Japan and China are different in many aspects，such as population，resources，administration，growth stage, electricity mix，and carbon emissions．However，both countries are taking effort to transition to low-carbon society. One of those measures is to promote the development of solar power．In this research, we analyzed the current state and mechanism of PV development in both Japan and China by using econometric model. System price, feed-in tariff (FIT), subsidy, transmission grid improvement, etc. were confirmed to be an influence factor of introduction of PV system for both Japan and China. Also, in order to promote the international competitiveness of domestic solar cells, it is indispensable to expand cumulative output.
Simulation analysis was also conducted on future targets formulated by the two countries. As a result, in reference case the tendencies continue as they are, it is predicted that Japan will reach a 130% completion of their objective by 2030, while China will have achieved a 142% by 2020. An effective way to further increase this spread could be found in the reduction of feed-in tariff policies ranges and interest rates, as well as in the increase of carbon taxes in Japan or their introduction in China, respectively.

View full abstract

The so-called ‘nudge’ approach, which gently prompts people to make better choices without restricting their freedom of choice, is coined in behavioral economics and is drawing attention in energy conservation in residential sectors. Utilizing a smartphone app as a simplified Home Energy Management System (HEMS) and sending push notifications in each user’s customized timing could be a flexible and efficient nudge for energy conservation. In the winter of 2017, we conducted interventions to provide feedback of each customer’s energy consumption or recommendations about electric appliances’ settings using the smartphone app. Analyzing a series of qualitative and quantitative data from the respondents, we show how the framework can promote energy conservation behaviors.

View full abstract

In this paper, we used an optimal power generation mix (OPGM) model, as well as meteorological data from 2000 to 2017, to assess the cost of achieving 100% renewable electricity mix in 2050 in Japan. Although the potentials of variable renewable energies, such as wind and solar PV, have been estimated to be large in Japan, grid-related system costs become significant in the cases with very high shares of variable renewables. Particularly, two factors affect the overall costs: The cumulative installed capacity of offshore-wind power, and the required capacity of electricity storage systems. The former is dependent on the curtailment ratio of onshore-wind and solar PV, whereas the latter is determined by the short-time “windless and sunless” factor, i.e. the maximum number of successive days with very small wind and solar power output. The analyses presented in this study highlight the necessity of using long-term meteorological data when estimating the economics of high penetration of variable renewables, as well as the importance of considering the risk of power supply disruption.

View full abstract

Platinum Group Metals (PGMs) are used in many applications because of their valuable properties such as high melting point and specific catalytic activity. Particularly, they play an important role in catalytic converters used by conventional and hybrid vehicles and in reaction catalysts of fuel cell vehicles (FCVs). Therefore, the introduction of next generation vehicles may significantly transform the pressure on PGMs. Besides, the geological (primary) resources of PGMs are highly concentrated in South Africa and Russia making its supply volatile. For these reasons, this study estimated secondary PGM reserves for Europe, Japan, and the United States until 2050. The results indicate that the introduction of FCVs will lead to an increase of secondary PGM reserves in the future. The difference in PGM secondary reserves due to the difference in introduction of FCVs are estimated to 1,424 tonnes in 2050. On the other hand, the increase caused by FCVs was found not significant because of the decrease in demand for catalytic converter for vehicles in the future.

View full abstract

This paper presents the change of CO₂ emission when battery energy storage systems (BESS) are used for increasing self-use of PV energy from rooftop panels, and for decreasing PV output curtailment. A traditional evaluation uses an annual CO₂ emission intensity and the charge-discharge loss is evaluated, and then the emission is increased. However, when PV system is largely penetrated and the PV energy curtailment is required by power system constraints, BESS can decrease the curtailment as well as the evening demand when the rate of thermal power is large, and increase the daytime demand when the rate of PV energy is high. So, BESS can decrease CO₂ emission considering hourly CO₂ emission intensity. Authors quantify these effects by use of an optimization model to minimize annual power generation costs, and a model to minimize annual costs of houses with PV and BESS, and then shows energy chain diagram including energy flow between generation plants and customers. The CO₂ emissions from business use customers with PV and BESS, and power charging demand for EV are also evaluated using hourly CO₂ emission intensity. Authors show BESS can decrease CO₂ emission.

View full abstract

As a countermeasure to global warming, in the housing related field, installation of PV to houses is being promoted by Building Energy Conservation Law, ZEH, LCCM housing and so on. In the automobile-related field, the spread of EV is expected. V2H that can use EV as an electric power storage equipment is also on sale. By using V2H, in the daytime EV can absorb PV surplus power and can supply its stored power to home in the nighttime. It can adjust demand-and-supply balance of power grid and also can reduce primary energy consumption and CO₂ emissions by utilizing PV to the full for home.
However, V2H is a new equipment which connects energy between an automobile and a home, therefore its quantification method and performance indices for home energy, including automobile, have not been established.
In this paper, we propose quantification method of home energy including automobile and electricity storage system and energy performance indicators, and compare gasoline cars, EV, various electricity storage systems by simulation based on the indices, and evaluate the effectiveness of V2H and CO₂ emissions reduction effect.

View full abstract