Demand For Energy Conservation Research Articles

Affordable generic digital twins for existing building environment management and an onsite deployment

The energy consumption during the operation and maintenance phase of buildings is huge. As the built-up area in China increases, the demand for energy conservation in existing buildings has become a key focus of its dual carbon policy. Intelligent operation and maintenance based on digital twins is an emerging means to reduce carbon emissions from buildings, but it faces some problems in the process of promotion. Complete digital and intelligent transformation requires significant investment and has certain requirements for project parties and operation and maintenance teams. Small businesses or individual households have relatively simple requirements for intelligent operation and maintenance scenarios and do not require complete digital twins. To address the above issues, this article uses an affordable universal digital twin framework to provide a digital solution for intelligent operation and maintenance of existing buildings. This solution allows networking communication between devices and uses IoT modules to monitor and control the environment. This digital twinning model can reduce the measurement and control of energy-consuming end devices without on-site transformation and has rich scalability. This article uses the solution to deploy an office at a university in Henan Province and specifically measures the power consumption of displays, indoor environment, and air conditioning. According to the needs, it expands the space occupation, fans, air handlers, lights, and other end devices of the digital twin. The digital twin accurately presents the energy consumption of the office during extreme weather conditions, which has an auxiliary role in promoting digital twins in the region and optimizing energy consumption in existing buildings.

A Fe(III)-driven strategy for efficient closed-loop recovery of critical metals from spent LiNixCoyMnzO2 powder

With the concepts of carbon peaking and carbon neutrality taking hold, the demand for recycling of spent lithium-ion batteries (LIBs) is increasing rapidly. However, current recycling methods are mostly faced with the dilemma of high cost and low efficiency and unable to meet the demand for energy conservation and consumption reduction. Here, inspired by the formation of acid mine drainage (AMD), we propose a Fe(III)-driven recovery approach, in which the leaching of valuable metals is enhanced by the addition of solid reagents Fe2(SO4)3 and pyrite (FeS2) to create an acidic reducing atmosphere. Under optimal conditions, the leaching efficiency of Ni/Co/Mn/Li reached 99.9%. In addition, NH3·H2O-NaOH was employed to adjust the pH of the leachate for stepwise precipitation of Fe and Ni/Co/Mn. Li was finally collected as Li2CO3 and Fe(III) could be recycled. We have also made attempts on Ni/Co/Mn co-precipitation and Li2CO3 resynthesis of regenerated LiNixCoyMnzO2 (NCM). It is predicted that this process can provide a green, efficient and economical closed-loop approach for cathode recovery of LIBs, with far-reaching implications for the entire battery recycling industry.

Modelling and onsite testing on dynamic thermal responses of built environment in passive solar rooms on Tibetan plateau

It of great importance in assessing built thermal environment level and evaluating corresponding indoor air conditioning demand for energy conservation in construction sectors. Nevertheless, because of the unique meteorological features in plateau area, classical building performance simulation approach contributes to thermal performance evaluation errors since most design codes or standards relies on low attitude regions. In this paper, a modified and improved dynamic thermal design model is put forward for built environment and energy consumption estimation for passive buildings for plateau buildings. Moreover, the simplified experiment is set up to monitor dynamic thermal responses for modelling building. The testing validation illustrate that the onsite measurement accuracy level is quite acceptable for engineering applications with less than 30% relative change range coefficient. Besides, the experiment data demonstrates that window-to-wall ratios, architectural orientation, thermal insulation coefficients, have substantial impacts for solar heat gains in plateau buildings. The study renders building design guidance for energy conservation in high altitude plateau areas.

Effects of fuel composite additives on the vibration, wear and emission performances of diesel engines under hot engine tests

Diesel engines applied for ships are currently facing an escalating demand for energy conservation and emission reduction, which has driven the application of fuel composite additives. Nevertheless, adverse phenomena affecting engine reliability have been observed in practical engine applications with unclear mechanisms. The present study investigated the vibration, wear, and emission performances of three types of composite additives with detergent and synergist function in a diesel engine. Vibration acceleration, cylinder temperature, NOx emission quantity, as well as the wear characteristics of cylinder liner-piston ring (CLPR) friction pairs were selected as characterization parameters. The results revealed that components of additives have a certain impact on vibration, wear, combustion, and emission performance. Specifically, additives of Type Ⅰ containing aviation kerosene and Type Ⅱ containing 2-Ethyl 1-hexanol and 2-Ethylhexyl nitrate compound in diesel were susceptible to cause aggravated engine vibration and thus lead to excessive wear. Furthermore, Type I exacerbates the thermal stress and worsens combustion stability, resulting in increased mechanical vibrations, cylinder temperature, and NOx emission. In contrast, addition of Type Ⅲ containing 2-nitro-propane and toluene results in improved reliability, demonstrating a 7.6% reduction in mechanical vibration energy and a 27.4% decrease in wear mass losses of piston rings, while effectively mitigating abnormal wear on the liner surface. Likewise, it also it also facilitates a mild combustion process and achieves better emission reduction results by reducing the NOx emission by 11.5% while slightly lowering the cylinder temperature by 0.74%.

Preparation and properties of CaCl2·6H2O/silica aerogel composite phase change material for building energy conservation

To meet the national demand for energy conservation and emission reduction, a shape-stable CaCl2·6H2O /silica aerogel composite phase change material (CPCM) for building energy storage was successfully developed. The CPCM was formed by using modified CaCl2·6H2O composed of CaCl2·6H2O (main PCM) and SrCl2·6H2O (nucleating agent) as PCM, and silica aerogel as carrier via physical blending method. The structure and properties of the CPCM were investigated by various techniques. The results showed that compositing of modified CaCl2·6H2O with silica aerogel could significantly reduce the thermal conductivity, effectively prevent leakage as well as lessen supercooling. The obtained CPCM with 75 wt% modified CaCl2·6H2O had suitable phase transition temperature (27.0 °C) with high latent heat (110.9 J·g−1), acceptable supercooling degree (1.6 °C), low thermal conductivity (0.1954 W/(m·K)) as well as excellent thermal reliability. The results obtained make the CPCM in this work promising for use in building thermal insulation materials.

Pyrolysis of lignocellulosic, algal, plastic, and other biomass wastes for biofuel production and circular bioeconomy: A review of thermogravimetric analysis (TGA) approach

Fossil fuels are currently the most significant energy sources. They are expected to become less available and more expensive, leading to a great demand for energy conservation and alternative energy sources. As a sustainable and renewable energy source, Biomass has piqued interest in generating bioenergy and biofuels over recent years. The thermal conversion of biomass through pyrolysis is an easy, useful, and low-cost process that can be applied to a wide variety of feedstocks. Pyrolysis characteristics of different feedstock samples can be analyzed and examined through thermogravimetric analysis (TGA). TGA has been an essential tool and widely used to investigate the thermal characteristics of a substance under heating environments, such as thermodegradation dynamics and kinetics. Studying the potential of waste biomass for generating sustainable bioenergy carves a pathway into a circular bioeconomy regime, and can help tackle our heavy reliance on nonrenewable energy sources. This study aims to give a deep insight into the wide use of TGA in aiding in the research and development of pyrolysis of different waste biomass sources. The thermal characteristics portrayed by different biomass wastes through TGA are discussed. The effects of significant pyrolysis operating parameters are also illustrated. A more comprehensive understanding of evolved products during the pyrolysis stage can be gained by combining TGA with other analytical methods. The pros and cons of using TGA are also outlined. Overall, an in-depth literature review helps identify current trends and technological improvements (i.e., integrating artificial intelligence) of TGA use with pyrolysis.

Energy Demand Modeling for the Eastern Economic Corridor of Thailand: A Case Study of Rayong Province

This paper assesses long-term energy consumption and greenhouse gas (GHG) emissions in Rayong Province which is one of the three provinces in the Eastern Economic Corridor (EEC) of Thailand. LEAP (the Low Emissions Analysis Platform) is used to project final energy demand for each economic sector by using the 2019 data as a base year. In the model, we defined the energy consumption into two scenarios; a business-as-usual (BAU) scenario and a low carbon scenario (LCS), to see different energy demand and CO2 emissions up to the year 2050. There are different assumptions between BAU and LCS in each sector such as energy efficiency improvement, shift to modern energy, the share of high energy-efficient vehicles, etc. In the BAU scenario, the final energy consumption needed by Rayong Province will increase with an average annual growth rate (AAGR) of 3.49%, while only 1.52% for the LCS. CO2 emissions in the LCS will be reduced by 41.7% by 2050 when compared with the BAU scenario. Most interestingly, even though energy demand in Rayong Province will be increasing up to 2050, CO2 emissions will peak about 2035 and then reduce. The industry and transport sectors are the most final energy consumption and the highest CO2 emissions. This is because EEC is driven by a production-based economy. The solution for this is to transform to alternative energies sourcing, shift all productions to sustainable ones, restructure the industrial estate to become the eco-industrial and GHG emissions management, which will also result in obvious carbon reduction. This kind of information will be beneficial to energy demand conservation and GHG emission mitigation at the provincial level which will depend on the energy policies initiated and implemented in the future.

Predictability of food supply modulates nocturnal hypothermia in a small passerine : Food supply and nocturnal hypothermia

The combination of short days and long cold winter nights, in temperate regions, presents a major challenge for small diurnal birds. Small birds regularly employ heterothermy and enter rest-phase hypothermia during winter nights to conserve energy. However, we know little about how environmental conditions, such as food availability, shape these strategies. We experimentally manipulated food availability in winter to free-living great tits Parus major. A 'predictable' and constant food supply was provided to birds in one area of a forest, while birds in another area did not have access to a reliable supplementary food source. We found that predictability of food affected the extent of nocturnal hypothermia, but the response differed between the sexes. Whereas male nocturnal body temperature was similar regardless of food availability, females exposed to a naturally 'unpredictable' food supply entered deeper hypothermia at night, compared with females that had access to predictable food and compared with males in both treatment groups. We suggest that this response is likely a consequence of dominance, and subdominant females subject to unpredictable food resources cannot maintain sufficient energy intake, resulting in a higher demand for energy conservation at night. (Less)

Predictability of food supply modulates nocturnal hypothermia in a small passerine.

The combination of short days and long cold winter nights, in temperate regions, presents a major challenge for small diurnal birds. Small birds regularly employ heterothermy and enter rest-phase hypothermia during winter nights to conserve energy. However, we know little about how environmental conditions, such as food availability, shape these strategies. We experimentally manipulated food availability in winter to free-living great tits Parus major. A ‘predictable' and constant food supply was provided to birds in one area of a forest, while birds in another area did not have access to a reliable supplementary food source. We found that predictability of food affected the extent of nocturnal hypothermia, but the response differed between the sexes. Whereas male nocturnal body temperature was similar regardless of food availability, females exposed to a naturally ‘unpredictable' food supply entered deeper hypothermia at night, compared with females that had access to predictable food and compared with males in both treatment groups. We suggest that this response is likely a consequence of dominance, and subdominant females subject to unpredictable food resources cannot maintain sufficient energy intake, resulting in a higher demand for energy conservation at night.

Environmental Impact Evaluation of Distributed Renewable Energy System Based on Life Cycle Assessment and Fuzzy Rough Sets

The distributed renewable energy system, integrating various renewable energy resources, is a significant energy supply technology within energy internet. It is an effective way to meet increasingly growing demand for energy conservation and environmental damage reduction in energy generation and energy utilization. In this paper, the life cycle assessment (LCA) method and fuzzy rough sets (FRS) theory are combined to build an environmental evaluation model for a distributed renewable energy system. The ReCiPe2016 method is selected to calculate the environmental effect scores of the distributed energy system, and the FRS is utilized to identify the crucial activities and exchanges during its life cycle from cradle to grave. The generalized evaluation method is applied to a real-world case study, a typical distributed energy system located in Yanqing District, Beijing, China, which is composed of wind power, small-scale hydropower, photovoltaic, centralized solar thermal power plant and a biogas power plant. The results show that the environmental effect of per kWh power derived from the distributed renewable energy system is 2.06 × 10−3 species disappeared per year, 9.88 × 10−3 disability-adjusted life years, and 1.75 × 10−3 USD loss on fossil resources extraction, and further in the uncertainty analysis, it is found that the environmental load can be reduced effectively and efficiently by improving life span and annual utilization hour of power generation technologies and technology upgrade for wind turbine and photovoltaic plants. The results show that the proposed evaluation method could fast evaluate the environmental effects of a distributed energy system while the uncertainty analysis with FRS successfully and effectively identifies the key element and link among its life span.

Energy intensity of wastewater treatment plants and influencing factors in China

The wastewater-energy nexus is an emerging concern in the wastewater treatment sector. Understanding the energy efficiency of wastewater treatment plants (WWTPs) and the factors that influence it will help to improve planning and managing in order to meet increasing energy conservation demands. In this study, we use a unique big dataset from a pollution source census of all WWTPs in China to establish a quantitative model that relates the energy consumption of WWTPs to major influencing factors. From our results, we found that WWTPs in China are more energy-intensive than their international counterparts. Influencing factors such as treatment scale, technology, treatment degree, load factor, sludge amount, age, topography and wastewater collection area all significantly affect energy efficiency. In terms of energy saving potential, if the influent chemical oxygen demand (COD) concentration is increased to >500 mg/L, the total energy consumption of the wastewater treatment industry can be reduced by at least 20%. Furthermore, potential energy conservation is 5.9% for increasing the load of sewage treatment plants and 3.2% for renovating old WWTPs. We prioritized approaches for WWTP energy conservation and ranked them as follows: 1) establishing rain and sewage diversion facilities and increasing the inlet concentration of pollutants; 2) expanding and improving the sewage treatment pipe network and increasing the utilization rate of WWTPs; and 3) renovating old WWTPs. Our findings provide insights for other countries to improve the wastewater-energy nexus in their wastewater treatment sector.

A design and experimental investigation of a large-scale solar energy/diesel generator powered hybrid ship

Due to the increasing demand for energy conservation and the reduction of emissions, renewable energy applications for ships have attracted a great deal of attention. In this paper, a 5000-vehicle space pure car and truck carrier (PCTC) is selected as the research object. Then, on the basis of the existing power system, a unified grid-tied/stand-alone solar system is designed with a built-in battery energy storage system. The system includes a solar energy generation unit, a battery storage system, a diesel generating set, grid-tied/stand-alone controlled inverters, a battery management system (BMS) and an energy management system. According to an analysis of the experimental data, it can be concluded that the use of solar energy hybrid power, in theory, can reduce fuel consumption by 4.02% and carbon dioxide (CO2) emissions by 8.55% a year.

A Review of Tip Clearance in Propeller, Pump and Turbine

Propellers, pumps, and turbines are widely applied in marine equipment, water systems, and hydropower stations. With the increasing demand for energy conservation and environmental protection, the high efficiency and the stable operation of pumps and turbine have been drawing great attention in recent decades. However, the tip clearance between the rotating impeller and the stationary shroud can induce leakage flow and interact with the main stream, introducing complex vortex structures. Consequently, the energy performance and the operation stability of pumps and turbines deteriorate considerably. Constant efforts are exerted to investigate the flow mechanism of tip-clearance flow and its induced influence on performance. However, due to various pump and turbine types and the complexity of tip-clearance flow, previous works are usually focused on a specific issue. Therefore, a systematic review that synthesizes the related research is necessary and meaningful. This review investigates related research in the recent two decades in the perspectives from fundamental physics to engineering applications. Results reveal the vortex types, trajectory, evolution, and cavitation behaviors induced by tip-clearance flow. It is concluded that the influence characteristics of tip clearance on energy performance are closely related to the machinery type. Tip-clearance size and tip shape are found to be crucial parameters for tip-leakage vortex (TLV). The proposed optimization schemes are also demonstrated to provide inspiration for future research. Overall, this review article provides a coherent insight into the characteristics of tip-clearance flow and the associated engineering-design applications. On the basis of these understandings, comments on conducted research and ideas on future research are proposed.

Eco-immunology in the cold: the role of immunity in shaping the overwintering survival of ectotherms.

The effect of temperature on physiology mediates many of the challenges that ectotherms face under climate change. Ectotherm immunity is thermally sensitive and, as such, environmental change is likely to have complex effects on survival, disease resistance and transmission. The effects of temperature on immunity will be particularly profound in winter because cold and overwintering are important triggers and regulators of ectotherm immune activity. Low temperatures can both suppress and activate immune responses independent of parasites, which suggests that temperature not only affects the rate of immune responses but also provides information that allows overwintering ectotherms to balance investment in immunity and other physiological processes that underlie winter survival. Changing winter temperatures are now shifting ectotherm immunity, as well as the demand for energy conservation and protection against parasites. Whether an ectotherm can survive the winter will thus depend on whether new immune phenotypes will shift to match the conditions of the new environment, or leave ectotherms vulnerable to infection or energy depletion. Here, we synthesise patterns of overwintering immunity in ectotherms and examine how new winter conditions might affect ectotherm immunity. We then explore whether it is possible to predict the effects of changing winter conditions on ectotherm vulnerability to the direct and indirect effects of parasites.

Investigation of microstructure and mechanical properties of friction stir welded AZ61 magnesium alloy joint

Abstract Increasing global demands for energy conservation and environmental protection led to the replacement of heavy components with lighter alloys. As magnesium alloys are believed to be unique candidates for lightweight applications and friction stir welding (FSW) is capable of joining magnesium alloys, in the current work, FSW joint of AZ61 Mg alloy has been fabricated. Microstructure and mechanical properties of the joints were evaluated. The elongated grains of the base metal were recrystallized in the stir zone and in transition zone during friction stir welding. The formation of finer grains in the stir zone of the joint is responsible for increase the hardness of the stir zone. The microhardness of base metal is higher than that of thermo-mechanically affected zone but lower than that of stir zone. The tensile strength of the weld was about 82% of the as-received base metal. The joint failed in ductile mode. This ductile failure of joint was due to the uniform deformation of material.

Experimental and Modeling Studies on Sulfur Trioxide of Flue Gas in a Coal-Fired Boiler

Various damages, including corrosion, fouling, and blue plumes, can be caused by sulfur trioxide (SO3) in the flue gas of a coal-fired boiler on boiler equipment and the atmospheric environment. The increasing demand for energy conservation and emission reduction requires accurate knowledge on predicting and controlling the SO3 concentration. Accurate knowledge on the effect of the factors that influence SO3 in flue gas is necessary as well. Therefore, in this study, various SO3 concentrations under different flue gas conditions are measured with measuring devices built based on controlled condensation and S balance methods. To further study the effect of the factors that influence SO3 in flue gas, an improved SO2/O2/H2O/CO2/CO/NO kinetic mechanism is built based on previously developed mechanisms and validated with previous experimental data. SO3 concentrations under the established flue gas conditions and with increasing residence time are numerically calculated. The SO3 concentration in flue gas is mai...

Non-parabolic interface motion for the one-dimensional Stefan problem: Neumann boundary conditions

In this work, we study the liquid-solid interface dynamics for large time intervals on a 1-D sample, with homogeneous Neumann boundary conditions. In this kind of boundary value problem, we are able to make new predictions about the interface position by using conservation of energy. These predictions are confirmed through the heat balance integral method of Goodman and a generalized non-classical finite difference scheme. Since Neumann boundary conditions imply that the specimen is thermally isolated, through well stablished thermodynamics, we show that the interface behavior is not parabolic, and some examples are built with a novel interface dynamics that is not found in the literature. Also, it is shown that, on a Neumann boundary value problem, the position of the interface at thermodynamic equilibrium depends entirely on the initial temperature profile. The prediction of the interface position for large time values makes possible to fine tune the numerical methods, and given that energy conservation demands highly precise solutions, we found that it was necessary to develop a general non-classical finite difference scheme where a non-homogeneous moving mesh is considered. Numerical examples are shown to test these predictions and finally, we study the phase transition on a thermally isolated sample with a liquid and a solid phase in aluminum.

Performance characterization of the membrane-based energy recovery system

Recently, the energy conservation demand attracted much attention, due to the depletion of energy resource and environmental impact caused by the increase in energy consumption. As well know, the heating, ventilation, and air-conditioning (HVAC) systems, which provide thermal comfort for occupants in buildings, account for a significant portion of global energy demand. Energy recovery is one of the key energy-efficient technologies, which reveals to deal with the increase of energy usage in building while maintaining indoor air quality. However, in the conventional heat recovery system, the sensible heat was recovered, but the latent heat was ignored. In this work, to evaluate the total energy saving potential, a novel energy recovery ventilator (ERV) model is developed with a semi-permeable membrane which can transfer both heat and moisture. A conjugate heat and mass transfer model subject to tropical climate condition is investigated by both analytical and numerical methods. The three-dimension ERV model is comprehensively studied by CFD simulation for analysis of critical parameters, such as velocity, temperature, humidity of supply and exhaust airflows. The numerical results showed that both sensible and latent effectiveness could be gained very high. Even that the latent effectiveness is lower than sensible effectiveness, the energy saving impact by dehumidification is considerable in the tropical climate.

Friction Stir Welding of Magnesium Alloys: A Review

The Increasing global demands for energy conservation and environmental protection have encouraged manufacturers to develop lightweight components. Magnesium alloys are characterized by unique properties and offer opportunities for lightweight applications. There is a challenge to join the materials with a variety of applications along with cheaper value and high strength to weight ratio. Friction stir welding (FSW) is a solid state joining process used for light weight alloys. In this article, the recent developments of the FSW of magnesium alloys are reviewed to assist researchers to develop an in-depth understanding of the current state of the Friction Stir Welding of Magnesium Alloys.

Building stock dynamics and its impacts on materials and energy demand in China

China hosts a large amount of building stocks, which is nearly 50 billion square meters. Moreover, annual new construction is growing fast, representing half of the world's total. The trend is expected to continue through the year 2050. Impressive demand for new residential and commercial construction, relative shorter average building lifetime, and higher material intensities have driven massive domestic production of energy intensive building materials such as cement and steel. This paper developed a bottom-up building stock turnover model to project the growths, retrofits and retirements of China's residential and commercial building floor space from 2010 to 2050. It also applied typical material intensities and energy intensities to estimate building materials demand and energy consumed to produce these building materials. By conducting scenario analyses of building lifetime, it identified significant potentials of building materials and energy demand conservation. This study underscored the importance of addressing building material efficiency, improving building lifetime and quality, and promoting compact urban development to reduce energy and environment consequences in China.