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Towards a Sustainable Island: Independent optimal renewable power generation systems at Gadeokdo Island in South Korea
Sustainable Cities and Society 23 (2016) 114–118
Contents lists available at ScienceDirect
Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
Short communication
Towards a Sustainable Island: Independent optimal renewable power generation systems at Gadeokdo Island in South Korea Eunil Park a , Sang Jib Kwon b,∗ a b
Korea Institute of Civil Engineering and Building Technology (KICT), Goyang, Republic of Korea Department of Business Administration, Dongguk University, Gyeongju, Republic of Korea
a r t i c l e
i n f o
Article history: Received 1 February 2016 Received in revised form 26 February 2016 Accepted 27 February 2016 Available online 2 March 2016 Keywords: Optimal solutions Gadeokdo Island Sustainable Island South Korea Renewable energy PV
a b s t r a c t Because of its high dependence on fossil fuels, the South Korean government has consistently endeavored to use renewable energy sources to operate power generation systems. The South Korean government has advised local communities and governments of the islands to establish independent renewable power generation systems, particularly since the installation, operation, and management of power generation systems to connect the islands to the electricity grids amount to large costs. As such, this study explores potential solutions for establishing independent renewable power generation systems in Gadeokdo Island, one of the largest islands in South Korea, by using the HOMER software. The simulation results show that wind turbines, PV panels, converters, and batteries can be used to operate the power generation systems for Gadeokdo Island. The current study presents an optimal renewable power generation system within the framework of the cost of energy (COE), renewable fraction, and total net present cost (NPC). The system achieves $0.326 per kWh of COE and 1.00 of renewable fraction. Both implications and limitations of the proposed system are discussed. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction With increasing interest in using alternative energy sources for producing electricity, the majority of developed countries have put in place policies and supporting plans for distributing alternative energy systems (Güler, Akda˘g, & Dinc¸soy, 2013). Following this global trend, the South Korean government actively supports the renewable energy industry and systems so as to reduce reliance on fossil fuels and increase national energy security (Hong, Bradshaw, & Brook, 2013; Huh & Lee, 2014; Kim, Baek, Park, & Chang, 2014; Park & Ohm, 2014). As such, the government offers financial assistance for the installation of solar and wind energy facilities when a local autonomous entity and a particular island aim at setting the facilities to become an energy-independent region (Huh & Lee, 2014; Hwang, 2013; Lewis, 2011). For example, Jeju Island, one of the biggest islands in South Korea, has attempted to develop an energy-independent system (Shin et al., 2013). However, because the local government
∗ Corresponding author at: Department of Business Administration, Dongguk University, 123 Dongdae-ro, Gyeongju-si, Gyeongsangbuk-do 780-714, Republic of Korea. E-mail addresses: [email protected] (E. Park), [email protected] (S.J. Kwon). http://dx.doi.org/10.1016/j.scs.2016.02.017 2210-6707/© 2016 Elsevier Ltd. All rights reserved.
of Jeju Island only aims at distributing and establishing renewable energy systems to lower the financial costs of energy consumption, there are no adequate studies presenting an optimal renewable energy solution for the island. South Korea is bounded by the Pacific Ocean on the east, west, and south, and includes more than 4000 islands. Therefore, developing independent renewable energy systems for these islands and minimizing the operation and management costs of the electricity grid are two of the most important issues while providing electricity to the islands (Hwang, 2013). The current study explores potential solutions for independent optimal renewable energy systems for one of the islands in South Korea. The study suggests solutions for Gadeokdo Island of Busan Metropolitan City, in the southeastern part of South Korea. This island mostly consumes electricity from the electricity grid connected to the grid system of Busan Metropolitan City. Based on the supporting plans and policies proposed by the South Korean central government, Busan local government has been building renewable power generation facilities to achieve an independent electricity system for the island. The current study employs the Hybrid Optimization of Multiple Energy Resources (HOMER) software introduced by the National Renewable Energy Laboratory, in order to find potential solutions for renewable energy systems and investigates several economic parameters including the net present cost (NPC) and cost of energy (COE).
E. Park, S.J. Kwon / Sustainable Cities and Society 23 (2016) 114–118
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Fig. 1. Map showing the geographic location of Gadeokdo Island.
1.1. Location and population Several prior studies were conducted to propose optimal renewable energy generation systems for islands in South Korea. Park, Yoo, Ohm, and Kwon (2016) proposed the optimal renewable electricity generation system for Geoje Island, one of the largest islands in South Korea. With the combination of wind turbines and photovoltaic (PV) arrays, the suggested system can sell the electricity through the currently used grid connection ($465,945) and achieve $0.472 per kWh COE. Yoo et al. (2014) attempted to the independent renewable electricity generation system for Ulleungdo island, one of the most eastern islands in South Korea. With two currently operated diesel generators, the system achieved 97.3% of renewable fraction with $0.334 per kWh COE. Moreover, because two diesel generators only produced the 3% amount of total electricity production, the possibility for the independent renewable electricity generation system was introduced. Chae, Lee, Won, Park and Kim (2015) proposed an inverted remote micro grid system for Gasado Island, one of the western islands in South Korea. The optimal configuration organized by PV arrays, wind turbines, diesel generators and batteries showed 94% of renewable fraction and $1.284 per kWh COE. Although there are several investigations in South Korea, only few studies were conducted to present economic feasibility tests of renewable electricity generation systems for the southern islands in South Korea. Therefore, the current study aims to present renewable electricity generation systems for Gadeokdo Island, one of the southern islands in South Korea.
Fig. 2. Average monthly solar radiation and clearness index for Gadeokdo Island.
demand for the island is calculated to be 33,954 kWh/d while the peak energy demand is calculated to be 2049 kW. The load factor of this island is computed as 0.691. 2.3. Solar energy information The 2013 data for daily solar radiation and solar clearness collected by the National Aeronautics and Space Administration (NASA) and the Korea Meteorological Administration (KMA) were used. The average annual solar clearness index is computed as 0.531, while the average daily radiation was calculated as 4.422 kWh/m2 /d. Fig. 2 shows the monthly average solar radiation and clearness index.
2. Status of Gadeokdo Island 2.4. Wind energy information 2.1. Location and population Gadeokdo Island is located in Busan Metropolitan city, in the southeastern area of South Korea, with coordinates 35.04 latitude and 128.83 longitude (Fig. 1), and an area of 20.78 km2 . The island has about 1300 households and 3800 residents.
The 2013 data for wind speed collected by the National Renewable Energy Laboratory (2014) were used. The annual average wind speed is calculated to be at 6.175 m/s. Fig. 3 shows the monthly wind speed. 3. Key parameters for the economic analysis
2.2. Load information 3.1. South Korea’s annual real interest rate The current energy demand of Gadeokdo Island is supplied mainly by the electricity grid. Based on data collected from the Korea Electric Power Corporation, the scaled annual average energy
The annual real interest rate is one of the most important input variables for a more realistic and accurate economic analysis. Based
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E. Park, S.J. Kwon / Sustainable Cities and Society 23 (2016) 114–118 Table 1 Optimal renewable power generation system for Gadeokdo Island.
Fig. 3. Monthly average wind speed for Gadeokdo Island.
on the equations and methods introduced by Dursun (2012), and the nationally official rate presented by the Bank of Korea (2014), an annual real interest rate of 3.02% in South Korea is used in this study. 3.2. Cost of energy (COE) and net present cost (NPC) The COE is measured as “the average cost per kWh produced by the system” (Park & Kwon, 2016). The total cost is calculated as “all consumed costs of the system’s components with other additional costs” (Park & Kwon, 2016). The COE is the most significant economic output, because all optimized results are evaluated by the COE level (Madlener & Sunak, 2011). The NPC is one of the main simulation results. The present value for establishing and operating the system is included in the lifecycle cost. The current study hypothesized that 20 years would be the lifetime of optimal solutions (following the national energy plans introduced by South Korean government; Lewis, 2011; Ryu, 2010), based on calculations following the stages introduced by Dursun (2012). 4. Renewable power generation systems As this study aims to explore potential optimal renewable energy power generation systems, various components such as PV panels, wind turbines, converters, batteries and the grid, are explored in order to enhance the feasibility of the potential systems. The HOMER software needs to process the installation, replacement, and operating costs components. This study set $1800 for installation costs, $1800 for replacement costs, $25 for operating costs of PV panel and PV panel lifetime with no tracking system
Components
Index
PV (kW) Wind (# of turbines) Battery Converter (kW) Grid (kW) Initial capital ($) Operating cost ($/year) Total NPC ($) COE ($/kWh) Ren. frac.
8425 765 15,775 2735 0 48,379,976 1,260,290 70,325,584 0.326 1.00
of 20 years, based on previously proposed parameters (Bekele & Tadesse, 2012; Park et al., 2016). A range of 0 to 30,000 PV panels is considered in the simulation. For the wind energy component, a generic 10 kW wind turbine was considered. Capital costs of $29,000, replacement costs of $25,000, operation and management costs of $400 as well as 25 meters for hub heights, and 25 years lifetime for the turbine were used (Ani, Nzeako, & Obianuko, 2012; Park & Kwon, 2016). A range of 0–1500 wind turbines was used for the simulation. To connect the energy flow between DC and AC components, an electronic converter was used. Installation costs of $800, replacement costs of $750, 90% of system efficiency, and 15 years lifetime for the converter were used. A range of 0–5000 kW for the converter capacity was used (Baek et al., 2016; Demiroren & Yilmaz, 2010). Batteries are one of the essential components of sustainable and renewable power generation systems. A Surretts-6CS25P battery model, with a capacity of 6 V, 1156 Ah, and 9645 kWh was used in the simulation. Installation costs of $1229, replacement costs of $1229, and operation and maintenance costs of $10 were used. A range of 0–30,000 battery units was considered (Ngan & Tan, 2012). 5. Results 5.1. Simulation results This study considered PV panels, wind turbines, batteries, converters, and the grid in the HOMER software for developing optimal renewable power generation systems for Gadeokdo Island. Table 1 presents the optimal configuration of the simulation results, while
Table 2 Annualized costs of the system. Components PV Wind Grid Battery Converter System
Capital ($/year) 870,894 637,019 0 1,113,382 157,065 2,778,359
Replacement ($/year) 482,193 0 0 1,328.614 100,814 1,911,621
O&M ($/year) 210,625 153,000 −375,649 157,750 27,350 173,076
Fig. 4. Cash flow summary for simulation results.
Salvage ($/year) −311,958 0 0 −487,444 −25,005 −824,408
Total ($/year) 1,251,754 790,019 −375,649 2,112,301 260,224 4,038,649
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Table 3 Annual electrical component production, load, and quantity. Component
Fig. 5. Average electricity production for simulation results.
Table 2 shows the potential system’s annualized costs. In addition, Table 3 shows the electricity component production, load, and quantity of the simulation. In order to maximize the reliability of electricity systems, based on the simulation results, it is recommended that all components, i.e., PV panels, wind turbines, batteries, converters, and the grid, be used in the systems. By being connected to the grid system and selling the surplus electricity, the potential system can give rise to large amounts of savings. The cash flow summary based on the results is presented in Fig. 4, while the monthly average electricity production is shown in Fig. 5. The results for the PV and wind turbine output are presented in Figs. 6 and 7, respectively. Figs. 8 and 9 show the information concerning the battery units employed in this study. The optimal solution further indicates that 1,884,207 kg of carbon dioxide, 8169 kg of sulfur dioxide, and 3995 kg of nitrogen oxides are emitted.
Production (kWh/year)
Fraction
PV array Wind turbines Grid purchases
12,415,346 15,551,936 0
44% 56% 0%
Total
27,967,282
100%
Load
Consumption (kWh/year)
Fraction
AC primary load Grid sales
10,193,286 1,994,601
84% 16%
Total
12,187,887
100%
Quantity
Value
Units
Excess electricity Unmet load Capacity shortage Renewable fraction
9,754,596 10,274 12,392 1.000
kWh/year kWh/year kWh/year –
6. Discussion This study was conducted to investigate possible renewable power generation systems for Gadeokdo Island in South Korea. In order to explore the systems, possible optimal solutions were presented employing the HOMER software. The main conclusions of the simulation are as follows: – The derived optimal and efficient case suggests the use of 8425 kW of PV panels, 765 wind turbines (generic 10 kW), 15,775 batteries (Surrette S6CS25P), 2735 kW of converters, and an electricity grid. – The results also show costs of $48,379,976 for initial capital, $1,260,290 for operation costs per year, $70,325,584 for the total NPC, $0.326 per kWh COE, and 100% of renewable fraction ratio.
Fig. 8. Battery frequency histogram for simulation results.
– Based on the simulation, a sale of 2,981,340 kWh per year via the electricity grid is possible. This means that the current electricity grid can be used as a useful outlet for the sale of electricity from renewable power generation systems. Although establishing renewable power generation systems requires a huge budget, it can be efficient and useful in the long term (Atieh & Al Shariff, 2015). In addition, the current electricity grid can be used for the sale of electricity produced by renewable
Fig. 6. PV output for simulation results.
Fig. 7. Wind turbine output for simulation results.
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Fig. 9. Battery bank state of charge for simulation results.
power components in the systems. Given alternating the current system which is fully maintained by the electricity grid, the following stages could be adopted. – Gradual stages for establishing a renewable power generation system for Gadeokdo Island should be developed to reduce dependence on the current grid system. – After the system reaches a level that is able to cover the amount of electricity used, the current grid system could be used as a reserve. – When the facilities achieve the planned solutions, the grid can be used to sell electricity. 7. Limitations The current study has several notable limitations. First, this study does not consider any supporting policy currently in place in South Korea. Because the South Korean government operates a number of supporting programs, including several carbon-associated policies and the RPS policy (renewable portfolio standard policy; Chen, Kim, & Yamaguchi, 2014; Kim, Park, Kim, & Heo, 2012), the current results can be improved by showing better economic outputs if those components were included. Second, the simulation results cannot be generalized, as this study was conducted for a specific location. Third, the study does not take into consideration any economic theories or the effects on the energy industry. Several prior studies indicated that a number of economic effects such as learning effects can have a notable impact on the energy industry (Ryu, 2010). Future studies should consider the above-mentioned shortcomings, employ the results of the current study as baseline, and use this study as a guideline. Acknowledgement This work was supported by the Dongguk University Research Fund of 2015. References Ani, V. A., Nzeako, A. N., & Obianuko, J. C. (2012). Energy optimization at datacenters in two different locations of Nigeria. International Journal of Energy Engineering, 2(4), 151–164. Atieh, A., & Al Shariff, S. (2015). Case study on the return on investment (ROI) for using renewable energy to power-up typical house in Saudi Arabia. Sustainable Cities and Society, 17, 56–60. Baek, S., Park, E., Kim, M. G., Kwon, S. J., Kim, K. J., Ohm, J. Y., et al. (2016). Optimal renewable power generation systems for Busan metropolitan city in South Korea. Renewable Energy, 88, 517–525. Bekele, G., & Tadesse, G. (2012). Feasibility study of small Hydro/PV/Wind hybrid system for off-grid rural electrification in Ethiopia. Applied Energy, 97, 5–15.
Chae, W. K., Lee, H. J., Won, J. N., Park, J. S., & Kim, J. E. (2015). Design and field tests of an inverted based remote microgrid on a Korean Island. Energies, 8, 8193–8210. Chen, W. M., Kim, H., & Yamaguchi, H. (2014). Renewable energy in eastern Asia: Renewable energy policy review and comparative SWOT analysis for promoting renewable energy in Japan, South Korea, and Taiwan. Energy Policy, 74, 319–329. Demiroren, A., & Yilmaz, U. (2010). Analysis of change in electric energy cost with using renewable energy sources in Gökceada, Turkey: An island example. Renewable and Sustainable Energy Reviews, 14(1), 323–333. Dursun, B. (2012). Determination of the optimum hybrid renewable power generating systems for Kavakli campus of Kirklareli University, Turkey. Renewable and Sustainable Energy Reviews, 16(8), 6183–6190. Güler, Ö., Akda˘g, S. A., & Dinc¸soy, M. E. (2013). Feasibility analysis of medium-sized hotel’s electrical energy consumption with hybrid systems. Sustainable Cities and Society, 9, 15–22. Hong, S., Bradshaw, C. J., & Brook, B. W. (2013). Evaluating options for sustainable energy mixes in South Korea using scenario analysis. Energy, 52, 237–244. Huh, S. Y., & Lee, C. Y. (2014). Diffusion of renewable energy technologies in South Korea on incorporating their competitive interrelationships. Energy Policy, 69, 248–257. Hwang, K. I. (2013). A feasibility study on the hybrid power generation system considering of electricity needs’ fluctuation of coastal area’s houses. Journal of the Korean Society of Marine Engineering, 37(8), 977–983. Kim, H., Baek, S., Park, E., & Chang, H. J. (2014). Optimal green energy management in Jeju, South Korea – on-grid and off-grid electrification. Renewable Energy, 69, 123–133. Kim, J., Park, J., Kim, H., & Heo, E. (2012). Assessment of Korean customers’ willingness to pay with RPS. Renewable and Sustainable Energy Reviews, 16(1), 695–703. Lewis, J. I. (2011). Building a national wind turbine industry: Experiences from China, India and South Korea. International Journal of Technology and Globalisation, 5(3), 281–305. Madlener, R., & Sunak, Y. (2011). Impacts of urbanization on urban structures and energy demand: What can we learn for urban energy planning and urbanization management? Sustainable Cities and Society, 1(1), 45–53. Ngan, M. S., & Tan, C. W. (2012). Assessment of economic viability for PV/wind/diesel hybrid energy system in southern Peninsular Malaysia. Renewable and Sustainable Energy Reviews, 16(1), 634–647. Park, E., & Kwon, S. J. (2016). Solutions for optimizing renewable power generation systems at Kyung-Hee University’s Global Campus, South Korea. Renewable and Sustainable Energy Reviews, 58, 439–449. Park, E., & Ohm, J. Y. (2014). Factors influencing the public intention to use renewable energy technologies in South Korea: Effects of the Fukushima nuclear accident. Energy Policy, 65, 198–211. Park, E., Yoo, K., Ohm, J. Y., & Kwon, S. J. (2016). Case study: Renewable electricity generation systems on Geoje Island in South Korea. Journal of Renewable and Sustainable Energy, 8(1), 015904. Ryu, C. (2010). Potential of municipal solid waste for renewable energy production and reduction of greenhouse gas emissions in South Korea. Journal of the Air & Waste Management Association, 60(2), 176–183. Shin, B. Y., Yoon, M., Suh, J. W., Jang, G., Choi, H. S., Seo, Y. J., et al. (2013). A study on Jeju power system considering smart grid elements. Journal of International Council on Electrical Engineering, 3(4), 300–305. The Bank of Korea. (2014). The National Finance Information.. http://www.bok.or.kr/ main/korMain.action Accessed 21.02.16 The National Renewable Energy Laboratory. (2014). Solar and Wind Energy Resource Assessment.. http://en.openei.org/apps/SWERA Accessed 21.02.16 Yoo, K., Park, E., Kim, H., Ohm, J. Y., Yang, T., Kim, K. J., et al. (2014). Optimized renewable and sustainable electricity generation systems for Ulleungdo Island in South Korea. Sustainability, 6(11), 7883–7893.
Contents lists available at ScienceDirect
Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
Short communication
Towards a Sustainable Island: Independent optimal renewable power generation systems at Gadeokdo Island in South Korea Eunil Park a , Sang Jib Kwon b,∗ a b
Korea Institute of Civil Engineering and Building Technology (KICT), Goyang, Republic of Korea Department of Business Administration, Dongguk University, Gyeongju, Republic of Korea
a r t i c l e
i n f o
Article history: Received 1 February 2016 Received in revised form 26 February 2016 Accepted 27 February 2016 Available online 2 March 2016 Keywords: Optimal solutions Gadeokdo Island Sustainable Island South Korea Renewable energy PV
a b s t r a c t Because of its high dependence on fossil fuels, the South Korean government has consistently endeavored to use renewable energy sources to operate power generation systems. The South Korean government has advised local communities and governments of the islands to establish independent renewable power generation systems, particularly since the installation, operation, and management of power generation systems to connect the islands to the electricity grids amount to large costs. As such, this study explores potential solutions for establishing independent renewable power generation systems in Gadeokdo Island, one of the largest islands in South Korea, by using the HOMER software. The simulation results show that wind turbines, PV panels, converters, and batteries can be used to operate the power generation systems for Gadeokdo Island. The current study presents an optimal renewable power generation system within the framework of the cost of energy (COE), renewable fraction, and total net present cost (NPC). The system achieves $0.326 per kWh of COE and 1.00 of renewable fraction. Both implications and limitations of the proposed system are discussed. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction With increasing interest in using alternative energy sources for producing electricity, the majority of developed countries have put in place policies and supporting plans for distributing alternative energy systems (Güler, Akda˘g, & Dinc¸soy, 2013). Following this global trend, the South Korean government actively supports the renewable energy industry and systems so as to reduce reliance on fossil fuels and increase national energy security (Hong, Bradshaw, & Brook, 2013; Huh & Lee, 2014; Kim, Baek, Park, & Chang, 2014; Park & Ohm, 2014). As such, the government offers financial assistance for the installation of solar and wind energy facilities when a local autonomous entity and a particular island aim at setting the facilities to become an energy-independent region (Huh & Lee, 2014; Hwang, 2013; Lewis, 2011). For example, Jeju Island, one of the biggest islands in South Korea, has attempted to develop an energy-independent system (Shin et al., 2013). However, because the local government
∗ Corresponding author at: Department of Business Administration, Dongguk University, 123 Dongdae-ro, Gyeongju-si, Gyeongsangbuk-do 780-714, Republic of Korea. E-mail addresses: [email protected] (E. Park), [email protected] (S.J. Kwon). http://dx.doi.org/10.1016/j.scs.2016.02.017 2210-6707/© 2016 Elsevier Ltd. All rights reserved.
of Jeju Island only aims at distributing and establishing renewable energy systems to lower the financial costs of energy consumption, there are no adequate studies presenting an optimal renewable energy solution for the island. South Korea is bounded by the Pacific Ocean on the east, west, and south, and includes more than 4000 islands. Therefore, developing independent renewable energy systems for these islands and minimizing the operation and management costs of the electricity grid are two of the most important issues while providing electricity to the islands (Hwang, 2013). The current study explores potential solutions for independent optimal renewable energy systems for one of the islands in South Korea. The study suggests solutions for Gadeokdo Island of Busan Metropolitan City, in the southeastern part of South Korea. This island mostly consumes electricity from the electricity grid connected to the grid system of Busan Metropolitan City. Based on the supporting plans and policies proposed by the South Korean central government, Busan local government has been building renewable power generation facilities to achieve an independent electricity system for the island. The current study employs the Hybrid Optimization of Multiple Energy Resources (HOMER) software introduced by the National Renewable Energy Laboratory, in order to find potential solutions for renewable energy systems and investigates several economic parameters including the net present cost (NPC) and cost of energy (COE).
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Fig. 1. Map showing the geographic location of Gadeokdo Island.
1.1. Location and population Several prior studies were conducted to propose optimal renewable energy generation systems for islands in South Korea. Park, Yoo, Ohm, and Kwon (2016) proposed the optimal renewable electricity generation system for Geoje Island, one of the largest islands in South Korea. With the combination of wind turbines and photovoltaic (PV) arrays, the suggested system can sell the electricity through the currently used grid connection ($465,945) and achieve $0.472 per kWh COE. Yoo et al. (2014) attempted to the independent renewable electricity generation system for Ulleungdo island, one of the most eastern islands in South Korea. With two currently operated diesel generators, the system achieved 97.3% of renewable fraction with $0.334 per kWh COE. Moreover, because two diesel generators only produced the 3% amount of total electricity production, the possibility for the independent renewable electricity generation system was introduced. Chae, Lee, Won, Park and Kim (2015) proposed an inverted remote micro grid system for Gasado Island, one of the western islands in South Korea. The optimal configuration organized by PV arrays, wind turbines, diesel generators and batteries showed 94% of renewable fraction and $1.284 per kWh COE. Although there are several investigations in South Korea, only few studies were conducted to present economic feasibility tests of renewable electricity generation systems for the southern islands in South Korea. Therefore, the current study aims to present renewable electricity generation systems for Gadeokdo Island, one of the southern islands in South Korea.
Fig. 2. Average monthly solar radiation and clearness index for Gadeokdo Island.
demand for the island is calculated to be 33,954 kWh/d while the peak energy demand is calculated to be 2049 kW. The load factor of this island is computed as 0.691. 2.3. Solar energy information The 2013 data for daily solar radiation and solar clearness collected by the National Aeronautics and Space Administration (NASA) and the Korea Meteorological Administration (KMA) were used. The average annual solar clearness index is computed as 0.531, while the average daily radiation was calculated as 4.422 kWh/m2 /d. Fig. 2 shows the monthly average solar radiation and clearness index.
2. Status of Gadeokdo Island 2.4. Wind energy information 2.1. Location and population Gadeokdo Island is located in Busan Metropolitan city, in the southeastern area of South Korea, with coordinates 35.04 latitude and 128.83 longitude (Fig. 1), and an area of 20.78 km2 . The island has about 1300 households and 3800 residents.
The 2013 data for wind speed collected by the National Renewable Energy Laboratory (2014) were used. The annual average wind speed is calculated to be at 6.175 m/s. Fig. 3 shows the monthly wind speed. 3. Key parameters for the economic analysis
2.2. Load information 3.1. South Korea’s annual real interest rate The current energy demand of Gadeokdo Island is supplied mainly by the electricity grid. Based on data collected from the Korea Electric Power Corporation, the scaled annual average energy
The annual real interest rate is one of the most important input variables for a more realistic and accurate economic analysis. Based
116
E. Park, S.J. Kwon / Sustainable Cities and Society 23 (2016) 114–118 Table 1 Optimal renewable power generation system for Gadeokdo Island.
Fig. 3. Monthly average wind speed for Gadeokdo Island.
on the equations and methods introduced by Dursun (2012), and the nationally official rate presented by the Bank of Korea (2014), an annual real interest rate of 3.02% in South Korea is used in this study. 3.2. Cost of energy (COE) and net present cost (NPC) The COE is measured as “the average cost per kWh produced by the system” (Park & Kwon, 2016). The total cost is calculated as “all consumed costs of the system’s components with other additional costs” (Park & Kwon, 2016). The COE is the most significant economic output, because all optimized results are evaluated by the COE level (Madlener & Sunak, 2011). The NPC is one of the main simulation results. The present value for establishing and operating the system is included in the lifecycle cost. The current study hypothesized that 20 years would be the lifetime of optimal solutions (following the national energy plans introduced by South Korean government; Lewis, 2011; Ryu, 2010), based on calculations following the stages introduced by Dursun (2012). 4. Renewable power generation systems As this study aims to explore potential optimal renewable energy power generation systems, various components such as PV panels, wind turbines, converters, batteries and the grid, are explored in order to enhance the feasibility of the potential systems. The HOMER software needs to process the installation, replacement, and operating costs components. This study set $1800 for installation costs, $1800 for replacement costs, $25 for operating costs of PV panel and PV panel lifetime with no tracking system
Components
Index
PV (kW) Wind (# of turbines) Battery Converter (kW) Grid (kW) Initial capital ($) Operating cost ($/year) Total NPC ($) COE ($/kWh) Ren. frac.
8425 765 15,775 2735 0 48,379,976 1,260,290 70,325,584 0.326 1.00
of 20 years, based on previously proposed parameters (Bekele & Tadesse, 2012; Park et al., 2016). A range of 0 to 30,000 PV panels is considered in the simulation. For the wind energy component, a generic 10 kW wind turbine was considered. Capital costs of $29,000, replacement costs of $25,000, operation and management costs of $400 as well as 25 meters for hub heights, and 25 years lifetime for the turbine were used (Ani, Nzeako, & Obianuko, 2012; Park & Kwon, 2016). A range of 0–1500 wind turbines was used for the simulation. To connect the energy flow between DC and AC components, an electronic converter was used. Installation costs of $800, replacement costs of $750, 90% of system efficiency, and 15 years lifetime for the converter were used. A range of 0–5000 kW for the converter capacity was used (Baek et al., 2016; Demiroren & Yilmaz, 2010). Batteries are one of the essential components of sustainable and renewable power generation systems. A Surretts-6CS25P battery model, with a capacity of 6 V, 1156 Ah, and 9645 kWh was used in the simulation. Installation costs of $1229, replacement costs of $1229, and operation and maintenance costs of $10 were used. A range of 0–30,000 battery units was considered (Ngan & Tan, 2012). 5. Results 5.1. Simulation results This study considered PV panels, wind turbines, batteries, converters, and the grid in the HOMER software for developing optimal renewable power generation systems for Gadeokdo Island. Table 1 presents the optimal configuration of the simulation results, while
Table 2 Annualized costs of the system. Components PV Wind Grid Battery Converter System
Capital ($/year) 870,894 637,019 0 1,113,382 157,065 2,778,359
Replacement ($/year) 482,193 0 0 1,328.614 100,814 1,911,621
O&M ($/year) 210,625 153,000 −375,649 157,750 27,350 173,076
Fig. 4. Cash flow summary for simulation results.
Salvage ($/year) −311,958 0 0 −487,444 −25,005 −824,408
Total ($/year) 1,251,754 790,019 −375,649 2,112,301 260,224 4,038,649
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Table 3 Annual electrical component production, load, and quantity. Component
Fig. 5. Average electricity production for simulation results.
Table 2 shows the potential system’s annualized costs. In addition, Table 3 shows the electricity component production, load, and quantity of the simulation. In order to maximize the reliability of electricity systems, based on the simulation results, it is recommended that all components, i.e., PV panels, wind turbines, batteries, converters, and the grid, be used in the systems. By being connected to the grid system and selling the surplus electricity, the potential system can give rise to large amounts of savings. The cash flow summary based on the results is presented in Fig. 4, while the monthly average electricity production is shown in Fig. 5. The results for the PV and wind turbine output are presented in Figs. 6 and 7, respectively. Figs. 8 and 9 show the information concerning the battery units employed in this study. The optimal solution further indicates that 1,884,207 kg of carbon dioxide, 8169 kg of sulfur dioxide, and 3995 kg of nitrogen oxides are emitted.
Production (kWh/year)
Fraction
PV array Wind turbines Grid purchases
12,415,346 15,551,936 0
44% 56% 0%
Total
27,967,282
100%
Load
Consumption (kWh/year)
Fraction
AC primary load Grid sales
10,193,286 1,994,601
84% 16%
Total
12,187,887
100%
Quantity
Value
Units
Excess electricity Unmet load Capacity shortage Renewable fraction
9,754,596 10,274 12,392 1.000
kWh/year kWh/year kWh/year –
6. Discussion This study was conducted to investigate possible renewable power generation systems for Gadeokdo Island in South Korea. In order to explore the systems, possible optimal solutions were presented employing the HOMER software. The main conclusions of the simulation are as follows: – The derived optimal and efficient case suggests the use of 8425 kW of PV panels, 765 wind turbines (generic 10 kW), 15,775 batteries (Surrette S6CS25P), 2735 kW of converters, and an electricity grid. – The results also show costs of $48,379,976 for initial capital, $1,260,290 for operation costs per year, $70,325,584 for the total NPC, $0.326 per kWh COE, and 100% of renewable fraction ratio.
Fig. 8. Battery frequency histogram for simulation results.
– Based on the simulation, a sale of 2,981,340 kWh per year via the electricity grid is possible. This means that the current electricity grid can be used as a useful outlet for the sale of electricity from renewable power generation systems. Although establishing renewable power generation systems requires a huge budget, it can be efficient and useful in the long term (Atieh & Al Shariff, 2015). In addition, the current electricity grid can be used for the sale of electricity produced by renewable
Fig. 6. PV output for simulation results.
Fig. 7. Wind turbine output for simulation results.
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Fig. 9. Battery bank state of charge for simulation results.
power components in the systems. Given alternating the current system which is fully maintained by the electricity grid, the following stages could be adopted. – Gradual stages for establishing a renewable power generation system for Gadeokdo Island should be developed to reduce dependence on the current grid system. – After the system reaches a level that is able to cover the amount of electricity used, the current grid system could be used as a reserve. – When the facilities achieve the planned solutions, the grid can be used to sell electricity. 7. Limitations The current study has several notable limitations. First, this study does not consider any supporting policy currently in place in South Korea. Because the South Korean government operates a number of supporting programs, including several carbon-associated policies and the RPS policy (renewable portfolio standard policy; Chen, Kim, & Yamaguchi, 2014; Kim, Park, Kim, & Heo, 2012), the current results can be improved by showing better economic outputs if those components were included. Second, the simulation results cannot be generalized, as this study was conducted for a specific location. Third, the study does not take into consideration any economic theories or the effects on the energy industry. Several prior studies indicated that a number of economic effects such as learning effects can have a notable impact on the energy industry (Ryu, 2010). Future studies should consider the above-mentioned shortcomings, employ the results of the current study as baseline, and use this study as a guideline. Acknowledgement This work was supported by the Dongguk University Research Fund of 2015. References Ani, V. A., Nzeako, A. N., & Obianuko, J. C. (2012). Energy optimization at datacenters in two different locations of Nigeria. International Journal of Energy Engineering, 2(4), 151–164. Atieh, A., & Al Shariff, S. (2015). Case study on the return on investment (ROI) for using renewable energy to power-up typical house in Saudi Arabia. Sustainable Cities and Society, 17, 56–60. Baek, S., Park, E., Kim, M. G., Kwon, S. J., Kim, K. J., Ohm, J. Y., et al. (2016). Optimal renewable power generation systems for Busan metropolitan city in South Korea. Renewable Energy, 88, 517–525. Bekele, G., & Tadesse, G. (2012). Feasibility study of small Hydro/PV/Wind hybrid system for off-grid rural electrification in Ethiopia. Applied Energy, 97, 5–15.
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