Globally, many countries are experiencing economic growth while concurrently increasing their energy consumption. Several have begun to consider a low-carbon energy mix to mitigate the environmental impacts caused by increased fossil fuel consumption. In terms of maximizing profits, however, power producers are not sufficiently motivated to expand capacity due to high costs. Thus, the Korean government initiated the Renewable Portfolio Standard (RPS), an obligation to generate a certain proportion of a producer’s total generation using renewable energy for power producers with capacities of 500 MW or more, and the Emissions Trading Scheme (ETS), designed to attain a carbon emissions reduction goal. We propose a mathematical model to derive the optimal operational strategy for maximizing power producer profits with a capacity expansion plan that meets both regulations. As such, the main purpose of this study was to obtain the optimal operational strategy for each obligatory power producer. To that end, we defined a 2 $\times$ 2 matrix to classify their types and to conduct scenario-based analyses to assess the impact of major factor changes on solutions for each type of power producer. Finally, for the power generation industry to operate in a sustainable and eco-friendly manner, we extracted policy implications that the Korean government could consider for each type of power producer.

Due to the heightened concerns of global environmental problems caused by the heavy use of fossil fuels, the sharp increase of energy use in the building sector has been recognized as an important environmental issue. One solution for efficient energy consumption in the building sector is building retrofits. This study proposes a two-stage integer programing model to select building retrofit materials and retrofit planning. The first model is based on a multi-objective optimization that derives an optimal retrofit strategy considering both energy savings and retrofit costs. Using the results of the first model, the second model finds an optimal retrofit plan to minimize losses for the building owner. Based on a real general hospital building in Korea, a simplified case building was used to verify the proposed models and for experimental analyses. According to the results of the second model, the building owner could adopt a building retrofit with less than 30–40% of the initial budget when compared to the total retrofit costs.