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Exhaust ventilation and corresponding outdoor air strategies are being implemented in high performance, new construction, multifamily buildings to meet program or code requirements for improved indoor air quality, but a lack of clear design guidance is resulting in poor performance of these systems despite the best intentions of the programs or standards.
The energy-saving potential of occupancy-centric smart thermostats has been extensively explored in simulations but lacked field testing for energy savings quantification and sensor performance assessment in real buildings. This paper presents a long-term field study conducted in a single-family home in Texas, U.S. to evaluate the performance of occupancy-centric controls (OCC) of HVAC (heating, ventilation, and air-conditioning) system in terms of energy savings, sensor accuracy, and impact on electric peak demand. The test site was equipped with a commercial off-the-shelf (COTS) smart thermostat and multiple occupancy presence sensors for OCC implementation. Additionally, a sub-metering system was installed to monitor electricity consumption of various end-use equipment, including the HVAC system. A supplementary device was installed to track the ground-truth occupancy for the accuracy evaluation of the occupancy presence sensor. Scenarios of baseline and OCC controls were alternated weekly over the 20-month testing period. The results indicated an effective OCC execution, as evidenced by indoor temperature profiles. During the 2023 cooling season, OCC achieved total energy savings of 1,958 kWh, corresponding to a 17.6% energy savings ratio. Under certain conditions, daily HVAC energy savings reached as high as 17 kWh, with a savings ratio of 35%. Sensor performance showed an overall accuracy of 83.8%, a False Positive Rate (FPR) of 12.8%, and a False Negative Rate (FNR) of 47.4%. A key limitation was the sensor’s inability to detect stationary occupants during sleep, leading to a midnight FNR of nearly 100% and significantly compromising thermal comfort. Additionally, the implementation of OCC resulted in extended periods of high electricity demand on summer afternoons, affecting occupant’s thermal comfort and posing potential challenges to community-level grid operations if OCC were widely adopted. Furthermore, this study addresses a critical research gap by empirically investigating energy-saving potential and occupancy sensor performance in residential buildings. Through a comprehensive field-testing study, the research examines the interrelationship between sensor accuracy, energy savings, and thermal comfort, an area that has received limited attention in the current literature.
Here hybrid manufacturing combines additive with subtractive machining operations which often require the use of a coolant, that can increase the humidity of the build chamber. The water vapor can be adsorbed on the powder surfaces and subsequently dissociate into hydrogen and oxygen during melting and can be absorbed by part during solidification. Here, we investigated the effect of build chamber humidity during hybrid manufacturing on the part quality on two most common classes of steels i.e., austenitic (316L) and ferritic (grade 91). We report that the humidity increase has a negligible effect on part performance of both classes of steels.
This research project evaluates post-retrofit performance measurements, energy use data and construction costs for 13 projects that participated in the National Grid Deep Energy Retrofit Pilot program. The projects implemented a package of measures defined by performance targets for building enclosure components and building enclosure air tightness. Nearly all of the homes reached a post-retrofit air tightness result of 1.5 ACH 50. Homes that used the chainsaw retrofit technique along with roof insulation, and wall insulation applied to the exterior had the best air tightness results and the lowest heating and cooling source energy use. Analysis of measure costs and project objectives yielded a categorization of costs relative to energy performance objectives. On average about ½ of the energy-related measure costs correspond primarily to energy-related objectives, and 20% of energy-related measure costs relate primarily to non-energy objectives.
It is important to have practical methods for constructing a good mathematical model for a building's thermal system for energy audits, retrofit analysis and advanced building controls, e.g. model predictive control. Identification approaches based on semi-physical model structures are popular in building science for those purposes. However conventional gray box identification approaches applied to thermal networks would fail when significant unmeasured heat gains present in estimation data. Although this situation is very common and practical, there has been little research to tackle this issue in building science. This paper presents an overall identification approach to alleviate influences of unmeasured disturbances, and hence to obtain improved gray-box building models. The approach was applied to an existing open space building and the performance is demonstrated.
Claims that savings realization is greater in energy savings performance contracts (ESPCs) are rampant at least among energy service company representatives and other ESPC cheerleaders. But hard supporting evidence for these claims has been virtually non-existent. The Department of Energy's Federal Energy Management Program uses its Compliance Tracking System (CTS) database to document the performance of federal buildings and projects towards meeting various federal energy-saving goals. This paper focuses on preliminary analysis from CTS to understand and compare the performance of federal ESPCs with projects that have been implemented with more conventional government appropriations funding. The authors have found preliminary evidence using CTS that shows markedly higher savings realization rates among ESPC projects than appropriations-funded ones. There are numerous caveats to the data comparison that clamor for further study, but the difference is still intriguing. If borne out, this finding will provide concrete support to the idea that ESPCs guarantees and measurement and verification, long touted by energy service companies (ESCOs) as offering savings assurance, may truly yield substantial benefits. If ESPCs actually do perform better (i.e., have higher realization rates and savings persistence) than conventional bid-to-spec projects, the perceived premium for conducting them may look like a very good deal after all.
This Building America Top Innovations profile describes the DOE-sponsored BEopt software, which ensures a consistent analysis platform and accurate simulations. Many BEopt algorithms have been adopted by private-sector HERS software tools that have helped improve the energy efficiency of tens-of-thousands of ENERGY STAR-certified homes.
Unique systems, methods, techniques and apparatuses for cloud-based control for power distribution systems are disclosed. One exemplary embodiment is a system comprising a microprocessor-based power management system in operative communication with a plurality of buildings located remotely from the power management system and a plurality of communication interface devices provided at corresponding ones of the plurality of buildings. The power management system is structured to perform a plurality of building unit-specific optimizations, evaluate a net power demand on the electrical power grid, reduce the net power demand on the electrical power grid while minimizing disruption to the resident-defined preference parameters, and transmit to each of the plurality of interface devices the one or more additional control commands corresponding to the specific building at which each interface device is provided.
To mitigate the variation in demand on the electric grid, thermal energy storage (TES) is an alternative to electric batteries or installing new peaking power plants. Stakeholders and policy makers across the United States have expressed interests in promoting TES, as demonstrated by the US Department of Energy’s Grid-Interactive Efficient Buildings program and the efforts of various state legislatures. However, the cost value provided by TES are unclear. If reliable cost benefits were determined, stakeholders would have a clearer picture of the financial returns that can be gained from their investment in TES. In this report, EnergyPlus was used to perform whole-building simulations for two residential buildings in Indianapolis and Atlanta. The HVAC system in both buildings were equipped with phase change material TES. The TES tank was charged in off-peak hours and discharged in peak hours to perform load shifting. First, the economic value implied by existing time-of-use (TOU) rates offered by utility companies was analyzed via whole-building simulation. Second, existing demand reduction (DR) incentives sourced from 3 different electrical grid administrators (i.e., California, Texas, and New England region) were surveyed to determine their implied value. Lastly, the economic value implied by different types of deferred peak power plants were reviewed. The full value of TES to the entire society consists of value to the utility, OEMs, facility installers, and other stakeholders. This report focuses on the value to the utility with emphasis on the deferred capital of peak power plant. The value from the deferred capital of peak power plant is manifested to the customer in the form of demand reduction program and Time-of-Use utility rate program. In this report, an initial proxy of the value of TES is made by assuming the deferred capital cost of power plant is the full value to reduce peak demand. Three levels of financial value of TES systems were assessed. Two are currently available to some residential customers: (1) the benefit from TOU pricing alone and (2) the benefit from TOU pricing in combination with DR incentive programs. The third level was computed as the full cost of deferred capital cost of peaking power plants. This represents the potential value that could be gained by the utilities or conceivably be offered to consumers.
Smart new building technologies that offer continuous dynamic optimization of Heating, Ventilation, and Air Conditioning (HVAC) control hold promise to advance building operations for efficiency and grid response. These technologies use data from the control system to determine the analytically optimal setpoints, and then write back the optimal setpoints into the control system to minimize system energy consumption or costs. There are limited studies documenting field validations of these technologies. This paper presents the results from a long-term field evaluation of a model-predictive HVAC optimization system that installed in four commercial buildings. Energy savings analysis was conducted based on pre/post submetered energy use. Across the cohort of evaluation sites, HVAC savings following the implementation of the optimization system were mixed, ranging from 0–9%. Analysis of site operational data showed that occupant comfort was neither positively nor negatively impacted. Key technology adoption considerations and recommendations are summarized in the paper. The technology performs best when HVAC systems are in good working condition, and can be exercised to achieve the full range of its optimized setpoints–however it may not provide extensive additional savings over cases where best practice sequences of operation and reset strategies are already comprehensively implemented.
To lead the low-carbon transition in global buildings, this study is the first to use the generalized Divisia index method (GDIM) to identify the factors driving carbon emissions and assess the decarbonization performance in commercial building operations (CBOs) of sixteen countries during 2000–2019. Results show that (1) while the global carbon emissions from CBOs have increased at a modest rate of 0.9%/yr, this trend runs counter to the declining emissions in the U.S. (-1.1%/yr) and the significant growth in China (14.4%/yr), which can be attributed to the impact of economy-related factors. (2) The U.S. and China, as the largest emitters, contributed 66.8% of the samples’ decarbonization of CBOs (919.1 million tons of carbon dioxide). (3) Most countries’ CBOs had a decarbonization efficiency level of less than 10%, except for Spain (27.8%). Spain excelled in both areas of per capita and per floor area with an average efficiency of nearly 30%. Moreover, ridge regression successfully confirms the stability of GDIM results and it should be noted GDIM has limitations in characterizing the end-use activity. Overall, this study tracks the historical decarbonization of global CBOs and offers benchmarks for different emitters to forecast the dynamic of building emissions along with economic booms.
This research project evaluates post-retrofit performance measurements, energy use data and construction costs for 13 projects that participated in the National Grid Deep Energy Retrofit Pilot program. The projects implemented a package of measures defined by performance targets for building enclosure components and building enclosure air tightness. Nearly all of the homes reached a post-retrofit air tightness result of 1.5 ACH 50. Homes that used the chainsaw retrofit technique along with roof insulation, and wall insulation applied to the exterior had the best air tightness results and the lowest heating and cooling source energy use. Analysis of measure costs and project objectives yielded a categorization of costs relative to energy performance objectives. On average about 1/2 of the energy-related measure costs correspond primarily to energy-related objectives, and 20% of energy-related measure costs relate primarily to non-energy objectives.
Over recent years, heat pump water heaters (HPWHs) have become more readily available and more widely adopted in the marketplace. For a 6-month period, the Building America team Consortium for Advanced Residential Buildings monitored the performance of a GE Geospring HPWH in Windermere, Florida. The study found that the HPWH performed 144% more efficiently than a traditional electric resistance water heater, saving approximately 64% on water heating annually. The monitoring showed that the domestic hot water draw was a primary factor affecting the system's operating efficiency.
The Buildings Technologies Office (BTO), within the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), is initiating a new program in Sensor and Controls. The vision of this program is: • Buildings operating automatically and continuously at peak energy efficiency over their lifetimes and interoperating effectively with the electric power grid. • Buildings that are self-configuring, self-commissioning, self-learning, self-diagnosing, self-healing, and self-transacting to enable continuous peak performance. • Lower overall building operating costs and higher asset valuation. The overarching goal is to capture 30% energy savings by enhanced management of energy consuming assets and systems through development of cost-effective sensors and controls. One step in achieving this vision is the publication of this Sensor Characteristics Reference Guide. The purpose of the guide is to inform building owners and operators of the current status, capabilities, and limitations of sensor technologies. It is hoped that this guide will aid in the design and procurement process and result in successful implementation of building sensor and control systems. DOE will also use this guide to identify research priorities, develop future specifications for potential market adoption, and provide market clarity through unbiased information.
An Environmental Assessment was performed of the proposed addition to building G-86 at the Mars Site, which will provide space for new electronic equipment to consolidate the Deep Space Network (DSN) support facilities from other Goldstone Deep Space Communication Complex (GDSCC) sites at the Mars Site, and will include a fifth telemetry and command group with its associated link monitor, control processor, and operator consoles. The addition of these facilities will increase the capability of the DSN to support future sophisticated NASA spacecraft missions such as the International Solar and Terrestrial Physics (ISTP) Program. The planned construction of this building addition requires an Environmental Assessment (EA) document that records the existing environmental conditions at the Mars Site, that analyzes the environmental effects that possibly could be expected from the construction and use of the new building addition, and that recommends measures to be taken to mitigate any possible deleterious environmental effects.
During the course of this project, an affordable and high performance ductwork system to directly address the problems of thermal losses, poor efficiency, and air leakage was designed. To save space and enable direct connections between different floors of the building, the ductwork system was designed in such a way that it occupied interior or exterior frame wall cavities. The ductwork system satisfied building regulations for structural support when bridging multiple floors, the spread of fire and smoke, and insulation to reduce the heat flow into or out of the building. Retrofits of urban residential buildings will be the main focus for the application of this ductwork system. Highly reflective foils and insulating materials were used to aid in the increase of the overall R-value of the ductwork itself and the wall assembly. It is expected that the proposed system will increase the efficiency of the HVAC system and the thermal resistance of the building envelope. The performance of the proposed ductwork design was numerically evaluated in a number of different ways. Our results indicate that the duct method is a very cost attractive alternative to the conventional method.
This article highlights the need for an active role for building physics in the development of near-zero energy buildings while analyzing an example of an integrated system for the upgrade of existing buildings. The science called either Building Physics in Europe or Building Science in North America has so far a passive role in explaining observed failures in construction practice. In its new role, it would be integrating modeling and testing to provide predictive capability, so much needed in the development of near-zero energy buildings. The authors attempt to create a compact package, applicable to different climates with small modifications of some hygrothermal properties of materials. This universal solution is based on a systems approach that is routine for building physics but in contrast to separately conceived sub-systems that are typical for the design of buildings today. One knows that the building structure, energy efficiency, indoor environmental quality, and moisture management all need to be considered to ensure durability of materials and control cost of near-zero energy buildings. These factors must be addressed through contributions of the whole design team. The same approach must be used for the retrofit of buildings. As this integrated design paradigm resulted from demands of sustainable built environment approach, building physics must drop its passive role and improve two critical domains of analysis: (i) linked, real-time hygrothermal and energy models capable of predicting the performance of existing buildings after renovation and (ii) basic methods of indoor environment and moisture management when the exterior of the building cannot be modified.
Over recent years, heat pump water heaters (HPWHs) have become more readily available and more widely adopted in the marketplace. For a 6-month period, the Building America team Consortium for Advanced Residential Buildings monitored the performance of a GE Geospring HPWH in Windermere, Florida. The study found that the HPWH performed 144% more efficiently than a traditional electric resistance water heater, saving approximately 64% on water heating annually. The monitoring showed that the domestic hot water draw was a primary factor affecting the system's operating efficiency.