Total Energy Utilization Efficiency Research Articles

Experimental study on enhanced heat transfer performances and optimized strategies of cascade sensible-latent heat storage radiator

Improving the thermal efficiency of radiator and minimizing the energy loss in distribution networks are crucial for space heating. However, existing studies primarily focused on optimizing the thermal performance or indoor environment of individual units, yet rarely revealed the enhanced heat transfer performance from initial power supply to final heat utilization. To address this gap, this study developed a cascade sensible-latent heat storage radiator, and improved the thermal performance in the following ways. Firstly, by adsorbing paraffin wax with expanded graphite, the thermal conductivity rose from 0.2 to 3.5 W/(m‧K). Secondly, through cascading sensible and latent heat storage bricks, the heat charging/discharging efficiency increased by 11.9 %/14.6 %. Finally, by enhancing the airflow from 0.05 to 0.28 m/s, the heat discharging efficiency and entransy dissipation amount increased by 15.8 % and 225.8 kJ‧K, respectively. The total energy utilization efficiency was improved by 7.4 %, and the dissatisfaction caused by draft and noise both met the personnel requirement. The total annual cost of developed radiator was merely 30 % and 60 % of the direct electric heating radiator and sensible heat storage radiator, respectively. Therefore, the sensible-latent heat storage radiator offered advantages in improving the energy utilization efficiency, indoor thermal environment and cost effectiveness performance.

Comprehensive evaluation of thermally conductive functional layer on snow-melting performance for electric heating bridge system

The most commonly used chemical salt agents for melting ice and snow can lead to the corrosion of the steel structure of the bridge deck, as well as potential pollution of nearby rivers and soil through infiltration and surface runoff. The heating bridge system with electric cable is a promising environmentally friendly technology for snow removal. However, the unique suspension and multi-layer characteristics of the bridge pavement make it challenging to efficiently transfer the heat generated by the electric heating bridge system to the pavement surface. To enhance snow-melting efficiency, a novel directional heat transfer electric heating bridge system with a thermally conductive functional layer (EHBS-TCFL) has been introduced. Initially, a series of tests, including thermal conductivity tests, compressive tests, and bending tests, were performed on TCFL with different mix ratios. Then the TCFL with the most favorable mix ratios was determined based on the fuzzy mathematics method. Subsequently, the heating and snow-melting performance of EHBS-TCFL was evaluated. The results indicated that the thermally conductive functional layer, which includes reduced iron powder with a water-cement ratio of 0.53 and an iron powder-cement ratio of 2, represents the optimal solution for achieving exceptional thermal conductivity, flexural strength, and compressive strength. Furthermore, the presence of TCFL positively impacts the enhancement and uniformity of surface temperatures, leading to a 12.7% increase in total energy utilization efficiency. This study offers significant potential for the application of snow-melting on bridge decks in cold regions.

Performance Evaluation of a Novel Multigeneration Plant of Cooling, Power, and Seawater Desalination Using Supercritical CO2 Partial Cooling, ME-TVC Desalination, and Absorption Refrigeration Cycles

Multigeneration systems have gained popularity and approval from scientific minds due to the enhancements these systems bring to total energy utilization efficiency. The use of waste heat from different thermodynamic cycles ensures deceleration of environment pollution. In this paper, a newly conceptualized poly-generation system combining power, cooling and desalination is proposed. Despite the high efficiency generated by the next generation supercritical CO2 (sCO2) Brayton cycles, the pre-coolers (cooling components) of the power block experience a substantial amount of low-grade energy loss. Utilizing this energy loss to increase thermal efficiency further has been the driving force behind this research. The proposed system has three subsystems which are sCO2 Partial cooling cycle with reheat for power generation, followed by a ME-TVC (multi-effect desalination-thermal vapor compression) cycle for producing fresh water and finally an absorption refrigeration cycle (ARC) to provide refrigeration effect. The waste heat from precoolers of sCO2 partial cooling cycle are being utilized by the desalination plant and refrigeration cycle for enhanced system performance. A comprehensive mathematical model is developed and a parametric assessment is performed. The parametric investigation focuses on the primary performance parameters, namely net power output, freshwater yield, energy utilization efficiency, coefficient of performance, and gain output ratio, to assess the multi-generation system's performance across various operational scenarios. The variables that are optimized are turbine inlet temperature of the sCO2 cycle, temperature difference of the generator and the evaporating temperature of the absorption cycle, the number and temperature of the effects of the desalination system. The results show that the greatest energy efficiency of the developed system is up to 70%. The 1st law energy efficiency is termed as Energy Utilization Factor (EUF) in the present work. This term adheres to the logic of the first law of thermodynamics by relating the total energy outputs to the system (work plus refrigeration capacity and heat supplied to the desalination plant) to the total energy input. Using the default parameters, the COP of the ARC is 0.667 and the EUF of the combined system is 59%. Both of these values are higher when compared to previous combined cycles found in literature.

Performance analysis of a novel combined cooling, heating and power system with solar energy spectral beam splitting

The solar energy spectrum absorbed and converted by PV modules is mainly located in the high-frequency band (380–1200 nm), while the spectral energy in other bands that fail to generate electricity is converted to heat and dissipated into the environment, which leads to lower energy utilization efficiency. Spectral beam splitting cascade utilization is a potential technology to improve the efficiency of solar energy utilization. In this paper, a novel combined cooling, heating and power system with solar energy spectral beam splitting was developed according to matching the energy grade and the operating characteristics of refrigeration cycles. The theoretical investigation carried the parameters distribution of energy load and efficiency out. The solar spectrum is divided into the high-frequency spectrum for electric power generation and the low-frequency spectrum for thermal energy harvesting. The spectrum energy after removing electrical power generation is recovered for fluid heating. The part of thermal energy with high temperature is used to drive the ejector refrigeration system to obtain the cooling capacity. Hot water is derived from low temperature thermal energy. Through the effective conversion of energy and heat recovery, the novel system ensures the efficiency of solar energy utilization and realizes a high-efficiency combined supply of cooling, heating and electricity. The total energy utilization efficiency and the total converted generation efficiency of the novel system can reach 82.7 % and 44.9 %, respectively, which is a remarkable improvement from 30.7 % of the conventional single photovoltaic system. The research results provide inspiration for the efficient utilization of solar energy and facilitate the realization of more application scenarios.

High efficient thermochemical energy storage of methane reforming with carbon dioxide in cavity reactor with novel catalyst bed under concentrated sun simulator

Thermochemical energy storage performance of methane reforming with carbon dioxide in cavity reactor under concentrated sun simulator has been experimentally and numerically studied. Novel catalyst bed with Ni/Al2O3 particles and perforated quartz encapsulation is proposed to perform high bed temperature for greenhouse effect, and then chemical energy storage efficiency and total energy utilization efficiency of experimental system can respectively reach as high as 41.1% and 80.3%. As concentrated heat flux increases or reactant flow rate decreases, methane conversion rises with bed temperature increasing, while chemical energy storage efficiency first rises and then falls for larger heat loss. As inlet mole fraction of methane increases, chemical energy storage efficiency firstly increases and then drops. Numerical model of cavity reactor under concentrated heat flux is established and validated. In catalyst bed, maximum reaction rate occurs near focal point, while reverse reaction occurs near its side. With the improvement of porosity in catalyst bed, methane conversion and thermochemical storage efficiency firstly increase and then decrease, while they gradually increase with heat conductivity of bed rising. In addition, optimal concentrated heat flux, flow rate, mole fraction of methane (0.5) and bed porosity (0.6) are derived for maximum chemical energy storage efficiency.

Electrochemical tuning of nickel molybdate nanorod arrays towards promoted electrocatalytic urea oxidization

Urea electrolysis enables simultaneous energy-saving hydrogen production and wastewater purification at a small thermodynamic potential of 0.37 V; however, the total energy-utilization efficiency is still substantially restricted by the sluggish kinetics of the urea oxidization reaction (UOR) at the anode. In this work, an electrochemical tuning strategy has been employed to obtain a Ni (III)-enriched catalyst by starting from NiMoO4∙xH2O nanorod arrays. It has been found that the electrochemical tuning not only modifies the valency state of Ni but also causes a dramatic change in stoichiometry and microstructure of the material, leading to significantly improved activities for UOR under alkaline conditions. Notably, the obtained catalyst delivers a current density of 100 mA cm−2 for UOR at the potential of only 1.36 V vs RHE, which surpasses the best-reported values for UOR catalysis at the same applied potential, demonstrating the great promise of the electrochemical tuning strategy in rational modifications of material towards promoted electrocatalysis.

Optimal Control Method and Design for Modular Battery Energy Storage System Based on Partial Power Conversion

This article addresses a bidirectional low power loss series-parallel partial-power modular converter (SPPC) suitable for series-connected high voltage large power battery energy storage system (BESS). A specific capacitor is placed on the top of the series battery packs, which voltage can be adjusted by the SPPC to compensate for the voltage fluctuation of the battery packs and the DC power line. The power loss and cost of the SPPC are relatively low since its rated power is reduced to about 22%–48% of the full-power converter. A 3 level distributed control method is proposed to achieve the fast transient response of the DC power line current and deal with the series inconsistency of battery packs during discharging and charging, further improving the total energy utilization efficiency (EUE) of the BESS. The critical design considerations for SPPC-BESS are analyzed. A bidirectional 800W phase-shift full-bridge (PSFB) converter hardware prototype along with the Gallium Nitride (GaN) devices is provided to verify the high efficiency of DC-DC sub-module. Then a simulation model of a 6.6kW SPPC-BESS with 3 sub-modules to verify the feasibility of the control method. Theoretical analysis proves that the total power loss of the SPPC is lower than the existing types of modular converters. The EUE of the SPPC-BESS is 1.7% higher than the conventional BESS when the average maximum available capacities of batteries attenuate to 80% of the initial maximum available capacity.

Thermodynamic Analysis of Combined Cooling Heating and Power System with Absorption Heat Pump Based on Small Modular Lead-based Reactor

Small Modular Lead-based Reactor (SMLR) has generated great interest in academic research all around the world due to its good safety characteristics and relatively high core outlet temperature. In this paper, a Combined Cooling Heating and Power (CCHP) system with usage of absorption heat pump, which couples with a SMLR, was proposed to fulfill the energy demands in remote areas. Thermodynamic analysis was implemented to improve the performance of the CCHP system based on SMLR. To meet the remote areas’ energy needs, the main parameters and mass flow rate of a 35 MWth SMLR design were analyzed. The SMLR CCHP with absorption heat pump system can provide electric power 12.5MWe, heating 9.5MWh, and cooling 2.54MWc. The total energy utilization efficiency of the system can be 69.12 %. This work can provide a reference in the design and optimization of the CCHP system to meet the energy demands in the remote areas.

Effect of the distribution density of biomass combined heat and power plant networks on total energy utilization efficiency

Combined heat and power (CHP) plants fueled by biomass can meet heating and power requirements for cold regions in winter. The objective of this research is to investigate the effect of the distribution density of biomass CHP plant networks on the total (heat and electricity) energy utilization efficiency. The distribution density is determined from the heat transmission threshold. The total energy utilization efficiency is determined from the demand distribution, the output efficiency, and the transmission losses of heat and electricity. To determine a suitable heat transmission threshold, a biomass CHP plant network model is derived to compare various candidate network plans with various heat transmission thresholds. Geographic information system software is employed to calculate the above factors, and the total energy utilization efficiencies of the various plans are compared. The results show that when the heat transmission threshold is low, the plant distribution density is high, and the size (capacity) of the CHP plants is small. Conversely, when the heat transmission threshold is high, the plant density is low and the size of the plants is large. A heat transmission threshold of 10 km results in a plant density that produces the greatest total energy utilization efficiency.

Comparative study on off-design characteristics of CHP based on GTCC under alternative operating strategy for gas turbine

As the rising proportion of natural gas in China energy structure, gas-steam combined cycle based CHP (combined heating and power) systems are expected to have wider applications. To study the performance of CHP systems under two different operating strategies, i.e., IGV (inlet guide vanes) strategy and TIT (turbine inlet temperature) strategy, a stage-stacking method was used for axial-flow compressor characteristics, a stage-by-stage model including blade cooling was adopted for the turbine, and analytical method was employed to solve HRSG (heat recovery steam generator) part-load performance. The model was validated by the field data from an existing MPCP1-M701F3 gas-steam combined cycle power unit. Maximum and minimum steam extraction lines for heating supply were obtained. The selection of operating point between the two lines to meet the same heating demand was discussed from the views of economic benefit and energy utilization efficiency. The results show that, compared to TIT strategy, CHP system with IGV strategy shows advantages in PES (primary energy saving) and total energy utilization efficiency whereas disadvantages in heat to power ratio under part-load conditions. Otherwise, for the same operating range of TIT, CHP system with IGV strategy can reach broader performance at the same steam extraction ratio.

An experimental investigation of dehumidifying and reheating performances of a dual-evaporator heat pump system in electrified vehicles

Climate control system in electrified vehicle is quite different from traditional internal combustion engine vehicle, as it cannot use the wasted coolant heat from engine to keep warm of the cabin. For the dehumidifying and reheating air in the electrified vehicle cabin, the use of a dual-evaporator heat pump system could improve the total energy utilization efficiency of the climate control system. In this study, an experimental dual-evaporator heat pump system was set up to investigate dehumidifying and reheating efficiency of a cabin in electrified vehicle. Two dehumidifying modes were chosen in this experiment. One was single-evaporator mode with indoor evaporator only, and the other was dual-evaporator mode with both indoor and outdoor evaporators. The dual-evaporator dehumidifying mode shows higher heat capacity, coefficient of performance, and outlet air temperature, while it has quite lower moisture extraction rate and specific moisture extraction rate compared to the single-evaporator dehumidifying mode. Therefore, a hybrid dehumidifying and reheating method was suggested as a possible option for realization of energy conservation without sacrifice of thermal comfort for passengers.

An Advanced Energy System Using a Small Fast Reactor as an Energy Source

An advanced energy system has been proposed that involves a supercritical carbon dioxide gas turbine fast reactor (S-CO2 FR) as a dispersed energy source, a new waste-heat recovery system from the FR, and a bioconversion system using the recovered waste heat. The FR with S-CO2 gas turbine achieves higher cycle efficiency than conventional sodium-cooled FRs with steam turbines, eliminating problems of conventional FRs related to safety, plant maintenance, and construction costs. The S-CO2 FR consumes minor actinide elements produced in light water reactors as fuel, thereby reducing long-lived radioactive wastes and environmental loads imparted by long-term geological disposal. The recovered waste heat is used for methane and methanol production through fermentation of human and animal wastes in cities and farms. The methane and methanol are easily transported and can accommodate demand changes; they are useful as fuel of fuel cells, automobiles, and gas turbine power plants. The total energy utilization efficiency in electricity and heat is estimated to be higher than 85%, contributing to saving of energy resources and reduction of greenhouse-gas emissions. Consumption of the waste products of cities and farms for production of methane and methanol fosters a recycling society. Compact and high-performance microchannel heat exchangers are used in the S-CO2 FR, the new waste-heat recovery system and the fermentation system.

Residential energy consumption and associated carbon emission in forest rural area in China: A case study in Weichang County

Rural energy consumption in China has increased dramatically in the last decades, and has become a significant contributor of carbon emissions. Yet there is limited data on energy consumption patterns and their evolution in forest rural areas of China. In order to bridge this gap, we report the findings of field surveys in forest villages in Weichang County as a case study of rural energy consumption in northern China. We found that the residential energy consumption per household is 3313 kgce yr(-1) (kilogram standard coal equivalent per year), with energy content of 9.7 x 107 kJ yr(-1), including 1783 kgce yr(-1) from coal, 1386 kgce yr(-1) from fuel wood, 96 kgce yr(-1) from electricity, and 49 kgce yr(-1) from LPG. Per capita consumption is 909 kgce yr(-1) and its energy content is 2.7 x 107 kJ yr(-1). Due to a total energy utilization efficiency of 24.6%, all the consumed energy can only supply about 2.4 x 107 kJ yr(-1) of efficient energy content. Secondly, household energy consumption is partitioned into 2614 kgce yr(-1) for heating, 616 kgce yr(-1) for cooking, and 117 kgce yr(-1) for home appliances. Thirdly, the associated carbon emissions per household are 2556 kgC yr(-1), including 1022 kgC yr(-1) from unutilized fuel wood (90% of the total fuel wood). The rest of emissions come from the use of electricity (212 kgC yr(-1)), coal (1301 kgC yr(-1)) and LPG (21 kgC yr(-1)). Fourthly, local climate, family size and household income have strong influences on rural residential energy consumption. Changes in storage and utilization practices of fuel can lead to the 10%-30% increase in the efficiency of fuel wood use, leading to reduced energy consumption by 924 kgce yr(-1) per household (27.9% reduction) and 901 kgC yr(-1) of carbon emissions (35.3% reduction).

Integration of Distributing Energy System II: Optimization

The optimization of the Distributed Energy System can improve the total energy utilization efficiency greatly and achieve energy saving. Based on the digital simulation software introduced by Part Ⅰ, the optimizations of matching parameters and structure can be achieved. The example results showed that numerical simulation can realize the optimization of matching parameters and economic operation parameters for the parts and the whole system, and the design result with the highest efficiency is obtained.

Part one: A novel model of HTPEM-based micro-combined heat and power fuel cell system

Fuel cell-based combined heat and power (CHP) systems have received increasing attention during the last decade. This is mainly due to the high efficiencies obtainable on even a small-scale system basis. The current paper focuses on the development of a complete model of a system consisting of the high-temperature proton exchange membrane (HTPEM) fuel cell stack based on PBI membranes, steam-reforming reactor, burner, heat reservoir and other auxiliary equipment included in a typical reforming-based fuel cell system. The model is implemented in the Matlab ® Simulink environment enabling both static system integration as well as dynamical control strategies to be evaluated. All results of the submodels correspond well with experimental results obtained. Additionally, a novel system integration of an HTPEM fuel cell and a steam reforming-based fuel processing unit is presented. The total energy utilization efficiency of the system modeled is as high as 90 – 100 % LHV depending on the operating point chosen, whereas the electrical efficiency can be up to 45 % LHV . This is more than 30% better than the best low-temperature PEM-based systems demonstrated today.

Analyzing the Energy Utilization Efficiency of Renewable Energy Resources. Part 1: Energy Analysis Method

Energy consumption depends mainly on the available amounts of local resources, which are closely connected with the present rural economy and living standards. Recently, there has been increasing interest in using energy and exergy modeling techniques for energy utilization assessments in order to attain energy savings, and hence financial savings. The energy utilization of a country can be evaluated using exergy analysis to gain insights into its efficiency. The present study, consisting of two parts, deals with analyzing the energy utilization efficiency of renewable energy resources (RERs). Part 1 uses energy analysis method, while exergy analysis method is applied to Part 2. In the analysis, Turkey with a projected population of 76,840,418 in 2010, is given as an illustrative example. RERs considered are residential-commercial and industrial subsectors used in the Turkish conversion. The energy efficiency values for Turkey's RERs are projected to be 60.99% in 2010. Besides this, total energy utilization efficiency values for those are expected to be 49.85% in the same year. The present study has clearly indicated the necessity of the planned studies towards increasing renewable energy utilization efficiency in the sub-sectors studied and especially the critical role of policymakers in establishing effective energy-efficiency delivery mechanisms throughout the country. It is also expected that this study will fill a considerably large gap since it is the first attempt towards analyzing Turkey's RERs in 2010 in terms of energy utilization efficiencies.

3534 超臨界CO_2サイクルの発電プラントへの応用と現状 : 先進エネルギーシステム(S49-5 超臨界CO_2サイクル(1),S49 原子炉システムおよびその要素技術)

The Advanced Energy System Project (AESP) aims to develop commercially viable systems and technologies that provide electricity and heat such as hydrogen, methane, methanol, fuel cells using heat from small nuclear reactors, gas-turbine power plants and the sun. AESP has three objectives: (1) Save energy resources and reduce global warming gas emissions, attaining total energy utilization efficiency higher than 85% through waste heat recovery and utilization. (2) Foster a recycling society that consumes that garbage, waste wood and used paper that are produced in urban centers, along with excreta produced through farming to generate hydrogen, methane and methanol for fuel cells using waste heat and solar energy. (3) Consume trans-uranium elements produced in light water reactors as fuel for the small fast reactors, and reduce long-lived radioactive wastes or environmental loads of long term geological disposal.

Conceptual Design of Low-Temperature Hydrogen Production and High-Efficiency Nuclear Reactor Technology

Hydrogen, a potential alternative energy source, is produced commercially by methane (or LPG) steam reforming, a process that requires high temperatures, which are produced by burning fossil fuels. However, as this process generates large amounts of CO 2 , replacement of the combustion heat source with a nuclear heat source for 773 - 1 173 K processes has been proposed in order to eliminate these CO 2 emissions. In this paper, a novel method of nuclear hydrogen production by reforming dimethyl ether (DME) with steam at about 573 K is proposed. From a thermodynamic equilibrium analysis of DME steam reforming, the authors identified conditions that provide high hydrogen production fraction at low pressure and temperatures of about 523 - 573 K. By setting this low-temperature hydrogen production process upstream from a turbine and nuclear reactor at about 573 K, the total energy utilization efficiency according to equilibrium mass and heat balance analysis is about 50%, and it is 75% for a fast breeder reactor (FBR), where turbine is upstream of the reformer.