| 摘要: | 近年來由於經濟、環境與化石能源耗竭等問題的浮現，以及再生能源對環境的正外部效益，使各國紛紛推廣再生能源的使用與發展來替代化石能源。但再生能源雖具環境友善性，其生產過程也可能對環境造成污染，故政府在制定再生能源發展政策時，除了利用各種經濟工具促進其發展外，也要針對其污染損害給予限制及懲罰，以導正負外部性造成之市場失靈。
本文主要探討在封閉與開放經濟體系下，政府最適再生能源政策的制定。在封閉經濟體系下，我們分析不同市場結構下最適再生能源政策為何。在開放經濟體系下，我們以一個兩國兩廠商雙占出口貿易模型，分析本國與外國政府在合作與不合作下之最適再生能源政策。
首先，在封閉經濟體系下，我們發現若市場結構為完全競爭，最適的污染排放稅率為皮古稅而最適淨再生能源補貼率大於再生能源的邊際效益，且廠商市場力量越強大則補貼率越高於皮古補貼。
其次，在開放經濟體系下，本國（再生能源出口國）與外國（再生能源進口國）不合作時，本國政府應對本國廠商污染排放課徵皮古稅，外國政府雖對外國廠商污染排放課稅，但其最適稅率低於邊際污染損害，且外國政府對外國廠商之淨再生能源補貼率亦會高於市場總再生能源產量的邊際效益。若兩國政府合作，制定聯合再生能源政策時，兩國最適之污染排放稅率會等於兩國廠商污染排放的邊際損害，但較不合作者為高。而兩國政府聯合最適之淨再生能源補貼率會高於兩國再生能源產出的邊際效益，但聯合補貼率會低於不合作下外國政府對外國廠商最適之淨再生能源補貼率。
Because of economic and environmental problems, exhaustion of fossil fuels, and the positive externality of renewable energy, all countries pay attention to renewable energy as a fossil fuel substitute. However, even though renewable energy is friendly to environment, the life cycle of renewable energy may pollute the environment. Therefore, governments have not only to develop the renewable energy but also to internalize the negative externalities from renewable energy.
This thesis studies the optimal policies of renewable energy in closed and open economies. In the case of closed economy, the optimal emission tax and energy subsidy are Pigouvian ones if the market structure is perfectly competitive. When the market structure is monopoly or oligopoly, the optimal emission tax is also a Pigouvian one. The optimal subsidy, however, is higher than the Pigouvian one. Moreover, the higher the market power, the higher the subsidy rate.
In the case of open economy, a two-country duopoly model is used to analyze. When two governments act noncooperatively, we find that the government who exports renewable energy would levy a Pigouvian tax on its domestic firm. The importer government would levy an emission tax which is lower than the Pigouvian tax and give a subsidy which is higher than the Pigouvian subsidy to its firm. When two governments act cooperatively, the cooperative tax is equal to the marginal damage and the cooperative subsidy is higher than the marginal benefit of total renewable energy. In addition, the cooperative tax and subsidy are higher and lower than the noncooperative tax and subsidy, respectively. |
