Potential For Improving Efficiency Research Articles

Challenges of combining different methods and tools to improve the performance monitoring in buildings: A case study of elementary schools and kindergartens

The European Union has identified buildings as the most promising targets for improving energy efficiency and has quantified a significant energy saving potential associated with the refurbishment of a building’s envelope and the installation of new technologies. The key objective of monitoring and modelling energy profiles in buildings is to provide the necessary background on energy consumption and to allow informed decisions to be made. The modelling usually starts with the integration of energy into the activity flow charts, which is the basis for the decisions on setting up the structure of energy cost centres.This paper evaluates the capabilities of data envelopment analysis in combination with energy cost centre based modelling for the electricity consumption analysis of a selected group of elementary schools and kindergartens. The electricity consumption data was obtained in cooperation with a local energy agency, which was acting as the energy manager for the selected group of buildings. The results confirmed the potential of combining the data envelopment analysis and the energy cost centre based modelling in order to properly identify the schools having the potential for energy efficiency improvements. Additionally, the combination of results obtained with the data envelopment analysis and the contextual parameters hidden in the structure of energy cost centres provides additional and valuable information for the energy manager and helps him with proper benchmarking of the analysed energy management practices. The results encouraged the energy manager to look for concrete opportunities to improve the energy efficiency and revealed that electricity savings of up to 14% could be achieved with better energy management in the selected group of buildings.

Assessment of efficiency improvement and emission mitigation potentials in China’s petroleum refining industry

The petroleum refining industry is an important energy conversion sector, providing both products and raw materials to a wide range of end-use sectors, including the transportation and chemical industries. This study uses a typical refinery process flow to develop a complex refining system by characterizing technical features and interrelationships of the refining units. Using this system we were able to develop the MESSAGEix-petroleum refining model to analyze energy consumption and emissions at the refining process level. The results indicate that China’s petroleum refining industry could reduce total energy use, circulation water consumption, and softened water consumption by 12%, 7%, and 80%, respectively. Additionally, the petroleum refining industry could reduce CO2, NOx, SO2, and PM2.5 emissions by 10%, 4%, 2%, and 1%, respectively, by 2050. However, emission sources have a significant influence on the emission reduction effect, and the reduction potential obtained through energy efficiency strategies is limited, especially for air pollutants. Therefore, policymakers should consider combining energy-efficiency measures and specific air pollution control options to better reach multiple targets. Finally, further directions for enhancing the representation of relevant subsectors in MESSAGEix are given.

Cost-effectiveness of energy efficiency improvements for a residential building stock in a Danish district heating area

The residential building stock holds a large energy efficiency improvement potential related to energy upgrading of the building envelope. Details about the heterogeneity of the building stock are paramount to perform a proper assessment of attractive energy efficiency improvements for end-users. Based on a sample of buildings, the study develops methods to identify potentials for heterogeneous building-tailored energy efficiency improvements, to reduce heat consumption, and evaluates their cost-effectiveness in the framework of a district heating area in Denmark. The study accounts for rebound effects and develops both technical (gross) and more realistic (net) potentials, allowing a more accurate analysis of attractive energy efficiency improvements. The analysis is novel as the underlying model relies on building characteristics rather than synthetic archetypes, which can lead to loss of diversity (e.g. in variation of costs and potentials) and thereby discarding cost-effective potentials. The analysis also investigates the sensitivity of the results to assumptions about the discount rate and focuses on the effect of exposing the end-user to different district heating tariffs and the consequent total cost-effective investments. The outcomes show that cost-effective energy efficiency improvements vary considerably, in size and type, among the heterogeneous building stock considered. In regard to district heating tariffs, when all the cost components are variable, the total cost-effective potential increases considerably, with specific energy efficiency improvements distributed differently among building categories, and with the cost components providing different incentives to invest. Heterogeneity, and different tariff policies, thus does matter, when evaluating economically attractive investments in energy efficiency improvements for buildings.

Composite index for energy efficiency evaluation of industrial sector: sub-sectoral comparison

The study investigates energy efficiency performance across 18 main industrial sub-sectors of Latvia in 2017. A composite index methodology was applied to develop energy efficiency index (EEI) that consists of 12 different explanatory indicators grouped in three main dimensions of energy efficiency – economic, technical, and environmental. The obtained results highlighted various opportunities for energy efficiency improvement in all the sectors of Latvian manufacturing industry. The results indicate that there is large potential for energy efficiency improvements in energy intensive sectors such as wood and non-metallic mineral manufacturing. The fundamental issues for each sector could be recognized and addressed to the policy makers.

Optimal Design of Combined Two-Tank Latent and Metal Hydrides-Based Thermochemical Heat Storage Systems for High-Temperature Waste Heat Recovery

The integration of thermal energy storage systems (TES) in waste-heat recovery applications shows great potential for energy efficiency improvement. In this study, a 2D mathematical model is formulated to analyze the performance of a two-tank thermochemical heat storage system using metal hydrides pair (Mg2Ni/LaNi5), for high-temperature waste heat recovery. Moreover, the system integrates a phase change material (PCM) to store and restore the heat of reaction of LaNi5. The effects of key properties of the PCM on the dynamics of the heat storage system were analyzed. Then, the TES was optimized using a genetic algorithm-based multi-objective optimization tool (NSGA-II), to maximize the power density, the energy density and storage efficiency simultaneously. The results indicate that the melting point Tm and the effective thermal conductivity of the PCM greatly affect the energy storage density and power output. For the range of melting point Tm = 30–50 °C used in this study, it was shown that a PCM with Tm = 47–49 °C leads to a maximum heat storage performance. Indeed, at that melting point narrow range, the thermodynamic driving force of reaction between metal hydrides during the heat charging and discharging processes is almost equal. The increase in the effective thermal conductivity by the addition of graphite brings about a tradeoff between increasing power output and decreasing the energy storage density. Finally, the hysteresis behavior (the difference between the melting and freezing point) only negatively impacts energy storage and power density during the heat discharging process by up to 9%. This study paves the way for the selection of PCMs for such combined thermochemical-latent heat storage systems.

Experimental and Computational Investigations of the Thermal Environment in a Small Operational Data Center for Potential Energy Efficiency Improvements

Abstract The share of equipment and power use in smaller data centers (DCs) is comparable with that of more massive counterparts. However, they grabbed less attention in the literature despite being less energy-efficient. This study highlights the challenges of setting up a computational fluid dynamics (CFD) model of a 180-m2 small-size high-performance computing (HPC) DC and the validation procedure leading to a reasonably accurate model for the investigation of the thermal environment and potential energy efficiency improvements. Leaky floors, uneven placement of computing equipment and perforated tiles preventing separation of hot and cold air, low-temperature operation, and excessive cooling capacity and fan power were identified sources of energy inefficiency in the DC. Computational fluid dynamics model predictions were gradually improved by using experimental measurements for various boundary conditions (BCs) and detailed geometrical representation of large leakage openings. Eventually, the model led to predictions with an error of less than 1 °C at the rack inlet and less than 5 °C at the rack outlet. The ultimate objective was to use the validated CFD model to test various energy efficiency measures in the form of operational or design changes in line with the best practices. Impact of leakage between the raised floor and the room, reduced airflow rate, cold-aisle and hot-aisle separation, workload consolidation, and higher temperature operation were among the phenomena tested by using the validated CFD model. The estimated power usage effectiveness (PUE) value reduced from 1.95 to 1.40 with the proposed energy efficiency measures.

Regenerative Organic Rankine Cycle as Bottoming Cycle of an Industrial Gas Engine: Traditional and Advanced Exergetic Analysis

This investigation shows a traditional and advanced exergetic assessment of a waste heat recovery system based on recuperative ORC (organic Rankine cycle) as bottoming cycle of a 2 MW natural gas internal combustion engine. The advanced exergetic evaluation divides the study into two groups, the avoidable and unavoidable group and the endogenous and exogenous group. The first group provides information on the efficiency improvement potential of the components, and the second group determines the interaction between the components. A sensitivity analysis was achieved to assess the effect of condensing temperature, evaporator pinch, and pressure ratio with net power, thermal efficiencies, and exergetic efficiency for pentane, hexane, and octane as organic working fluids, where pentane obtained better energy and exergetic results. Furthermore, an advanced exergetic analysis showed that the components that had possibilities of improvement were the evaporator (19.14 kW) and the turbine (8.35 kW). Therefore, through the application of advanced exergetic analysis, strategies and opportunities for growth in the thermodynamic performance of the system can be identified through the avoidable percentage of destruction of exergy in components.

High-Performance 4WD Electric Powertrain With Flywheel Kinetic Energy Recovery

Four-wheel-drive (4WD) full-electric powertrains offer great potential for vehicle performance and efficiency improvements. This study introduces a novel 4WD electric powertrain that significantly increases the overall powertrain performance and battery lifespan. The proposed powertrain benefits from a new compact and highly efficient flywheel-based kinetic energy recovery system (KERS) that enables us to overcome most of the shortcomings of the conventional battery-based KERS. The utilized KERS is capable of capturing or providing much higher mechanical power than its electrical power ratings. Meaning that, without overloading, the powertrain can capture more mechanical power than traction motors’ nominal values. Moreover, since a significant part of the energy exchange takes place in mechanical form, only a portion of the initial kinetic energy (slip energy) needs to be converted into electrical form and be processed electrically. In the proposed powertrain, there is no energy exchange necessary between the battery and the powertrain during each accelerations or braking event, thus also reducing the battery power rating. Mathematical modeling and simulations were performed using space vector modeling method for the proposed powertrain. The results prove the functionality of the proposed 4WD powertrain. Experimental results are also presented for the proof of the concept.

Comparative study of two lay-up sequence dispositions for flexible skin design of morphing leading edge

Morphing leading edge has great potential for noise abatement and aerodynamic efficiency improvement. The drooping effect is realized by bending of the flexible skin which encloses to form the leading edge. Since the flexible skin is often made of composite laminates of Glass Fiber Reinforced Plastics (GFRP), the lay-up sequences have become the determinant, which affects not only the morphing quality but also the manufacturing complexity. Two optimizing methods of lay-up sequences are comparatively studied. In the first method, the laminal quantities in 0°, ±45° and 90° vary independently, while in the second one, the concept of isotropic laminate unit [0/45/−45/90]s is employed and the unit quantity is the unique variable. Final evaluation demonstrates that for both methods there is insignificant impact to the overall morphing quality; however, specific concern is equally necessary for these two methods to the tip of the leading edge where the skin is at its minimum thickness and bears the most severe bending deformation. In terms of computational efficiency and post-processing labor, the second method has better performance.

Analysis of energy efficiency improvement and carbon dioxide abatement potentials for Swiss Food and Beverage sector

The food and beverage (F&B) production is the second most energy consuming industry sector, consuming up to 14% (22 PJ) of the Swiss industry's total final energy (TFE) and emitting 14% (0.6 million tonnes) of the industry's total CO2. In the period from 2004 to 2017, the sector's energy consumption has been increasing at a faster rate than production, which implies deterioration of energy efficiency (EE). Against the background of implicit EE improvement target of 26% between 2017 and 2050 under the assumption of constant future production, this study investigates the options of realizing the target. The process-related (e.g. excluding building envelope) technical EE improvement potential of the Swiss F&B sector is estimated at 25% whereas the currently commercially available energy-efficient technologies can potentially reduce 18% of the sector's current TFE. The cost-effective potential estimated by means of a bottom-up approach (cost curves) ranges from 14% to 16% for energy efficiency and 18% to 21% for CO2. Results of sensitivity analysis indicate that low energy prices may act as a barrier for the adoption of cross-cutting technologies. A qualitative analysis of emerging technologies presented along with the detailed cost-effectiveness analysis of commercially available energy-efficient technologies can help to overcome the techno-economic barriers and achieve the implicit EE improvement target of the Swiss F&B sector.

Off‐Gas Waste Heat Recovery for Electric Arc Furnace Steelmaking Using Calcium Hydroxide (Ca(OH)2) Dehydration

Off‐gas waste heat recovery for electric arc furnace (EAF) steelmaking is challenging because high off‐gas velocity, fluctuating temperature, and high dust contents must be considered. In addition to the harsh off‐gas conditions, a heat storage system must be included to balance power‐off times of the EAF during taping or charging. However, waste heat recovery offers a significant potential for further efficiency improvements in EAF steelmaking. Herein, a novel process concept for extraction, storage, and utilization of off‐gas waste heat via entrained flow dehydration of calcium hydroxide (Ca(OH)2) for efficient power generation is described. The use of waste heat exchangers is avoided, and small heat storage units are achieved. The process concept, Ca(OH)2 dehydration and heat storage mechanism as well as important process parameters are discussed. Finally, the energy balance of the waste heat recovery process and further process improvements are presented.

Comparative analysis of the R&D investment performance of Korean local governments

This study examines Korea's research and development (R&D) investment performance at the local government level using slack-based model data envelopment analysis (SBM-DEA). The SBM methodology, which has replaced the traditional DEA model, is expected to provide more reliable empirical results for R&D investment performance. We confirm the statistical reliability of our results by conducting bootstrapping. The average score of Korea's R&D investment performance is 67.7%, implying that there is a 32.3% potential for efficiency improvement. Among the 16 local governments examined, Seoul, Gwangju, Daegu, and Gangwon show better performance with an average value higher than 0.8. We decomposed R&D investment efficiency into pure R&D investment technical efficiency and scale efficiency and derived implications regarding the input scales. We also reported benchmark information from trend-setting local governments that indicate ideal input mixes for fast-following local governments. Since no local government was found to be in the CRS group, we suggest that all local governments should transform their R&D investment input mix toward upscaling or downsizing.

Efficient Flywheel-Based All-Wheel-Drive Electric Powertrain

All-wheel-drive (AWD) multimotor electric powertrains offer greater potential for system performance, efficiency, and reliability improvements. In this article, a new AWD electric powertrain that can increase the overall powertrain efficiency and battery lifetime is introduced. The proposed powertrain is based on a compact and efficient flywheel-based kinetic energy recovery system (KERS) that overcomes most of the shortcomings of the conventional electric KERS. Here, a significant part of the mechanical power transfer takes place without conversion to electrical power. Therefore, a selectable fraction of the recoverable kinetic energy is processed by power electronics. Thus, no energy exchange is necessary between the battery and the powertrain during acceleration and deceleration, resulting in a reduced battery power rating. This article compares the proposed powertrain with a conventional AWD electric powertrain. Mathematical modeling and simulations based on the space vector method were used for both powertrains that show the advantage of the proposed powertrain over the conventional one. The experimental data are also presented from our proof of the concept laboratory setup.

Tackling the energy efficiency gap in the Irish residential sector

The residential sector holds significant potential for improvements in energy efficiency in Ireland. Retrofit activity, however, can be difficult to instigate despite the presence of government incentives and cost-effective investment opportunities. The failure of individuals and organisations to invest in cost-effective energy efficiency measures is often referred to as ‘the energy efficiency gap’. Here, two separate, but not mutually exclusive, potential contributing factors for this phenomenon are discussed in detail: behavioural anomalies and modelling miscalculations. The relevance of these factors in the context of the Irish residential sector is introduced, and this is followed by a review of intervention literature seeking to increase energy efficiency programme adoption rates by addressing behavioural failures. An examination of domestic and international evidence shows a consistent overestimation by ex-ante models of energy-saving benefits. The paper concludes that addressing behavioural and informational factors can have a positive influence on energy efficiency adoption, but this needs to be complemented with additional policy measures to sufficiently rectify current low rates of uptake in the Irish residential sector. Simultaneously, further action will be needed to better calibrate engineering models using data gathered from ex-post field experiments.

Assessment of the Agricultural Water Use in Jericho Governorate Using Sefficiency

Addressing water use efficiency in the Middle East is challenging due to the geopolitical complexity, climatic conditions and a variety of managerial issues. Groundwater is the dominant water resource for Palestinians, while aquifers are shared with their neighbours. We assessed in this study the efficiency of the agricultural water use in Jericho, which we defined as the Water Use System (WUS), and its impact on the main source, the Eastern Aquifer Basin (EAB), using the Sustainable Efficiency (Sefficiency) method. The assessment considered the objectives’ difference between the farmers in the region and the water managers. As Sefficiency requires, the analysis also considered in addition to the quantities of the different water path types within our WUS, their quality and beneficial weights. The results highlighted efficiency improvement potentials, a substantial number of unreported abstractions and an impact of the use of chemical substances on the main source. In addition, through hypothesizing four scenarios, we demonstrated that: 1. Improving the quality of returns has a great positive impact. 2. Increasing water abstractions is not beneficial if it is not linked to an increase in yield production. 3. Precipitation rates can influence water use efficiency. 4. More careful treatment of the unwanted plants and a selection of high socio-economic value crops would enhance Sefficiency.

Experimental Analysis of an Ultra-Compact Combustor Powered Turbine Engine

Abstract The innovative ultra-compact combustor (UCC) is an alternative to traditional turbine engine combustors and has been shown to reduce the combustor length and offer potential improvements in combustion efficiency. Prior UCC configurations featured a circumferential combustion cavity positioned around the outside diameter (OD) of the engine. This configuration would be difficult to implement in a vehicle with a small, fixed diameter and had difficulty migrating the hot combustion products at the OD radially inward across an axial core flow to present a uniform temperature distribution to the first turbine stage. This study draws from preliminary computational analysis which enabled experimental testing of a new UCC configuration that featured a smaller diameter circumferential cavity that exhausted axially into a dilution zone positioned just upstream of the nozzle guide vanes. The combustor was sized as a replacement burner for the JetCat P90 RXi small-scale turbine engine and fit inside the engine casing. This combustor configuration achieved a 33% length reduction compared to the stock JetCat combustor and achieved comparable engine performance across a limited operating range. Self-sustained engine operation was achieved with a rotating compressor and turbine making this study the first to achieve operation of a UCC-powered turbine engine.

Potential efficiency improvements in fast-neutron semiconductor sensors from finely detailed structuring: A study by simulation including dead layers

The neutron sensor in an active neutron-sensitive personal dosemeter typically comprises a planar silicon diode topped with a converter layer. Neutrons interact in the converter to produce charged particles that are then detected in the diode. However, in the dosimetrically important energy region of a few keV to a few MeV, the efficiency of such devices is small because of the small cross section for producing the charged particles and their very limited range within the converter. The efficiency can in principle be improved by etching fine structures such as trenches or wells in the silicon, and filling these with the converter, so that a considerably larger amount of converter is within one particle range of the silicon. This study quantifies the potential improvements in efficiency for a selection of structure sizes and fast monoenergetic neutron energies. It also investigates how seriously these improvements are degraded if there is a dead layer at the surface of the silicon.

ASSESSMENT OF ENERGY EFFICIENCY OF CUSTOMER CARE BUILDINGS OF TELECOMMUNICATIONS COMPANIES IN SELECTED TOWNS IN NIGERIA

The importance of energy to human development cannot be overemphasized as it is a key determinant of economic development of all nations. However, the supply of energy has hardly ever been sufficient to meet up with the ever increasing demands exerted by multiplying population and industrialization. Buildings are accountable for nearly 40% of the total global annual energy consumption most of which is used for lighting and air conditioning. With the building sector having a relatively high potential for energy efficiency improvements compared to other sectors, this research therefore assessed the energy efficiency of the customer care buildings of telecommunication companies in selected towns in north-west Nigeria. This was done by finding out where and how energy is being used in the buildings by estimating the energy consumption of the buildings through assessment of the energy bills and a preliminary energy audit and benchmarking with set standard. Descriptive statistical analyses was done and it was found that 85.71% of the buildings have their HVAC systems consuming over 50% of their total energy with an average consumption of 74.58% per year. Also 57.14% of the buildings have higher energy use and energy use intensities than the benchmarks. It was concluded that the major energy consuming systems are the HVAC and lighting. It is therefore recommended that grid electricity which is the main source of energy to the buildings should be stabilized; while greater advantage should be taken of passive ventilation and cooling rather than mechanical HVAC systems.

Investigating the potential for genetic improvement of nitrogen and phosphorus efficiency in a Swiss large white pig population using chemical analysis.

Pig production contributes to environmental pollution through excretion of phosphorus and nitrogenous compounds. European pig production requires annual imports of currently 36 million tons of soya bean, because domestic plant protein sources often do not meet the required protein quality. Most of the mineral phosphate sources are also imported. It is therefore desirable to improve nutrient deposition efficiency through selective breeding, that is to realise similar growth rates and carcass compositions as currently achieved but with a lower intake of dietary crude protein or phosphate. For a preliminary evaluation of the potential of selecting for increased nutrient deposition efficiency, we estimated genetic parameters for nitrogen and phosphorus efficiencies in a Swiss Large White pig population including 294 individuals. Nutrient efficiency phenotypes were obtained from wet‐chemistry analyses of pigs of various live weights. Heritability of nitrogen efficiency was estimated at 41%. Heritability of phosphorus efficiency was very low (0.3%), but positive genetic correlations with nitrogen efficiency suggest that breeding for nitrogen efficiency would positively affect phosphorus efficiency. Further studies are needed to improve the quality of estimates and to obtain accurate high‐throughput measures of nutrient efficiency to be implemented on farms.

Energy efficiency trade-offs in small to large electric vehicles

BackgroundAs electric kick scooters, three-wheelers, and passenger cars enter the streets, efficiency trade-offs across vehicle types gain practical relevance for consumers and policy makers. Here, we compile a comprehensive dataset of 428 electric vehicles, including seven vehicle types and information on certified and real-world energy consumption. Regression analysis is applied to quantify trade-offs between energy consumption and other vehicle attributes.ResultsCertified and real-world energy consumption of electric vehicles increase by 60% and 40%, respectively, with each doubling of vehicle mass, but only by 5% with each doubling of rated motor power. These findings hold roughly also for passenger cars whose energy consumption tends to increase 0.6 ± 0.1 kWh/100 km with each 100 kg of vehicle mass. Battery capacity and vehicle mass are closely related. A 10 kWh increase in battery capacity increases the mass of electric cars by 15 kg, their drive range by 40–50 km, and their energy consumption by 0.7–1.0 kWh/100 km. Mass-produced state-of-the-art electric passenger cars are 2.1 ± 0.8 kWh/100 km more efficient than first-generation vehicles, produced at small scale.ConclusionEfficiency trade-offs in electric vehicles differ from those in conventional cars—the latter showing a strong dependency of fuel consumption on rated engine power. Mass-related efficiency trade-offs in electric vehicles are large and could be tapped by stimulating mode shift from passenger cars to light electric road vehicles. Electric passenger cars still offer potentials for further efficiency improvements. These could be exploited through a dedicated energy label with battery capacity as utility parameter.