Energy Star Research Articles

Electric Water Heater Modeling for Large-Scale Distribution Power Systems Studies with Energy Storage CTA-2045 Based VPP and CVR

As the smart grid involves more new technologies such as electric vehicles (EVs) and distributed energy resources (DERs), more attention is needed in research to general energy storage (GES) based energy management systems (EMS) that account for all possible load shifting and control strategies, specifically with major appliances that are projected to continue electrification such as the electric water heater (EWH). In this work, a methodology for a modified single-node model of a resistive EWH is proposed with improved internal tank temperature for user comfort modeling and capabilities for conservation voltage reduction (CVR) simulations as well as Energy Star and Consumer Technology Association communications protocol (CTA-2045) compliant controls, including energy storage calculations for “energy take”. Daily and weekly simulations are performed on a representative IEEE test feeder distribution system with experimental load and hot water draw (HWD) profiles to consider user comfort. Sequential controls are developed to reduce power spikes from controls and lead to peak shavings. It is found that EWHs are suitable for virtual power plant (VPP) operation with sustainable tank temperatures, i.e., average water temperature is maintained at set-point or above at the end of the control period while shifting up to 78% of EWH energy out of shed windows per day and 75% over a week, which amounts to up to 23% of the total load shifted on the example power system. While CVR simulations reduced the peak power of individual EWHs, the aggregation effect at the distribution level negates this reduction in power for the community. The EWH is shown as an energy constant load without consistent benefit from CVR across the example community with low energy reductions of less than 0.1% and, in some cases, increased daily energy by 0.18%.

Assessing Office Building Marketability before and after the Implementation of Energy Benchmarking and Disclosure Policies—Lessons Learned from Major U.S. Cities

An increasing number of U.S. cities require commercial/office properties to publicly disclose their energy performance due to the adoption of energy benchmarking and disclosure policies. This level of transparency provides an additional in-depth assessment of a building’s performance beyond a sustainability certification (e.g., Energy Star, LEED) and may lead less energy-efficient buildings to invest in energy retrofits, therefore improving their marketability. However, the research is scarce on assessing the impact of such policies on office building marketability. This study tries to fill this gap by investigating the impact of energy benchmarking policies on the performance of office buildings in four major U.S. cities (New York; Washington, D.C.; San Francisco; and Chicago). We use interrupted time series analysis (ITSA), while accounting for sustainability certification, public policy adoption, and property real estate performance. The results revealed that in some cities, energy-efficient buildings generally perform better than less energy-efficient buildings after the policy implementation, especially if they are Class A. The real estate performances of energy-efficient buildings also exhibited continuously increasing trends after the policy implementation. However, due to potentially confounding factors, further analysis is required to conclude the policy impacts on energy-efficient buildings are more positive than those on less energy-efficient buildings.

Stellar features of strange dark energy stars

Dark energy stars are theoretical objects that could potentially provide an explanation for the observable properties of black holes, including their event horizons and emission of the Hawking radiation. Because of this, they are considered to be an important area of research in modern theoretical physics and could help to answer fundamental questions about the Universe and the nature of dark energy. So, identifying and characterizing dark energy stars are a theoretically active and significant field in literature. In this context, for a theoretical model describing a new static symmetric singularity-free anisotropic dark energy star in view of the Rastall theory of gravity, which is an alternative to the general theory of relativity and is consistent with a wide range of astronomical observations, we focus our awareness in the present study on the modified field equations as well as the hydrostatic equilibrium expression and then discuss the corresponding solutions. It is shown that this new-type dark energy star meets all the necessary astronomical requirements, including stability and feasibility can potentially represent a compact cosmic structure.

How energy benchmarking in healthcare facilities supports greenhouse gas emission reduction.

Energy benchmarking of Horizon Health Network's facilities has been the foundation of an energy management system for the health authority that has led to greenhouse gas emission reductions. Benchmarking energy consumption and appropriately understanding the true impact of energy consumption is the first step in setting target greenhouse gas emission reduction. ENERGY STAR® Portfolio Manager® is the benchmarking tool used by Service New Brunswick for all Government of New Brunswick owned buildings, including all 41 owned Horizon healthcare facilities. This web-based tracking tool then produces benchmarks which supports identification of energy conservation opportunities and efficiencies. Progress for energy conservation and efficiency measures can then be monitored and reported. Since 2013, this approach has supported 52,400metric tonnes reduction in greenhouse gas emission from Horizon facilities.

A High Voltage Gain Interleaved DC-DC Converter Integrated Fuel Cell for Power Quality Enhancement of Microgrid

Fuel cells have drawn a lot of interest in recent years as one of the most promising alternative green power sources in microgrid systems. The operating conditions and the integrated components greatly impact the quality of the fuel cell’s voltage. Energy management techniques are required in this regard to regulate the fuel cell’s power in a microgrid. The active/reactive power in the microgrid should be adjusted in line with US Energy Star’s regulations whereas the grid current needs to follow the standard set by IEEE 519 2014 to enhance the power quality of the electrical energy injected into the microgrid. Uncontrolled energy injection from the fuel cell can have serious impacts including superfluous energy demand, overloading, and power losses, especially in high power and medium voltage systems. Although fuel cells have many advantages, they cannot yet produce high voltages individually to compensate for the demand of a microgrid system. Due to these reasons, the fuel cell must be interfaced with a DC-DC converter. This research proposes a novel high voltage gain converter integrated 1.26 kW fuel cell for microgrid power management that can boost the fuel cell’s voltage up to 20 times. Due to this high voltage gain, the voltage and current ripple of the fuel cell is also reduced substantially. According to the analysis, the proposed converter demonstrated optimal performance when compared to the other converters due to its high voltage gain and extremely low voltage ripple. As a result, the harmonic profile of the microgrid current persists with a reduced THD of 3.22% and a very low voltage ripple of 4 V. To validate the converter’s performance, along with extensive simulation, a hardware prototype was also built. The voltage of the fuel cell is regulated using a simplified proportional integral controller. The operating principle of the converter integrated fuel cell along with its application in microgrid power management is demonstrated. A comparative analysis is also shown to verify how the proposed converter is improving the system’s performance when compared against other converters.

Analysis of the boundary condition and equation of state in radiating stars

A model of a radiating star undergoing gravitational collapse is constructed by systematically studying both the boundary condition and equation of state for the first time. The resulting system of partial differential equations is analysed using Lie symmetries. The group analysis produces new classes of exact solutions with acceleration, expansion and shear in the presence of the cosmological constant. Known exact solutions are recovered as special cases of our solutions. In particular, we regain the Euclidean star model which is the relativistic version of the Newtonian star. The range of the equation of state parameters allows the solution to be interpreted as barotropic matter stars or dark energy stars. A particular case shows that the model is physically reasonable and the energy conditions are satisfied.

Dark Energy Star: Physical Constraints on the Bounds

AbstractIn the present article, we explore a new solution to the Einstein‐Maxwell field equations to describe spherically symmetric, charged and anisotropic dark energy stars. The interior of such stars containing two non‐interacting fluids like dark and normal matter with a relation that the dark energy density is proportional to the energy density of a isotropic matter. We have used modified chaplygin gas equation to define the dark energy part. Also we have defined the interior space‐time through Krori‐Barua (KB) space‐time and matched it with the exterior Reissner‐Nordström space‐time. The well‐behaveness of the physical attributes have been discussed by plotting graphs for three specific compact objects with respect to our solutions. We conclude that all the physical attributes satisfy the required conditions for viability as well as stability and hence our model can be used to characterize dark energy stars for a set of parametric values belong to the present study.

Stripped-envelope stars in different metallicity environments

Stripped-envelope stars can be observed as Wolf-Rayet (WR) stars or as less luminous hydrogen-poor stars with low mass-loss rates and transparent winds. Both types are potential progenitors of Type I core-collapse supernovae (SNe). We used grids of core-collapse models obtained from single helium stars at different metallicities to study the effects of metallicity on the transients and remnants these stars produce. We characterised the surface and core properties of our core-collapse models and investigated their ‘explodability’ using three criteria. In the cases where explosions are predicted, we estimated the ejecta mass, explosion energy, nickel mass, and neutron star (NS) mass. Otherwise, we predicted the mass of the resulting black hole (BH). We constructed a simplified population model and find that the properties of SNe and compact objects depend strongly on metallicity. The ejecta masses and explosion energies for Type Ic SNe are best reproduced by models with Z = 0.04 that exhibit strong winds during core helium burning. This implies that either their mass-loss rates are underestimated or that Type Ic SN progenitors experience mass loss through other mechanisms before exploding. The distributions of ejecta masses, explosion energies, and nickel mass for Type Ib SNe are not well reproduced by progenitor models with WR mass loss, but are better reproduced if we assume no mass loss in progenitors with luminosities below the minimum WR star luminosity. We find that Type Ic SNe become more common as metallicity increases, and that the vast majority of progenitors of Type Ib SNe must be transparent-wind stripped-envelope stars. We find that several models with pre-collapse CO masses of up to ∼30 M⊙ may form ∼3 M⊙ BHs in fallback SNe. This may have important consequences for our understanding of SNe, binary BH and NS systems, X-ray binary systems, and gravitational wave transients.

A Highly Efficient PFC Flyback Converter for Residential Lighting with Universal Input

This paper describes a power-factor-corrected-based flyback converter for low-power domestic lighting. The proposed flyback converter works in a discontinuous-conduction mode (DCM) and provides enhanced power-quality (PQ). In low-power residential lighting, the flyback converter is significantly preferred over non-isolated converters owing to its numerous advantages, such as its low component count, cost-effective solution, and safe operating conditions. The proposed DCM-based flyback converter has a simple circuit configuration and lower total harmonic distortions (THD) of input current by about 15% with an input power factor of around 0.97. A hardware prototype has been developed and examined at different AC source voltages to validate the feasibility and effectiveness of a proposed model. Experimental results show that the whole system efficiency satisfies Energy Star standards with 91.04 percent efficiency at a rated load of 24 Watts and 220 V AC mains and also fulfilled the stringent limits as per IEC61000-3-2 Class D standards.

Radial pulsations, moment of inertia and tidal deformability of dark energy stars

We construct dark energy stars with Chaplygin-type equation of state (EoS) in the presence of anisotropic pressure within the framework of Einstein gravity. From the classification established by Iyer et al. (Class Quantum Grav 2:219, 1985), we discuss the possible existence of isotropic dark energy stars as compact objects. However, there is the possibility of constructing ultra-compact stars for sufficiently large anisotropies. We investigate the stellar stability against radial oscillations, and we also determine the moment of inertia and tidal deformability of these stars. We find that the usual static criterion for radial stability dM/drho _c >0 still holds for dark energy stars since the squared frequency of the fundamental pulsation mode vanishes at the critical central density corresponding to the maximum-mass configuration. The dependence of the tidal Love number on the anisotropy parameter alpha is also examined. We show that the surface gravitational redshift, moment of inertia and dimensionless tidal deformability undergo significant changes due to anisotropic pressure, primarily in the high-mass region. Furthermore, in light of the detection of gravitational waves GW190814, we explore the possibility of describing the secondary component of such event as a stable dark energy star in the presence of anisotropy.

Improvement of information support to promote the economic advantages of energy saving under the conditions of military conflicts

Energy consumption is the most important strategy for improving economic efficiency and decarbonization. State energy saving measures aimed at promoting changes in sustainable habits and procedures can significantly save energy consumption. Information support for promoting the economic benefits of energy saving under the conditions of military conflicts needs more attention. The leading methodological tools were the methods of observation, comparison, as well as historical method. The research reported here showed that the aggression on the part of the Russian Federation required states to urgently improve the system of implementation of national information policies in order to increase the level of energy saving and energy efficiency. The EU's plans to reduce energy consumption "Play your role" and "Save energy" are aimed at informing the public about the need to contribute to energy saving processes. It is proved that currently in the EU, 80 % of member states ensure the effective implementation of new state campaigns for information support to promote the economic benefits of energy saving. Awareness-raising campaigns such as EPAH, I Have Influence, Green Ambassadors, EU4Energy's energy awareness campaign in collaboration with EU NEIGHBORS east are noteworthy. This activity and the set of energy labeling measures ENERGY STAR and EPREL can become the basis for the implementation of public education programs at educational institutions during the period of military instability in Ukraine. A promising vector of further scientific research will be the analysis of the practice of implementing information support to popularize the economic benefits of energy saving on the territory of Ukraine during the aggravation of the military conflict on the territory of the state

Explaining the Changes in the Greenhouse Gas Emissions of New York City Buildings

Greenhouse Gas (GHG) emissions are among the major causes of the rise in the global temperature and global warming. US commercial and residential New York City (NYC) buildings emit a high amount of GHG each year. Several past studies have introduced prediction models for the GHG emission of buildings. However, the factors that contribute to the changes in GHG emission patterns over time are less explored. In this paper, the New York Local Law 84 datasets for four consecutive years from 2017 to 2020 are used to explore which changes in building attributes would increase/decrease GHG emission over time. A Random Forest prediction model in combination with a variable importance analysis is conducted to identify the most important factors contributing to the observed increasing or decreasing GHG emission patterns. The results show that Energy Star Score is a significant factor in explaining an increasing GHG emission pattern. Similarly, the reduction in the GHG emission levels can be explained by the success in maintaining the Energy Star Score and significant reduction in the electricity and gas consumption of the buildings. The findings of the study can be used to prioritize actions and design appropriate policies to reduce the GHG emission of buildings.

The mass–radius relation for quark stars in energy–momentum squared gravity

We study the structure of quark stars (QSs) adopting homogeneously confined matter inside the star with a 3-flavor neutral charge and a fixed strange quark mass ms. We explore the internal structure, and the physical properties of specific classes of QSs in the recently proposed energy–momentum squared gravity (EMSG). Also, we obtain the mass–radius (M–R) and mass–central energy density (M–ρc) relations for QS using the QCD motivated EoS. The maximum mass for QSs in EMSG is investigated depending on the presence and absence of the free parameter α. Furthermore, the stability of stars is determined by the condition dMdρc>0. We observe that consideration of the EMSG has specific contributions to the structure of QSs.

Dark energy star in gravity's rainbow

The concept of dark energy can be a candidate for preventing the gravitational collapse of compact objects to singularities. According to the usefulness of gravity's rainbow in UV completion of general relativity (by providing a new description of spacetime), it can be an excellent option to study the behavior of compact objects near phase transition regions. In this work, we obtain a modified Tolman-Openheimer-Volkof (TOV) equation for anisotropic dark energy as a fluid by solving the field equations in gravity's rainbow. Next, to compare the results with general relativity, we use a generalized Tolman-Matese-Whitman mass function to determine the physical quantities such as energy density, radial pressure, transverse pressure, gravity profile, and anisotropy factor of the dark energy star. We evaluate the junction condition and investigate the dynamical stability of dark energy star thin shell in gravity's rainbow. We also study the energy conditions for the interior region of this star. We show that the coefficients of gravity's rainbow can significantly affect this non-singular compact object and modify the model near the phase transition region.

Why is it still too warm or cold in my house? Examining the relationships between energy efficient capital and household energy insecurity

This paper examines the relationships between energy efficient (EE) capital technology and household energy insecurity in the United States. The theoretical model of these relationships employs household production theory to capture the demand for and production of household energy services, and a stochastic production frontier approach to describe how having access to and the usage intensity of EE capital technology could help alleviate inefficiency in the production of household energy services. A working hypothesis formulated from the theoretical model posits that having EE capital technology in the home will reduce the level of household energy insecurity experienced. The extent of energy insecurity experienced is inferred from an energy insecurity index value assigned to each household, generated via the application of a dichotomous Rasch model to questions contained in the 2015 Residential Energy Consumption Survey. Noting the potential simultaneous relationship that exists between a household having access to and the usage intensity of EE capital technology and the experience of being energy insecure, an instrumental variables approach was employed to estimate a series of ordered logit models. Results suggest access to EE capital technology in the form of Energy Star® appliances, Energy Star® windows, or a SMART thermostat does not reduce the probability of experiencing a greater level of energy insecurity. Nor does the usage intensity of EE capital. Thus, policy instruments designed to alleviate household energy insecurity may need to go beyond simply helping households obtain EE capital technology.

Neural responses clarify how ecolabels promote sustainable purchases

While behavioral and policy interventions such as ecolabels (e.g., the Energy Star label) promote sustainable purchases, the reason for their influence remains unclear. We combined incentive-compatible purchasing experiments, neuroimaging assessments, and a national stated choice survey to examine how the Energy Star label might influence choices of light bulbs within individuals, across individuals (n = 36), and out-of-sample in a national survey (n = 1550). Presence of the Energy Star label increased activity in neural regions associated with positive affective responses that predicted purchasing (e.g., the Nucleus Accumbens or NAcc), particularly in more impulsive individuals. Group-averaged NAcc activity could also account for consumer demand for similar sustainable product combinations in a national survey. These findings suggest that ecolabels may leverage affective responses in individuals as well as markets to promote sustainable purchases, which might inform the promotion of sustainable products.

The weather affects air conditioner purchases to fill the energy efficiency gap

Energy efficiency improvement is often hindered by the energy efficiency gap. This paper examines the effect of short-run temperature fluctuations on the Energy Star air conditioner purchases in the United States from 2006 to 2019 using transaction-level data. Results show that the probability of purchasing an Energy Star air conditioner increases as the weekly temperature before the transaction deviates from 20–22 °C. A larger response is related to fewer cooling degree days in the previous years, higher electricity prices/income/educational levels/age/rate of owners, more common use of electricity, and stronger concern about climate change. 1 °C increase and decrease from 21 °C would lead to a reduction of total energy expenditure by 35.46 and 17.73 million dollars nationwide (0.13% and 0.06% of the annual total energy expenditure on air conditioning), respectively. Our findings have important policy implications for demand-end interventions to incorporate the potential impact of the ambient physical environment.

An optimized solution for retrofitting building façades: Energy efficiency and cost-benefit analysis from a life cycle perspective

The study aims to conduct a comprehensive cost-benefit analysis (CBA) for incremental energy star ratings in Melbourne and Perth by upgrading the thermal performance of the building façade. CBA is performed over 20, 40, and 60 years by considering the refurbishment of an existing building façade or a newly constructed house to ensure the highest energy efficiency at the lowest reasonable cost. The hybrid approach of using a dynamic energy simulation tool (FirstRate5) and @RISK optimizer provides a feasible solution for obtaining a specific star rating. This study shows energy saving costs can offset the additional investment of insulation levels and energy-efficient glazings. However, life cycle energy savings are minimized after a certain point of supplementary yield insulations, such as ceilings R(6) and walls R(3). Hence the results are evaluated in terms of financial appraisals, such as net present value (NPV), benefit-cost ratio (BCR), internal rate of return (IRR), and other indicators for incremental star-rated designs. The results of the financial appraisals recommend upgrading the obligatory star rating from 6-star to 8-star is a cost-effective solution irrespective of climate and time horizon. Sensitivity indices of design variables exhibit the significance of functionality and cost implications in the established energy rating scheme. Possible economic recession (at > 7%) due to COVID and the Ukraine war, the investment coefficient (r ≤ −0.56) with NPV increases significantly against energy savings cost (r ≥ 0.8). Given the present energy rating scheme, these findings provide an exhaustive perception of policy implications.

Anisotropic compact stars with Tolman 𝕍 solution in f(ℛ,𝒯2) gravity

The main purpose of this paper is to study the physical characteristics and stability of anisotropic compact stars in energy–momentum squared gravity. We use Tolman [Formula: see text] solution and consider specific models of this theory to study the viable features of SAX J1808.4-3658, 4U 1538-52 and Her X-1 stars. We explore the behavior of energy density, pressure components, anisotropic factor, energy conditions and equation of state parameter in the interior of considered stars. To check the stability of these stars, we examine the behavior of causality conditions, Herrera cracking approach and adiabatic index. It is found that all the required conditions are satisfied for the proposed models, thus the considered stars are viable as well as stable in this modified theory.

Ranking Qi Wireless Power Transmitters by Efficiency

The Wireless Power Consortium (WPC) Energy Star Task Force (ESTF), comprised of engineers from major cellphone and consumer electronics manufacturers, test houses, and others, developed a proposed efficiency-test protocol for the U.S. Environmental Protection Agency (EPA), intended to rank Qi wireless power transmitters on the basis of power-transfer efficiency. Key to this test protocol is the assumption that a single, optimally designed test receiver may be used to accurately assess transmitter efficiency and enable ranking. The possibility exists that phones using different power receiver designs (e.g., different “friendly metal” profiles, different electrical designs) will interact with transmitters and report different rankings for a given transmitter, thus invalidating the proposed test protocol. Experiments to prove or disprove the assumption that a single optimized receiver can be used as a proxy to fairly compare and rank the real-world power-transfer efficiency performance of Qi wireless power transmitters were conducted. As a result of these experiments, the WPC has concluded that because of receiver–transmitter interaction, it is not possible to rank transmitters by efficiency for more than one receiver design but decreasing the transmitter’s standby power could save as much energy over a 24-h period as improving full-power efficiency by 10%.