習熟−環境評価サイクルを考慮した住宅用太陽光発電の普及促進政策の総合評価

抄録

Most of renewable energies are in the early stage of an industry and have environmental value. Therefore, this uniqueness must be taken into account when we consider economic policies such as subsidies to promote such technologies. Previously we constructed a growth model of renewable energies, in which the learning effect dominating the cost of the early stage of industries and the demand of consumers for environmental value were considered. In this study we connected the above growth model with the comprehensive socio-economic optimizing model, and examined the effect of economic policies such as a greenhouse gases emission tax and a subsidy the whole Japanese economy, and the total amount of greenhouse gas emissions with the residential photovoltaic industry as a case study. In the growth model, the demand change when renewable energy industries are subsidized with a restricted budget and the parameter changes with social cognition by the diffusion of renewable energy itself are also considered. The socio-economic optimizing model consists of the input-output relationship for monetary balance, some macroeconomic balances and GDP as the objective function.
We examined first the effect of a promotion policy consisting of a tax on greenhouse gas emissions and a subsidy for the residential photovoltaic industry financed by the tax income. The simulated period was from 2005 to 2015 and the policy was introduced in 2007. The photovoltaic cell increased proportionally to the tax rate and significant growth was observed in 2007, the first year of the promotion policy. However, predicted photovoltaic power supply in 2015 was no more than 0.8% of the total demand and this suggests the promotion policy for a single industry is insufficient to contribute to a decrease in global warming. As for the total national economic and environmental effect, both GDP and total greenhouse gas emissions decreased with introduction of the emission tax. Next, we examined the case when total emissions were restricted. Diffusion of the residential photovoltaic industry was also remarkable early in the simulated period. GDP increased when the emission tax and subsidy was introduced into the simulation, indicating the promotion policy for renewable energy industries may be effective even for the economy, under strict restriction on greenhouse gas emissions.
The results of the simulation showed that the promotion policy is effective for increasing production of the residential photovoltaic industry, for reduction in total greenhouse gases emissions and for an increase in GDP when the total emissions of greenhouse gases are restricted. Further studies are planned on a comprehensive promotion policy for renewable energy contributions to mitigate global warming and energy resource depletion by expanding this simulation model to other renewable energies and reconsidering the whole energy system.

JEL Classification: C63, O13, Q42, Q48, Q54