This study investigates the installation potential of small-scale ground-mounted photovoltaic power generation system (PV) based on land use data. The potential capacity is calculated for the installation in the forest area close to residential area mainly in countryside, in which the further installation of PV together with a battery energy storage system (BESS) contributes to improve electricity supply resiliency. The results show that the ground-mounted PV installation can be available on 60e GW scales although further impact assessments on various factors such as landscape are needed.

In this study, we evaluated the wide-area photovoltaic potential of parking areas in Tokyo's 23 wards using parking data from Open Street Map (OSM). The impact of shading, a major challenge in urban PV system deployment, was calculated as a shading loss correction factor using Digital Elevation Model (DEM) and Digital Surface Model (DSM) data in geographic information system (GIS). For weather factors that cannot be considered in GIS analysis, we combined a conversion model from solar radiation to electricity generation based on Japan Meteorological Agency data with correction factors to evaluate generation potential considering both shading and weather conditions.

Recent studies have demonstrated that the accuracy of numerical weather prediction (NWP) models in solar radiation forecasting can be enhanced by incorporating machine learning (ML) techniques. However, ML models are inherently dependent on historical data, which raises concerns about their ability to adapt to evolving atmospheric conditions over time. In this study, we investigate the temporal robustness and generalizability of ML-based solar radiation forecasting models by utilizing long-term reanalysis datasets. Our objective is to evaluate how well these models maintain performance across different time periods and to identify potential limitations in their adaptability to changing climate patterns.

We have been developing a solar power generation forecasting system based on ground observations. This system calculates power generation using an ANN that incorporates observed and predicted data as input. Previous ANN models used one-minute interval data and humidity as inputs. However, in reality, measurement intervals are longer, and humidity is not measured. Therefore, this study investigated whether an ANN model adapted to these conditions is effective.

In this study, the electricity consumption of a convenience store (CVS) located in Sapporo City was investigated and analyzed Based on this, a simplified 3D model of the target store was created, and the incident of solar radiation on the roof and exterior walls was calculated through simulations. Using the obtained solar radiation data, the potential photovoltaic (PV) power generation and the energy self-sufficiency ratio of the store were estimated. Furthermore, simulations were conducted for cases with reduced window areas to examine the effects of window reduction on indoor visibility and power generation performance.

This study examined the power generation of a photovoltaic system installed in an urban ZEB-certified building in Osaka, considering the impact of shadows cast by surrounding buildings. The results showed that, under current conditions where surrounding buildings are present, the generated power was approximately 82% lower compared to the scenario without surrounding structures.

With the aim of improving the supply capacity of an existing island-type microgrid, verification was conducted using ETAP simulation to consider an energy-efficient and effective expansion method. The simulation targeted rural areas of Tanzania and reproduced the expansion of the microgrid. It was confirmed that by installing additional equipment such as PV and BESS in high-load areas and areas with high residential loads, wiring losses were reduced by 2.3 kW and 2.2 kW, respectively, compared to installation in areas near the generators, and that distributed installation stabilized the bus voltage.

This study estimates output curtailment at 28 solar power plants across Japan using local weather data and actual generation records. A monthly correction method is proposed to improve the accuracy of generation estimates without curtailment. Over a two-year period, significant regional differences in curtailment rates were observed, with Kyushu showing the highest values. The analysis reveals the impact of curtailment rules and proxy control on generation losses. Furthermore, discrepancies of up to 34% between area-wide and site-specific curtailment rates were identified.

Consider PBL education using Generative AI which is rapidly progressed. in learning and inference with LLM. The author is aiming at studying feasibility of active learning inputted multimodal information using NotebookLM. It is target that for solar car project and energy management, knowledge databasing tacit knowledge and experiences of educator in terms of effective dialogue learning.

We are developing a simulation model for agrophotovoltaics solar power generation systems designed for rice cultivation. To verify the accuracy of this model, we conducted comparisons using data from previous shading experiments conducted at multiple locations. In experimental reports using shade cloth and black fiberglass nets, yield changes relative to light transmittance or shading rate have been reported. We simulated these shade materials as semi-transparent solar cells and compared the calculated yield ratios with observed values. Verification was performed using data from three locations: Chikusei City in Ibaraki Prefecture (2018-2023), Nagaoka City in Niigata Prefecture (2015-2017), and Shangao County in Jiangxi Province, China (2021). Although some outlier years were identified due to abnormal weather conditions or fertilization methods, overall good agreement was confirmed between simulation results and experimental observations.

This study presents a new simulation algorithm for agrophotovoltaics that places crop growth models at its core. Unlike conventional approaches extending photovoltaic power generation simulations, this method modifies meteorological data based on panel installation to assess crop yields across farmland. We developed rice growth model plugins by providing source code and agricultural literature to generative AI, achieving several times faster development than conventional methods. The simulation creates 2D maps of both solar radiation and crop yields, enabling proper evaluation of panel installation effects on agricultural production.

The new Basic Plan for Food, Agriculture and Rural Areas, approved by the Cabinet in fiscal year 2025, states that agrivoltaics can no longer expect the same level of profitability as in the past due to the decline in the Feed-in Tariff (FIT) purchase price. To promote the future adoption of photovoltaics on agricultural land, this study analyzes the conditions under which sufficient profit can be secured to contribute to agricultural production, with a particular focus on small-scale agrivoltaic systems installed in paddy fields, which account for the majority of farmland in Japan.

Knowledge regarding the power generation efficiency and crop yield of agrivoltaics is extremely limited. When solar panels with a 33% shading rate were installed in a paddy field in 2016, the yield reduction rate was 6.3%. In 2017, cultivation was conducted with multiple shading rates, and a yield of over 80% was achieved with a 40% shading rate. In the 2018 experiment, contrary to the hypothesis, no correlation was found between solar Irradiance and crop yield. Since rice growth is a function of the cumulative temperature, temperature distribution measurements under the mounting frame were taken in 2019, but the cumulative temperature was same at all locations. However, there were differences in yield among the blocks. An analysis of the temperature records confirmed that high-temperature damage was occurring under the frame, but it would be avoided by controlling the angles of panels.

Over 200 municipalities have achieved regional energy self-sufficiency exceeding 100%, and efforts to reach 100% renewable energy are beginning to advance toward realizing regional decarbonization. Meanwhile, in Europe, energy communities are included in the Renewable Energy Directive, and institutionalization is progressing. Domestically, initiatives like solar sharing are advancing under local leadership, with 88 proposals selected as Decarbonization Pioneer Regions. This paper analyzes the current status and challenges of regional decarbonization and achieving 100% renewable energy, and examines strategies for their realization.

A method for estimating spectral global solar irradiance on tilted surface under all weather conditions was examined by combining estimation equations for the spectral global horizontal irradiance, spectral diffuse horizontal irradiance, and broadband Perez model which calculate the broadband diffuse solar irradiance on tilted surfaces. The estimated spectral global solar irradiance on tilted surface was compared with measured values and evaluated. It was found that the broadband Perez model overestimates the spectral global solar irradiance between 0.3 and 0.4 µm on tilted surface by increasing circumsolar irradiance components in intermediate sky and clear sky conditions.

A method for estimating spectral global solar irradiance on tilted surface under all weather conditions was examined by combining estimation equations for the spectral global horizontal irradiance, spectral diffuse horizontal irradiance, and spectral Perez model which calculate the spectral diffuse irradiance on tilted surfaces. In the spectral Perez model, the atmospheric brightness and clearness parameters included in the broadband Perez model are determined for each wavelength. The reliability of the estimated spectral global tilted irradiance was evaluated.

In this report, the estimation method of spectral diffuse fraction (SDF) based on clearness index is presented in order to estimate spectral diffuse horizontal solar irradiance from spectral global horizontal solar irradiance. Estimation accuracy of spectral diffuse solar irradiance calculated from spectral global horizontal solar irradiance was examined using the Erbs model based on broadband diffuse fraction and the new SDF model. It was found that the estimation errors based on the SDF model with correction factors for air mass and precipitable water were smaller than those based on the Erbs model, particularly in the ultraviolet to visible wavelength range.

Like last year, many areas experienced record high temperatures this year. This marks the beginning of the second phase of global warming, when the oceans absorb less carbon dioxide and release it into the atmosphere. Due to rising sea levels, the Japanese archipelago has become easy to shake like a ship, and large earthquakes are increasing. As a result of analyzing the occurrence pattern of recent large earthquakes, it was found that distant earthquakes are induced alternately by the seesaw phenomenon of the Japanese plate with Tokyo as the center of gravity fulcrum, in addition to the effects of snow load and atmospheric pressure fluctuation.

In recent years, with growing awareness of energy conservation, the efficient operation of water thermal storage tanks has attracted increasing attention. In stratified thermal storage tanks, there is concern that the discharge flow from the distributor may disturb the thermal stratification, resulting in reduced storage efficiency. This study aims to propose an improved distributor design to maintain thermal stratification and enhance heat exchange efficiency. This paper reports the results of flow measurements to characterize the discharge airflow from the distributor.

This invention was devised with the aim of more effectively using the formula for calculating the rate of heat transfer coefficient (Q = hA (T2 - T1)), compared to the conventional method of transferring temperature to water that has mainly been heat exchange.
Specifically, the water tank acts as a heating device, and a system is created that transfers heat from all directions.
Furthermore, by incorporating solar energy, energy savings can be achieved.

A 6-year operational analysis was conducted on the solar water heating system installed at the convention center. The results showed an average solar fraction of approximately 10%. The recorded solar heat utilization amount was less than half of the estimated collector heat collection, indicating significant heat loss in the collector piping. Furthermore, the storage tank is operating at half its design capacity, which is also considered to be suppressing the thermal collection.

An atmospheric water harvesting device consisting of solar collector, silica gel bed, sensible heat exchanger, and Peltier device is under development. This report outlines the system design and basic experiments on three types of silica gel (A, B, C). Samples were exposed to 23-25℃ and 50-70% RH for 18 hours, then heated at 55-70℃ for 6 hours, repeated over 1 week. Type A showed the highest desorption capacity and was selected for use. Based on heat exchanger performance and ambient air conditions, 30 kg of Type A silica gel was adopted.

To accurately predict the heat collection performance of PV/T solar panels, it is essential to determine the overall heat loss coefficient of the collector from measured data. However, this requires calculating the temperatures of the PV module and the cover glass. In this study, these temperatures were obtained through an iterative convergence of the collector’s heat balance equations, and the overall heat loss coefficient was then determined. As a result, the proposed method achieved more accurate predictions of the heat collection performance than conventional approaches, and its applicability to other panels was also confirmed.

In this study, simulation calculations are conducted on a system that combines low-temperature regenerative desiccant air conditioners with PV/T solar panels to evaluate their synergistic effects. The system’s energy-saving performance is verified and quantitatively evaluated by comparing it with a conventional desiccant air conditioning system.

This report presents the part of research and development on high-efficiency collectors. Using the new ultra-high-efficiency selective absorbing films, we are conducting research and development on the shape of collector plates that can gather even more solar heat, as well as on structures that prevent collected heat loss.

This result was utilized in the prototype production of a high-efficiency heat collector.

To control the invasive alien species Alternanthera philoxerodies using non-chemical electrical discharge weeding, discharge treatments were applied to experimental Eruca vesicaria or wild Alternanthera philoxerodies, varying the applied voltage or discharge time as parameters. The effects on plant mortality were statistically analyzed using ANOVA on visual scoring. The results showed that control efficacy increased with higher values for both parameters, with the effect of applied voltage being particularly pronounced. This was also confirmed by observations of the plant cells of Alternanthera philoxerodies. Furthermore, the stem's resistance value decreased with the extent of damage after discharge, and the values showed significant differences between the two plants depending on their structure.

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 rather simple constituent resin, and cellulose under the earth’s gravity at ordinary temperature and atmosphere pressure. In the course of this study, the author found a 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 in candle combustion and a cellulose combustion mechanism forming levoglucosan by radical transferring chain reaction and a combustion reaction of the latter releasing CO. In this report, soot formation mechanism from CO in cellulose combustion is presented.

In order to supply methane at low cost using sweet potato as raw material, mixed fermentation condition of cow dung and sweet potato was examined. As a result, the methane production rate increased three-fold compared to cow manure alone, reaching 1.4 L d^-1l-sol^-1. This exceeds the 1.2 L d^-1l-sol^-1 achieved by co-fermenting sewage sludge with sweet potato, demonstrating that the size and cost of the cow manure anaerobic digester can be significantly reduced.

In order to reduce CO₂ emission from industrial segment, biomethanol has been investigated as one of the alternative fuel and energy carrier. We report herein the biomethanol production from biogas via photochemical reaction using chloride dioxide under room temperature and atmospheric conditions. The scale-up tests were examined using 5 L and 100 L-scale photochemical mini-plant. The conversion ratios from methane to methanol in both cases were reached above 80%.

This study investigates the indoor environment and energy balance of the HEAT20 G3 compliant house in Kiryu City, Gunma Prefecture. A two-year field survey was conducted to evaluate indoor temperature and humidity, as well as energy balance. This paper reports the measurement results of indoor temperature, humidity and energy balance, together with seasonal variations in heating and cooling system operation, thermal comfort, and indoor air quality.

Thermal environment control in large spaces such as gymnasiums has gained importance due to climate change and urbanization. This study targets a gymnasium in Kawasaki, Japan, where floor-supply air conditioning is planned to improve comfort. A CFD model reproduced the current thermal environment, and simulations evaluated the effects of enhanced insulation and floor-supply air distribution. Results showed that, compared to wall-supply, floor-supply achieved more uniform temperatures, reduced vertical gradients, and maintained comfortable air velocities. The study confirms the effectiveness of floor-supply systems in improving comfort and energy performance in gymnasiums.

During summer cooling operation, the opening and closing of automatic doors allows hot, humid outdoor air to infiltrate while letting cool indoor air escape. This deteriorates the thermal environment of the entrance area and increases the air conditioning loading rate, leading to energy waste. As a countermeasure, we propose adjusting the opening and closing time of the automatic door. This study uses unsteady CFD to predict and evaluate the amount of outdoor air infiltration and the temperature/airflow distribution in the entrance area under different opening and closing times. The aim is to quantify the impact on energy consumption and provide a basis for optimizing opening and closing times and improving comfort.

This paper investigates methods to smooth photovoltaic generation (PV) power fluctuations using a reversible cell integrating a water electrolyzer and fuel cell. Two power smoothing methods are compared: an exponential smoothing method and a hydrogen-producing smoothing method. The study considers different types of reversible cells—PEM, alkaline, and solid oxide—and simulates their response delays as first-order lag systems. Results show that the hydrogen-producing smoothing method achieves a higher smoothing effect (80.0%), outperforming the exponential smoothing method by 22.4 points. When the response delay of the reversible cell is small (τ < 300), the hydrogen-producing smoothing method significantly reduces grid power fluctuations. However, its advantage diminishes as response delay increases.

Recent studies have explored using energy shifts to level annual demand. However, storing energy in batteries results in significant power loss due to self-discharge. While hydrogen energy storage is less efficient than batteries in terms of conversion efficiency, it does not cause time-dependent energy losses like self-discharge, making it suitable for long-term storage. Therefore, this study aims to use hydrogen to level out the long-term fluctuating components of annual demand, thereby reducing the required installed capacity of thermal power generators during peak demand periods. The verification results confirmed that introducing a hydrogen storage system successfully reduced the required equipment capacity of thermal power generators.

Ammonia has attracted attention as a hydrogen carrier, and its electrochemical synthesis under ambient conditions is considered as a promising approach to achieve a hydrogen-based society by effectively utilizing intermittent renewable energy. The purpose of this study is to develop ammonia electrosynthesis catalysts that operate under ambient conditions by utilizing Prussian Blue analogs (PBAs). Microwave irradiation was employed to synthesize iron–zinc PBA nanoparticles on the surface of Ketjenblack (KB) with the aim of achieving nanoscale particle sizes and enhancing their catalytic performance. The PBA particle size was successfully reduced to 11 nm by using composed of with KB and either poly(4-vinylpyridine) or polyvinylpyrrolidone. The catalytic activity of the obtained materials for electrochemical ammonia synthesis was evaluated using a cell with a triple-phase boundary, resulting in a Faradaic efficiency of 3.6% and an ammonia formation rate of 60 nmol h^-1 cm^-2.

In this study, we aimed to develop a highly active Fe/N/C-type non-precious metal oxygen reduction catalyst by hydrothermally synthesizing a composite of Ketjenblack (KB) and g-C₃N₄. Transmission electron microscopy (TEM) observations revealed that the spherical KB and sheet-like g-C₃N₄ were well intertwined, indicating successful composite formation. In addition, the effect of the mixing sequence of the metal sources (Fe and Zn) and the ligand (1,10-phenanthroline) on the catalytic activity was investigated by comparing four different synthesis routes for the g-C₃N₄/KB composite. Electrochemical measurements revealed that the catalyst precursor prepared in the coexistence of Fe and Zn tended to exhibit higher activity.

Air conditioners for heating supply heat several times as much as that of electricity they consume. In this study, ambient heat used for heating in residential air conditioners is quantified. For that purpose, we estimate the number of residential air conditioners in existence in FY2023 in both warm and cold regions. We adjust the amounts of the ambient heat used by air conditioners in cold regions considering those climates by using JIS standard and then calculate the amounts considering insulation of houses and actual usage time.

Under a feed-in tariff (FIT) scheme this study examines the economic implications of solar power curtailment in Kyushu, Japan. By defining the potential market value of curtailed electricity, it analyzes how benefits and burdens are distributed among renewable producers, retailers, conventional generators, and consumers. Two utilization scenarios—daytime load creation and battery-based time shifting—are compared. The findings suggest that under current institutional and cost conditions, benefits concentrate on specific actors while consumer burdens persist. Policy implications include separate metering and low-priced mechanisms for curtailed energy, compensation for fair benefit allocation across stakeholders.

This report will take into account differences in the types of local governments and changes in energy supply and demand due to the spread of renewable energy in municipalities, the spread of energy-saving machinery, vehicles, and buildings and houses, the effects of reducing CO₂ emissions, and the reduction in utility bills and economic effects.

An analysis of long-term changes in waste volume and composition was conducted based on 26 years of general waste disposal surveys. Total waste generation per person has decreased nationwide. Cluster analysis of trends across prefectures revealed that the 47 prefectures can be classified into four distinct patterns. In particular, prefectures with high waste discharge volumes in 1998 decreased significantly. The recycling rate increased until 2010 and then remained stable at approximately 20%. The amount of direct recycling showed a significant decrease in paper materials. Conversely, PET bottles, plastics, and other items steadily increased.

This study presents the design of a gravity energy storage system (GESS) aimed at medium- to long-term energy storage over periods ranging from several days to several months. The proposed system is characterized by its low cost and absence of self-discharge, making it suitable for long-duration applications. Assuming deployment within Japan, the design was developed in compliance with domestic regulations and standards. To facilitate future implementation, the design methodology was systematized to streamline the basic engineering process. A standard specification was established, consisting of a lifting height of 30 meters and a weight mass of 11.2 tons. Under these conditions, the system can deliver 1 kW of power for 32 minutes, with an estimated round-trip efficiency of 58%.

To optimize a sand packed type thermal storage tank, a heat source and a heat collection pipe were placed on the concentric axis of a cylindrical thermal storage tank 20 m long, with a packed bed diameter of 3 m and insulation thickness of 5 m, and charge/discharge cycle simulation was performed in which the tank was heated for 12 hours at a maximum of 60 kW and a maximum of 1200 °C, and then the inlet air was set at 279 °C and a constant speed of 5 m/s to release heat for 12 hours. By reducing the non-temperature-fluctuation portion of the packed bed and setting the packed bed diameter to 1.68 m and the insulation thickness to 3.56 m, the volume of the thermal storage tank was reduced by 54 % while maintaining the same amount of heat collected per cycle.

In the water supply system, there are set lower and upper limits for water pressure, and in flat areas, it must be constantly pressurized, which naturally requires pump power. Most of the water sources in Chino City are spring water. In 1-2 locations, water is drawn from deep wells through boring and used as drinking water. The abundance of water sources at the foothills of the mountains is presumed to be one of the roots of the city's historical development. This study examines the potential of utilizing this water source for small hydroelectric power generation from an environmental perspective, as well as the use of the water from the deep wells outside of peak electricity demand periods (such as late-night power). As a result, if the water tank is designed with ample capacity, it is expected that electricity demand will be shifted and the resilience of the water supply system will be improved.

At an accommodation facility utilizing regional energy in Kawasaki Town, Miyagi Prefecture, energy acquisition and usage were evaluated based on primary energy. Regional energy acquired amounted to 60,924 MJ, while regional energy used totaled 53,537 MJ. In the acquired energy, 88% was utilized.

Based on the relationship between actual solar power generation and electricity demand, we clarify the relationship between solar power generation, battery storage equipment, and energy independence in passive houses, where heating loads are significantly reduced in winter, with the aim of achieving ZEH (100% energy independence) throughout the year.

Year-round measurement is being performed under actual living environment in LCCO₂ minus home which was built in Asahikawa-shi, Hokkaido. After replacing the domestic hot water system and following a change in occupants, the energy consumption for each end use and the efficiency of the hot water supply equipment were analyzed. The study examined differences in energy consumption resulting from equipment retrofitting and variations in lifestyle.

To determine the optimal equipment capacity for a school equipped with evacuation shelter functions from both economic and resilience perspectives, a power transmission simulation was conducted. Assuming normal and emergency load profiles based on the facility scale, the 20-year economic performance and the ability to supply emergency loads continuously for 72 hours were evaluated. The optimization was carried out with the aim of maximizing resilience while minimizing the total system cost. As a result, the economic optimal equipment capacity was 77 kW of PV and 0 kWh of BESS, while the resilience optimal equipment capacity was 17 kWh of BESS for a school (whole floor area: 5600 m², evacuation shelter (gym): 1000 m², shelter capacity: about 300 people). Integrating both aspects, the overall optimal equipment capacity was 77 kW of PV and 17 kWh of BESS.

In this paper, we quantitatively investigated, using a voltage circle diagram, the PV system control conditions for a distribution system in which only large-capacity PV systems are connected at the end, so that not only the voltage at the PV system interconnection point but also the voltage on the line is kept within an appropriate range by appropriately adjusting the PV system power factor and reverse current.

This study examines EV charging infrastructure in Fukuoka City and its integration with surplus urban energy to support sustainable mobility. A survey from 2021–2024 showed steady growth of charging stations, especially standard chargers in urban areas. Simulation of surplus energy revealed high-density zones, such as Hakata and Tenjin, where utilizing surplus energy for EV charging can reduce grid loads and enhance renewable energy use. Reusing existing gasoline stations as charging hubs proved effective for expanding infrastructure without new land. An optimized siting model proposed 80 new stations, achieving five-minute access coverage and improving urban energy efficiency.

With the aim of achieving a carbon-neutral society by 2050, renewable energy is becoming the primary power source. In particular, solar power generation equipment, which is central to renewable energy, is expected to continue to be introduced in large quantities.

In this study, we therefore examined the introduction methods of solar power generation systems and energy storage systems. Specifically, we considered cases where the energy storage system is an AC system and a DC system.