Energy Flow Diagrams Research Articles

New Perspective on the Augmented Taiwan Energy Flow Diagram

This work promotes an advanced alternative of energy flow that is more informative and comprehensive to facilitate a better understanding of the whole national or regional energy situation. The 2017 Energy Flow of Taiwan is illustrated as an example. This innovative energy flow captures the entire picture of the utilization of primary energy for a year, therein it points out each individual primary and secondary energy supply and demand, as well as further information of the flows. Especially, it is revealed in this study the comparative efficiencies of utilization of gross energy from the difference between each providing group and corresponding receiving groups. Thus, the analysis can serve as a benchmark for the government’s reference to develop or make improvements towards more efficient and better strategies of future energy use. The proposed advanced alternative of energy flow in Taiwan is suitable for promotion to analyze the energy flow in other countries or regions.

Application of a Conceptual Ecological Model to Predict the Effects of Sand Mining around Chilsan Island Group in the West Coast of Korea

Chilsan Island Group, located on the west coast of South Korea, has been recognized as a critical breeding and nursery ground for endangered seabirds because food is abundant and human activity is low. Chilsan Island Group has been under protection as a Natural Monument (Article no. 389) since 1997, but attempts were made in 2004 to exploit the coastal sands around the islands. A conceptual ecological model (CEM) was employed with energy flow diagram (EFD) to predict the effects of sand mining on the islands’ ecosystem. The results showed that sand mining activities caused long-term damage to benthic ecosystems and threatened seabird communities by reducing fish populations throughout the food web. The changes in energy flow in the ecosystem due to sand mining operations predict that reduction in secondary production of benthic animal communities might reduce energy transfer to humans and seabirds by 30%. Different ranges of uncertainty provided by the Monte Carlo simulation lead to the conclusion that sand mining could bring about undesirable consequences. One concern is that such negative consequences would have a much more severe impact on seabirds than humans because seabirds cannot compete effectively against humans for the limited food sources. In this study, the complex interrelationships between ecosystem members were simplified and a CEM was established to clearly identify which elements would be affected. The CEM with EFD was found to be helpful in promoting communication between stakeholders, and it is expected to be widely used as a decisionmaking tool by public officials.

Enhancing Conceptual Knowledge of Energy in Biology with Incorrect Representations

Energy is an important concept in all natural sciences, and a challenging one for school science education. Students' conceptual knowledge of energy is often low, and they entertain misconceptions. Educational research in science and mathematics suggests that learning through depictive representations and learning from errors, based on the theory of negative knowledge, can potentially foster students' knowledge of abstract concepts such as energy. Thus, we propose here an instructional approach that combines these two strategies to foster conceptual knowledge of energy. It involves inserting an error in a biological energy flow diagram, an error that we derived from two prevalent misconceptions about energy: 1) plants get some of their energy from the soil or 2) energy cycles in an ecosystem. The approach's effect on students' conceptual knowledge of energy was tested in an intervention study with pre-post design and 304 ninth grade students (M = 14.79 years). Students who successfully identified and explained the error achieved larger gains in conceptual knowledge than students learning with a correct diagram. Thus, the proposed instructional approach holds promise for improving energy teaching.

Energy and exergy analyses of a solar powered multi-effect cooling cycle

This study aims to assess the thermodynamic performance of a novel solar powered multi-effect cooling cycle through the cascaded utilisation of energy and exergy. The effects of parameters such as: direct normal irradiation (DNI), turbine inlet temperature, turbine back pressure, and evaporator temperature of ERC were ascertained on the energetic and exergetic performance of the cycle. Exergy destruction occurs throughout the plant components is quantified and illustrated using an exergy flow diagram, and compared to the corresponding energy flow diagram. The exergy efficiency of the cycle was significantly less than its corresponding energy efficiency. Computational analysis further revealed that the maximum exergy losses of more than 34% occur in the solar field followed by 7.25% and 6.75% in the components of ARC and CRC, respectively. Percentage of these exergy losses indicates the sites where the efforts should be made to improve the real performance of proposed cooling cycle.

A FBS-based energy modelling method for energy efficiency-oriented design

Energy efficiency-oriented design is highly valued in reducing the energy consumption during product use and models for characterizing energy consumption are widely regarded as essential prerequisites of energy efficiency-oriented design. Unfortunately, correlating energy consumption with the products’ design features during the design process is a difficult task. To address this challenge, this paper uses the Function-Behaviour-Structure (FBS) ontology as a bridge to link design features and energy consumption throughout the design process and proposes a FBS-based energy modelling method. This method divides the energy modelling process into two steps. The first is to identify the required energy information and characteristics from available data on the design. The second step is to arrange the obtained information in a logical order to create energy models. Two tools, namely the modified FBS framework and the energy flow diagram, are introduced to aid designers in respectively dealing with the two energy modelling steps. To demonstrate this method, a case study considering mechanical linkage servo press is carried out.

Energy and exergy based evaluation of the renovated Afyon geothermal district heating system

In this study, the exergy and energy analyses of the Renovated Afyon Geothermal Heating System (NAFJET), which was completely renovated in the Afyon province of Turkey between the years 2011–2013, were conducted. The exergy destruction in the overall geothermal district heating system (GDHS) was quantified and illustrated using exergy flow diagrams. Both energy and exergy flow diagrams were presented for comparison purposes. The analyses revealed that the exergy destruction in the system took place particularly due to the exergy of the thermal water (geothermal fluid) re-injected, the heat exchanger losses, the losses of all pumps and pipeline loses, accounting for 15.94%, 12.44%, 5.52% and 5.52% of the total exergy input to the system. Both energy and exergy efficiencies of the overall system were investigated, and they were found to be 46.17% and 60.63%, respectively.

Distinguishing complex ideas about climate change: knowledge integration vs. specific guidance

ABSTRACTWe compared two forms of automated guidance to support students’ understanding of climate change in an online inquiry science unit. For specific guidance, we directly communicated ideas that were missing or misrepresented in student responses. For knowledge integration guidance, we provided hints or suggestions to motivate learners to analyze features of their response and seek more information. We guided both student-constructed energy flow diagrams and short essays at total of five times across an approximately week-long curriculum unit. Our results indicate that while specific guidance typically produced larger accuracy gains on responses within the curriculum unit, knowledge integration guidance produced stronger outcomes on a novel essay at posttest. Closer analysis revealed an association between the time spent revisiting a visualization and posttest scores on this summary essay, only for those students in the knowledge integration condition. We discuss how these gains in knowledge integration extend laboratory results related to ‘desirable difficulties’ and show how autonomous inquiry can be fostered through automated guidance.

Modelling of Sudan’s Energy Supply, Transformation, and Demand

The study aimed to develop energy flow diagram (Sankey diagram) of Sudan for the base year 2014. The developed Sankey diagram is the first of its kind in Sudan. The available energy balance for the base year 2012 is a simple line draw and did not count the energy supply by private and mixed sectors such as sugar and oil industries and marine and civil aviation. The private and mixed sectors account for about 7% of the national grid electric power. Four energy modules are developed: resources, transformation, demand, and export and import modules. The data are obtained from relevant Sudanese ministries and directorates and Sudan Central Bank. “e!Sankey 4 pro” software is used to develop the Sankey diagram. The main primary types of energy in Sudan are oil, hydro, biomass, and renewable energy. Sudan has a surplus of gasoline, petroleum coke, and biomass and deficit in electric power, gasoil, jet oil, and LPG. The surplus of gasoline is exported; however, the petroleum coke is kept as reserve. The deficit is covered by import. The overall useful energy is 76% and the loss is 24%. The useful energy is distributed among residential (38%), transportation (33%), industry (12%), services (16%), and agriculture (1%) sectors.

Solar driven DCMD: Performance evaluation and thermal energy efficiency

This paper presents the experimental results of a solar driven DCMD plant. The plant comprises four main loops. The first loop consists of the solar with a total area of 20m2. The PV panels make up the second loop, which has a peak output of 1.48kWpeak. The third loop in the DCMD represents three modules with a total area of 3.39m2. The fourth loop is a thermal sink with a cooling water capacity of 103L/h. Two heat exchangers are installed within the plant. The DCMD performance was evaluated in two modes, with the HRD (arrangement B) and without the HRD (arrangement A), during two days under various operating parameters. The permeability coefficient of the membrane was 3.27×10−7L/m2sPa. The distillate per module was 3.31L/h and 4.59L/h for arrangements A and B, respectively. Thermal energy efficiency indicated that a fraction thermal energy was lost to the surroundings, and the balance was divided into two fractions, useful and non-useful heat. The STECmin was 2342kW/m3 for the arrangement A and 1609kW/m3 for the arrangement B. Energy flow diagrams confirmed the positive impact of the HRD with a positive contribution of 3.77kW.

Dynamic Programming-Based Energy Management System for Range-Extended Electric Bus

The heavy computational burden associated with the application of the traditional DP strategy to the energy management of range-extended electric buses poses a serious problem. On the basis of one Chinese typical urban bus driving cycle, an optimal control strategy is designed according to the SOC consumption trend, which is optimized by the DP algorithm. The dissipative energy and the energy-traction efficiency are our evaluation indices. The energy efficiencies of the powertrain system and components are analyzed by the energy flow diagram method. The results show that when the range-extended electric bus runs 35 Chinese typical urban bus driving cycles, the energy consumption and the energy efficiency of the powertrain system, which are optimized by the traditional DP strategy, can reach 2844.28 MJ and 31.29%, respectively. Compared with the traditional bus, the energy consumption can be reduced by 31.08%. The energy consumption and the energy efficiency of the powertrain system, which are based on one driving cycle optimal strategy, can reach 2857.69 MJ and 31.14%, respectively. The energy consumption is 0.47% higher than that with the traditional DP strategy, but the computation time is reduced by 96.85%.

Fuel Economy Analysis of a Series Hybrid Electric Bus with LowSpeed Shutdown Control Strategy

The series hybrid electric bus that is demonstrated operating in China has the problem of non-ideal fuel economy for the conventional auxiliary equipment can’t shut down the engine. Based on the series hybrid electric bus using electric auxiliary equipment, a control strategy is proposed based on the combination of engine low-speed shutdown and load following. The main control variables are battery SOC and vehicle speed, and the engine low-speed shutdown is realized. Three different driving cycles are employed: Chinese city driving cycle, Zhuzhou city of Hunan province driving cycle, and Hefei city of Anhui province driving cycle. By using the analysis method of the energy flow diagram, the fuel economy in different driving cycles is compared and analyzed. The simulation results show that the control strategy of the engine low-speed shutdown affects little on fuel economy in different driving cycles. All the fuel-saving ratios of the series hybrid system in different driving cycles can reach above 25%.

Sankey diagram framework for energy and exergy flows

Energy flow diagrams in the form of Sankey diagrams have been identified as a useful tool in energy management and performance improvement. However there is a lack of understanding on how such diagrams should be designed and developed for different applications and objectives. At the national level, a framework matching features of Sankey diagrams with various objectives of energy performance management provides better understanding how Sankey diagrams can be designed. As part of the framework, boundaries outlined around a group of facilities provide a refined representation of sub-systems that trace energy use in various conversion devices, products and services, which identifies potential areas for energy savings. There are some differences between energy flows and exergy flows represented in Sankey diagrams. Furthermore, exergy flow Sankey diagrams offer advantages in identifying potential areas for energy savings. This is illustrated at a national level, using UK’s industrial heating processes that overlays both energy and exergy flow diagrams.

Performance of a standalone wind-hydrogen power system for regions with seasonal wind profile: A case study in Khaf region

The present study was aimed at performance and energy analysis of a hybrid wind-hydrogen power system. Such system consists of wind turbines, batteries for the short time energy storage, electrolyzer, fuel cell and hydrogen tank for long time energy storage. The proposed configuration is used to supply energy demand of a region with discrete seasonal wind speed regime. Temporary wind energy profiles restrict using batteries for electricity storage as they lose much electrical stored energy for the long time. Based on direct wind turbine usage, batteries and hydrogen storage, different energy supply strategies are introduced and analyzed to power the household electricity demand. The energy flow diagrams are presented and the system performances for proposed strategies are compared to illustrate the advantages and importance of various options to supply the energy demand. This paper investigates the possibility of using hydrogen storage system for regions with discrete seasonal wind regime (i.e., monsoon). A case study is done using practical data from the Khaf region in Iran. The results revealed that the wind speed profile has a very significant effect on the optimum system configuration and performance. The overall efficiency of the system was found to be 16.75%.

Estimation of parasitic losses in a proposed mesoscale resonant engine: Experiment and model

A resonant engine in which the piston-cylinder assembly is replaced by a flexible cavity is realized at the mesoscale using flexible metal bellows to demonstrate the feasibility of the concept. A four stroke motoring technique is developed and measurements are performed to determine parasitic losses. A non-linear lumped parameter model is developed to evaluate the engine performance. Experimentally, the heat transfer and friction effects are separated by varying the engine speed and operating frequency. The engine energy flow diagram showing the energy distribution among various parasitic elements reveals that the friction loss in the bellows is smaller than the sliding friction loss in a typical piston-cylinder assembly.

Mapping the Energy Flows of Coal Utilization in China: The Methodology and Case Studies for the Year 2005 and 2010

This manuscript developed two methodologies of mapping energy flows of coal utilization in the form of Sankey diagrams: one was energy allocation diagram without illustrating any energy losses and the other was energy efficiency diagram illustrating main energy losses. Based on the methodologies, energy flow diagrams of China's coal utilization in the year 2005 and 2010 were presented. The two diagrams divided coal utilization into four stages from raw coal supply, by coal products supply and coal conversion, to energy end-use. Comparing with previous studies, some technical details were further introduced into the mapping, including coal preparation and the distribution of end-use energy such as electricity, heat and coke etc. Based on the results, the main characteristics of coal utilization in China and its main changes from 2005 to 2010 were discussed.

Analysis of an evaporator-condenser-separated mechanical vapor compression system

An evaporator-condenser-separated mechanical vapor compression (MVC) system was presented. The better effect of descaling and antiscaling was obtained by the new system. This study focused on the method of thermodynamic analysis, and the energy and exergy flow diagrams were established by using the first and second law of thermodynamics analysis. The results show that the energy utilization rate is very high and the specific power consumption is low. Exergy analysis indicates that the exergy efficiency is low, and the largest exergy loss occurs within the evaporator-condenser and the compressor.

Assessing global resource utilization efficiency in the industrial sector

Designing efficient energy systems, which also meet economic, environmental and other objectives and constraints, is a significant challenge. In a world with finite natural resources and large energy demands, it is important to understand not just actual efficiencies, but also limits to efficiency, as the latter identify margins for efficiency improvement. Energy analysis alone is inadequate, e.g., it yields energy efficiencies that do not provide limits to efficiency. To obtain meaningful and useful efficiencies for energy systems, and to clarify losses, exergy analysis is a beneficial and useful tool. Here, the global industrial sector and industries within it are assessed by using energy and exergy methods. The objective is to improve the understanding of the efficiency of global resource use in the industrial sector and, with this information, to facilitate the development, prioritization and ultimate implementation of rational improvement options. Global energy and exergy flow diagrams for the industrial sector are developed and overall efficiencies for the global industrial sector evaluated as 51% based on energy and 30% based on exergy. Consequently, exergy analysis indicates a less efficient picture of energy use in the global industrial sector than does energy analysis. A larger margin for improvement exists from an exergy perspective, compared to the overly optimistic margin indicated by energy.

Synergistic CO<sub>2</sub> and Air Pollution Reduction Based on Multi-Objective Programming

With increasing frequency of hazards caused by global climate change, the importance of regulating carbon dioxide emission and coping with climate change has been recognized by the entire society. This paper utilized an Energy Flow Diagram to incorporate the energy supplies, conversion and final consumption for analyses. A multi-objective programming model was established to reduce the economic investment on the reduction of air pollution and carbon emission, and applied in a case study of Tianjin, one of the economic hubs of North China. This study can be potentially useful for making decisions on the synergistic CO2and air pollution reduction and solving conflicts between economic development and environmental protection in China.

Energetic, exergetic, economic and environmental evaluations of geothermal district heating systems: An application

This study deals with an energetic and exergetic analysis as well as economic and environmental evaluations of Afyon geothermal district heating system (AGDHS) in Afyon, Turkey. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, specific exergy index, exergetic improvement potential and exergy losses. And, for economic and environmental evaluations, actual data are obtained from the Technical Departments. The energy and exergy flow diagrams are clearly drawn to illustrate how much destructions/losses take place in addition to the inputs and outputs. For system performance analysis and improvement, both energy and exergy efficiencies of the overall AGDHS are determined to be 34.86% and 48.78%, respectively. The efficiency improvements in heat and power systems can help achieving energy security in an environmentally acceptable way by reducing the emissions that might otherwise occur. Present application has shown that in Turkey, geothermal energy is much cheaper than the other energy sources, like fossil fuels, and makes a significant contribution towards reducing the emissions of air pollution.

Modelling of Distribution Losses in an Urban Environment and Strategies for Distribution Loss Reduction

Minimising distribution losses shall be one of the key objectives of a distribution electric utility, even though they do not constitute major operational or quality of supply problems. The negative impact of distribution losses on the economics of utility operation is often passed down as costs to customers. The percentage of distribution losses is one of the important indicators to evaluate the performance of a distribution electric utility, network. Distribution losses in an electric utility are two fold viz. technical losses(TL) and non-technical losses (NTL). Technical and non-technical losses require continuous efficient management by utilities to ascertain the factors responsible for them and to take corrective actions to minimize them. The investment needed to reduce technical losses is significantly high compared with investment needed to reduce non-technical losses. This implies that the utilities may have to concentrate on nontechnical loss reduction prior to reducing technical losses. The main scope of this paper is to formulate a strategy to minimize distribution losses in the Electricity Distribution Network of an Urban Environment. This paper, describes the causes for the distribution losses and quantifies technical losses and non-technical losses at each level of the distribution network with the development of an energy flow diagram. Computation of the optimum level of distribution losses for an urban distribution network has also been presented, with the barriers and the strategies for distribution loss reduction, are discussed.