. Compared with traditional office spaces, co-working space typically offers more efficient layouts and higher utilization of the available square footage, with more celluralized office spaces across the floor to cater to various occupant needs. Globally, there is no dedicated ventilation code requirement or guideline for co-working spaces and most of co-working space use the traditional office buildings ventilation code for building design and calculations. In this article, we will investigate the office building ventilation codes in two main regions of the world – Asia Pacific (APAC) and North America (NA) to show a comparison between various countries and how these impact the growing co-working space designs. The main focus for ventilation code requirements is typically two-fold - how much CFM of outside air is required per person, and then how the code calculates the number of people to include in the design. It is interesting to notice that the ventilation rates calculated by following local codes from different regions vary from each other. Providing more than intended outside air rates could result in more cooling load, filtering demand, larger HVAC space needs and more energy in HVAC systems. Further, bringing in more Outside Air than is required for the real-time use of the space is even more of an issue in regions with relatively higher percentages of contaminants in the outdoor air - poor outdoor air quality and massive ventilation rate will result in high air filtration requirements and excessive energy consumption in ventilation systems. This article aims to raise awareness of the impact of office building codes to co-working designs and some of the key design impacts that these impose on existing building stock. [ABSTRACT FROM AUTHOR]