As the adoption of renewable energy continues to expand, securing supply-demand balancing capacity in the power system has become a critical challenge. Solar power generation is highly dependent on weather conditions, leading to significant short-term fluctuations that can affect the stability of the power system. This study aims to assess short-term fluctuations in solar power generation to ensure sufficient adjustment capacity within the power system.

Specifically, we cluster the solar power generation data, estimated from weather data at a 5-minute granularity, based on the clearness index using the x-means method. Subsequently, we use neural networks within each cluster to predict the minimum power generation over a 30-minute period at a 1-minute granularity.

This approach provides insights into the characteristics of short-term fluctuations in solar power generation and aims to contribute to ensuring flexibility in the supply-demand adjustment market. It is expected that this method will contribute to improving the overall stability of the power system.

We have developed a model to foresee a large error in irradiance forecast by analyzing the variation of weather parameter values forecasted with Weather Research and Forecasting (WRF) Ver. 3, in which the different combinations of physical schemes are used. This paper evaluates the improvement of foreseeing accuracy of large forecast error by using WRF Ver. 4. In addition, this paper discusses the effect of supplementary using Convective Available Potential Energy (CAPE) for the performance improvement.

We have been developing a prediction system for solar power generation by ground observation. Until now, we have predicted solar irradiation assuming single-layer cloud. However, multilayer clouds are often observed. Therefore, we study the concept of solar irradiation forecasting considering changes in solar irradiation caused by 2-layer clouds.

In order to utilize solar power generation, which is increasingly being introduced in large quantities, as a main power source in the future, it is important to suppress the uncertainty of power generation amount and the loss of power generation opportunities. It is necessary to predict the amount of power generated and to provide early warning of contamination and deterioration, which in some cases was difficult to judge using conventional PR values. We present the results of evaluating the effectiveness of quantity prediction and diagnostic methods using actual data.

This study explores the impact of load profile variability on optimal PV and BESS capacities in a diesel generator generator-based microgrid using HOMER Pro software simulations. By analyzing the variability of Day-to-Day and Time-Step effects, the research assesses how these factors influence energy modeling accuracy, and microgrid stability. Simulated profiles are compared to real Japanese residential load data to evaluate precision along with the load data from a Tanzanian village for the potential estimation of PV and BESS capacities using Peak Power Ratio metric.

Using a small small-scale experimental microgrid constructed on the university campus, consisting of a solar power generation system, a battery energy storage system, and a diesel generator (biodiesel), a simulated load was operated simulating a rural village in Tanzania, and the power losses that occurred were experimentally understood. It was found that the accuracy of the simulation could be improved by setting the converter efficiency to a value 5 % lower than the rated value and adding about 15% to the total load input to simulate wiring losses. As a result, the net present cost increased by about 15 %.

In recent years, the rapid expansion of renewable energy, as typified by solar cells, has been remarkable. At the same time, the spread of energy in local areas is expected. However, as peak power generation times are concentrated, electric power companies continue to be forced to curtail output, and the output curtailment is said to amount to the equivalent of five nuclear power plants. In order to smooth out the fluctuations in renewable energy after each home consumes it as a load, a large-capacity storage battery is required. One way to avoid this is to lay low-voltage lines between neighboring homes and exchange power with each other. In this study, we conducted a simulation using two homes equipped with solar power generation systems and storage batteries as a prototype.

This study undertakes the development of an optimal PV-diesel hybrid power system tailored to the specific energy landscape of Vimtim Mubi, Nigeria, utilizing real-world wind speed, solar radiation, and diesel cost data. Employing HOMER simulation, the research meticulously assesses the technical and financial viability of this hybrid configuration. Additionally, a rigorous performance comparison is conducted between the PV-diesel system and the conventional grid-connected alternative, offering crucial insights into the potential advantages and economic feasibility of adopting hybrid renewable energy solutions in regions grappling with energy access and reliability challenges, with implications for sustainable electrification efforts in similar communities worldwide.

A regional micro-grid is usually built to for business continued plan to supply electric power during a long blackout due to a big disaster. So the economic efficiency of regional micro-grid is not usually established. The implementation of a regional micro-grid has not been progressing. Kandenko constructed a regional micro-grid in Isumi City in 2023. We carried out the awareness activities. For example the introduction screens of the regional micro-grid was installed to Isumi City Office. In this paper we show the several usual activities and the countermeasure to the short circuit which is one of the technical issues.

In Japan, the number of local governments declaring themselves zero-carbon cities has reached more than 1,100, but the development of roadmaps for regional decarbonization is still in its infancy. Among them, 82 proposals have been selected as Decarbonization Leading Aeas and are starting to move toward achieving 100% renewable energy in their regions. Therefore, we will analyze examples in the Decarbonization Leading Areas and the status of solar PV penetration in the region and examine issues and measures to promote the deployment of solar PV in the region.

Photovoltaic (PV) systems are expected to reduce fossil fuel use and carbon dioxide emissions, and provide distributed energy systems and self-sufficiency. However, installing many PV systems has resulted in the amount of energy generated exceeding the amount of energy demanded, which is being dumped as it is. This has led to the development of V2H (Vehicle to Home) technologies that combine Feed-in Tariff (FIT) systems and PV systems with storage battery systems. PV systems are subject to weather conditions and energy supply risks, and many researchers are actively researching the optimal use of PV systems. This study examines efficient ways to use surplus energy from PV systems. In this study, we built a machine learning model to calculate urban surplus energy in Daimyo, Fukuoka City, as a target area, developed a Geographic Information System (GIS) based urban surplus energy visualization tool, and examined efficient ways to use surplus energy.

This study aims to develop an off-grid facility in Kuroshio-cho, Kochi Prefecture, which will function as a clinic and health center during normal situations and as a medical aid station and disaster countermeasure branch office during emergencies. As a result, it was found that the indoor air temperature and relative humidity during examination hours would be approximately 23 - 25°C and 20 - 40%, respectively. In particular, the relativehumidity tends to be lower than that of a typical living room and needs to be improved, especially in the context of off-grid conversion.

This study aims to develop an off-grid facility in Kuroshio-cho, Kochi Prefecture, which will function as a clinic and health center during normal situations and as a medical aid station and disaster countermeasure branch office during emergencies. As a result, it was found that the indoor air temperature and relative humidity during examination hours would be approximately 25 - 26°C and 60 - 70%, respectively. In particular, the relative humidity tends to be higher than that of a typical living room and needs to be improved. Also, Electricity consumption was measured for each use, and the amount of electricity required in each room under normal and emergency conditions was identified.

We evaluated the heating, cooling, and thermal storage capacities of “Momo no Yado” in Kawasaki Town, Miyagi Prefecture, Japan, which aims to be a ZEH. The renewable energy equipment used in this accommodation is solar panels, a solar water heater, a wood-fired boiler, and groundwater. For heating, each room maintained more than 20°C and sufficient heating capacity was confirmed. The cooling capacity was sufficient to provide an adequate cooling experience. The thermal storage performance was calculated to be 4.5 MJ/K by calculation and 4.3 MJ/K by theory, which is close to the value obtained.

This paper clarifies the relationship between passive design and energy independence by examining passive design (insulation performance, openings, solar gain and solar shading) at the planning stage and evaluating energy independence through solar power generation.

The current status of energy conservation and energy generation of a ZEB certified building and the amount of electricity generated by photovoltaic systems due to the influence of surrounding buildings in urban areas were studied. The subject building was 108% ZEB in total for energy conservation and energy generation at the design stage, but was nearly ZEB at 86.1% to 95.7% for the three years after construction was completed.

This study demonstrate the effectiveness of the hiroen as a thermal buffer space of a wooden building renovated from traditional timber house in satoyama. The effectiveness of hiroen as a thermal buffer space was confirmed by the thermal environment during cooling and heating. In addition, the temperature of under floor air supplied to hiroen is affected the concrete foundation thermal storage.

In this paper, in cooperation with the Support Center for the Elderly, lifestyle support program for preventing heat stroke was implemented and its educational effect was verified. Followings are findings. 1) The majority of residents had a significant decrease in MRT and WBGT due to living and housing support. 2) Lifestyle of the elderly including air conditioner usage changed into three groups (patterns) through the experience-based lifestyle support program.

When evaluating the radiation environment in outdoor or indoor spaces, view factor and solid angle of surrounding objects are important evaluation indices. In this study, we aim to develop a simple method for evaluating the outdoor and indoor radiation environment by projecting surrounding objects onto a unit sphere.

This paper describes the results of entropy analysis in human body and built thermal environment. Followings are found. In case of heat stroke onset, accumulated entropy generation of human core is 69% in comparison with in case of air conditioning. This shows another significance being different from core temperature 38℃ and more in a definition of heatstroke. Entropy disposal is essential to ensure adequate entropy generation for all the working subsystems. On the other hand, if subsystems are regarded as a system forming multiple-layer structure, excessive entropy disposal from even one subsystem causes hindrances the whole system’s sustainable activity.

Under a feed-in tariff (FIT) scheme this study assesses the impact of photovoltaic (PV) generation on wholesale electricity market and consumer economic benefits. To compare counterfactual electricity prices without PV and real prices with PV, an empirical analysis is performed with data on electricity prices, electricity demand and PV generation in Japan utilizing a structural model of electricity prices. The results indicate the positive consumer economic benefits owing to introduction of PV in recent years. These benefits mainly arise from cost reduction due to increasing PV generation under high electricity demand typically in summer.

In order to curb global warming in Japan, efforts to reduce CO₂ emissions, known as “local decarbonization,” are being promoted in local communities. However, there is a problem that renewable electricity is separated into electricity value and non-fossil value when it is connected to the power grid. So, non-fossil value, which is important to curb global warming, is drained out of renewable electricity generation areas. This problem is an adverse effect of the Feed-In Tariff/Premium (FIT/FIP) system, and what should be done to avoid resource nationalism will be discussed.

Local governments have the potential to significantly reduce emissions by improving energy efficiency and using renewable energy. Businesses, households, and public facilities within each local government spend huge amounts on utility bills, much of which is wasted outside the region. There are economic benefits from measures to reduce utility bills, contracts with local companies to implement the measures, and revenue from renewable energy power generation by local entities. This report estimates the actual state of energy-related CO₂ emissions in municipalities, estimates measures to reduce emissions up to 2050, and estimates the reduction in utility bills and economic effects of the measures.

Thermochemical energy storage (TCES) utilizes the heat from chemical reactions, and is one of the most promising TES technologies, with the potential for higher energy efficiency than other TES methods. The perovskite oxide systems are known to involve a variation of non-stoichiometry (δ) beyond wide range of working temperature during the charging/discharging step. In this study, the redox reactivity, TCES capacity, and working temperature of calcium-manganese perovskite oxide under various oxygen partial pressures were investigated for use in next-generation CSP. Furthermore, thermochemical storage units were prepared using the powder sample. The thermal stability of thermochemical storage unit was tested in electric furnace.

Several solar thermochemical reactors have been developed to split water by a two-step water-splitting cycle with redox metal oxide utilizing concentrated solar thermal energy in sunbelt region. A windowed solar reactor using a reactive foam device made of redox metal oxide is one of the promising reactor. In this study, small foam devices of metal-doped ceria (CeO₂) were fabricated and tested on their reaction performances in a lab-scale windowed reactor using a 3kW_th sun simulator. The foams of Fe or Ni-doped ceria produced more than twice as much as hydrogen in comparison to benchmark CeO₂ foam.

The purpose of this study is to generate hydrogen using solar energy and the metal oxidation reaction of zinc. A Fresnel lens is used to concentrate sunlight to heat and evaporate Zn, which is then reacted with superheated steam to generate and collect ZnO and H2. The generated ZnO is then heated by concentrating sunlight again to regenerate Zn. Normally, a Fresnel lens is used as a heat collector to use sunlight as energy, but this time an electric furnace was used instead of sunlight to perform a simplified experiment. The maximum amount of hydrogen obtained was 756 mL when the experimental conditions were H2O: 18.11 g, Zn: 5.98 g. From this, it can be expected that the amount of hydrogen obtained will increase when the amount of superheated steam reacted with the amount of zinc to be reacted is about 3 to 4 times the mass. If there is a sufficient amount of superheated steam relative to the amount of zinc, the amount of hydrogen obtained will increase, but if there is an insufficient amount of superheated steam, the amount of hydrogen obtained will decrease.

We research the reaction of zinc oxide with a view to the sustainable generation of hydrogen energy. We have made it to reduce zinc oxide by extracting it heat required for the reduction reaction from sunlight. We used an electric furnace to investigate the relationship between zinc oxide and heat. Because it was difficult to adjust the heating temperature of zinc oxide with sunlight. As a result, we found that the reduction amount reached 1.00g. i.e. I think the reduction rate became 100%. But the reduction amount was 0.01g with sunlight. This is the task. I have been implementing new equipment to increase the reduction amount.

This study researched the ratio of PV/T solar panel and solar heat collector area and tank capacity that can improve cooling efficiency in a PV/T solar panel system with an ejector refrigeration cycle. Simulation results show that a larger ratio of solar heat collectors can increase the amount of heat collection and improve cooling efficiency. It was also shown that by reducing the capacity of the heating tank, and using the cooling tank, which is used only in summer, for heating in winter, the tank capacity can be reduced while improving the efficiency of cooling, heating and hot water supply.

With the recent issue of energy conservation in buildings, the utilization of solar thermal energy is attracting attention. This study examines the integration of a thermal storage system with the building frame and its use as an under-floor thermal storage and radiant floor heating system. The annual indoor environment of the house with this system and its energy-saving effects are reported in this paper.

There is concern that developing countries and other countries will face a global shortage of drinking water in the future, and it is essential to secure this water. In order to prevent the uneven distribution of water resources, water production technologies that consume less energy are important. In this context, solar distillation systems using renewable energy are attracting attention. In this study, in order to achieve efficient production using this additional technology, a numerical analysis considering the promotion of condensation by ion wind on the outer surface of the pipe revealed that the distance between the underside of the ceiling plate and the top of the condensing pipe affects the amount of condensation.

An atmospheric water generation system composed of a Peltier unit, a heat-collecting silica gel chamber, and a simulated thermal storage tank was created. Through experiments and theoretical investigations of each component, modeling was performed. In the assessment of the model's validity, a tendency was observed where the estimated temperatures at each location were close to the measured values. The estimation of the condensed water volume was improved to about 25% relative error, and the simulated therma l storage tank, which had the highest approximation accuracy, achieved an outlet temperature estimation with a precision of -1% to 2%.

The economic feasibility of very small-scale wood biomass boilers with a thermal output of 50 kW or less, which are installed in a small store and an office, was evaluated. The wood fuel system was found to be economical under default conditions. It was also found that in order to ensure its economic efficiency, it would be necessary to reduce construction costs, ensure stable procurement of higher-quality wood chips with lower price, and to receive public funds.

The problems of biomass boilers include (1) combustion difficulties and low heat generation due to the high water content of the wood chips used as fuel, (2) deterioration in thermal efficiency due to exhaust heat during operation. In this study, a dryer resembling a solar chimney is installed outside the combustion chamber of a biomass boiler to generate natural convection using the heat energy emitted from the biomass boiler, with the aim of reducing the moisture content of the wood chips. This enabled the wood chips to be dried in a short time.

This study analyzed the relationship between outdoor air conditions and integrated heat rate in order to optimize the energy efficiency of biomass power generation and solar water heating systems in cold regions. The study examined how outdoor air conditions, such as ambient temperature and solar radiation, affect the integrated heat rate.

This research investigates a biomass gasification system for power generation in rural communities of developing countries, using a Uflow biomass gasifier (20 kW) developed at Ashikaga University. Unlike traditional systems that utilize reciprocating or modified diesel engines, which face tar-related issues, this study employs a rotary engine coupled to a generator, avoiding tar-related problems. Woody biomass was used as feedstock, and experiments evaluated system performance at different engine speeds and operational modes. Results showed up to 6 hours of continuous power generation, with fuel consumption rates varying by engine speed, and cold gas efficiency reaching 79.8% at 3200 rpm.

Oil-producing microalgae are attracting attention as a biofuel other than grain. One of the challenges in producing biomass fuels from microalgae is the low Energy Profit Ratio (EPR), the ratio of energy obtained to energy input in the cultivation process. In this study, we focus on the light transmittance and design of organic photovoltaic cells (OPVs) and aim to improve the EPR by using blue OPVs that allow the light necessary for microalgae photosynthesis to both culture and generate electricity.

In order to reduce the primary energy consumption of newly constructed buildings, insulation, energy conservation, and energy generation are being promoted. Photovoltaic power generation is widely used for energy generation, however the installation capacity is limited in urban apartment buildings due to the small roof area. In this study, the biogas power generation using disposer wastewater was focused on, because the facility can be used in combination with the photovoltaic power generation. The pretreatment and operating condition to realize the miniaturization of gasification equipment were investigated.

Aiming at understanding more efficient and cleaner combustion of woody biomass, and providing the combustor that emit less carbonous harmful substance such as carbon monoxide and soot, the author is investigating methods to burn a candle, that is composed of more simple constituent resin, under the earth’s gravity at ordinary temperature and atmosphere pressure. In the course of this study, the author found the method to burn a candle with momentary spherical blue flame and with long lasting half spherical blue flame and the existence of diatomic carbon and methylidyne radicals in the blue flame of a candle that lead to a proposal of new polycyclic aromatic hydrocarbon and soot formation mechanism of radical polymerizations and hydrocarbon combustion reaction. Those radical reaction gave an insight into a proposal of a cellulose combustion reaction presented in this report that is suggestive to improve woody biomass combustion.

Smart agriculture using greenhouses is expected to be a solution to food shortages. However, smart agriculture uses machinery, which requires electricity. As a source of electric power, Organic Photovoltaics (OPV) are installed in greenhouses, and solar matching, in which crops are grown under the OPV, is expected to be utilized. However, there is concern that the transmittance of OPV may affect crop cultivation. In this study, we aim to realize solar matching by using wavelength conversion sheets to amplify light in the wavelength band that is effective for crops.

In recent years, the introduction of photovoltaic (PV) power generation, storage batteries, and electric vehicles (EV) has been increasing, and smart communities (SC) that use these as a local power source have attracted attention. In addition, SCs can enter the Balancing market (BM) by utilizing the supply-demand adjustment capability of SC components, and they can be considered for operation to recover equipment costs. Therefore, this study uses mixed integer programming to optimize the power operation at the time of market participation and quantitatively demonstrates the economics of SCs and their potential for adjusting electricity supply and demand.

Proper assumption of severe load conditions is necessary in transmission line outage work planning. In recent years, renewable energy sources such as PV have been introduced into the grid in large quantities, and grid congestion caused by the large introduction of the power sources and uncertainty has become an issue, making it difficult to assume loads that satisfy the severe conditions. In this paper, a power system model with a large amount of PV is created, and optimal tidal flow calculations are performed using the severe condition as the objective function to analyze the adequate severe condition, which will contribute to future outage work planning.

One of the issues that arise when a large number of PV systems are installed is the phenomenon of voltage fluctuations in the distribution system, and it is known that reverse power flow from PV systems can cause voltage rises and drops in the distribution system. The authors have also proposed a method using the area on a vector diagram as an analysis method for the effective power.

In this paper, by focusing on a different area on the vector diagram, it is clarified that the value of the area can be expressed as the active and reactive power as it is, and the maximum value of each active and reactive power in this case is obtained.

This study examines multi-objective operational optimization using tidal flow optimal calculation and the epsilon constraint method for a power system that assumes the mass introduction of PV. Specifically, Pareto solutions are calculated for fuel costs, CO₂ emissions, and transmission losses, and correlations among several objective functions are design variables analyzed to reveal the characteristics of the target optimization problem. Based on the analysis results, we will also examine the extraction of information that will contribute to the optimization of grid operations, where further PV installation is expected by self-organizing maps.

To reproduce the LIB battery performance, data from various literatures was collected and fitted to the main deterioration factor characteristic graphs. As a result, it was confirmed that the deterioration factor FEC has a power function, the temperature has a composite function of the Arrhenius and inverse Arrhenius equations, and the C rate has a cubic function. By incorporating these functions, a deterioration model with a maximum RMSPE of 4.97 % was created. In addition, the model described in the book and the created model were evaluated in terms of deterioration transition and in a 15-year charge/discharge simulation assuming an ordinary home.

In photovoltaic power generation systems, there are failures such as cell failure and increase in series resistance of strings, and fault detection is very important. However, with conventional technology, it is difficult to detect because it depends on the intensity of solar radiation and the weather. The purpose of this study is to develop a technique to detect the type and extent of failure in a solar cell string by measuring the impedance of the string. In this paper, we report the results of experiments on the impedance of photovoltaic modules.