# Analysis and Prioritization of the Floating Photovoltaic System Potential for Reservoirs in Korea
## 1 Introduction  
To reduce greenhouse gas (GHG) and protect the environment, renewable energy sources are increasingly utilized worldwide. According to Renewable Capacity Statistics [1], the total renewable power capacity for power generation is 2179 GW in 2017, with an 8.3% increase over the previous year. In particular, the growth rate of photovoltaic (PV) energy is prominent because the price of solar panels is steadily declining, and various stimulus policies are being implemented. PV energy is considered to be one of the most promising energy alternatives due to its ubiquity and sustainability. Particularly in South Korea, PV energy is spreading very quickly after the introduction of the Renewable Portfolio Standards (RPS) program, which requires electricity providers to increase their renewable energy production. PV energy is the renewable energy that accounts for the largest portion in Korea today, except for waste energy and bio-energy. According to the Korea New and Renewable Energy Center (KNREC, Yongin, Korea), renewable energy supply ratio in Korea is about 19.5%, 61.7%, 4.3%, and 2.5% for solar, biomass, hydro, and wind, respectively in 2016. The supply of PV energy in Korea was only 7.6 toe (tonne of oil equivalent) until 2006 but increased to a value of 1092.8 toe in 2016. This is because government policies have been actively implemented, and the public has become actively engaged inPV projects to generate profits by selling the produced electricity. However, the excessive installation of PV facilities has caused various problems. In addition to the damage to the landscape caused by the installation of solar panels, the residents of areas where the panels have been installed have been inconvenienced by the reflected light and increase in the ambient temperature. In addition, solar panels that are swept away in the event of landslides or typhoons can cause safety accidents. In recent years, there has been an increase in complaints from local residents, as the solar power generation business has become a means of speculation in the area of PV power generation. These problems can be even more significant in countries such as South Korea, where available land is scarce, so that there is not enough area for the installation of solar panels. Therefore, floating PV systems, which can overcome or alleviate these problems, have attracted considerable attention in these countries. In addition to being able to utilize the reflected light from the water surface, the floating PV is known to be about 11% more efficient than the terrestrial solar panel due to the temperature reduction effect in water [2]. Solar panels that cover the water can also reduce evaporation [3] and prevent algae [4] due to shadows by the panels. In other words, the floating PV is advantageous in terms of efficiency and environmental aspects, in addition to the lack of need for land. Because of these advantages, floating PV systems installed on water bodies, such as reservoirs or dam lakes, have increased worldwide and have already been deployed in several countries, including South Korea, Japan, China, and the US [5]. Although most technological growth occurred between 2007 and 2014, the global installed capacity for floating PV has increased significantly since 2015. Floating PV installations in the world were estimated at 94 MW by 2016, of which about 60% were known to be installed in Japan [6]. In 2017, however, the world's largest floating PV system was installed on the pit lake of a coal mine in China and is known to have capacity of 40 MW. The system is composed of 120,000 solar panels, supplying the electricity needs of 15,000 households [7]. Recently, South Korea has been rapidly improving its floating PV technology and increasing installation capacity. The Korea Water Resources Corporation (K-water, Daejeon, Korea) carried out the first demonstration project in South Korea at the Hapcheon reservoir in 2014 with a capacity of 100 kW.