Energy storage systems are crucial in dealing with challenges from the high-level penetration of renewable energy, which has inherently intermittent characteristics. For this reason, various incentive schemes improving the economic profitability of energy storage systems are underway in many countries with an aim to expand the participation rate. The electricity charge discount program, which was introduced in 2015 in Korea, is one of the policies meant to support the economic feasibility of demand-side energy storage systems. This paper quantitatively evaluated the impact of the electricity charge discount program on the economic feasibility of behind-the-meter energy storage systems. In this work, we first summarized how electricity customers can benefit from behind-the-meter energy storage systems. In addition, we represented details of the structure that make up the electricity charge discount program, i.e., how the electricity charge is discounted through the discount scheme. An optimization problem that establishes a charge and discharge schedule of an energy storage system to minimize each consumer’s electricity expenditure was defined and formulated as well. The case study results indicated that the electricity charge discount program has improved the profitability of behind-the-meter energy storage systems, and this improved profitability led to investment in behind-the-meter energy storage systems in Korea. As a result of the electricity charge discount program, Korea’s domestic demand side energy storage system market size, which was only 27 billion dollars in 2015 in Korea, has grown to 825 billion dollars in 2018.

As part of efforts to cope with climate change, countries around the world have decided to supply photovoltaic (PV) power. However, since the integration of PV affects the reliability and stability of a power system, increasing the penetration of PV generation requires better system flexibility. For this reason, many countries have recently established policies to disseminate energy storage systems (ESS). In this paper, we aim to evaluate the effectiveness of policies regarding ESS as a way to increase PV integration. We analyzed whether the policies were effective in spreading ESS to eventually increase PV integration. To do this, we first described the Korean government's policy of establishing a profit structure for ESS through the Renewable Energy Certificate (REC) market and analyzed its effects on economic feasibility. We also analyzed how much the investment in ESS for PV integration has risen and assessed the contribution of spreading ESS to disseminate PV power. We found that ESS for the integration of PV have grown to a 41.0% share of Korea's ESS market in kW, and 32.8% in kWh, while expanding the PV market by 13.7%.Sustainability 2019, 11, 4337 2 of 17 decrease and strong governmental dissemination policies led this trend [3]. For example, the capital cost of utility scale PV for 2018 fell to about 25% compared to 2010. On the other hand, during the same period, the capital cost of coal fired power, gas power, and nuclear power, have changed little or even increased.In addition, developed countries such as the United States and European countries are endeavoring to cope with climate change and to lead energy transition with the expansion of renewable energy. The United States has decided to cut its GHG emissions by 26-28% from 2005 levels by 2025, according to the INDC submitted to the UN on 31 March 2015 [5]. It plans to cut about five billion tons by 2020, which is a 17% reduction compared to 2005, and 4.3 billion tons, which is a 26-28% reduction, by 2025. To that end, the Environmental Protection Agency (EPA) announced a Clean Power plan for carbon-dioxide reduction on 23 October 2015 [6]. This guideline aims to reduce GHG emissions in power generation by expanding natural and renewable energy and reducing the use of fossil fuels. On 10 October 2017, the abolition plan containing the review result based on the reconsideration request was submitted, and the Affordable Clean Energy Rule was proposed on 21 August 2018 [7,8]. As a result, the proportion of coal-fired power decreased from 50% in 2005 to 30% in 2017, natural gas power increased from 19% to 32%, and non-hydro renewable energy, such as wind and solar, increased from 2% to 10%, and CO 2 emissions decreased by 27% [9].In Japan, which has decided to reduce GHG by 26% by 2030 compared to 2013, the nation's total GHG emissions decreased by 3.0% year-on-year in 2014 [10]. Despite the decrease in the proportion of nuclear-power generation, carbon-dioxide emissions decreased because of the decrease of petroleum thermal power, the increase of renew...