Energy Utilization System Research Articles

Performance characteristics of flat-plate oscillating heat pipe with porous metal-foam wicks

In this study, a flat-plate oscillating heat pipe (FPOHP) with its channel bottom covered by sintered copper-foam wicks was fabricated. The overall size of FPOHP is 150 mm × 100 mm × 7.5 mm, having rectangular cross-section channels with a hydraulic diameter of about 1.64 mm. The start-up and heat transfer performance of the porous-based FPOHP were experimentally investigated and compared with a conventional smooth-channel FPOHP at the vertical orientation. Ethanol was used as the working fluid at a volumetric filling ratio of about 50%. Experimental results showed that the copper-foam wicks enabled a profound improvement in the FPOHP performance and reduced the start-up temperature and time duration significantly. Compared with the conventional FPOHP, temperature fluctuations with smaller amplitudes and better temperature uniformity were observed for the porous-based FPOHP. However, local dry-out appeared earlier in the porous-based FPOHP when the power input was greater than about 207 W because the robust nucleation boiling induced vapor layer covered the wicks, preventing the backflow of liquid to the evaporator and causing the heat transport limitation. To extend the applicable possibility of porous-based FPOHPs in thermal management of high energy utilization systems, the re-design and re-fabrication of copper-foam wicking structures are required.

Concepts and characteristics of a U-shaped docking well geothermal heat extraction system

Environmental pollution in China is getting worse. The effective use of geothermal energy can solve the problem of greenhouse gas emissions. This paper introduces a new type of medium-deep geothermal energy utilization system named U-shaped docking well geothermal heat extraction system and analyzes its characteristics. The results show that the system can meet the needs of daily heating, and the heat transfer effect of this system is greater than the concentric casing heat exchange systems. This study provides a new idea for the use of medium-deep geothermal energy.

Simulation of design and operation of hydrogen energy utilization system for a zero emission building

Nearly 40% of the total greenhouse gases (GHGs) are emitted from the energy consumption in buildings in Japan, which should be reduced to address global warming. A hydrogen energy utilization system with renewable energy (RE) was designed by MATLAB/Simulink simulations for realizing a zero emission building (ZEB), comprising a hydrogen-producing electrolyzer, a hydrogen storage tank, fuel cell, and battery for short-term power storage with estimated specifications of 3.0 Nm3/h, 36 Nm3, 4.2 kW, and 10 kW/17 kWh, respectively. We identified a small low-rise building (total floor area: ∼1000 m2, demand: ∼5 kW) as the planned ZEB to construct and operate a bench-scale system. A 20-kW photovoltaic (PV) system was selected as the RE source. Two hydrogen production processes (constant power of 10 kW or with excess PV power) were evaluated by simulating 48-h operations on fine and cloudy days, where the former showed higher efficiency. The results with excess power on a fine day agreed well with that of actual operation, validating our simulation models. Further, the constant case was suitable for practical application.

Effective utilization system of renewable energy through the use of vehicle

Electric Vehicle (EV) and Fuel Cell Vehicle (FCV) can be used not only as transportation for people and goods but also for storage and transportation of energy. As a method to realize this philosophy, a new system which has two storage methods has been proposed. The first method: photovoltaic power generator (PV) power is stored as electricity in the EV battery. The second method: PV power is stored as thermal energy in the Heat Pump Water Heater (HPWH) which converts electricity into a thermal energy such as the hot water.In this paper, some new energy systems which combine PV, EVs and heat pump water heater (HPWH) are compared and studied. In these systems, PV power is stored as electricity in the EV battery, and as thermal energy in the HPWH. As the result, a novel energy system which combines PV, AI-EVs and HPWH is able to reduce CO2 emissions by more than 75% with high economic efficiency. In order to expand the new system, a novel concept vehicle by using bio-fuel such as AI-EV is effective. Additionally, the quantity of the renewable fuels necessary for the adjustment among seasons in the new system is less than 20% of present fossil fuel consumption when all energy is substituted by renewable energy.

LNG cold energy utilization: Prospects and challenges

Liquefied natural gas (LNG) is widely used in many countries around the world primarily as a mode of transport for natural gas. However, massive amount of energy (around 830 kJ/kg of LNG) is wasted during the regasification process in the LNG regasification terminals. Therefore, the technologies to utilize the LNG cold energy have received significant attention over recent decades. In this paper, we review various studies on the current LNG cold energy utilization systems, including power generation, air separation, desalination, cryogenic carbon dioxide capture, and NGL recovery. Utilizing LNG cold energy on such systems can improve the energetic and exergetic efficiencies significantly. Furthermore, several potential applications to utilize LNG cold energy in the future are proposed and discussed to broaden the perspectives of the researchers in the community. Among these potential applications, recovering LNG cold energy on cold chain for food transportation, data center cooling and hydrate based desalination are very promising. Finally, the limitations and challenges to be addressed for LNG cold energy utilization are discussed in detail.

Control Strategy for the Energy Optimization of Hybrid Regenerative Braking Energy Utilization System Used in Electric Locomotive

The braking process of electric locomotive is featured by short braking time, large braking power, large voltage fluctuations, etc. Faced with the problem of low utilization of braking energy and high investment cost of the current regenerative braking energy utilization systems, an energy optimization scheme is proposed in this paper by combining the control strategy for energy storage and energy optimization. The regenerative braking energy utilization system is modeled by analyzing the braking process of electric locomotive. The instantaneous absorption reference powers of the energy storage subsystem and energy feedback subsystem in braking process are obtained according to the established mathematical model. The energy storage subsystem uses super capacitor and adopts a power-current dual closed-loop control strategy. The energy feedback subsystem adopts a voltage-current dual closed-loop control strategy. Through the tracking control of the instantaneous power, a reasonable distribution of the regenerative braking energy is achieved between the energy feedback subsystem and energy storage subsystem, thereby increasing the utilization efficiency of the two subsystems. Finally, the performance of the proposed scheme is verified by simulation and experiment.

Feasibility analysis of a concentrating photovoltaic-thermoelectric-thermal cogeneration

This paper provides a novel solar energy utilization system that firstly achieves the cogeneration of photovoltaic, thermoelectric and high-grade heat. The novel concentrating photovoltaic-thermoelectric-thermal cogeneration system can overcome almost all of the disadvantages of the existing systems and provide a better way for solar energy utilization. The operating temperature, energy and exergy efficiency of the new system and the existing systems in different weather and seasons are first compared to demonstrate the superiority of the new structure. The new system is then optimized by investigating the effect of controlled temperature and thermoelectric structure on the hybrid performance to improve the solar energy utilization. Finally, the system array is proposed to reduce the system cost, and the economic analysis of the systems is conducted. The results indicate that when the solar irradiance is high, the new structure can well mitigate the temperature fluctuation caused by the varying solar irradiance and keep the photovoltaic cell operating at a safe temperature. The new system provides more exergy output than the existing systems because it produces both electricity and high-grade thermal output. When the solar irradiance is low, the new system behaviors similar to the concentrating photovoltaic-thermoelectric hybrid system, but it also provides more exergy output. All of the results demonstrate the significant advantages of the new system: efficient, stable and secure.

Progress in biosynthesis of phycobiliprotein

Photosynthesis has existed on the earth for about 4 billion years, and the photosynthetic organisms have emerged with the production of photosynthesis. In order to effectively capture light energy and adapt their living environment, algae and higher plants have evolved different light-harvesting antenna systems during the long evolution, one is the chlorophyll based light harvesting systems present mainly in terrestrial organisms, such as higher plants; and the other is the phycobiliprotein (PBP) based phycobilisome system mainly in aquatic organisms, such as cyanobacteria, red algae and cryptophytes. As a special light-harvesting pigment-protein complex, PBP can not only capture light energy, also shows many unique characteristics, such as good fluorescent properties and lots of pharmaceutical activities. Therefore, PBPs have been extensively studied and commercially used in foods, cosmetics, biotechnology detection, pharmacological and medicine fields. Due to its broad excitation spectrum, nontoxic, stable fluorescence and high quantum yield, PBPs have also employed as valuable fluorescent probes for immunological diagnosis. At present, there are mainly two ways to obtain fluorescent PBPs, one is to purify PBP directly from natural algae, and the other is to express recombinant PBP using genetic engineered host cells. Purification of PBPs from natural algae has many disadvantages, such as higher cost, complicated processes, and many by-products. Using genetically engineered cell biotechnology, large-scale and low-cost production of recombinant PBPs can be achieved, which can help solve problems such as source, quality control and so on. Since natural PBPs are mostly in the form of polymers such as trimers or hexamers, it is difficult to study the assembly process. Through genetic engineering techniques, monomers or subunits can be obtained, which will help to study the assembly process of PBP. In addition, novel recombinant PBPs can be produced by molecular design to improve their fluorescence and biological activity. The study of the biosynthesis will help to elucidate the relationship between the structure and spectral properties of PBPs and provide a basis for the construction of solar energy utilization systems. This review mainly focuses on the progress of combinational biosynthesis and in vivo reorganization of PBP in heterologous genetically engineered host cells, with emphasis on different genes coding for apo-PBPs and genes coding for different enzymes which catalyze the production of phycobilins from endogenous heme, along with the recent progress of three types of lyases which catalyze the covalently binding of phycobilins with apo-PBPs. The possible applications of these valuable recombinant PBPs were proposed as well.

Empirical and machine learning models for predicting daily global solar radiation from sunshine duration: A review and case study in China

Accurate estimation of global solar radiation (Rs) is essential to the design and assessment of solar energy utilization systems. Existing empirical and machine learning models for estimating Rs from sunshine duration were comprehensively reviewed. The performances of 12 empirical model forms and 12 machine learning algorithms for estimating daily Rs were further evaluated in different climatic zones of China as a case study, i.e. the temperate continental zone (TCZ), temperate monsoon zone (TMZ), mountain plateau zone (MPZ) and (sub)tropical monsoon zone (SMZ). The best-performing model at each station and the overall best model for each climatic zone were selected based on six statistical indictors, a global performance index (GPI) and computational costs (computational time and memory usage). The results revealed that the machine learning models (RMSE: 2.055–2.751 MJ m−2 d−1; NRMSE: 12.8–21.3%; R2: 0.839–0.936) generally outperformed the empirical models (RMSE: 2.118–3.540 MJ m−2 d−1; NRMSE: 12.1–27.5%; R2: 0.834–0.935) in terms of prediction accuracy. The cubic model (M3), modified linear-logarithmic model (M5) and power model (M10) attained generally better ranks among empirical models based on GPI. M3 was the top-ranked model in TMZ and MPZ, while general best performance was obtained by M5 and M2 in SMZ and TCZ, respectively. ANFIS, ELM, LSSVM and MARS obtained generally better performance among machine learning models, with the overall best ranking by ANFIS in TCZ and SMZ and by ELM in MPZ and SMZ. XGBoost (8.1 s and 74.2 MB), M5Tree (11.3 s and 29.7 MB), GRNN (12.3 s and 295.3 MB), MARS (14.4 s and 42.6 MB), MLP (22.4 s and 41.3 MB) and ANFIS (29.8 s and 23.1 MB) showed relatively small computational time and memory usage. Comprehensively considering both the prediction accuracy and computational costs, ANFIS is highly recommended, while MARS and XGBoost are also promising models for daily Rs estimation.

A thermodynamic analysis and economic evaluation of an integrated cold-end energy utilization system in a de-carbonization coal-fired power plant

Huge amount of cold-end energy discharged from the CO2 capture/compression process is not thermodynamically satisfactory for monoethanolamine (MEA)-based de-carbonization coal-fired power plants. In this study, an improved cold-end energy utilization concept for a MEA-based de-carbonization coal-fired power plant was innovatively proposed, which highly integrates the CO2 capture/compression, steam bleeding, and boiler air pre-heating processes to cascade utilize the system cold-end energies, and beneficially supplies the heat required for solvent regeneration and air preheating. To be specific, three paths have been adopted: (1) reboiler condensate recirculation: part of the reboiler condensate is recirculated to mix with the steam bleed to provide the heat for solvent regeneration; (2) absorption heat transformer (AHT): upgrading the reboiler condensate heat for solvent regeneration; and (3) multi-stage air heating: cascade utilization of the heat discharged from coolers within CO2 capture/compression process to preheat combustion air prior to the flue gas-air preheater, saving part of the flue gas heat to be used in a more cascade way. The mass and energy balance of the proposed system and the overall system performance were determined using the process simulation. The energy saving mechanism of the adopted three paths were investigated through adopting the graphical exergy analysis for the reboiler block and air preheating process. The cost of electricity (COE) and cost of CO2 avoided (COA) of the proposed system were also determined. Results showed that the energy efficiency of the proposed system could be 3.2 percentage points higher than that of the conventional de-carbonization plant without cold-end energy utilization. The COE and COA of the proposed system were reduced by 8.0% and 22.2%, respectively.

Transient response of waste heat recovery system for hydrogen production and other renewable energy utilization

In this paper, a 1 kW ORC experimental system is built. Using R123 as the working fluid, transient responses of Basic ORC (BORC) and ORC with a regenerator (RORC) are both tested under critical conditions. A total of four experiments are carried out, including: (1) Case 1: the working fluid pump is suddenly shut down; (2) Case 2: the working fluid is overfilled or underfilled; (3) Case 3: the torque of the expander is suddenly loss. (4) Case 4: the cooling water pump is suddenly shut down. All the major quantities such as the output power and torque of the expander, temperatures and pressures at the inlet and outlet of the expander, temperatures at the inlet and outlet of the condenser are measured. The transient responses of the two systems under the controlled critical conditions are tested and compared, some physical explanations are provided. It is found that RORC is more stable than BORC because of the regenerator. Regenerator should act as a “pre-heater” or “pre-cooler” under the critical conditions thus improving the stability of RORC. When the working fluid in the system is underfilled or leaked, the system performance is extremely unstable. Otherwise, when the working fluid is overfilled, the trend of the curves are similar to the optimal working condition but with weaker performances. We also find that if the working fluid pump is shut down when working fluid is overfilled, the rotation speed and shaft power output of the expander will increase significantly, the unique phenomenon can be used to estimate whether the working fluid in the system is overfilled.

4-6-3 建物付帯型水素エネルギーシステムの開発とその運転

4-6-3 建物付帯型水素エネルギーシステムの開発とその運転

Coordinated DG-Tie planning in distribution networks based on temporal scenarios

Optimal planning of distributed generation (DG) in distribution networks is key for improving energy utilization efficiency and system operation benefits. Considering the uncertainties and temporal correlations of DG output and load demand, a multi-scenario chance-constrained economic model for DG planning is established in this paper. The model considers the comprehensive benefits of environmental, reliability and other aspects, as well as the active curtailment management of DGs. Thereafter, the model is extended to the coordinated planning of both DGs and tie lines, which is formulated as a multi-objective model. An improved genetic algorithm based solving strategy integrated with game multi-objective decision method is proposed. The feasibility and effectiveness of the proposed models are verified on the IEEE 33-bus distribution system. The impacts of natural resource distribution, confidence level, unit environmental cost and other parameters are investigated as well. The case studies also prove the integration of complementary DG generation could help improve the maximum capacity of DG and indicate the environmental benefit is the vital incentive to introduce DG into the distribution network.

Numerical simulation of flow field in umbrella wind turbine

Umbrella wind turbine can control the swept area by adjusting the shrinking angle of the rotor so as to ensure that output power is near the rated value. This is very helpful for the utilization of wind energy in sandstorms and typhoon-prone areas of our country. In this paper, Fluent software is used to simulate the velocity field and pressure field of 5kW Umbrella Wind Turbine at 0° 45°and 60°angle of contraction. The results provide a theoretical basis for further improving the power adjustment mechanism of Umbrella Wind Turbines, At the same time, it also provide a reference for our country to perfect the wind energy utilization system about the typhoon environment in the coastal areas.

(Invited) Designing Efficient Photoelectrochemical Solar Energy Conversion Devices and Their Integration with Redox Flow Battery Devices

Due to the intermittent nature of sunlight, practical solar energy utilization systems demand both efficient solar energy conversion and inexpensive large scale energy storage. We will first discuss the rational design and demonstration of efficient photoelectrochemical hydrogen generation systems using efficient semiconductors and earth-abundant catalyst materials. We have further developed novel hybrid solar-charged storage devices that integrate regenerative photoelectrochemical solar cells and redox flow batteries (RFBs) that share the same pair of redox couples. In these integrated solar flow batteries (SFBs), solar energy is absorbed by semiconductor electrodes and photoexcited caries are collected at the semiconductor-liquid electrolyte interface and used to convert the redox couples in the RFB to fully charge up the battery. When electricity is needed, the charged up redox couples will be discharged on carbon electrodes to generate the electricity as in a RFB. We have demonstrated that such SFB devices can be charged under solar light without external electric bias and deliver a high discharge capacity comparable with state-of-the-art RFBs over many cycles. After developing silicon solar cells and high performance solar cells, carefully matching them with various organic or inorganic redox couples, and optimizing several generations of SFB device designs, we have recently achieved integrated SFB device with an overall direct solar-to-output electricity efficiency (SOEE) of 14%. These high performance SFBs can serve as distributed and standalone solar energy conversion and storage systems in remote locations and enable practical off-gird electrification.

Analysis of thermal deposition of MgCl2·6H2O hydrated salt in the sieve-plate reactor for heat storage

Hydrated salt thermochemical energy storage which utilizes reversible gas–solid reactions to store heat for charging and release heat for discharging has a promising application in the energy utilization system. A novel sieve-plate hydrated salt thermochemical energy storage system (TCES) with the reactive porous bed of MgCl2·6H2O is investigated, and the mathematical equations describing the heat and mass transfer for the TCES are developed to analyze the effects of the geometric parameters of reactor and operating conditions on the thermal decomposition of MgCl2·6H2O salt during charging (dehydration). The rises of the sieve plate number and length within a certain degree cause the shorten time to reach the equilibrium extent conversion at input temperature. The δ, ratio of channel width h1 to reactive bed thickness h0, needs to be optimized to achieve higher dehydration efficiency. More residence time of heating gas and more heat storage can be achieved with the relatively higher input temperature. The kinetic factor needs to be above Rkin = 1 · 10−3 s−1 to avoid lower extent conversion and larger time length for the reactive bed to reach the equilibrium phase at input temperature. The dehydration efficiency in the reactive bed and the heat utilization rate of heating gas in the charging are related to the heating gas velocity. The simulations agree with the published TGA-DSC testing results. For the current mode, the reactor with a 6 sieve plates of L0 = 24–26 cm and a δ = 0.8 flow channel as well as the relatively higher thermal conductivity and operating temperature within a certain degree in the reactive bed are proposed.

Investigation of technical gaps between DEMO blanket and HCCR TBM

Korea has own programs toward DEMO and fusion reactors that will require further improved DEMO blanket and energy utilization systems. Primary goals of DEMO blanket development in Korea are to develop and verify the integrated blanket design tools; to develop blanket materials, cooling and tritium fuel cycle technologies; and to develop and evaluate fabrication and joining technologies. The concept of helium-cooled ceramic reflector (HCCR) blanket is adopted to be tested in ITER as Test Blanket Module (TBM). Currently, the design and R&D activities are mainly performed through the ITER TBM program in Korea. It is expected to demonstrate the major objectives of the breeding blanket: extraction of heat from burning plasma, tritium self-sufficiency and its integrity within the whole systems considering safety features. Although TBM program will provide very essential data and experience, there will be a considerable technical gap from DEMO blanket. This paper presents the technical gap in the main technical categories of the breeding blanket based on the experience of the development of HCCR TBM and breeding blanket. It is found that still about 60–70% of the DEMO blanket technology can be achieved through the HCCR TBM depending on the technology maturity level, and some ways to DEMO blanket from HCCR TBM are proposed.

P-03 都市・地域レベルの脱炭素化に向けた下水熱エネルギー利用システムの統合デザイン

P-03 都市・地域レベルの脱炭素化に向けた下水熱エネルギー利用システムの統合デザイン

An MILP Method for Design of Distributed Energy Resource System Considering Stochastic Energy Supply and Demand

A distributed energy resource (DER) system, which can be defined as a medium or small energy conversion and utilization system with various functions for meeting multiple targets, is directly oriented towards users and achieves on-site production and energy supply according to users’ demands. Optimization research on system construction has recently become an important issue. In this paper, simple stochastic mathematical equations were used to interpret the optimal design problem of a DER system, and based on this, a novel method for solving the optimization problem, which has multi-dimensional stochastic uncertainties (involving the price of input-energy and energy supply and demand), was put forward. A mixed-integer linear programming (MILP) model was established for the optimal design of the DER system by combining the ideas of mean value and variance, aiming to minimize the total costs, including facility costs, energy purchase costs, and loss caused by energy supply shortage, and considering the energy balance and facility performance constraints. In the end, a DER system design for an office building district in Xuzhou, China, was taken as an example to verify the model. The influences of uncertainty on the selection of system facilities and the economic evaluation were analyzed. The result indicated that uncertainty of energy demand played a significant role in optimal design, whereas energy price played a negligible role. With respect to economy, if uncertainties are not considered in system design, it will result in a short supply, and therefore the total cost will increase considerably. The calculation convergence was compared with previous work. The implementation results showed the practicality and efficiency of the proposed method.

Large-area seepage and heat transfer model of beach well infiltration intake system for seawater source heat pump

The seawater source heat pump (SWHP) has attracted significant attention as a renewable energy utilization system. The beach well infiltration intake system (BWIS) effectively improves the stability, reliability, and energy-efficiency of SWHP systems in cold climate areas. A seepage and heat transfer model is established for scientific BWIS applications. MATLAB is used to analyze solutions for the seepage model, as well as to obtain a numerical solution for the heat transfer model. The analytical solution for the seepage model is a fast-solving method compared with the numerical solution. The method explicitly analyzes the qualitative and quantitative relationships among influencing factors of the system. In the heat transfer model, the advection term dominates the heat transfer, while the conduction term can be ignored. A BWIS for SWHP systems is tested and the simulation results agree with the measured data. The simulation model is used to analyze BWIS performance. All system influencing factors are identified and classed according the model. The results demonstrate the usefulness of the simulation model, thereby validating the method as a potential engineering tool for BWIS design.