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DOE OSTI2023

Occupant thermal comfort inference using body shape information

Occupant thermal comfort may be inferred and improved using body shape information. Height, weight, and shoulder circumference of an occupant of a room may be obtained using a depth sensor. A model may be utilized that is trained on a dataset including information reflecting of occupant comfort within the room versus temperature, the model receiving, as inputs, the height, the weight, and the shoulder circumference of the occupant and environmental information and outputting a comfort class. A temperature set-point for is identified which the room occupant is identified by the model as having the comfort class being indicative of user comfort. Heating, ventilation, and air conditioning (HVAC) controls are adjusted for the room to the identified temperature set-point.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Results from Laboratory and Field Study of Thin Triple Pane Windows

Heat transfer through windows accounts for a significant percentage of a building’s energy use and adds substantially to the peak cooling load of a home. In recent years, improvements in glass manufacturing have enabled the use of a very thin central pane of glass similar to a cell phone screen to produce a thin triple-pane window, for finished insulated glass units (IGUs) with an overall thickness similar to standard double-pane windows. Because this highly insulating “thin triple” glass product can be incorporated into almost any existing window frame and can be fabricated at a modest added cost, the U.S. Department of Energy sponsored laboratory and field demonstration testing of thin triple-pane windows to validate thermal performance and installation requirements in real-life field settings. Thin triple pane windows were evaluated at the PNNL Lab Homes, a matched pair of manufactured houses located on PNNL’s campus in Richland, Washington and also at 16 different field study sites around the country. The experimental results include a comparison of heating, ventilation, and air-conditioning (HVAC) energy usage, condensation potential, occupant comfort, sound infiltration, and thermal performance. Field study data will be gathered through June of 2022; preliminary results are being shared in this paper. The lab houses are identical except that the reference house had standard double pane windows with assembly U-0.66 and the test house had thin triple pane windows with assembly U-0.19. Across the experimental test days, the daily HVAC savings ranged from 0.2 to 18.7 kWh (3%–18%) for the heating season and from 2.5 to 8.0 kWh (23%–41%) for the cooling season. The higher thermal performance of the thin triple-pane windows also reduced the condensation potential on the interior surface during winter months and provided more even distribution of temperatures throughout the home in comparison to the baseline. In addition to the added thermal performance, the thin triple-pane windows demonstrated significant acoustic benefits, reducing sound infiltration by 8 dB to 10 dB. For the field test portion of the project thin triple pane insulated glass units were produced by two different manufacturers, and then installed without modification into the ½” IGU pockets of the standard double pane frames of four other manufacturers. Field tests performed on existing homes in Washington, Montana, Colorado, and New York compared thin triple pane retrofits to original window conditions (before and after). Field tests at new construction sites in Minnesota, Michigan, and New York compared thin triple pane windows to commercially available solutions such as double pane or traditional triple pane (with a standard-thickness center pane). Field test work is ongoing, but preliminary results appear to follow the sound, surface temperature, and energy improvement results from the Lab Homes comparison. Additionally, reports from builders and installers indicate that thin triples require almost no added time or effort to install and look nearly identical to other windows, indicating the possibility of offering next-level performance with a product that requires very little modification to current production or installation practices, long considered a major barrier to technology uptake in the construction market.

energy efficiency, home retrofit, Windows, window ↗

DOE OSTI2022

Load Shifting with Space Conditioning Heat Pumps During Heating Season in the Pacific Northwest

Ductless mini- and multi-split heat pumps are commonly deployed in Pacific Northwest residences, which historically have inefficient space heating and no space cooling. Heat pumps provide these residences with more energy-efficient space heating in the winter and space cooling for increasingly warm summer periods. For many of these applications, heat pumps add a new electrical load at the residence, compelling regional utilities to seek to understand their impacts on the electrical grid and opportunities for load management. In coordination with regional utilities, this study examined the winter load-shifting potential of residential multi-split heat pumps with variable capacity technology. The study included nine residential sites with a total of 20 ductless indoor units, which underwent simulated smart grid control. Grid control functionality was provided through the CTA-2045 communication protocol and included offsetting temperature setpoints for individual indoor units in the study. Field data collection included whole-house and heating, ventilation, and air conditioning electrical power consumption; indoor zone temperatures; occupant surveys; and CTA-2045 curtailment data for both baseline and simulated load-shifting events by site. This paper provides an overview of the load-shifting strategies and aggregated results from winter data collection.

ASHRAE, Heat pump, energy effciency, residential b↗

DOE OSTI2020

Challenges and Solutions in Operation and Lay-Up of the Modular Caustic- Side Solvent Extraction Unit - 20078

The Modular Caustic-Side Solvent Extraction (CSSX) Unit (MCU) was designed and constructed to provide interim salt waste processing so that the Liquid Waste Disposition Program (LWDP) could continue waste removal and tank closure until start-up of the Salt Waste Processing Facility (SWPF). MCU processes Clarified Salt Solution (CSS), or salt solution (SS) that has undergone actinide removal/filtration, to produce two waste streams: the cesium laden Strip Effluent (SE), which is incorporated into glass at the Defense Waste Processing Facility (DWPF), and the cesium depleted Decontaminated SS (DSS), which is incorporated into grout at the Saltstone Production Facility (SPF). MCU completed start-up in 2008 with an initial operating life of 3 years and design life of 5 years. Prior to reaching the end of the design life, multiple critical components were upgraded and/or replaced to mitigate risks associated with any delays in SWPF start-up. During the remainder of operation (until June 2019), MCU was challenged to maximize processing with minimal additional modifications to repair/improve aging infrastructure, while maintaining low levels of risk to workers and the environment. Notable challenges during the extended operating life of the facility involved both mechanical and operational issues. Two of the most significant issues were the increased frequency of Process Vessel Ventilation (PVV) High Efficiency Particulate Air (HEPA) filter change-outs and the biofouling of the SE coalescer (SEC). The major impacts of both issues were that replacement of these components 1) resulted in high exposure to workers, and 2) required substantial downtime, thus hindering achievement of processing goals. PVV HEPA filter replacements are required based on dose rate and differential pressure (dP) limits. After introducing a higher-curie feed to MCU, the operating time between change outs was reduced by approximately half. SEC replacements are required based on dP limits. After restarting from an extended outage, the operating life of the SEC was significantly reduced by more than half due to biofouling. As a result of extensive troubleshooting and process improvements, the facility was able to recover performance and extend the operating life of the PVV HEPA filters and the SEC media. Through troubleshooting both of these issues, the facility was also able to learn from prior experience and adapt in order to minimize down time and maintain throughput. Although the facility took advantage of short periods of downtime to perform nonintrusive troubleshooting and minor corrective/preventative maintenance activities, longer outages were periodically required for corrective maintenance involving process cell entry. During these outages, remote tools and specialized shield plates were employed to minimize dose to workers. Mock-ups of non-routine maintenance activities were critical to early identification of potential issues and improvements, which shortened outage duration. Consistent with the facility's operational strategy, evolutions needed for MCU layup were identified and sequenced to ensure safe conditions within the facility, meet pre-defined criteria for lay-up configuration, and protect workers, while minimizing the impact to SWPF integration. De-inventory and flushing of process areas was prioritized so that the total residual inventory was reduced as efficiently as possible. This paper discusses lessons learned and best practices from troubleshooting unique issues, performing complex maintenance activities, and implementing a layup strategy that best supports the overall system mission. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Distribution Development for Residual Inventory at the New York West Valley Site - 20400

The New York State Energy Research and Development Authority (NYSERDA) is the owner of the Western New York Nuclear Service Center (WNYNSC), a 1,351 ha site located approximately 48 km south of Buffalo, New York. In 1962, Nuclear Fuel Services, Inc. (NFS) entered into Agreements with the Atomic Energy Commission and New York State to construct the first commercial reprocessing plant of nuclear fuel in the United States. NFS, a private company, built and operated the spent fuel reprocessing plant and waste disposal facilities, processing 640 Mg of spent nuclear fuel from 1966 to 1972 under an Atomic Energy Commission license. Nuclear fuel reprocessing operations ended in 1972 and never reopened, leaving behind radioactive and chemical wastes. Operations led to contamination in a number of facilities and locations. Some of that contamination has migrated from waste disposal zones to other layers, formations, and features on and off the WNYNSC. Phase I decommissioning activities are ongoing and involve the removal of a number of areas and structures that have been associated with contamination. The purpose of this work is to outline the approach for characterizing contamination not associated with disposed wastes, contaminated structures, or specific releases. In this work, the term, residual radiological activity, is used to describe environmental contamination that exists subsequent to the completion of Phase I decommissioning activities, that is not associated with disposed wastes, contaminated structures, or specific releases. Contamination from the Site was quantified relative to data that characterize the concentrations of radionuclides that exist in background. Background concentrations are those present in the area but having no influence from Site related activities. The existence of residual radiological activity that is elevated relative to background has the potential to contribute to future risks to human health and the environment. As a consequence, the residual inventory information is used to inform the West Valley Probabilistic Performance Assessment (PPA) model to characterize potential future risks to human health and the environment. The centralized West Valley Data Management System (DMS) was the source of information for the data assembled in this analysis. The DMS is a fairly large compilation consisting of thousands of records from investigation studies, with sample dates ranging from 1990 to present. Samples from monitoring wells, boreholes, geoprobe studies, surface water, surface soils, storm water outfalls, ventilation stack filters, plant and animal tissues, and more are included in the DMS. Results are typically reported in units of activity per unit volume. For the purpose of the analyses presented here, all results were converted into consistent units of pCi per unit volume. Since 1990, data have been collected from various locations across the WNYNSC at different times with varying frequency over the course of several decades. As a consequence, a number of potential issues can arise with respect to the assembly of a dataset that is deemed adequate for the characterization of residual radiological activity. These issues were assessed and resolved to the extent possible through careful consideration of the properties of the distributions. The intent was to use data which characterize the current state of the Site. Radionuclides can be designated to one of several groups depending on their origin. In this work the groups considered were 1) Naturally Occurring Radioactive Material (NORM), 2) fallout, and 3) Other (including power plant, medical research, etc). This grouping is a useful construct with respect to the interpretation of fixed laboratory results. For example, NORM radionuclides that exist within a decay chain should have approximately equivalent distributions of concentrations if they are representative of background conditions. Insights such as these can be used as a check to identify sample results that need to be further investigated or omitted due to issues associated with reported results from fixed laboratory analyses. This type of analysis provided a foundation for the assessment of the adequacy of sample results for use in subsequent components of an assessment. The general process for the assessment of residual radiological contamination at the Site consists of a sequence of several steps. First, for each analyte, several statistical tests were performed to assess the weight of evidence against the null hypothesis that the mean of the distribution of concentrations was equal to zero. If the mean of the distribution of concentrations for a given radionuclide was not found to be greater than zero, then it was removed from consideration as a component of the residual radiological contamination. If there was significant evidence to reject the hypothesis of the mean being equal to zero, the second step was to compare the distribution of the data from the Site to that of the corresponding background. A suite of tests was used to compare the distributions of the site and background data. The results of these tests were collectively used to determine if site data are elevated relative to background. The third step was to develop distributions using a Bayesian framework to characterize the distribution of mean of the increment present above background for each of the radionuclides. The Bayesian model implemented allowed for the comparison of site-specific records to background concentrations to better approximate contamination attributed to the Site. A final screening step was employed for radionuclides that exceed background. This screening step compared 95% upper confidence limits (UCLs) from the increment distribution developed in the previous step to the risk screening levels. This approach yields a list of analytes that were determined to be elevated relative to background.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2023

Development of A Hardware-In-the-Loop (HIL) Testbed for Cyber-Physical Security in Smart Buildings

As smart buildings move towards open communication technologies, providing access to the Building Automation System (BAS) through the building's intranet, or even remotely through the Internet, has become a common practice. However, BAS was historically developed as a closed environment and designed with limited cyber-security considerations. Thus, smart buildings are vulnerable to cyber-attacks with the increased accessibility. This study introduces the development and capability of a Hardware-in-the-Loop (HIT) testbed for testing and evaluating the cyber-physical security of typical BASs in smart buildings. The testbed consists of three subsystems: (1) a real-time HIL emulator simulating the behavior of a virtual building as well as the Heating, Ventilation, and Air Conditioning (HVAC) equipment via a dynamic simulation in Modelica; (2) a set of real HVAC controllers monitoring the virtual building operation and providing local control signals to control HVAC equipment in the HIL emulator; and (3) a BAS server along with a web-based service for users to fully access the schedule, setpoints, trends, alarms, and other control functions of the HVAC controllers remotely through the BACnet network. The server generates rule-based setpoints to local HVAC controllers. Based on these three subsystems, the HIL testbed supports attack/fault-free and attack/fault-injection experiments at various levels of the building system. The resulting test data can be used to inform the building community and support the cyber-physical security technology transfer to the building industry.

Li, Guowen↗

DOE OSTI2024

The role of air sealing while ground source heat pump system retrofits in the U.S. single-family houses

Widespread commercial adoption of ground source heat pumps (GSHP) is hindered by the relatively high initial cost associated with drilling boreholes in the ground to deploy ground heat exchangers. Reducing the energy demand of buildings has the potential to reduce the required borehole length and the associated drilling costs. In single-family residential buildings, air sealing can significantly lower heating energy usage, according to recent studies and reports. Thus, air sealing in conjunction with GSHP retrofits can lower the required GSHP system's capacity and borehole length to meet the thermal demands of the buildings. In order to understand the role of combining air sealing with GSHP retrofit quantitatively, the current study employs a whole building energy simulation tool integrated with an advanced design tool for the ground heat exchanger to determine changes in required GSHP capacity, total borehole length, and building energy consumption for with- and without-air sealing in single-family houses in 3 climate zones in the United States. The study considers one representative city for each climate zone, Phoenix, AZ for a hot climate, Seattle, WA for a moderate climate, and Minneapolis, MN for a cold climate. The results from this study show that reducing air infiltration from 0.8 ACH to the minimum ventilation requirement (0.35 ACH) can reduce borehole length requirement by up to 24% in Phoenix, 32% in Seattle, and 70% in Minneapolis. A similar magnitude of reduction can be seen for GSHP capacity and total building energy usage as well.

Prem Anand Jayaprabha, Jyothis Anand↗

DOE OSTI2024

Learning-Based Building Flexibility Estimation and Control to Improve Microgrid Economics and Resilience: Preprint

This paper proposes a learning-based building flexibility estimation and control framework to improve system economics and resilience. A data-driven building load flexibility model consisting of weather forecasting and estimating load consumption is proposed to quantify building heating, ventilation, and air conditioning (HVAC) load flexibility. A reinforcement learning-based microgrid controller is proposed to dispatch distributed generators, distributed energy resources, and build HVAC loads while taking flexibility information as one of the inputs. Simulation analysis is conducted on the model of a real microgrid in California. The effectiveness of the proposed learning-based building flexibility estimation and control in reducing microgrid energy costs and improving the sustainability of critical loads is demonstrated.

building load flexibility↗

DOE OSTI2024

Paths Forward: Approaches to Achieve Plug and Process Load Efficiency and Control in Commercial Buildings: Preprint

To accomplish net-zero carbon in the built environment by 2050, we must equitably decarbonize commercial buildings, which includes reducing plug and process loads (PPLs). PPLs are plug-in or hardwired electric and gas loads that are not directly associated with major building end uses like lighting and heating, ventilating, and air conditioning. PPLs account for a growing portion of U.S. commercial building energy consumption. Although commercial building PPL strategies and technologies are available today, they have not been adopted at a level sufficient to achieve significant savings and load flexibility across the building stock. In our "Pathways to Plug and Process Load Efficiency and Control" study, we investigated why these technologies and strategies have not seen widespread adoption and identified five behavior and technology pathways to increase PPL reduction in commercial buildings. In this paper, we expand beyond identifying the pathways and discuss approaches for achieving them. We discuss the importance of collecting and sharing data and case studies on PPL energy consumption and savings from control technology implementation, including code-required measures, for increasing adoption. Centralizing case studies and data, engaging industry organizations, and promoting awareness of PPL efficiency benefits to relevant groups are also key approaches. Additionally, funding, incentives, and rebate programs play important roles in driving PPL efficiency and control adoption. Finally, we discuss integrating PPL efficiency into broader company goals, such as environmental, social and governance (ESG) strategies and green building certifications, to further drive adoption.

adoption pathways↗

DOE OSTI2024

Multi-Fidelity Modeling and Control for Building Temperature Control

The ability to control energy loads such as a building's heating, ventilation, and air conditioning (HVAC) system can help facilitate increased penetration of variable renewable energy sources into the electric grid. To be able to control these HVAC systems more effectively, detailed simulations of the corresponding building physics is becoming increasingly important. These detailed simulations can be complex, nonlinear, and can require immense computational power when used in an advanced control method such as model predictive control (MPC), prompting the need to explore less computationally intensive strategies. In this work, a multi-fidelity approach is proposed to combine samples from a complex, high-fidelity model with a simple, low-fidelity model within the MPC control loop. More specifically, the parameters of a reduced-order, linear building model are periodically updated with knowledge from its high-fidelity counterpart - an EnergyPlus model - in an online fashion using a Gaussian Process surrogate model. Hence, highly accurate predictions of current and future conditions in a building are maintained with a substantially reduced computational burden compared to using the high-fidelity models alone. In other words, this linear parameter varying model preserves the low computational requirements of a low-order linear model while accurately modeling a building's dynamics. This allows a building controller to take highly informed actions without requiring a large computational budget.

building modeling↗

DOE OSTI2024

Unlocking the Path to Decarbonized Building Thermal Systems: Strategies for Designers and Contractors: Preprint

The design and construction community plays a pivotal role in facilitating the transition to decarbonized thermal systems that maintain human comfort while reducing building emissions. Through the U.S. Department of Energy Better Buildings initiative's Design and Construction Allies, a cohort of leading architecture, engineering, and construction firms have identified top ranked barriers that designers and contractors face when implementing solutions for building owners. These barriers to decarbonizing thermal - especially heating - systems include equipment availability; electrical capacity constraints; space allocations; complex system configurations; and lack of experience in designing, installing, and maintaining heat pumps. These impediments significantly amplify the risk and financial burden associated with the adoption of decarbonized solutions. The barriers also decrease the likelihood that designers, contractors, and owners will adopt decarbonization strategies without clear plans and guidance on how to implement these solutions, mitigate risk, and overcome the identified barriers. The National Renewable Energy Laboratory, the Design and Construction Allies, and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers have developed "how to" thermal decarbonization guidance based on best practices. The subjects covered range from the role of energy efficiency in facilitating decarbonized heating solutions to strategies for decarbonizing new and existing heating, ventilating, and air-conditioning systems. The focus is on overcoming barriers so that energy-efficient, electrified buildings - both new and retrofit - become the industry standard. This paper outlines 1) the method used to collect and organize this guidance, 2) industry barriers to decarbonization, and 3) decarbonization techniques that have broad market applicability.

building heating↗

DOE OSTI2024

Practical challenges of model predictive control (MPC) for grid interactive small and medium commercial buildings

To the urgent call for mitigating climate change, substantial initiatives have been undertaken to deploy grid-interactive heating, ventilation, and air-conditioning (HVAC) controls, such as model predictive control (MPC) for buildings. These efforts typically aim to curtail peak energy demand, shift load and enhance overall energy efficiency. With the recent development of low-cost MPC technologies that don’t require extensive instrumentation or manual modeling, small and medium commercial buildings (SMCBs), which rarely utilize advanced HVAC control systems, have become candidates for grid-interactive efficient buildings (GEBs). However, despite the potential benefits and maturity of the technology itself, several practical challenges remain in real-world implementation. In this paper, we share the practical challenges that we have encountered in implementing and testing three types of MPC solutions (ON/OFF unit, dualfuel, and VRF systems) on multiple SMCB sites. We describe the MPC deployment process and discuss the lessons learned. The site selection, eligibility, and retrofit availability (e.g., utility price structure, thermostat communications, etc.) are the main discussion points at the beginning of the project. Also, the modeling automation and the best practices for interacting with endusers and handling erroneous situations are presented for successful operations.

woo Ham, Sang↗

DOE OSTI2024

Brick Schema Standardized Plug Load Control Strategies for Load Reduction: Preprint

Plug loads comprise a significant percentage of commercial building energy consumption. Applying intelligent controls to turn off plug loads when unused can provide dynamic load reduction and flexibility, which are key traits of grid-interactive efficient buildings. This capability is important for equitable decarbonization as it can enable disadvantaged communities to electrify buildings without costly upgrades to electrical infrastructure. In this work, we present the effectiveness of various control strategies along with the operational lessons that informed their design. During a three-year period, we operated over 600 smart outlets in 12 university office buildings. The attached plug loads consisted primarily of printers, TVs, water dispensers, and copiers. After recording baseline power measurements for one year, we designed plug load control (PLC) strategies for each plug load type, use, and for different risk tolerance levels because PLC can potentially be disruptive to daily work. We used the Brick Schema to facilitate the management of plug load locations and other metadata. For advanced controls, we integrated the smart plugs with heating, ventilation, and air conditioning (HVAC) systems through the campus building automation system. We found static schedules to be the least disruptive and most predictable for occupants, resulting in 38% and 66% energy savings in two studies. For printers, print server-triggered PLC produced 86% savings, the highest of all strategies with minimal occupant impact. Scheduling of water dispensers and digital signage TVs produced 49% and 70% savings respectively with opportunities to improve performance with the use of HVAC occupancy data.

ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION↗

DOE OSTI2024

On the Corrosion Response of Novel Heat Exchangers Manufactured by Casting of Al-Ce-Mg Alloy

Developing low-cost and durable heat exchangers is critical for next-generation heating, ventilation, air conditioning, and refrigeration systems. The emerging requirement to minimize the total refrigerant charge inventory while ensuring a uniform distribution of refrigerant has led to the deployment of advanced manufacturing strategies. At the same time, corrosion is a longstanding issue for metal components, especially those used in heat exchanger (HX) applications. In this study, Al-Ce-Mg alloy-based HXs have been investigated. The corrosion resistance of HXs prototype manufactured by the casting process has been examined and the potential of a new manufacturing approach has been explored to meet the requirements of emerging needs.

Brechtl, Jamieson↗

DOE OSTI2024

Optimization of R290 variable geometry heat exchangers

Air-to-refrigerant heat exchangers (HX) are vital components in Heating, Ventilating and Air Conditioning and Refrigeration (HVAC&R) equipment. Recent literature has proposed utilizing shape-optimized, non-round tubes to reduce component size and refrigerant charge, thus enabling the adoption of low-GWP natural refrigerants like R290. However, most designs are restricted to fixed tube configurations, limiting the overall performance potential. In this work, multi-objective optimization is used in a staged approach to develop variable geometry multi-pass air-to-R290 HXs with minimal volume and airside pressure drop. Non-round tubes are used throughout the domain and each pass may have different tube arrangements to maximize HX performance. Compared to conventional fin-tube HXs, the optimized designs demonstrate more than 60% reductions in envelope volume, 30% reductions in face area, and up to 24% reduction in airside pressure drop. Additionally, the refrigerant charge reduction was up to 64%, thus enabling safe use of flammable and mildly-flammable refrigerants.

42 ENGINEERING↗

DOE OSTI2024

Experimentation on Finned-Tube Microchannel Heat Exchanger Incorporating Phase Change Material and R-410A

Integrating latent heat thermal energy storage, particularly phase change materials (PCM), in building heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems, offers substantial benefits for peak load shifting and energy efficiency. While numerous studies explore PCM-embedded heat exchangers (PCM-HX) using single-phase heat transfer fluids, there needs to be more investigation regarding PCM-HX utilizing two-phase refrigerant flow. This gap is even more pronounced for microchannel heat exchanger (MCHX) configurations. In this study, an MCHX-based PCM-HX was built and tested to analyze and evaluate the performance of a PCM-HX operating with a two-phase refrigerant as the working fluid. A commercially available MCHX condenser unit was embedded with 2.6 kg of RT35 PCM and tested using R-410A as the working fluid, using an in-house test loop to control the refrigerant inlet conditions precisely. Thin and minimally invasive T-type thermocouples traced the temperature evolution along MCHX channels and tube banks. Additional larger T-type thermocouple probes at the refrigerant inlet and outlet measured the average power of the PCM-HX during condensing tests, ranging from 0.7 kW to 1.6 kW based on mass flow rates varying from 3.5 g/s to 8 g/s. This experimental study on MCHX-based PCM-HX with a two-phase refrigerant has the potential to offer practical design guidelines for the direct integration of PCM-TES in HVAC&R systems without the use of a secondary loop, while caution is advised to avoid a substantial increase in the refrigerant charge amount.

42 ENGINEERING↗

DOE OSTI2023

Hydrogen Equipment Enclosure Risk Reduction through Earlier Detection of Component Failures

Hydrogen component reliability and the hazard associated with failure rates is a critical area of research for the successful implementation and growth of hydrogen technology across the globe. The research team has partnered to quantify system risk reduction through earlier detection of hydrogen component failures. A model of hydrogen dispersion in a hydrogen equipment enclosure has been developed utilizing experimentally quantified hydrogen component leak rates as inputs. This model provides insight into the impact of hydrogen safety sensors and ventilation on the flammable mass within a hydrogen equipment enclosure. This model also demonstrates the change in safety sensor response time due to detector placement under various leak scenarios. The team looks to improve overall hydrogen system safety through an improved understanding of hydrogen component reliability and risk mitigation methods. This collaboration fits under the work program of IEA Hydrogen Task 43 Subtask E Hydrogen System Safety.

CFD↗

DOE OSTI2022

Development of a water source heat pump hardware-in-the-loop (HIL) testing facility for smart building applications

Over the last decade, the global fight against climate change through electrification has led to an increase in research on building heating, ventilation, and air conditioning (HVAC) systems that utilize intelligent control algorithms to provide demand-side grid service while maintaining the thermal comfort of building occupants. As the pivotalpoint between building electricity consumption and indoor thermal comfort, high-efficiency electrical heatpumps are at the center of these emerging studies, and various grid-interactive and occupant-comfort control algorithms have been developed for them. The impact of these algorithms on the heatpump operation andperformance under different weather, building load, and grid requests calls for investigation and verification via experimental tests with actual heat pumps integrated with real-time building and grid responses. This study presents a Water-Source Heat Pump Hardware-in-The-Loop (HIL) Test Facility developed with the capability to perform such tests. The hardware configuration for this testfacility introduces a hydronic system that emulates the conditions for the heat pump water-side, and a duct system that emulates conditions for the heat pump airside. Both data acquisition and emulator control are implemented through the National Instruments (NI) LabVIEW software running on an NI PXIplatform. The HIL mechanism based on the hardware-software integration that allows the testbed to communicate with a generic simulation environment is also discussed. Currently, the test facility setup includes a single heatpump and virtual building model in EnergyPlus coupled with an occupant behavioral model in MATLAB. Preliminary test results of the current setup demonstrate the building load emulator's ability to track the simulated gone temperature with a Root Mean Square Deviation (RSME) below 0.12°C (0.216°F). An uncertainty analysis based on sensor accuracies shows that the heat pump coefficient of performance (COP) can be measured with a relative uncertainty of 10.4% in cooling and 3.7% in heating. Apartfrom the current testing on a single heat pump, the test facility also provides the flexibility to include additional heat pumps to form a heat pump cluster, as well as coupling the heat pump with active thermal storage to provide enhanced demandflexibility.

Calfa, Caleb↗