Based on the advanced FCVS technology, such as a gas-liquid mixing nozzle and a multi-layer metal fiber filter, and a silver zeolite filter for the purpose of removing organic iodine. we have developed a demonstration machine for a large-capacity air purification system that purifies a large amount of contaminated air. With this acceleration and centrifugal force field of water, almost all of the fine particles in the bubbles can be transferred to the liquid phase water and dissolved. We have developed a demonstration machine of an air purification system that can remove fine particles and viruses in the air of 100 m3/h with a single nozzle and we also developed a large-capacity air purification system that can purify 2400 m3 of air per hour with 24 nozzles. The FCVS system, which is high-performance and passively activated by using SRV, is thought to help eliminate obvious infringement of personality rights, avoid litigation outages, and promote public acceptance for nuclear power to restart.
A filtered containment venting system (FCVS) is considered an effective system that can enhance the capability to suppress or prevent severe accidents by reducing the pressure, steam water, and flammable gas in containment vessels. The water inventory in a wet-type FCVS plays an important role that affecting the retention efficiency of FCVS. However, a high water level of the FCVS may affect the performance of the liquid droplet separator due to the high entrainment rate. To overcome this, in this study, perforated metal sheet plates were installed on the upper part of the large-scale FCVS to decrease the entrainment rate. The void fraction measurements and entrainment rate estimation were carried out for FCVS with and without the punching plates. It showed that the perforated plates have significant contributions to decreasing the entrainment rate of FCVS, therefore, it allows to increase in the initial water level of the scrubber tank.
Since various gases such as CO are generated by MCCI (Molten Core Concrete Interaction), this is suppressed by injecting water into the lower part of the containment vessel. In order to install silver zeolite in the containment vessel and confirm whether it can play an auxiliary role in the hydrogen recombiner, we conducted joint research with PSI on the effects of CO and other substances on hydrogen reactivity. AgX exhibits a remarkable hydrogen-catalyzed reaction as before in a water vapor-free environment. Furthermore, it was found that when carbon monoxide coexists, CO is also removed. On the other hand, it was found that when the water vapor content is 85% or more and the air content is extremely low at 7%, the catalytic reaction between hydrogen and carbon monoxide is unlikely to occur. The amount of hydrogen treated was calculated from the results of the AgX hydrogen reaction test. Under the conditions of sample temperature 170 ° C, residence time 0.092 seconds, air 45%, hydrogen 5%, water vapor 9%, and atmospheric pressure, it was found that the hydrogen processing capacity per AgX unit weight was 0.207 kmol / kg or more of hydrogen.
Through the research of Filtered Containment Venting System (FCVS), air purification methods have been developed, such as technologies of scrubbing, metal fiber, silver zeolite and mobility. Using these technologies, we have been studying the further improvement of air purification systems in the nuclear field. In this study, we conducted adsorption experiments using several metal fiber filters and evaluated the effect of the metal fiber wire diameter on the decontamination factor (DF). It was found that metal fibers with fine wires made a significant contribution to the removal of materials with minute particles. In addition, particles adsorbed on the filter were photographed using a scanning electron microscope (SEM) to research the correlation between fiber line diameter and adsorbed particle size.
The metal fiber filters and silver zeolite (AgX, etc.) that have a proven track record in Filtered Containment Venting System(FCVS) are nonflammable and can be used even at high temperatures. And also scrubbing technology is greatly improve the decontamination factor (DF) of radioactive substances. By applying these technologies, we propose to make the air purification system more robust and smaller, and making it mobile. The system is expected to be used in a wide variety of ways such as by moving to an emergency evacuation site or a highly polluted place in the event of an accident to supply clean air for reducing the exposure of local residents and radiation workers. We manufactured the prototype of portable air purification system in 2020. Performance tests such as DF tests were conducted in 2021. As a result, we confirmed the high adsorption performance of organic iodine and the high collection rate of barium sulfate.
Of the radioactive substances generated during a nuclear accident, noble gas is difficult to remove, so a noble gas hold-up system using activated carbon is applied, and it is released after waiting for the decay of radioactivity. We have developed a silver zeolite "XeA" as a noble gas adsorbent to replace activated carbon, and evaluated its noble gas retention performance. As a result, it was found that the xenon holding time under dry air was 480 minutes for XeA compared to 6 minutes for activated carbon, and XeA had 80 times the holding performance of activated carbon. From this, there is a possibility that the existing system using activated carbon can be reduced to 1/80 size. We also propose a system that uses this XeA in combination with a filter that does not transmit xenon.
Due to the March 11, 2011 14:46 M9 Great East Japan Earthquake, composed power sources of electric power and energy in Japan has changed significantly. A large amount of solar power generation has been introduced in power systems of Japan. On the other hand, solar power generation has inherent characteristics that the power generation output fluctuates greatly depending on rain clouds. Power supply is required to maintain a stable power in power systems. This paper describes solar power generation output on rainy weather and snowfall, the importance of power interchange between electric power areas, and nuclear power plants as compensated power for stable power supply considering world trends.
Nuclear power generation is a stable basic power source that does not emit CO2 on the premise of ensuring safety, and has recently been re-evaluated as an attractive option from the viewpoint of energy security and environmental protection. Factors such as the recent sluggish power demand, power grid capacity limits, and initial investment limits to avoid risks do not favor large-scale plant output. In order to globalize nuclear power generation to mitigate the greenhouse effect, we need a small modular reactor (SMR) that can be easily adopted in any country and can be modularized and manufactured in factories with short construction periods.
The concept of the reactor introduced in this section has a simplified BWR (LSBWR) configuration with a low output, long operating cycle, and comprehensive safety features, which was presented in 1999 at the annual meeting of the JSME and ICONE11 by Narabayashi et, al. To be economically competitive, the LSBWR design includes system and structural simplifications, modularity for short construction times, and increased availability. Comprehensive safety features are not intended to be evacuated by reliable equipment or systems such as lower core layout, IVR features, and hybrid ECCS including passive system. The concept proposed here is to provide flexibility for different site conditions and power demands, reduce investment risk and promote public acceptance. Finally, the author also introduces a new SMR named LLBWR, which uses a reactor internal recirculation pump (RIP) for the purpose of load follow with fluctuating renewable energy and enhance facilitates for stable grid control.
Japan Atomic Energy Agency is developing an innovative design system named ARKADIA to achieve the design of an advanced nuclear reactor as a safe, economic, and sustainable carbon-free energy source. ARKADIA consists of three systems: the Enhanced and AI-aided optimization System (EAS), the Virtual plant Life System (VLS), and the Knowledge Management System (KMS). In the first phase of its development, ARKADIA-Design for design study and ARKADIA-Safety for safety assessment are being developed individually. In this paper, focusing on the ARKADIA-Design, the progress in the development of optimization processes in the fields of the core design, the plant structure design, and the maintenance schedule planning are introduced. Design optimization is actualized using the modules for evaluation in the EAS, numerical analysis in the VLS, and knowledge base in the KMS. After setting design parameters, objective function and its elements, and constraints, necessary numerical analyses for the plant performance evaluation are performed in the VLS, and specific plant parameters regarding objective function are checked and modified to close to the optimized ones. The outlines of the optimization process on a representative problem are described in the fields.
The cooling of the residual core materials after the fuel discharge from the SFR core in the core disruptive accident can significantly affect the distribution fraction of the core materials which is an important factor for the in-vessel retention (IVR). The cooling of the residual core materials is called “in-place cooling”. For the evaluation of the in-place cooling, behavior in a SFR core was simulated by SIMMER-III, and method of phenomena identification and ranking table (PIRT) was applied based on the analysis result. Experiment which focuses on the thermal-hydraulic phenomena which were extracted by the PIRT was conducted in the framework of EAGLE-3 project. Continuous oscillation of sodium level which can occur in the phase of in-place cooling of SFRs was observed in the experiment, and analysis by the SIMMER-III was conducted. By investigation of the analysis result, difference between the experiment and analysis results was revealed to be due to remaining and occupation of non-condensable gas above the sodium level which would be unrealistic in the experiment. Gas mixture model between non-condensable gas and sodium vapor was developed to solve this problem, and coincidence between experiment and analysis results was largely improved by this new model.
In Japan Atomic Energy Agency, the design optimization method for plant structure has been developed on the process to output optimal solution of the thickness of reactor vessel wall against thermal transient and seismic loads in a sodium-cooled fast reactor (SFR) as a representative problem in its design study. Resistance characteristic of the wall on the load derived from thermal transient is one of the most important factors for safety estimation on the structural integrity in the SFR system. Failure probability of components against thermal transient was set to one of variables forming elements in the objective function for a common scale to compare with other variables in different failure mechanisms such as mechanical failure by seismic motion. Thermal transient load was primarily considered in this study. In the iterative process to achieve the optimal solution, a number of evaluations to measure the influence on the load derived from thermal transient was necessarily conducted in accordance with the number of design parameters. More reduction of required time for evaluations in the iterative process is desired in the design study. To perform the iterative evaluation process efficiently, therefore, the automatization of parametric analyses was implemented in the optimization process.
In the core disruptive accidents (CDAs) of sodium-cooled fast reactors (SFRs), the eutectic reaction between boron carbide (B4C) as a control rod material and stainless steel (SS) as a structural material could occur below the melting points of both B4C and SS. Therefore, the loss of control rod materials and the movement of these reaction products toward inside or outside of the original core region could affect the core reactivity in CDAs of SFRs. In this study, the immersion tests using the B4C pellets with the molten SS were conducted to evaluate the CDA consequences in SFRs such as the contact event of solid B4C with molten core materials including SS under the condition of anticipated transient without scram (ATWS). Based on the reduction thicknesses of B4C pellets after the tests, the reaction rates were discussed.
Sodium-cooled fast reactors have intrinsic safety features decreasing reactor power during the increase of the core inlet temperature by the feedback reactivity due to the core deformation. It is necessary for the composition of the core highly of secure to understand the influence of the safety features with high accuracy. In this paper, to enable the plant dynamics analyses taking account of the thermal stratification in the cold pool, the 1D-CFD coupling method in which CFD was applied to the cold pool was applied to the ULOHS (Unprotected Loss Of Heat Sink) test performed in the experimental fast reactor EBR-II in the U. S. and the evaluation of the core inlet temperature could be improved. By using this 1D-CFD coupling method, sensitivity analyses concerning the core bowing reactivity were carried out with the aim of improving the evaluations of the core deformation reactivity. Through the numerical analyses, the applicability of the core bowing reactivity model to the test could be indicated.
Considering the recent large-scale earthquakes, if the 3D seismic isolation device using laminated rubber, etc., which is being studied in large-scale reactor, is adopted as it is in the SMR class, there is a possibility that the economic efficiency, which is the advantage of SMR, will be impaired due to scale disadvantages. Furthermore, the vertical function of the 3D seismic isolation device must continue to support its own weight during the life of the plant and softly follow an earthquake that suddenly occurs at a certain moment. We report on the study of seismic ground motion reduction measures in a floating building that can be applied to SMR as a highly feasible seismic isolation mechanism that can achieve both high reliability and excellent economic efficiency for these required functions.
In high temperature gas-cooled reactors (HTGRs), Tri-isotropic (TRISO)-coated fuel particles are employed as fuel. In the high burnup coated fuel particle, stress due to fission gas pressure and irradiation-induced pyrolytic carbon (PyC) shrinkage is introduced into the coating layers and consequently the stress could cause failure of coating layers under high burnup irradiation condition. A failure model has developed to predict failure fraction of TRISO-coated particle under high burnup irradiation. In the model, failure probability is strongly dependent on the irradiation characteristics of PyC. This paper describes the outline of the failure model and evaluation result of high burnup fuel irradiation experiment by the model.
Identifying accident scenarios that could lead to severe accidents and evaluating their frequency of occurrence are essential issues. This study aims to establish the methodology of the dynamic Probabilistic Risk Assessment (PRA) for sodium-cooled fast reactors that can consider the time dependency and the interdependence of each event. Specifically, the Continuous Markov chain Monte Carlo (CMMC) method is newly applied to the SPECTRA code, which analyzes the severe accident conditions of nuclear reactors, to develop an evaluation methodology for typical external hazards. Currently, a fault-tree model of air coolers of decay heat removal system is implemented as the CMMC method, and a series of preliminary analysis of the plant's transient characteristics under the scenario of volcanic ashfall has been conducted.
The seismic evaluation of key components such as the reactor vessel is important for the seismic probabilistic risk assessment in sodium-cooled fast reactors. In the past, the correlation of the fatigue failure and the integrated vibration energy to the component was applied to the failure evaluation in the seismic assessment. The objective of this study is to develop a failure probability evaluation method, which evaluates integrated vibration energy to the component during an earthquake. The fatigue failure evaluation method is investigated with simple vibration examination to failure. The vibration examination with the simple examination specimens, of which main vibration mode is the bending vibration, has been carried out by the random wave. This paper describes the estimation of the integrated vibration energy with the random waves. The integrated vibration energy of the random wave was compared with the integrated vibration energy of the sine wave by the integrated energy per unit time. The integrated vibration energy of the random wave is in the range of the approximate line, which is estimated with the integrated vibration energy of the sine wave. The evaluation method investigated in this study is expected to estimate the integrated energy with the random wave by the integrated energy with the sine wave.
Tornado PRA is an effective method to quantitatively evaluate tornado hazard impact on a nuclear power plant relative to the overall plant risk. Tornado hazard is generally classified into three categories, i.e., wind pressure load, negative pressure load, and impact load of tornado-borne missiles. The risk owing to tornado-borne missile impact on components and structures is supposed to be most significant among them, because the effects of the wind pressure load and the negative pressure load are usually negligible on components and structures with seismic resistance design, which are rigid enough to withstand postulated seismic load in Japan. Therefore, the authors have developed a probabilistic tornado-borne missile analysis code, TONBOS-pro, and an evaluation code of annual strike probability of tornado-borne missiles, TOMAXI-pro, which are intended to be used for tornado PRA. In this paper, we explain the primary features and sample results of both codes, with describing the future direction of their application to tornado PRA.
An equipment, with a plate heat exchanger, for testing seawater side fouling was operated for an extended period using seawater as the cooling heat source. The effectiveness of the electromagnetic processing equipment for marine biofouling was examined. The following results were obtained: 1) The overall heat transfer coefficient decreased by 25.7% without electromagnetic processing equipment and 21.7% with electromagnetic processing equipment compared to that at the start of the experiment. 2) The fouling factor 30 days after the start of the experiment was 7.08×10-5 m2 ·K/W without electromagnetic processing equipment and 6.34× 10-5 m2 ·K/W with electromagnetic processing equipment.
Clamp-on ultrasonic flowmeters are useful devices to measure flow rates in existing pipes. The steam wetness increases with heat losses and the liquid film and droplets flow in the wet-steam flows. It is reported that the error of the flow rates tends to increase with the wetness fraction because of the changes in the velocity distribution in the wet steam and the effect of the liquid holdup. Therefore, it is important to estimate the flow regime of the wet-steam flow in the pipe. This study proposed a flow pattern recognition method using a machine learning based on the guided wave that is the propagated ultrasound through the pipe wall. The guided wave changes depending on the flow regime due to the fluctuations at the liquid-gas interface. Using the received ultrasonic signals of the guided wave in stratified flow, annular mist flow, and transition between them were used as the teaching data, and the other conditions were tested for the flow pattern recognition. Flow patterns were accurately predicted in adiabatic air-liquid two-phase and wet-steam flows in horizontal pipes. Furthermore, it was shown that the selection of the guided wave region is important to predict the flow pattern in various pressure conditions using the same teaching data.
Ultrasonic phased array is a phase composite imaging technology developed in the radar field and has recently been used for nondestructive inspection of power generation equipment. However, scattered waves in the inspection target make it difficult to distinguish a flaw from scattering from the edge surface. In this study, we developed a method to discriminate flaws with high accuracy by adjusting parameters such as output voltage and receiver sensitivity to make it easier to see the flaws and by deep learning of the optimized flaw images. First, actual measurements were made using an ultrasonic phased-array flaw detector on a stainless-steel specimen. Next, a model was created to discriminate the presence or absence of flaws using transition learning, one of the machine learning methods. As a result, we found that the highest accuracy was achieved when transition learning was performed using inceptionv3 and resnet101, a convolutional neural network architecture. These results show that the method developed in this study is effective for nondestructive inspection.
In recent years, replacement of existing gas turbines with non-fossil fuels has been considered for the purpose of reducing CO2 emissions. In this study, a method for evaluating gas turbine characteristics when the composition of the combustion gas is varied is investigated by numerical analysis. The results of the performance evaluation based on a combination of flow coupled analysis including heat transfer in the blade solids and heat balance, as well as blade temperature evaluation, are reported. While detailed performance prediction for the entire turbine became possible, issues related to the evaluation of the effects of turbulence and radiation on the prediction of blade cooling efficiency were clarified.
In premixed charge compression ignition, the combustion chamber is divided into two and one is auto-ignited first. The other receives compression (rapid compression), which has a faster than piston compression, in addition to piston compression. Ignition timing prediction by Livengood-Wu integral was investigated by numerical simulation by changing the timing and strength of rapid compression. As a result, it was found that when the end gas part receives rapid compression before auto-ignition, the stronger the rapid compression, the smaller the Livengood-Wu integral value at the time of auto-ignition.
Superheaters are essential components in a coal-fired power plant because they keep the highest tube wall temperature points in the radiant boiler. The pressurized steam flowing in the superheater tubes is heated via the thermal radiation and convection from the combustion gas. To prevent the bursting of superheater tubes caused by the thermal fatigue for stable and safe plant operation, precisely predicting complex heat transfer characteristics, and estimating the local temperature and heat flux of the superheater are necessary. In this study, a computational fluid dynamics model of the boiler and the second and third superheaters in a coal-fired power plant was developed using radiation model (DO model) and turbulence models (k-ε RNG model). In the third superheater, the tube wall temperature and heat flux became large in the upper and middle parts of the superheater, where the combustion gas flow around the superheater was high, whereas those at the bottom of the superheater were significantly small due to the dead water region of the gas.
Japan Atomic Energy Agency (JAEA) is developing the evaluation method for a two-phase flow in the reactor core by the simulation code based on the Volume Of Fluid (VOF) method. However, it is impossible to simulate boiling on the heating surface in the large-scale domain like fuel assemblies by this type of simulation method since the simulation of boiling based on the VOF method needs the fine meshes which sufficiently resolve the initiation of boiling. Therefore, JAEA started to develop a simplified boiling model applied for the two-phase flow in the fuel assemblies. In this study, the simulation of the convection boiling on a vertical heating surface is simulated using the developed simplified boiling model. The comparison between the simulation results and experimental results showed the excellent reproducibility of the heat flux and velocity dependency on the passage time length of the bubble.
Heat pipe is a simple heat transfer device widely used in microelectronics cooling. It has a capillary structure called wick on its inner wall to convey condensate from a heat release section to a heated section. Nanoparticle layer is extremely thin and has strong capillary force. Hence, it could be used as the wick of heat pipes or vapor chambers to contribute downsizing them. Also, it is known that silica particles can be used to form a nanoparticle layer on the pipe inner wall as the wick of the heat pipe. It can achieve better heat transfer performance than the normal heat pipe containing a screen mesh in it. In this research, three types of nanoparticles were used to form the nanoparticles layer in heat pipe. It was explored experimentaly how the the heat transport performance depends on the nanparticles construting the wick.
Boiling is used for high heat flux devices because of its high heat transfer coefficient. The critical heat flux (CHF) is known as the coolability limit since it is the threshold value at which the boiling transition occurs. Due to the industrial demands, systematic approaches are required to investigate CHF enhancement. Therefore, We set metal mesh seat on the heat transfer surface, and conducted pool boiling experiments with liquid film retention structure. We demonstrated CHF enhancement with those structures and discussed the relationship between structural parameters and CHF enhancement effect.
Saturated pool boiling experiments were carried out to explore the wall material effect on the critical heat flux (CHF). It was found that the CHF value is higher for the wall material of higher thermal conductivity. To develop a mechanistic model to describe the present experimental results, it was postulated that the CHF condition is reached when the local wall temperature in the dry area formed beneath the nucleation bubble exceeds the critical value and the temperature rise is mitigated for the high thermal conductivity wall since the heat dissipation from the dry area to the surrounding area is pronounced. It was shown that the present model well describes the experimental results obtained in this work.
To confirm the accuracy of predicting the pressure loss of an evaporator tube with a diameter used in boilers and under high heat flux conditions, the pressure loss in the tube was calculated using representative prediction equations and compared with experimental values. the test was conducted under the condition that water was used as the working fluid and the pressure was 8 -16 MPa. As a result, it was confirmed that the predicted value of pressure loss obtained by Thoms method agreed well with the experimental value even under the condition of high heat flux below CHF. On the other hand, to predict the friction loss under the condition of high heat flux and the regions from sub-cool to low steam quality, it is necessary to consider liquid temperature rise near the wall and subcooled flow boiling as previously reported. For subcooled flow boiling, it was confirmed that the prediction accuracy of friction loss was improved by using the simple calculation method of Sekoguchi.
A flow channel with an inner diameter of 1 mm or less is called a microchannel and is used in various devices, so it is required to elucidate its flow characteristics. Most of the studies so far have used Newtonian fluid as the test liquid, and few have used non-Newtonian fluid. However, non-Newtonian fluids are also used in equipment such as micro reactors, and singular points such as expansions may be provided inside for more efficient mixing. Therefore we investigated the effect of non-Newtonian fluid on the flow characteristics of microchannel with a sudden expansion. As the test liquid, water was prepared as the Newtonian fluid, and two types of polymer, i.e., CMC and CBP aqueous solutions with different concentrations were prepared as the non-Newtonian fluid. In the channel flow in the test microchannel with sudden expansion, the pressure change at the expansion of each test liquid was measured. Then, the expansion loss coefficient was calculated from the experimental pressure change data. As the result, by plotting the expansion loss coefficient against the Reynolds number, a clear difference in the tendency of the expansion loss coefficient was confirmed between the viscoelastic fluid and the non-viscoelastic fluid. This may indicate that the size of the vortex generated in the expanding part changes depending on the degree of viscoelasticity.
current-voltage (MCV) and machine learning. The electrical probe sensor with MCV measures the voltage vector V reflecting the spatial distribution of bubbles in the cross-section of the pipe. The MCV is composed of multiple pairs of electrodes which are processed by Lasso to select the electrode pairs with high dependency for determining the void fraction and flow regime. The machine learning which is plural long short term memory (pLSTM) estimates α based on the identified time-dependent flow regime. In the experiments, V was measured by MCV under the conditions of 15 points of liquid and gas flow rate in gas-liquid upward flows for training, moreover, another four points were used for testing. To provide the in-situ true value of void fraction, the electrical probe sensor is used. As the results, the estimated void fraction is achieved by 5% error and the mean absolute error ε between electrical probe sensor and drift flux model, as the empirical true value, is achieved by 8.2% and 8.7%, respectively.
A novel geometry, which named provisionally as "basement and radial configuration", was proposed and investigated in this paper. The geometry gives a vibration-free and kinematic energy fluctuation-free property to motions of plural parts; i.e. pistons. In this study, a prototype three-cylinder internal combustion engine based on the geometry was designed and manufactured. A trial operation of the prototype engine resulted in achievement of firing operation without any support of electrical motor and so on. In this paper the pressure variations in the three combustion chambers on the firing condition was provided.
The purpose of this study is to investigate the performance of hot water supply system using ground source heat pump that use direct expansion method. An underground heat exchanger adopted an open-type water well. The underground heat exchanger is 30 m length heat collection tubes inserted into a 40 m depth water well. The structure of the underground heat exchanger consisted of three 6.35 mm copper tubes and one 9.52 mm copper tube connected at the bottom. The refrigerant is used 1.0 kg of R32 and the capacity of the hot water tank is 460 L. The performance of this system is compared with the case of using a closed-type underground heat exchanger. The system coefficient of performance (SCOP) obtained in this experiment is 2.55.
This paper summarizes the results of 240 hours of continuous cooling and heating operation of a direct-expansion type ground source heat pump with a three-branch copper-tube heat exchanger. The output power of the heat pump is 6.8 kW for cooling and 8.9 kW for heating. U-shaped underground heat exchangers with a copper pipe length of 30 m on each side were inserted into three boreholes of 30 m depth. During the cooling operation, the amount of release heat to the underground was 8.0 kW, the power consumption was 1.3 kW, and the COP was 6.0. During the heating operation, the amount of extracted heat from the underground was 7.4 kW, the power consumption was 2.2 kW, and the COP was 3.6. The effect of heat extraction and dissipation during the heating and cooling operations on the ground temperature was also investigated.
The energy transition toward carbon neutrality in 2050 is progressing, and attention is being paid to demand-side energy resources to absorb the fluctuations in the output of variable renewable energy. The objective of this research is to construct an easy-to-adopt methodology for virtual power plants that the method can be adopted for arbitrary demand-side energy resources such as district heating and cooling system and water distribution system by using a part of measured process variable values, to respond against demand response signal in any time. The proposed VPP method is composed of a process modelling method for an optimal operational planning problem and a time series forecasting method as well as an optimization algorithm that fulfils the requirements of a given demand response event. This paper represents the three models to identify input-output characteristics of demand-side energy resources. Quadratic polynomials, piecewise linear approximation and discretization by basis coding are taken up as models and their respective characteristics are discussed.
A combined heat and power (CHP), also called “co-generation”, is one of the technologies to effectively reduce energy supply costs and CO2 emissions. The co-generations can be more effective by networking their owners via power grid as in a microgrid. This study develops a power and heat supply system model, and analyzes the effects of co-generations on energy supply costs and CO2 emissions when consumers are networked together. The capacities and operation patterns of power and heat supply technologies without CO2 emission constraints are optimized to minimize the energy supply costs of the entire system. The results show that the total energy supply cost can be reduced by 18% without increasing CO2 emissions when all consumers are networked. Further, we analyze the impact of absence of a portion of consumers to the microgrid on the reduction effect of cost and CO2. Here, we assume that 25%, 50%, and 75% of the detached houses in the target system is absent from the microgrid. Under these conditions, the optimal operation pattern is to run the gas engine co-generations owned by the business and commercial buildings. As a result, the fewer amount of cost and CO2 is reduced by the networking because of the lower efficiencies of power generation and heat utilization.
In the present study, the characteristics of thermal efficiency and turbine power outputs are investigated for power generation system of waste heat energy from ship engine using HFO-1234yf as an environmentally acceptable green refrigerant. Also, these characteristics of HFO-1234yf are compared with that of conventional working fluids such as HFC-245fa, ammonia, and isopentane. The cycle simulations are carried out with both cases of warm water temperature difference and cold water temperature difference varies. In terms of cycle thermal efficiency, the values of HFO-1234yf were smaller than that of other working fluids. The turbine power outputs were comparable to that of HFC-245fa and isopentane in each case. From these results of cycle simulations, HFO-1234yf can be appropriate candidate for HFC-245fa as a working fluid of power generation system of waste heat energy from marine engine.
The scope of this feasibility study is a small output Organic Rankine Cycle (ORC) less than 20kW. In this study, the evaluation method of a turbine efficiency which is the major component of the ORC was examined, moreover, the performance of the ORC was evaluated based on the turbine efficiency using the heat source of Obama hot spring in Unzen City. The outlet temperature of the turbine applied the insulation treatment was almost same the temperature without the treatment. This result indicates the influence of the heat absorption on the turbine of the ambient temperature for the working fluid is small. The adiabatic efficiency in the turbine test itself was about 7.9%. It indicates the working fluid absorbed the mechanical frictional heat generated inside the turbine. In the verification test of Obama hot spring, the thermal efficiency of the prototype ORC was 2.4%. The turbine efficiency at the operating point in the turbine test was 21.2%, whereas the turbine efficiency in the ORC verification test was 19.2%.
Wind and solar power generations are attracting attention as a countermeasure to global warming, but the output fluctuations occur in their large-scale introduction. This paper analyzes how to mitigate the output fluctuations of these variable renewable energies (VREs) in Hokkaido. In the analysis, the output patterns of 20 wind and 10 solar powers were set by the hour, and the total annual cost was calculated to be the minimum using a linear programming. If a large amount of variable renewable energy is introduced, a surplus of electricity is generated even with the introduction of countermeasures for output fluctuation. In this paper, EVs and FCVs were introduced as an effective way to use surplus power. In the case with EVs, the results showed that surplus power can be reduced by about 70% with no restrictions. The total annual cost in the FCV case is relatively higher, but becomes lower than that in the EV case given the constraint of a full charge at 4:00 am with the VRE share higher than 60%. In the range of VREs share below 20% and above 70%, it is cost effective to produce hydrogen in each region, and in the range of 30~60%, it is cost effective to transport hydrogen from northern Hokkaido to central Hokkaido.
In a liberalized market, the penetration of renewable energy is strongly affected by the interactions between power producers and retailers. The multi-agent model has been widely to analyze such interactions in wholesale electricity markets. However, at least in Japan, there is few studies validating if agent simulations can reproduce the power generation mix and contract prices in the real market. Therefore, this study constructed a multi-agent model that expresses the transactions in the wholesale electricity market to investigate the influence of interactions among market players on the power source selection of entire market. Further, we investigated the impact of massive installation of variable power sources in the future. The average power generation mix and contract prices in real market are reproduced to some extent while there are still problems in reproducing the soaring prices in winter. The simulations of massively installing renewables suggest that the market price would be lower than before the installation and the agent raised the price to maximize profits. Further, the contract price seldom changes even if the power source composition changed due to the increase in the bid price of the power generation agent.
In this study, a tidal current energy is focused in ocean-based renewable energies. Collecting a tidal flow is very important because it is generally known that a power available from a stream of water is proportional to the cube of the free stream velocity of the current. In this research, a bi-directional turbine system is investigated for a tidal flow that changes the direction periodically. Numerical investigations are conducted on a bi-directional spiral flow collector which has 1.8 times larger maximum diameter than the turbine diameter. Calculated results showed that the collector with eight guide vanes was the highest angular moment at turbine inlet. The axial velocity at turbine inlet was larger for smaller value of the vane skew angle, whereas the tangential velocity at the turbine inlet was larger for larger value of the vane skew angle. As the results of both the profiles of axial and tangential velocity, the angular moment took the local maximum value at around the angle of 180 deg. in this study.
In an oscillating water column (OWC) based wave energy generator, an air turbine is operated through bi-directional airflow generated by the reciprocating motion of water column in the air chamber. Although this turbine have a unique geometry so that can always rotate same direction in the bi-directional airflow, it is difficult to design the cascade and to improve the efficiency, in comparison with the conventional turbines for unidirectional flow. A sail wing turbine, which is generally used for wind power generation, is adopted as a turbine for wave energy conversion. A wind tunnel test under steady flow and a CFD analysis were conducted to investigate the turbine performance with guide vanes in this steady.
In an oscillating water column (OWC) based wave energy device which is one of the wave energy utilization techniques, the water column in the air chamber is oscillated by wave motion at first, and it generates bi-directional airflow. Then, the bi-directional airflow drives an air turbine, and the turbine converts the pneumatic energy into the mechanical energy. The air turbine requires a special geometry so that it can always rotates in the same direction in the bi-directional airflow. A counter-rotating impulse turbine for wave energy conversion was proposed by M. E. McCormick in 1978. However, the detailed performance of this turbine obtained in experiments has not been clarified to data. In this study, the performance of this turbine is investigated experimentally by using a wind tunnel with a radial fan.
Small-scale hydropower is one of the important alternative energy, and is expected because of its large amount of energy and high capacity factor. However, small hydropower generation over 10kW have problems that there is a limit to the installation place and the environmental load is relatively large. Therefore, we focused on pico hydropower less than 1 kW, which can be applied to agricultural pipelines and has a low environmental load. Since pico hydropower has the problem of low efficiency, we adopt contra-rotating rotors that can be expected to achieve high performance. It is necessary to develop small hydroturbines that can keep high performance over a wide flow rate range. In previous research, performance characteristics for contra-rotating small hydroturbines were investigated by experiments and numerical analysis, and the possibility of higher performance was shown. As the next step, his research is on the verification stage in field experiments. Therefore, we investigated the head and flow rate of the field and obtained the theoretical power. Next, we considered miniaturization and designed small hydroturbines having a 50mm rotor diameter which were suitable for the field. Then, we evaluated their performances and internal flows by numerical analysis.
In order to develop an in-line small hydroturbine that can generate 300W at a small flow rate of 3l/s, we adopted a contra-rotating rotors to achieve both miniaturization and high efficiency of our hydroturbine in this study. A centrifugal rotor that can be applied to small flow rates and high heads is used for a front rotor, and a hybrid rotor that combines a mixed flow rotor and an axial flow rotor is used for the rear rotors with the propose of recovering the same head as the front rotor. However, the performance characteristics of the front rotor for a base model without a volute tends to be low in a small flow rate 3l/s. Therefore, a volute is adopted to improve the performance characteristics of the front rotor. Then we investigated the feasibility of an in-line small hydroturbine capable of generating 300W at a small flow rate of 3l/s by numerical analysis.
A prototype of a 7 m diameter Butterfly Wind Turbine equipped with a new over-speed control system using movable arms was developed. A unit consisting of a movable arm (MA) and an aileron installed below the MA is inclined according to the balance of the centrifugal force, the aerodynamic force, and the gravitational force acting on the unit. The slant angle of a movable arm (and an aileron) was measured to show the behavior. It was clarified that the slant angle amplitude was different between the state where the aerodynamic force was dominant and the state where the centrifugal force was dominant. In the aerodynamic dominant state, the azimuth angle in which the slant angle took the maximum depended on the wind speed level. The measured maximum rotation speed of the wind turbine is currently less than the design maximum rotation speed, and the operation is as expected.
This paper describes the performance of an orthopter-type wind turbine with S-shaped and flat plate blades using wind tunnel experiment and the numerical simulations. The effect of the span length of S-shaped blades on the power and the flow structures around the blades is investigated. The orthopter-type wind turbine is one of the variable-pitch vertical-axis wind turbine of which each blade rotates on their own axis meanwhile all of blades rotate on its main axis. This configuration ensures that the blades rotate around their own axis by 360° during each two-full revolution of the main rotor. The diameter of the wind turbine with two blades D is 510 mm. The chord length c and the span length h are 400 mm. The averaged power coefficient CP with S-shaped blades is smaller than that with flat plates in the wind tunnel experiments. The result of 2.5D-numerical simulation is almost same as the result of 2D-numerical simulation. The result of 3D-numerical simulation is almost same as the result of experiments. In case of 2.5D-numerical simulation, a roller vortex that is the cause of the increment of the torque of the wind turbine is made in the concave side of S-shaped blade. However, a roller vortex is not made in case of 3D-numerical simulation.
In this study, wind tunnel experiments were conducted to clarify the wake behavior of vertical axis wind turbines and the loads generated on wind turbines operating in the wake. To clarify the wake behavior, the downstream velocity field was measured for cases with one and two upstream wind turbines. To clarify the loads generated on the turbine operating in the wake, the rotational torque and streamwise force generated on the test turbine were measured in the downstream area of the turbine. As a result of the experiment, the wake of a vertical axis wind turbine has an asymmetric velocity distribution with respect to the rotor center, and that the load fluctuations occurring on a wind turbine operating at the boundary between the velocity deficit region and the freestream region are larger than those operating in the freestream region.
To reduce both the platform motion and dynamic loads of floating offshore wind turbine-generator systems, feedforward control for high wind speed regions is developed by combining with the wind speed previewed by a nacelle-mounted lidar. First, the wind speed preview using a nacelle-mounted lidar was simulated by considering the floating platform velocity and the temporal difference of laser casting. Feedforward control, in which the blade pitch is manipulated according to the previewed wind speed so as to maintain the rated generator speed, is combined with gain-scheduling feedback control of the generator speed. This feedforward control is characterized by employing the first-order lag filter with the delay compensator for the previewed wind speed. The effectiveness of the developed feedforward-feedback controller is analyzed through an aero-elastic-hydro-control coupled nonlinear dynamic simulation of a 5-MW floating offshore wind turbine-generator system under turbulent wind fields and irregular wave height variations.
We discussed the effect of the stall control on a horizontal axis wind turbine having a blade with a flap at the trailing edge based on blade element momentum theory. The flap blade proposed in this study does not have any mechanical moving parts, moreover, it has feature ensuring long-term reliability. The flap blade has an advantage for increasing the lift coefficient than the symmetrical blade until the stall point. Thus, the flap blade can increase the initial torque for the wind turbine. The flap blade increased the drag coefficient than that of the symmetric blade in the stall condition, that is, in the large attack angle. The increase of the drag contributed for suppressing the torque of the wind turbine. Therefore, to increase the drag using the flap blade has advantage for the stall control in the strong wind condition.