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Liquid Desiccant Air Conditioning and Dehumidification (LDAC) has been emerging in the past 10 to 15 years as an energy-saving alternative design for applications that require high moisture removal and a Cleantech solution that has the potential to provide significant energy savings when applied to more broad markets. Buildings are the primary users of electricity in the U.S., consuming about 75% of the total electricity produced and about 40% of all U.S. primary energy use and associated greenhouse gas (GHG) emissions. A substantial portion of that energy is used for air conditioning and dehumidification. Furthermore, the U.S. Department of Energy (DOE) reports that U.S. buildings account for 35% of the U.S. carbon dioxide emissions that drive the climate crisis. One specific application that requires significant moisture removal is the indoor cultivation of legal cannabis. It is estimated by the DOE that by the end of this decade, electrical energy usage by indoor cannabis operations will be on par with the electrical energy consumed by either data centers or for the recharging of electrical vehicles. More recent projections indicate cannabis sales are expected to double from 2021 to 2030. As such, more efficient and economical methods of climate control are necessary for more widespread application in cannabis operations to reduce the energy requirements. The added emphasis should be on methods to first reduce the energy required before building the electrical generating infrastructure to support such growing industries. Climate control of indoor cannabis cultivation is one such aspect where energy-efficient air conditioning and dehumidification can contribute to reducing the projected energy usage by end of this decade. This paper gives an overview of a standalone LDAC system and a hybrid LDAC combined with an air handling unit. This paper will present indoor grow room case studies from a side-by-side installation of a hybrid LDAC unit and Desiccant Wheel (DW) air handling system in two identical cannabis grow rooms. Integration with a Combined Heat and Power (CHP or cogeneration) plant onsite supplying energy for both the technologies will be examined. Further, comparative energy analyses of LDAC, DW technology, and other widely used technologies in the HVAC indoor growing environment will be discussed. This will be the first comprehensive, side-by-side performance and energy analysis of competing desiccant (LDAC and DW) technologies in a controlled, indoor agriculture environment. [ABSTRACT FROM AUTHOR]

When looking at energy usage in most life science & healthcare facilities, some may be surprised to hear that HVAC systems in the Northeast generally make up 50-65% of the overall usage. Many efforts have been made over the years to create better and more efficient systems to reduce that percentage. From the broad umbrella of the International Energy Conservation Code to local authorities, such as Local Law 97 in NYC, the trend to energy efficiency is becoming less of an optional upgrade and more of a mandatory requirement when considering HVAC design. With this trend towards implementing energy recovery in HVAC design, it can be a particular challenge in life science & healthcare applications. One of the largest challenges to implementing energy recovery in these applications is how to safely recapture heat from "dirty air" spaces such as isolation rooms, hazardous lab exhaust, etc. This paper will present the currently available HVAC energy recovery systems and their applicability and effectiveness within these specialty systems. The information in this paper is intended to convey how these energy recovery systems can be applied in life science & healthcare applications. It will review the limitations of air-to-air energy recovery being implemented in "dirty air" systems and common pitfalls to be aware of when determining the right system for various applications. Finally, this paper intends to identify the opportunities for the implementation of these energy recovery systems within existing life science & healthcare facilities and help guide facilities in making an educated design decision. [ABSTRACT FROM AUTHOR]

A review of scholarly research indicates that the savings from utility bills and improved Indoor Environmental Quality (IEQ) in Passive House buildings relative to conventional construction are not guaranteed. This paper proposes a potential approach for creating calibrated energy models to reduce the gap between measured and simulated energy use and validating the energy reduction of Passive House over conventional buildings. A case study approach is followed wherein IEQ indicators are modeled in multifamily residential buildings. The two buildings - one following conventional and the other following Passive House construction standards - have similar layouts and identical orientations in climate zone 5A. A whole building calibrated simulation approach is presented in the comparison of the performance of the two buildings. Compliance with ASHRAE guidelines, and data-driven energy models, based on data collection using ECMs and utility bills of the buildings are used as the basis of performance characterization. This paper introduces a comparative approach to investigating IEQ such as thermal comfort and indoor particle concentration in Passive House buildings compared to conventional buildings. [ABSTRACT FROM AUTHOR]

The need for reducing carbon emissions from buildings has led to the adoption of absolute performance targets such as thermal energy demand intensity (TEDI) and energy use intensity (EUI) as part of building regulations and client design guidelines. This paper presents how, as airtightness and fabric efficiency in buildings increase, building process loads including ventilation and appliance selection become a determinant factor affecting TEDI. The commonplace practice of using energy recovery in the ventilation equipment has left process ventilation from cooking and clothes drying as the remaining ventilation need requiring ducting to outside and with no heat recovery in place. Traditionally, equipment and appliances selected for kitchen extract and clothes drying are ducted to outside and, while this paradigm remains, ventilation heat losses and unnecessary façade penetrations complicate achieving TEDI targets. As electric or induction ranges replace natural gas cooking in residential and commercial settings due to decarbonization and indoor air pollution, kitchen hoods extracting to outside become redundant. The need for increased airtightness is likely to also make vented clothes dryers redundant due to potential depressurization, thermal bridge on the envelope, or wasted heat. Instead, it can be replaced with condensing clothes dryers, reducing the number of façade penetrations or the need for make-up air. This case study shows how, by rethinking equipment and appliance selection, a women's shelter located in ASHRAE climate zone 6 achieved its TEDI target. The intention of this paper is to raise awareness of the intersection between appliance selection, airtightness and ventilation in buildings and how this becomes more relevant when designing in cold climates. [ABSTRACT FROM AUTHOR]

Energy efficiency in the building sector can lead to a significant reduction of the total carbon footprint in the environment produced by buildings. Hence, designing efficient building systems and controls is crucial to decreasing building energy consumption and carbon emission. This paper proposes to utilize both ducts of the dual VAV system configuration simultaneously to minimize energy usage and maximize efficiency. One air handling unit can be operated as a dedicated outdoor air unit to serve the ventilation load while the other serves the building load. To attain the benefits of a dual VAV system in this way, a specific control sequence is proposed in this paper. Single duct VAV, single duct fan-powered VAV, dual duct with common outdoor intake, and dual VAV systems are modeled for a case study multi-zone building to demonstrate this concept. Annual heating, cooling, and fan energy consumption of these four systems are then compared to evaluate the energy savings. After that, field studies are performed for a single duct VAV system as the baseline and dual VAV system in the fully instrumented HVAC lab at the University of Cincinnati, Ohio. It is observed in the simulation studies that using both VAV systems simultaneously leads to significantly lower heating and fan energy consumption for the case study building. Moreover, the field experiment result validates the simulation results, and about 29% fan power savings are obtained over 24 hours by using this configuration. Thus, this study demonstrates the potential of adopting a dual VAV system widely over the other three baselines to achieve energy efficiency with the proposed sequence of control in multizone buildings. [ABSTRACT FROM AUTHOR]

The current generation of energy codes were born in the 1970s with the sole purpose of conserving energy in homes and buildings, and with no guidance surrounding renewable energy generation or grid integration for those structures. Over the intervening decades, that singular purpose has been complemented by increasing demands to reduce greenhouse gas emissions and to utilize a lower-carbon mix of fuel types. At the same time, the falling costs of renewable energy options, especially solar, have raised the importance of an optimizing calculus between renewable supply options and energy demand reduction options. The paper first reviews the framework for establishing the renewable/efficiency balance in California's Title 24-2019 Residential code. Based on additional analysis, the paper then presents a new framework that encompasses the range of U.S. climate zones and building types covered by the model energy codes, with a special focus on single family homes. This optimization framework is analyzed for its implications to update prescriptive, performance, and rating (such as the Energy Rating Index, or ERI) compliance paths in the model codes. The calculus is also examined for its application in determining impacts of renewable/efficiency combinations on electric grid stability. Additional topics covered include accounting for procuring onsite and offsite renewable energy and for measuring increases in building resiliency. The paper then offers recommendations for code developers by addressing the underlying code issues with regards to accounting, reporting, compliance, and enforcement. [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]

On average, up to 40% of the energy consumed in buildings is spent on space heating or cooling (Adegbenro et al., 2021). Finding the optimum temperature setpoint to save energy while maintaining occupants' comfort has been an ever-challenging issue in most spaces, particularly in open spaces with collective users. To save energy, Facilities-Managers (FMs) use the human comfort zone for temperature and humidity to determine the HVAC setpoints. This practice can, however, result in occupants' dissatisfaction with the thermal environment due to their diverse thermal preferences. In buildings where occupants have control over the ambient temperature of the space, users often change the thermostat setpoints to an unnecessarily high or low value, as they believe it will result in a more immediate temperature change. They then often forget to return the temperature to the base setpoint, resulting in unpredictable changes in energy consumption and operating costs. The solution to this unfortunate reality lies in a better understanding of building occupants' behavior and preferences to efficiently control energy consumption while increasing the thermal comfort among occupants. This research investigates the impact of live IoT temperature data on users' thermal satisfaction with work environments. We present a pilot study, that uses an open-plan workplace on the Carnegie Mellon University campus. An Occupant-Centric Digital Twin (OCDT), a term coined by the first author of this paper, is used in this study to provide a live thermal map to occupants. OCDT displays the real-time temperature data of the existing indoor microclimates on a large screen in the open workplace. A grid of IoT sensors was used to capture temperature changes in discrete locations. The live thermal map enables occupants to make choices about where to work so that it matches their individual thermal preferences. With the rise of 'hot-desking' as a flexible organizational office strategy, the OCDT can provide increased agency to occupants to identify zones that meet their needs without compromising energy efficiency. We posit that this approach will result in higher thermal satisfaction and reduced energy consumption. [ABSTRACT FROM AUTHOR]

Urban building energy modelling (UBEM) plays an essential role in the global climate action plans by analyzing the energy supply at urban or city scales and estimating the energy demand and the gas emission of different sectors. Moreover, policies and measures such as clean grid strategies, demand response programs, and dynamic pricing policies, that have been put in place as part of these plans rely heavily on the results of UBEM models to represent more realistic energy use and environmental impact at different temporal and spatial scales. However, the unsolved performance gap issue (i.e. discrepancy between the model predicted results and the actual performance) stands in the way of the effectiveness and the reliability of the developed models. One of the most acknowledged reasons behind such an issue is the uncertainty in modelling occupants' behaviours (OB) in this context. Therefore, many research efforts focused on investigating different modelling approaches to improve the level of details of occupant-related features in UBEM models. However, the capability of the developed models to be integrated into the currently available UBEM tools is still questionable. This caused many practitioners and UBEM users to rely on simple fixed schedules instead of examining stochastic models with a higher level of detail when needed. To this end, this paper aims to review the currently available OB models and compare them with respect to inputs, used algorithms, their expected outputs, as well as their integration capability into the commonly used UBEM tools. The results of this investigation can be used to develop guidelines for modelling OB aspects for the different applications of urban building energy simulation, as well as identify areas of improvement in the commonly used UBEM tools. [ABSTRACT FROM AUTHOR]

Indoor air quality is increasingly recognized as a serious health hazard in many international environments. During the recent pandemic, this concern was amplified as Covid-19-related mortality closely correlated with poor air quality. Even a comparatively small decline in the Air Quality Index (AQI) can be linked to a sharp mortality increase. Worsening air quality levels are compounded by distinct air-quality issues in different geographical areas. In the face of this serious and wide-ranging threat, the common solutionâ€"introducing a high MERV-rated filterâ€"comes up short, as these filters create back pressure that often exceeds the capacity of the HVAC systems in which they are installed. High-backpressure filters also use more energy and require frequent filter changes, making them more expensive to maintain and bad for the environment. This paper describes a new form of electrostatic filtration that is ideal for international markets since it has a uniform performance, low back pressure, is energy efficient, and can be tuned to perform at a range of filtration levels depending on demand. This is accomplished by varying voltage applied to the ionization stage of the filter. In this study, we operate an electrostatic filter with a variable power source set to vary filtration level according to a variety of operating algorithms and compare the resulting energy use to standard air filters. [ABSTRACT FROM AUTHOR]

In 2019, the UK became the first major economy to pass laws to reduce its greenhouse gas emissions to net zero by 2050. Meeting this ambitious target not only requires a shift in energy supply from fossil fuels to low carbon energy sources, but also a reduction in energy demand through the roll-out of energy efficiency improvements to existing buildings. The UK has some of the oldest and most inefficient housing stock in Western Europe and the building sector is responsible for approximately half of energy consumption. The present work has a strong focus on exploring low carbon heat supply tehcnologies could be applied to existing housing stock, using the London Borough of Islington (LBI) as a case study. The applicability of low carbon energy efficiency measures to a range of different building archetype prominent within LBI is discussed and evaluated. The methodology implemented includes both qualitative and quantitative assessment of the opportunities and benefits, with a focus on applicability, cost, and carbon savings associated with two low carbon heat supply options. The overall evaluation approach presented in the paper is applicable to other urban areas in the UK and elsewhere. Key conclusion from the study and planned next steps are also discussed. [ABSTRACT FROM AUTHOR]

The distribution and delivery of fuels to the built environment is a mega-scale form of seasonal energy storage in the United States, delivering greater than 600 GW of energy during the winter, often in the form of heating, and with storage built up over periods of 6-8 months. Combined with Canada, this distribution system serves 85 million homes and businesses with a network spanning 5.4 million km. With increasing efforts to reduce the impact of buildings on the environment, the greater than 1,000 Mt CO2e/year emitted from this fuel consumption must be mitigated. In addition to energy efficiency and conservation, which remain the pillars of any climate mitigation scheme, one pathway to reduce CO2e emissions from buildi ngs is displacing delivered fossil fuels (e.g. natural gas) with low or zero carbon fuels, which can include methane-based fuels and hydrogen, generated from renewable energies/feedstocks or employing integrated carbon capture. Seeking to scale-up the generation and distribution of these low or zero carbon fuels in many regions throughout the U.S. and Canada, utilities are demonstrating the injection, blending, and delivery of these fuels. Of particular note are the hydrogen-focused demonstrations, which seek to quantify the risks and benefits of distributing hydrogen using legacy and purpose-built infrastructure, and its impacts on the downstream homes and businesses, with activity in numerous large metropolitan areas and in cold and hot climate zones alike. This paper provides an overview of these North American utility projects, which displace delivered fossil fuels with low or zero carbon fuels, from the end user perspective and with a focus on the hydrogen-based fuels, both blended and 100%. The authors compare and contrast these projects with similar projects abroad, where in the U.K., Germany, and Japan, for instance, significant fractions of homes and businesses already enjoy access to these non-fossil fuels. Finally, using the historical transition from manufactured gases to widespread distribution of natural gas, a ~30 year transition that occurred from the 1920s to the 1950s, the authors draw comparisons between this significant historical energy transition to the modern context, considering safety implications, regionality, impacts on HVAC equipment, and the role of codes and standards. [ABSTRACT FROM AUTHOR]

This paper presents the major findings from ASHRAE Research Project RP-1848, which documents the contributions made by ASHRAE and its members to advanced research, higher education, industry guidelines, and professional development. Such contributions are classified into five major categories: (1) building energy efficiency, (2) human health and comfort, (3) minimizing human impact on the environment, (4) industry and commerce, and (5) education and professional training. In each of these categories, facts and data were collected from multiple sources to assess ASHRAE's impact on different aspects of the industry, including government regulations; design, building, and testing guidelines in industry; academia and education; and influences on other professional societies or organizations. [ABSTRACT FROM AUTHOR]

The climate crisis currently being faced by humanity is going to increase extreme weather events which are likely to make long-duration power outages for communities increase in frequency and duration. Microgrids are an important part of electrical resilience for connected communities during power outages. They also can have transactive potential to save energy on electric loads through coordinating distributed energy resources. Microgrids are expensive though. Making electric load coverage available nearly 100% of the time given known design basis threats and component failure statistics is one of the largest drivers of cost. Such high availability is non-negotiable for critical applications such as life saving equipment in a hospital but could perhaps be compromised for less critical loads. This paper documents an analysis that used the Microgrid Design Toolkit and EnergyPlus simulation results with two energy retrofit options exercised. The results show how increasing energy efficiency and reducing availability to 90% and 80% reduced the calculated price of a photovoltaic and battery storage microgrid in a New Mexico neighborhood by 63% and 70%, respectively. A microgrid with 80% availability with 48-hour islanded run-time capability is therefore suggested as a low-cost method for accelerating microgrid infrastructure penetration into the residential sector. Such an "underbuilt" microgrid will significantly increase resilience even though it will not guarantee energy security for the non-critical applications in residential households. This will in turn accelerate the growth of storage potential across communities providing greater grid flexibility. The results of the study also show how increased insulation applied to the proposed residential community can be less expensive than creating a larger microgrid that carries larger electric loads. The likelihood that energy retrofits are a better investment than a larger microgrid is inversely proportional to availability. Here, availability is a metric equal to the percentage of the demand load served by the microgrid during power outages, not including the startup period. [ABSTRACT FROM AUTHOR]

Space heating and cooling use represents about 40%-50% of total annual energy and is usually the highest end use in homes. Therefore, matters impacting space conditioning may have significant impact on home energy use. Correct refrigerant charge, preventative maintenance, and air distribution duct location, design, airtightness and insulation integrity can have significant impacts upon energy use. Inadequate duct design and installation can result in elevated total external static pressure, which can have significant impacts on performance. This research project was designed to investigate the cooling performance impacts of increased static pressure, which often results from poor design and installation practices. Two identical university lab homes sited next to each other were used with a metal duct system in one home and a flex duct system in the other. Each duct system had the same general layout within a vented attic. Space conditioning was provided by identical two-stage split-DX heat pumps having the same model numbers. The air handlers used electronically commutated motors that delivered design airflow across a wide range of static pressure. Energy use, temperatures and relative humidity and refrigerant line temperatures and pressure were monitored. An initial test 1 compared quality duct design, sizing, and installation meeting industry standards for each duct type. The metal duct system at 0.34 in WC (85 Pa) was used as a baseline of comparison to the flex duct at 0.44 in WC (110 Pa). Two additional tests were run with the flex system at higher static pressures. Test 2 operated the flex system at 1.00 in WC (249 Pa), which represented high compression and some poor radius turns. Test 3 operated the flex system at 0.82 in WC (204 Pa), which represented more typical installation practice. There were significant central fan energy impacts. Observed impacts of duct static pressure upon the ECM fan energy found flex duct energy increases of 33%, 148%, and 72% for tests 1, 2, and 3 respectively. This paper further discusses a comparison of the daily cooling energy impacts by condensing unit and air handler fan for typical summer days as well as an annual energy impact between the metal duct and 0.82 in WC (204 Pa) flex duct for three different locations in climate zone 1 and 2. Implications of over-compression of metal duct exterior FSK insulation wrap upon energy was also discussed. [ABSTRACT FROM AUTHOR]

The energy use for indoor and greenhouse horticulture has grown dramatically over the past 15 years, driven both by the legalization of medical and recreational marijuana and the increasing interest in sourcing ingredients from local farms year-round. Nationally, indoor horticulture facilities were estimated to consume 20 billion kWh of electricity in 2012 corresponding to 1% of electricity use nationally (Mills, 2012). Since 2012 nearly 18 states have legalized recreational marijuana and many more have seen growth in the local food movement, only increasing demand from these facilities. Because of the desire to recreate optimal outdoor growing conditions, indoor horticulture facilities typically have energy use intensities (EUIs) that are twice that of fast-food restaurants and can exceed even data centers. The lighting power density (LPD) in the facilities can be 80 times that of the lighting power density in office buildings and the lights operate on average 18 hours per day. Thus, most of the energy used in these facilities is for lighting and HVAC and dehumidification systems to maintain ideal temperature and humidity levels. In 2017, the American Society of Agricultural and Biological Engineers (ASABE) released ANSI/ASABE Standard S640 which established a metric, µmol/J (micromoles per Joule), to measure the photonic efficacy of lighting used in horticultural applications. In 2018 the Design Lights Consortium (DLC) began establishing criteria for LED luminaires for these applications. In due time, the 2021 International Energy Conservation Code (IECC), Title 24-2022, and many other standards, including ASHRAE 90.1, have adopted or are considering lighting photonic efficacy limits in indoor horticulture facilities, driving significant energy savings. Utilities also have begun to offer incentives to reduce energy use in these facilities using DLC's LED photonic efficacy threshold of 1.9 µmol/J. The 2021 IECC also for the first-time established insulation criteria for the envelope of heated greenhouses. This paper describes the technical and policy considerations used at the national, state, and local levels to reduce energy use from these facilities and the potential for an addendum to ASHRAE 90.1 on new lighting efficacy requirements. The authors also provide recommendations for future steps in standards to reduce the energy use of HVAC and lighting loads in both indoor horticulture facilities and greenhouses. [ABSTRACT FROM AUTHOR]

As building designs become more and more energy-efficient, occupant behavior has emerged as one of the most important factors affecting thermal comfort and energy consumption, in particular in the residential sector. Since occupant behavior exhibits a strong variability from day to day and from a dwelling to another, stochastic models have been developed to avoid the drawback of fixed schedules in the design phase. These models can provide more information to practitionners, but they can be quite time-consuming and complex to operate. This paper introduces a practical and simplified way to consider the spectrum of occupant related aspects in the residential sector by generating three strategically chosen schedules representing the complete range of behaviors. Findings showed that simplified schedules yield similar annual aggregated results compared to the detailed profiles. The method allows to better estimate possible building energy consumption and thermal comfort and to compare design solutions considering different occupants. [ABSTRACT FROM AUTHOR]

This paper investigates the independent impact of several different existing building commissioning (EBCx) measures on peak electric demand, to help understand measures to prioritize based on peak demand savings along with the usually-assessed energy consumption savings. The investigation involves developing separate EnergyPlus™ models for each EBCx measure, and comparing the peak electric demand generated by each model with a baseline model. The pre-EBCx and post-EBCx models are based on a community college campus which underwent an EBCx project between 2014 and 2015, resulting in an average of 34% savings in energy consumption and peak demand. The total peak demand reduction determined from the individual EBCx measures was only 26% compared to the measured reduction of 34%. Applying an outside air temperature reset schedule to AHUs' supply air temperature (SAT) setpoints reduced peak demand by an average of 16.7%, mainly due to the reduction of unnecessary cooling and reheating, especially in winter. The optimization of AHU control schedules, which minimized the unnecessary operation of some units during peak hours produced peak demand savings of 6%, while the optimization of space temperature setpoints contributed another 3%. While other measures impact electric demand during non-peak hours, none produced peak electric demand reduction greater than 1%. Other measures did not generate peak demand savings while still generating energy consumption savings, mainly for the reason of not having an impact during peak hours. [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]

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]

In this paper the energy potential of a Double Skin Façade integrating Semi-Transparent Photovoltaics (DSF-STPV) is investigated for DSF-STPV configurations for different climatic regions. The Double Skin Façade (DSF) consists of Semi-Transparent Photovoltaics (STPV) as the exterior layer and an Insulating glazing unit as the interior layer of the DSF-STPV. Semi-Transparent Photovoltaics (STPV) can be integrated on Double Skin Facades (DSF) to enhance the electrical and thermal performance of a building. A mechanically or naturally ventilated DSF, can enhance the natural/cross ventilation of building, can extract heat from the DSF and increase the Coefficient of Performance (COP) of an air source heat pump based mechanical system, or it can introduce fresh air directly to the building. In addition, the integrated STPV, can control the solar gains and the levels of the daylight into the zone. A mathematical model was developed t? simulate the performance of the system, to predict the temperature distribution and airflow within the DSF and the active and passive effects the DSF-STPV has on the energy consumption of the adjacent perimeter zones. The simulation model is based on a finite difference thermal network and can be utilized to perform parametric analyses. A parametric analysis is carried out to determine the values of critical design and operating parameters that minimize the overall energy consumptions, while guaranteeing satisfactory thermal comfort for the occupants,. Specifically, a comprehensive case study for a three-story office building located in four different climate zones is performed. These four climate zones are simulated for nine different DSF-STPV cavity widths, five different velocity set-points and 10 different operating strategies. The numerical results show that, depending on the climate of the region and the depth of the cavity, different strategies should be implemented. By suitably optimizing the DSF-STPV design and operation, the energy demand of the adjacent perimeter zones can be covered by the generated PV electricity, facilitating to reach the goal of net zero energy building. [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]

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]

ASHRAE Standard 100, Energy Efficiency in Existing Buildings, is an ASHRAE Standard aimed at increasing existing building energy efficiency through the use of best operation and maintenance procedures, evaluation of actual building energy use, and verified energy performance improvements. Most buildings seeking compliance with Standard 100 must compare their energy performance with established energy use intensity (EUI) targets. Under Standard 100, buildings that do not already meet their designated EUI target are required to conduct an energy audit, implement efficiency measures, and prove that their new EUI meets the target. While Standard 100 allows for local jurisdictions to develop their own EUI targets, it also provides a table of default energy targets for commercial buildings that are based on the Commercial Building Energy Consumption Survey (CBECS) and energy modeling. This paper derives localized Standard 100 EUI targets for 11 United States cities across 7 climate zones using local benchmarking data collected through annual building energy benchmarking ordinances. These localized targets were compared to the default energy targets available in Standard 100. Nearly half of the targets developed were within 20% of the default ASHRAE Standard 100 energy targets. Large differences between the default and localized targets indicate that (1) localized development of energy performance targets can better align building performance targets with energy efficiency or greenhouse gas emissions goals, and (2) the default Standard 100 energy targets may benefit from future refinements. [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]

Full autonomy is the ultimate goal of the building industry to achieve energy optimality. Buildings have non-stationary and complex dynamics, as the state space to describe their behavior is significantly large and intractable. Existing control approaches are not appropriate to meet the requirements of building automation since they are black-box methodologies which fail to provide a system-level optimal control solution for buildings. They are also static which makes them unable to adapt as the dynamics of the buildings vary. Moreover, model-free approaches are only valid for a specific building and lack the ability to extend to other buildings. This paper offers a Deep Digital Twin approach as a new artificial intelligence structure for building automation platforms. The Deep Digital Twin utilizes a physics-based ontology to provide a self-knowledge of the building operation, and the cause-and-effect interrelation between building subsystems which enables future-forward energy efficient control of the building at the system level. [ABSTRACT FROM AUTHOR]

Water heating is a major energy consumption in the US residential sector. According to the annual energy outlook of the EIA (EIA 2021), the total US national primary energy efficiency of water heating is only 60%. Heat pump water heaters can significantly increase the thermal efficiency of water heating. Electric powered heat pump water heaters are already commercially available in the US. On the other hand, no fuel-fired heat pump water heaters are available, but two are in development, both employ absorption cycle. Thermally driven ejector heat pumps have been discounted for their low efficiency and narrow operating range. In this paper we present performance analysis of a novel ejector heat pump for water heating that overcomes the shortcomings of conventional ejector heat pumps. The heat pump uses binary fluid mixture and active back pressure control. The use of the binary mixture results in high thermal efficiency and the active back pressure control widens the operating range of the heat pump. Two configurations of the heat pump are presented and analyzed. The maximum achievable COP of each was 1.95 and 1.7 at output heating capacities of 5.7 and 6.7 kW, respectively. [ABSTRACT FROM AUTHOR]

Historical structures incur diverse challenges associated with energy consumption, specifically those surrounding opportunities for potential improvements. In the U.S., heating and cooling of spaces can account for up to half of all energy usage within a home. As a result, identification of cost-effective methods towards enhancing energy efficiency represents critical information for homeowners and businesses alike, and a measurable estimator of potential monetary investment and return. In this paper, a novel DC-powered picogrid is developed to support a local weather station adjacent to a residential home in order to optimize its energy consumption. Though regional meteorological data is readily available from numerous online cloud-services, in-situ environmental measurements afford more building-specific insights, ranging from wind direction and speed, humidity and dew-point levels, and UV and irradiance measurements. When coupled with on-site renewable energy generation such as solar and wind power, this weather data can drive real-time electrical management decisions (e.g., storing or expending battery energy, selling electricity to the grid, etc.), and also be leveraged for daily and weekly power consumption and generation forecasting. These findings illustrate the benefits of DC-powered designs, and the capability of low-cost sensors to improve residential energy administration. [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]

Waterside economizers afford an excellent opportunity to reduce chilled-water plant energy use when air-side economizing is not viable, but they are frequently sub optimally designed and controlled. This paper discusses sequences of operation for waterside economizers developed as part of ASHRAE Research Project (RP) RP-1711, Advanced Control sequences for HVAC Systems—Phase II: Central Plants and Hydronics Systems, based on prior art and researcher experience and provides context for the underlying best practice mechanical design assumptions underpinning those sequences. [ABSTRACT FROM AUTHOR]

Occupants' presence, activities, and interaction with buildings' systems play a vital role in modeling household energy demand. However, the currently available energy models overlook this essential parameter by oversimplifying occupants' parameters and neglecting the population's heterogeneity, leading to overestimating the peak loads and improper systems' sizing. In this context, developing scalable, adaptable, and representative occupancy models is essential for developing reliable energy models. The literature showed various attempts to build such data-driven occupancy models, increasing interest in developing survey-based models using the Time Use Surveys (TUS) data. The TUS-based models showed promising results in simulating occupancy, activities, and related energy consumption. However, the Canadian TUS data is rarely used for calibrating TUS-based models, and representative district-scale occupancy profiles are essential for applying research activities on Canadian residential districts. In this paper, a bottom-up TUS-based model is proposed to simulate a residential district occupancy schedule in Canada during weekdays and weekends. The model is based on the Monte Carlo Semi-Markov method with an adjustable spatial scale from a single building to the district level. The proposed model is adjustable in terms of number of activities and the temporal resolution based on required application and granularity level, and it considers the impact of occupants characteristics (age, gender,..etc.). and day type on the generated activities profiles. The obtained occupancy schedules are valuable inputs for enriching urban building energy models, especially designing demand response programs and integrating renewable energy systems applications. [ABSTRACT FROM AUTHOR]

Retrofitting existing buildings shows promise for reducing energy consumption and greenhouse gas emissions. However, selecting the appropriate energy retrofit strategy (or strategies) requires careful planning, detailed information about a building’s current condition and historical energy consumption patterns, and evaluation of multiple retrofit options. One retrofit strategy, using phase-change materials (PCMs) as a relatively straightforward means of increasing the thermal mass of an existing building, continues to be of interest to building owners, operators, and utilities alike. Despite the seeming ease of installation (e.g., PCMs can be layered on top of existing acoustical ceiling tiles rather than removing drywall to add insulation to exterior walls), a few primary factors need to be considered before applying PCMs in existing buildings. This paper presents a novel process for selecting PCMs for building energy retrofits, comprising an evaluation of both the candidate building as well as the PCM. This process includes goal setting for the energy retrofit as well as the PCM installation, evaluation of an existing building to ensure that it is a good candidate for PCM integration, and, finally, analyzing the energy-savings potential of PCM integration as a retrofit strategy. This process was developed based on the results of five case studies conducted by the authors, including three experimental commercial building PCM installations as well as simulation results from two residential buildings. The authors present how the application of this process would have changed the choices made by stakeholders involved in the cases studied, thereby avoiding some of the less desirable results of those projects. [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]