Electricity prices have been rising in Japan in recent years, and dependence on thermal power generation, which is susceptible to rising procurement costs due to rising prices of liquefied natural gas (LNG) and coal, has been cited as one of the reasons. As a countermeasure to this problem, coupled with the recent movement toward decarbonization, there is a movement to promote the introduction of renewable energy, including solar power generation, whose prices have fallen in recent years. The purpose of this study is to quantitatively understand the causal relationship of the impact of renewable energy and thermal power generation on electricity prices by conducting a causal inference analysis using propensity scores. At that time, the degree of influence of various influencing factors on area prices was considered based on the analysis results of area prices in the two power service areas. As a result, increasing photovoltaic power generation was confirmed to have the effect of lowering area prices in two power service areas. On the other hand, it was confirmed that thermal power generation has the effect of increasing area prices in two power service areas.

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Future massive introduction of renewable power generation can cause a large amount of surplus power. The surplus power will be utilized effectively for charging Electric Vehicles (EVs) if the charging demand is shifted to the time when the surplus power is enough while without compromising the convenience of EVs utilization as vehicles. This study proposes a Charging Promotion Time Zone (CPTZ) to which the charging demand is shifted depending on EV owners’ decision for charging in consideration of change in charging cost affected by electricity supply and demand balance. As a result, daily cumulative irradiance works as a measure to determine the length of CPTZ in a day and to promote the charging decision by EV users during CPTZ. The annual EV charging demand met by renewable power supply is increased to about 50% from 40% in the case without the CPTZ. The sensitivity analysis on the kW capacity of charger for EVs for commuting purpose shows that the ratio of charging demand met by renewable power supply and the annual peak of overall charging demand is the same regardless of charger kW capacity because the charging demand is effectively dispersed within CPTZ.

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The basic experiments on the plasma arc radiation heating in a direct current (DC) electric furnace equipped with one electrode have been conducted, and based on the experimental results, the heat transfer to scrap, the scrap melting and the molten scrap movement have been estimated. It has become clear that the scrap melting behaviors have been started from the scrap surface melting by the arc radiation heating. In the future, it is necessary to develop the research as follows. (1) In order to efficiently melt the scrap in the heat transfer area that receives the arc, it is necessary to optimize the heat transfer area diameter, the arc radiant heat amount and the heated scrap properties (particle size, etc.). (2) Based on the basic experimental results, the influence of factors governing the scrap melting should be quantified. In particular, it is extremely important to estimate the scrap melting existing in the area far from the heat receiving area. (3) In addition to the DC furnace equipped with one electrode, it is necessary to estimate the melting behaviors in an alternating current (AC) furnace equipped with three electrodes.

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