Opportunities and Challenges of Solar and Wind Energy in South Korea: a Review

sustainability

Review Opportunities and Challenges of Solar and Wind Energy in South Korea: A Review

Mohammed H. Alsharif * ID , Jeong Kim and Jin Hong Kim Department of Electrical Engineering, College of Electronics and Information Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea; [email protected] (J.K.); [email protected] (J.H.K.) * Correspondence: [email protected]; Tel.: +82-2-6935-2650; Fax: +82-2-3408-4329

Received: 1 May 2018; Accepted: 30 May 2018; Published: 1 June 2018

Abstract: South Korea is the ninth biggest energy consumer and the seventh biggest carbon dioxide emitter in global energy consumption since 2016. Accordingly, the Korean government currently faces a two-fold signiﬁcant challenge to improve energy security and reduce greenhouse gas emissions. One of the most promising solutions to achieve the goals of sustainable development, energy security, and environmental protection is intensifying the role of renewable energy in electricity production. To this end, the Korean government plans to increase investments in the green energy ﬁeld, where solar and wind energy will soon play a decisive role toward meeting energy demands and achieving a climate-friendly environment. In this context, this study discusses the future of solar and wind energy in South Korea in four key aspects: (i) opportunities and potential achievement of the vision of government; (ii) potential daily energy output across different geographical areas; (iii) current status and prospects; and (iv) challenges and potential solutions.

Keywords: South Korea; renewable energy; sustainability; solar energy; wind energy; green energy

1. Introduction Energy security is one of the key issues in industrial countries, such as South Korea, which has been ranked as the ninth biggest energy consumer worldwide since 2016 [1]. In December 2017, the total energy production of the country was 441.2 TWh (Figure1). Energy security is defined as the uninterrupted availability of energy sources at an affordable price in the long term, that is, involving timely investments to supply energy in line with economic developments and environmental needs and in the short term by focusing on the ability of the energy system to react promptly to sudden changes in supply and demand. Several factors should be considered to guarantee energy security, such as energy sources, energy production and demand, operational expenditure (OPEX), and environmental issues [2]. Unfortunately, 84% of South Korea’s energy supply relies on non-renewable sources (coal, oil, and gas) [1,3], which represent the bulk of the country’s total imports because South Korea lacks these resources [4]. Figure1 presents a comprehensive vision of the energy sources, strategies, and policies of South Korea in 2017. However, the use of non-renewable sources is a growing concern for the government as it aims not only to reduce OPEX but also to decrease the overall environmental effects [5] because South Korea is, globally, the seventh biggest carbon dioxide (CO2) emitter [3]. One of the most promising solutions to achieve the goals of sustainable development, energy security, and environmental protection is intensifying the role of renewable energy for electricity production, especially because South Korea has renewable natural resources that enable it to pursue a sustainable energy strategy that combines energy, environment, economy, and society [5]. Moreover, the country’s rapid deployment of renewable energy and energy efficiency and its technological diversification of energy sources has resulted in significant energy security and

Sustainability 2018, 10, 1822; doi:10.3390/su10061822 www.mdpi.com/journal/sustainability Sustainability 2018, 10, 1822 2 of 23

Sustainability 2018, 10, x FOR PEER REVIEW 2 of 23 economic beneﬁts. Hitherto, the Korean government has been seeking to increase the percentage contributioneconomic benefits. of renewable Hitherto, energy the Korean from 6.5% government in 2017 has (Figure been1 )seeking to 11% to by increase 2030 according the percentage to the contribution of renewable energy from 6.5% in 2017 (Figure 1) to 11% by 2030 according to the “Fourth Basic Plan for New and Renewable Energy” [6,7]. Such an increase is sought to achieve “Fourth Basic Plan for New and Renewable Energy” [6,7]. Such an increase is sought to achieve efﬁcientSustainability development 2018, 10, x FOR and PEER to REVIEW ensure the sustainability of clean energy provision with improved2 of 23 efficient development and to ensure the sustainability of clean energy provision with improved planning [8,9]. planningeconomic [8,9]. benefits. Hitherto, the Korean government has been seeking to increase the percentage contribution of renewable energy from 6.5% in 2017 (Figure 1) to 11% by 2030 according to the “Fourth Basic Plan for New and Renewable Energy” [6,7]. Such an increase is sought to achieve efficient development and to ensure the sustainability of clean energy provision with improved planning [8,9].

Figure 1. Summary of energy sources, strategies, and policies of South Korea in December 2017 [10]. Figure 1. Summary of energy sources, strategies, and policies of South Korea in December 2017 [10]. Abbreviations: thou, thousand; bil, billion; mil, million; toe, tonne; KSA, Kingdom of Saudi Arabia; Abbreviations:UAE, United thou,Arab Emirates; thousand; bbl, bil, barrel; billion; LNG, mil, liquefied million; natural toe, tonne; gas. KSA, Kingdom of Saudi Arabia; UAE,Figure United 1. ArabSummary Emirates; of energy bbl, sources, barrel; st LNG,rategies, liqueﬁed and policies natural of South gas. Korea in December 2017 [10]. Abbreviations: thou, thousand; bil, billion; mil, million; toe, tonne; KSA, Kingdom of Saudi Arabia; The government will devote increased attention to solar and wind energy, which will play UAE, United Arab Emirates; bbl, barrel; LNG, liquefied natural gas. significantThe government roles in meeting will devote energy increased demands and attention in achieving to solar a climate-friendly and wind energy, environment which will in the play signiﬁcantlong-termThe roles plan government in of meeting the government. will energy devote demandsThe increased vision and ofattention the in government achieving to solar a andis climate-friendly to windincrease energy, the energy which environment contributionwill play in the long-termof significantsolar planstations roles of the and in government. meeting wind farms energy The to demands 14.1% vision and ofand the 18in.2%, governmentachieving respectively, a climate-friendly is to increaseof the total the environment renewable energy contribution in energy the of solarproductionlong-term stations byplan 2035 and of the wind(Figure government. farms 2) [5,11]. to The 14.1% Accordingly, vision and of the 18.2%, governmentsolar respectively,and wind is to increaseenergy of the researchthe total energyrenewable will contribution continue energy to productiondominateof solar bySouthstations 2035 Korea (Figureand inwind the2)[ farmscoming5,11 ].to Accordingly, decades14.1% and [12]. 18 .2%, solar respectively, and wind energyof the total research renewable will continueenergy to production by 2035 (Figure 2) [5,11]. Accordingly, solar and wind energy research will continue to dominate South Korea in the coming decades [12]. dominate South Korea in the coming decades [12].

Figure 2. Korean government’s long-term plan for new and renewable energy supply 2014–2035 [11]. Figure 2. Korean government’s long-term plan for new and renewable energy supply 2014–2035 [11]. Figure 2. Korean government’s long-term plan for new and renewable energy supply 2014–2035 [11]. Sustainability 2018, 10, 1822 3 of 23

South Korea lies between 35.9◦ N latitude and 127.7◦ E longitude and has a temperate climate with four distinct seasons and signiﬁcantly abundant sunlight and wind across different geographical areas [13]. The average daily solar radiation in South Korea is estimated to be 4.01 kWh/m2, varying between 2.56 kWh/m2 in December and 5.48 kWh/m2 in May, which is considered relatively high compared with other countries located at similar latitudes [14–16]. The average wind speed is estimated at 4.0 m/s, varying between 3.5 m/s in September and 4.6 m/s in March. Although the average wind speed may be low, the wind can generate a high amount of energy in winter, especially on the east and southeastern coasts, during strong surges of cold air, in which the wind speed reaches up to 8.5 m/s [17]. Accordingly, South Korea has an abundant potential for using these two renewable resources to generate energy, and endeavors for research and development in this area continue. As a major contribution, this study discusses these two main renewable resources in terms of opportunities and potential for achieving the government’s vision, potential daily energy output across different geographical areas, current status and prospects, and challenges and potential solutions. The rest of this study is organized as follows. Section2 highlights the data sources for this study and collection methods. The opportunities, potential energy output across different geographical areas, current status, and the Korean government’s long-term plan and prospects, as well as the challenges and limitations of solar and wind energy are discussed in Sections3 and4, respectively. A summary of the key recommendations to ensure energy sustainability and improved planning in the future concludes the study in Section5.

2. Data Sources and Collection Methods For the assessment of the solar and wind energy sectors and the exploration of the aspects of their development and the possibility of increasing their contribution in the future, knowing the current contribution of both forms of energy to total energy production is important. For the same reason, knowing the long-term plans of the future government about increasing the percentage of contribution of solar and wind energy to the total energy production and how comprehensively a government can advance these plans is also important. The sources of information in this field are numerous and diverse. In this study, several data factors were considered: the accuracy, suitability, adequacy, and timeliness of data. Therefore, we collected data from original and reliable sources, especially government agencies that are considered a good source of information in this field. Accordingly, the latest updated annual reports and periodic publications from the Korea Meteorological Administration (KMA) [14], National Institute of Meteorological Sciences (NIMS) [16], Korean Statistical Information Service (KOSIS) [18], Korean Ministry of Trade, Industry and Energy (MOTIE) [19], Korea Energy Economics Institute (KEEI) [20], and the Korean Energy Agency (KEA) [11] were comprehensively reviewed and analyzed. Moreover, the “Seventh Basic Plan for Long-Term Electricity Supply and Demand” [21] and the “Second South Korea Energy Master Plan” [22] that were developed by the Ministry of Trade, Industry, and Energy were reviewed. These national plans provide detailed information about the increase of installed capacity and a prediction of yearly electricity consumption until 2035. We also obtained data from studies that were published by reputable journals in this field. In this study, a combination of quantitative and qualitative approaches is adopted to maintain a balanced discussion in the main sections and ensure readability through a smooth flow of ideas. Each section presents a comprehensive discussion of the following areas: (i) opportunities and potential of using energy; (ii) comparison and analysis of the energy output across different geographical areas; (iii) current status and prospects; and (iv) challenges and potential solutions. The latest updated annual reports and periodic publications are reviewed in the following order:

(a) publications of central, state, and local governments; (b) technical reports and publications of the industry; and (c) articles by research scholars, universities, and economists. Sustainability 2018, 10, 1822 4 of 23 Sustainability 2018, 10, x FOR PEER REVIEW 4 of 23

3. Solar Energy ThisThis sectionsection presents presents a comprehensivea comprehensive vision vision about ab theout opportunities, the opportunities, comparison comparison and analysis and analysis of solar energyof solar output energy across output different across geographical different areas, geographical current status, areas, and prospects.current Furthermore,status, and thisprospects. section highlightsFurthermore, the challengesthis section and highlights limitations the of challe a solarnges energy and system.limitations of a solar energy system.

3.1. Opportunities and Potential of Solar EnergyEnergy South KoreaKorea isis located located between between 35.9 35.9°◦ N N latitude latitude and and 127.7 127.7°◦ E longitudeE longitude with with excellent excellent potential potential for usingfor using solar solar energy. energy. The averageThe average daily solardaily radiation solar radiation in South in Korea South is Korea estimated is estimated to be 4.01 to kWh/m be 4.012, varyingkWh/m2 between, varying2.56 between kWh/m 2.562 inkWh/m December2 in December and 5.48 kWh/mand 5.482 kWh/min May2 [ 14in– May16], as[14–16], shown as in shown Figure 3in. TheFigure monthly 3. The variationmonthly variation of solar radiation of solar radiation is largely is attributed largely attributed to the shift to inthe the shift elevation in the elevation angle of theangle sun. of Thethe sun. amount The ofamount direct solarof direct radiation solar inradi winteration in Southwinter Korea in South is 330–590 Korea is MJ 330–590 in December, MJ in 390–590December, MJ in390–590 January, MJ and in 370–470January, MJ and in February370–470 MJ [16 ].in The February rainy weather [16]. The in earlyrainy summer weather decreases in early thesummer global decreases horizontal the irradiance global horizontal in June and irradiance July. in June and July.

Figure 3. Monthly average daily solar radiation in South Korea [[23].23].

However, solar radiation varies from one city to another. The map of average daily solar However, solar radiation varies from one city to another. The map of average daily solar radiation radiation in Figure 4 reveals the high average daily solar radiation of over 5 kWh/m2 obtained in the in Figure4 reveals the high average daily solar radiation of over 5 kWh/m 2 obtained in the southeastern southeastern coastal area, including Jeju Island. By contrast, monthly average daily solar radiation is coastal area, including Jeju Island. By contrast, monthly average daily solar radiation is lowered to lowered to approximately 4.7 kWh/m2 in the northwestern region around Seoul, whereas Gochang, approximately 4.7 kWh/m2 in the northwestern region around Seoul, whereas Gochang, located at the located at the western coast of South Korea, shows the lowest monthly average daily solar radiation western coast of South Korea, shows the lowest monthly average daily solar radiation of 4.48 kWh/m2. of 4.48 kWh/m2. However, solar radiation in South Korea is considered relatively high compared with However, solar radiation in South Korea is considered relatively high compared with other countries other countries located at similar latitudes. For example, the annual average global horizontal located at similar latitudes. For example, the annual average global horizontal irradiation in Jeonju, irradiation in Jeonju, South Korea (latitude 36° N, longitude 127° E) is 4.01 kWh/m2, compared with South Korea (latitude 36◦ N, longitude 127◦ E) is 4.01 kWh/m2, compared with the 3.64 kWh/m2 of the 3.64 kWh/m2 of Tokyo, which is located at a similar latitude, but at a longitude of approximately Tokyo, which is located at a similar latitude, but at a longitude of approximately 139◦ E[15]. Moreover, 139° E [15]. Moreover, South Korea has more than 470 MJ distribution in Gyeongsang and east coast South Korea has more than 470 MJ distribution in Gyeongsang and east coast regions in December, regions in December, and cumulative distribution is over 470 MJ in most parts of the country except and cumulative distribution is over 470 MJ in most parts of the country except Jeolla’s west coast, Jeolla’s west coast, Ulleungdo, and Dokdo areas in January. Cumulative distribution is more than 450 Ulleungdo, and Dokdo areas in January. Cumulative distribution is more than 450 MJ in most areas MJ in most areas of Gyeongsang in February [16]. Accordingly, South Korea’s climatic conditions are of Gyeongsang in February [16]. Accordingly, South Korea’s climatic conditions are desirable for desirable for extending the utilization of photovoltaic (PV) systems due to the high amount of solar extending the utilization of photovoltaic (PV) systems due to the high amount of solar radiation radiation received throughout the year. received throughout the year. Sustainability 2018, 10, 1822 5 of 23 Sustainability 2018, 10, x FOR PEER REVIEW 5 of 23

Figure 4. Map of average daily solar radiation of South Korea [24]. Figure 4. Map of average daily solar radiation of South Korea [24].

3.2. Statistical Analysis and Comparisons 3.2. Statistical Analysis and Comparisons The daily energy output (E) of a PV system is directly proportional to the total solar panel area The daily energy output (E) of a PV system is directly proportional to the total solar panel or photovoltaic array area (A), efficiency of solar panel (r), daily average solar radiation (H), and area or photovoltaic array area (A), efficiency of solar panel (r), daily average solar radiation (H), performance ratio (PR). The E increases with a large A. Meanwhile, the A of the solar system is and performance ratio (PR). The E increases with a large A. Meanwhile, the A of the solar system is limited. Thus, the factor that can increase the E at limited A is solar radiation, where the output energy limited. Thus, the factor that can increase the E at limited A is solar radiation, where the output energy of the solar system increases with increasing solar radiation at constant A. However, PV panels offer ofrelatively the solar low system efficiency increases at 4–12% with increasing for thin film solar panels radiation and under at constant 22% forA. However,crystalline PVpanels panels [25,26], offer relativelywhich affect low the efficiency production at 4–12% of energy for thin regardless film panels of the and availability under 22% of forsolar crystalline radiation. panels In addition, [25,26], whichdirt, dust, affect tree the debris, production moss, of sap, energy water regardless spots, snow of the, and availability mold significantly of solar radiation. affect the Inperformance addition, dirt, of dust,PV panels, tree debris, thereby moss, causing sap, water further spots, reduction snow, in and the mold overall significantly efficiency. affect Accordingly, the performance the E of ofa PV PV panels,system thereby can be calculated causing further by using reduction the formula in the [23,27,28] overall efficiency. Accordingly, the E of a PV system can be calculated by using the formula [23,27,28] E = A × r × H × PR (1)

where A is the total solar panel area (m2);E r =isA the× solarr × H panel× PR yield or efficiency (%); which is calculated(1) based on the electrical power (kW) of one solar panel divided by the area of one panel (m2); H is the where A is the total solar panel area (m2); r is the solar panel yield or efﬁciency (%); which is calculated daily average solar radiation (kWh/m2); and PR is the performance ratio, and coefficient for losses 2 H basedrange on between the electrical 0.5 and power 0.9 with (kW) default of one value solar = 0.75. panel divided by the area of one panel (m ); is the 2 daily averageEquation solar (1) shows radiation that the (kWh/m energy); output and PR of isPV the depends performance on manufacturing ratio, and coefﬁcientfactors besides for losses solar rangeradiation. between To conduct 0.5 and 0.9the with analysis default and value comparison, = 0.75. a Sharp ND-250QCs model (polycrystalline) of Sustainability 2018, 10, 1822 6 of 23

Equation (1) shows that the energy output of PV depends on manufacturing factors besides solar Sustainability 2018, 10, x FOR PEER REVIEW 6 of 23 radiation. To conduct the analysis and comparison, a Sharp ND-250QCs model (polycrystalline) of PV Sustainability 2018, 10, x 2FOR PEER REVIEW 6 of 23 PVwith with an areaan area of 10 of m 10is m considered2 is considered in this in study this to study examine to examine the possibility the possibility of using PVsof using for residential PVs for residentialconsumptionPV with anconsumption area (private of 10 use), (privatem2 is representing considered use), representing 38.5%in this of study total38.5% to consumption of examine total consumption the (Figure possibility1 (Figure). Sharp of using 1). ND-250QCs Sharp PVs ND- for has a voltage of 29.80 V , current of 8.40 A, and power of 250 W with an area of 1.6 m2. More details 250QCsresidential has aconsumption voltage ofdc 29.80 (private Vdc, uscurrente), representing of 8.40 A, and38.5% power of total of consumption250 W with an (Figure area of 1). 1.6 Sharp m2. More ND- about the electrical and mechanical characteristics of this kind of PV are provided in [29]. Figure2 5 details250QCs about has athe voltage electrical of 29.80 and V dcmechanical, current of characteristics8.40 A, and power of this of 250 kind W withof PV an are area provided of 1.6 m in. More [29]. Figurepresentsdetails 5 about thepresents average the the electrical daily average energy and daily mechanical output energy for output the characteristics four fo citiesr the with four of thethis cities lowestkind with of solar thePV radiationlowestare provided solar in decreasing radiation in [29]. inorder—Gangneung,Figure decreasing 5 presents order—Gangneung, the Gochang, average Wonju, daily Gochang, energy and Seoul. output Wonju, The fo results rand the Seoul.four presented cities The with inresults Figure the presentedlowest4 reveal solar that in radiation theFigure daily 4 revealenergyin decreasing that output the ofdailyorder—Gangneung, PV isenergy estimated output to be Gochang,ofat PV least is estimated 5Wonju, kWh across and to Seoul.be different at least The cities, 5results kWh which presentedacross can different satisfy in Figure primary cities, 4 whichhouseholdreveal can that satisfy energy the daily primary consumption. energy household output ofenergy PV is consumption. estimated to be at least 5 kWh across different cities, which can satisfy primary household energy consumption.

Figure 5. Average daily energy output for four cities with the lowest daily solar radiation. FigureFigure 5.5. AverageAverage dailydaily energyenergy outputoutput forfor four cities with the lowest daily solar solar radiation. radiation. However, increased attention is devoted to Seoul city (capital) because it has the largest energy However,However, increased increased attentionattention isis devoteddevoted to Seoul city (capital) because because it it has has the the largest largest energy energy consumption compared with other cities; this consumption includes roughly half of the population, consumptionconsumption comparedcompared withwith otherother cities;cities; this consumptionconsumption includes includes roughly roughly half half of of the the population, population, as well as most industrial and commercial areas [18]. Figure 6 shows the monthly average of solar asas well well as as most most industrial industrial andand commercialcommercial areasareas [[18].18]. Figure 66 showsshows thethe monthlymonthly average of solar radiation in Seoul city over 37 years (1 January 1981 to 31 December 2017) according to the hourly radiationradiation inin SeoulSeoul citycity overover 3737 yearsyears (1(1 JanuaryJanuary 1981 to 31 December 2017) 2017) according according to to the the hourly hourly solar radiation data obtained from the KMA [30]. Table 1 presents the basic statistics related to the solarsolar radiation radiation datadata obtainedobtained fromfrom thethe KMAKMA [[30].30]. Ta Tableble 11 presentspresents thethe basicbasic statisticsstatistics related to the collected data. collectedcollected data. data.

FigureFigureFigure 6. 6.6. Monthly MonthlyMonthly average averageaverage of of solar solar radiatio radiationradiationn inin SeoulSeoul city city over over 37 37 years. years.

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Table 1. Summary of the descriptive statistics of the solar radiation data from KMA

Variables Value of Daily Average Value of Monthly Average Number of readings 13,513 444 Minimum (W/m2) 9.4 85.6 Maximum (W/m2) 676.2 377 Mean (W/m2) 244.6 244 Median (W/m2) 244.8 244.5 Standard deviation 117.25 58.6 Range 666.8 291.4

Figure6 indicates that the highest average value of solar radiation was 338.7 W/m 2 on May, whereas the lower adjacent was 251.1 W/m2 and the upper adjacent was 377 W/m2. The red cross represents the outliers with almost all outliers being lower adjacent. Thus, the outliers should not be considered to reduce their effect on the collected data, in which the two lower outliers were 209.2 W/m2 and 224.8 W/m2, which occurred on May 1990 and 1981, respectively. The lowest average value of solar radiation was 166.1 W/m2 on December, whereas the lower adjacent was 129 W/m2 in December 1992 and the upper adjacent was 207.7 W/m2 in December 1985. The two lower outliers 98.3 W/m2 and 113.4 W/m2 occurred in December 1990 and 1991, respectively. By contrast, September witnessed the largest variation in solar radiation which may be attributed to seasonal weather fluctuations in this period of the year. Hence, solar energy is considered the most promising energy source among all renewable energy sources due to its suitability for application in vast areas of South Korea and in remote areas where electrification progress and success rates are remain low due to geographical limitations and challenging terrains, making access to these sites difficult [31]. Moreover, the deployment of solar energy systems includes many benefits for environment, economy, and society. Perhaps the most important benefit is its environment friendliness with its negligible emissions of harmful gases or pollutants; wherein, an emission of approximately 0.7 kg of CO2 is prevented when generating solar power per each kWh [32]. In addition, solar energy systems have low operation and maintenance costs. The following section highlights in details the current status of installed solar stations in terms of locations and capacity and discusses the cumulative energy production of solar stations over the last decade (2007–2016). In addition, the next section presents the government’s future vision and plans for its solar energy project.

3.3. Current Status and Prospects Solar energy is considered to be the most important renewable energy in South Korea and the capacity of the PV systems installed in South Korea is rapidly increasing as shown in Figure7. The cumulative capacity of PV systems in 2016 was 5000 MW which amounted to 32.5% of the total capacity of new and renewable energy in South Korea [33]. The proportion of the PV systems was 26.3% in 2015 and the increase in the relative proportion of the PV systems continued in recent years. The installed PV systems are classified into two types in accordance with those purposes. A solar power plant is for the commercial profits and the others are for the private use. In South Korea, the commercial PV systems are usually installed and the total cumulative capacity of the commercial PV systems was 4450 MW in 2016. On the other hand, the total cumulative capacity of the PV systems for the private use was only 551 MW [34]. In 2017, South Korea has 5.7 GW of generating capacity from solar power and 1.2 GW from wind power [35]. Moreover, the Korean government seeks to increase contribution of the solar power to 37 GW and wind power to 16.5 GW by 2030 [33,36]. The largest solar power plant in South Korea was recently constructed in Haenam, South Jeolla Province. The installed capacity of the system is amounts to 57 MW with which the electricity can be supplied to more than 20,000 families [34]. Moreover, the construction of the biggest floating solar power plant in the world is expected to be finished by 2020. The power plant will be Sustainability 2018, 10, 1822 8 of 23 capable of generating 100 MW of electricity that will be sufficient to supply power to approximately

140,000Sustainability residents 2018 [, 3710,]. x FOR PEER REVIEW 8 of 23

5000 5000 4500 4000 3615 3500 3000 2481 2500 2000 1467 1500 959

Total capacity (MW) Total capacity 730 1000 524 650 357 500 81 0 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

FigureFigure 7. 7.Cumulative Cumulative solar power power capacity capacity in inSouth South Korea. Korea.

The largest solar power plant in South Korea was recently constructed in Haenam, South Jeolla Furthermore, the Korean government has established basic and detailed action plans for the Province. The installed capacity of the system is amounts to 57 MW with which the electricity can be technicalsupplied development to more than and 20,000 supply families expansion [34]. Moreover of the renewable, the construction energy, of and the gradual biggest floating decrease solar in use of coal andpower fossil plant fuel in [the19]. world In the is plans, expected the renewableto be finished energy by 2020. percentage The power of the plant total will energy be capable consumption of will begenerating expanded 100 up MW to 11%of electricity by 2030 that [6]. will Also, be the sufficient solar and to supply wind energypower willto approximately be promoted 140,000 as the most importantresidents energy [37]. sources with cutting down the role of the waste energy. Accordingly, the waste energy proportionFurthermore, of the new the and Korean renewable government energy willhas decreaseestablished to basic 29.2% and (67.0% detailed in 2014) action and plans the solarfor the energy proportiontechnical will development increase to and 14.1% supply (4.9% expansion in 2014) of by th 2035e renewable [11], as energy, shown and in Figure gradual2. decrease To accomplish in use this goal,of the coal Korean and fossil government fuel [19]. wouldIn the switchplans, th thee renewable new and renewableenergy percentage energy of market the total of Southenergy Korea consumption will be expanded up to 11% by 2030 [6]. Also, the solar and wind energy will be from the government-driven deployment to the market with the public–private partnership. promoted as the most important energy sources with cutting down the role of the waste energy. 3.4. ChallengesAccordingly, and the Potential waste energy Solutions proportion of the new and renewable energy will decrease to 29.2% (67.0% in 2014) and the solar energy proportion will increase to 14.1% (4.9% in 2014) by 2035 [11], as shownDespite in theFigure many 2. To beneﬁts accomplish offered this goal, by solarthe Korean cells, government some challenges would switch should the be new considered. and The followingrenewable paragraphenergy market highlights of South and Korea discusses from th thee government-driven most important challenges.deployment to the market with the public–private partnership. A. Cost 3.4. Challenges and Potential Solutions People strongly want to use solar energy systems, particularly for residential or personal consumption.Despite However, the many costbenefits is aoffered major by limitation solar cells, for some the widespreadchallenges should application be considered. of solar The energy. Accordingfollowing to theparagraph International highlights Energy and disc Agencyusses the [38 most], comparing important the challenges. cost of generating electricity from variousA. technologiesCost relies on the levelized cost of energy (LCOE) method. LCOE represents the per-unit value of the total cost (i.e., capital, operation, and maintenance fuel); it can be calculated using People strongly want to use solar energy systems, particularly for residential or personal the equationconsumption. [25,38 However,] cost is a major limitation for the widespread application of solar energy. According to the International Energy Agency [38], comparing the cost of generating electricity from OC r × (1 + r)T various technologiesLCOE =relies on the levelized× CRF cost+ OMC of energy+ FC (LCOE) with CRFmethod.= LCOE represents the per- (2) unit value of the total costCF (i.e.,× 8760 capital, operation, and maintenance fuel); (it1 can+ r be)T −calculated1 using the equation [25,38] where OC is the overnight construction cost (or investment without accounting for interest payments(2) LCOE = during construction), OMC is the series of annualized operation and maintenance (O&M) costs, FC is where OC is the overnight construction cost (or investment without accounting for interest payments the series of annualized fuel costs, CRF is the capital recovery factor, CF is the capacity factor, r is the during construction), OMC is the series of annualized operation and maintenance (O&M) costs, FC discountis the rate, series and of annualizedT is the economic fuel costs, life CRF of is the the plant. capital recovery factor, CF is the capacity factor, r is theFigure discount8 summarizes rate, and T LCOE,is the economic O&M, life and of fuel the plant. costs for the baseload technologies of electricity generation at 3% discount rate based on the International Energy Agency (IEA) report [38]. It is clear that the LCOE for various scenarios of solar technologies—namely, residential, Sustainability 2018, 10, 1822 9 of 23 Sustainability 2018, 10, x FOR PEER REVIEW 9 of 23 commercial,Figure and 8 summarizes large ground-mounted—are LCOE, O&M, and fuel US$ costs 155.56/MWh for the baseload (US$ technologies 0.156/kWh of = electricity 170.04 South Koreangeneration Won), at US$ 3% discount 122.56/MWh rate based (US$ on the 0.123 Internat /kWhional Energy = 134.07 Agency Won), (IEA) and report US$ [38]. 101.86/MWhIt is clear that the LCOE for various scenarios of solar technologies—namely, residential, commercial, and large (US$ 0.102/kWh = 111.18 Won), respectively. By contrast, LCOE for conventional energy technologies ground-mounted—are US$ 155.56/MWh (US$ 0.156/kWh = 170.04 South Korean Won), US$ coal-pc800122.56/MWh is US$ (US$ 77.66/MWh 0.123 /kWh = (US$ 134.07 0.078/kWh Won), and US$ = 85.02 101.86/MWh Won), (US$ coal-pc1000 0.102/kWh is = US$ 111.18 74.30/MWh Won), (US$respectively. 0.074/kWh By = contrast, 80.66 Won), LCOE andfor conventional combined energy cycle gastechnologies turbine coal-pc800 (CCGT) is US$ US$ 77.66/MWh 121.82/MWh (US$(US$ 0.122/kWh 0.078/kWh = 132.98= 85.02 Won).Won), coal-pc1000 Despite the is sustainedUS$ 74.30/MWh decrease (US$ in 0.074/kWh the costs = of80.66 solar Won), energy and over the lastcombined few years, cycle gas LCOE turbine of solar(CCGT) energy is US$ technology121.82/MWh is(US$ still 0.122/kWh higher compared = 132.98 Won). with Despite conventional the technologiessustained for decrease electricity in the generation costs of solar [39,40 energy]. The ov mainer the reason last few for theyears, signiﬁcant LCOE of increase solar energy in LCOE of solartechnology energy is technology still higher compared is the large with variations conventional in technologies capital costs. for Capitalelectricity cost generation accounts [39,40]. for over 80% ofThe LCOE main reason for solar for the energy significant technology increase andin LCOE accounts of solar for energy under technology 60% in conventionalis the large variations fossil fuel technologiesin capital (e.g., costs. coal, Capital gas cost combined accounts cycle)for over [38 80].% Fuel of LCOE costs for are solar the energy major technology component and in accounts the majority for under 60% in conventional fossil fuel technologies (e.g., coal, gas combined cycle) [38]. Fuel costs of fossil fuel technologies. Moreover, fossil fuels produce negative externalities at the local level are the major component in the majority of fossil fuel technologies. Moreover, fossil fuels produce (e.g.,negative local air externalities pollution) andat the global local level level (e.g., (e.g., local GHG air pollution) emissions), and whereas global level solar (e.g., energy GHG technologies emissions), do not. Evidently,whereas solar comparing energy technologies solar energy do technology not. Evidentl withy, comparing fossil fuel solar technologies energy technology without with accounting fossil for thesefuel externalities technologies would without be biased.accounting for these externalities would be biased.

Figure 8. LCOE, O&M, and fuel costs for baseload technologies of electricity generation with various Figure 8. LCOE, O&M, and fuel costs for baseload technologies of electricity generation with various scenarios of solar technologies. scenarios of solar technologies. To overcome this challenge, the solution has two points that should be achieved with the support Toand overcome encouragement this challenge, of the government: the solution has two points that should be achieved with the support and encouragementi. In the last decade, of the government:solar energy technology has experienced strong support of the government through various policies. After nearly one decade (2002–2011) of experience with feed-in tariffs i. In the last decade, solar energy technology has experienced strong support of the government (FITs), South Korea replaced FITs with the renewable portfolio standards (RPS) scheme in 2012 through[41]. The various renewable policies. portfolio After nearlystandards one (RPS) decade subsidies (2002–2011) policy of led experience to increase with the feed-in tariffscompetitiveness (FITs), South of Koreasolar energy replaced and FITsrelated with indu thestries renewable by reducing portfolio costs and standards encouraging (RPS) new scheme intechnological 2012 [41]. The developments renewable through portfolio competition standards among (RPS) both subsidies renewable policy sources led and to electricity increase the competitivenesssuppliers. RPS refers of solar to regulations energy and that related requir industriese electric power by reducing suppliers costs to supply and encouraging a minimum new technologicalpercentage or developments amount of their through loads through competition eligible among renewable both energy renewable sources. sources RPS andapplies electricity to suppliers.13 electricity RPS suppliers. refers to regulationsThe annual renewable that require energy electric quota power of individual suppliers suppliers, to supply which a minimum is percentagefixed until or 2022, amount is calculated of their loadsby multiplying through eligibletheir total renewable electricityenergy generation sources. (excluding RPS applies that to 13from electricity renewables) suppliers. by the The annual annual obligatory renewable RPS pe energyrcentage. quota Thisof percentage individual was suppliers, initially set which at is ﬁxed until 2022, is calculated by multiplying their total electricity generation (excluding that from renewables) by the annual obligatory RPS percentage. This percentage was initially set at 2% in 2012 and is planned to reach 10% by 2022 [42,43]. However, still need to overcome a few Sustainability 2018, 10, 1822 10 of 23

technical, ﬁnancial, regulatory, and institutional barriers. Accordingly, the complementary policies to alleviate market risks for small suppliers may be required. An optional FIT for small increments in capacity is a probable policy option. Besides, better ﬁnancing infrastructure needs to be devised by cooperation between NGOs and government organizations to spur the PV industry and boost the consumption of its products. Thus, we can conclude that the continued support for several decades through policies is necessary to maintain and enhance the growth of solar energy. ii. Despite the huge technical potential for large-scale deployment of solar energy technologies with acceptable cost in South Korea, the country needs to increase the independence of manufacturers and reliance on local solar cell manufacturers to greatly reduce costs and enhance the growth of solar energy.

B. Energy Source Solar energy availability is intermittent and unpredictable and can only be used during the day. Solar energy is also vulnerable to changes in weather conditions such as sudden onsets of cloudy or rainy weather [44]. Fortunately, competent short and long-term forecasting and careful planning and analysis help us to arrive at an optimal solution to these limitations. Moreover, uninterrupted power supply may be ensured through the design of the solar system: i. Stand-alone solar system (off-grid PV solar power): The territory of South Korea has approximately 3000 islands, of which around 500 are inhabited. Most of these islands are quite far from the mainland, and the supply of electricity from the mainland to such islands is unfeasible. Currently, most of these islands use diesel generators to produce electricity. Thus, stand-alone PV systems are ideal for remote rural areas and applications wherein other power sources are either impractical or unavailable. To ensure an uninterrupted power supply, a solar system should be coupled with storage devices or other energy sources. However, batteries are important elements and the heart of any stand-alone solar power system, whether that is using a large array of panels to power a home or farm. During hours of sunshine, the PV system is directly fed to the load, with excess electrical energy being stored in the batteries for later use. During the night, or during a period of low solar irradiance, such as a cloudy or rainy day, energy is supplied to the load from the battery. ii. Hybrid solar system (on-grid PV solar power): A solar system connected to the power grid is the most commonly used system in major cities and solar power plants. The hybrid solar system saves more money with solar panels through better efﬁciency rates and net metering, as well as lowering equipment and installation costs. Batteries and other stand-alone equipment required for a fully functional off-grid solar system are unnecessary in the hybrid solar system. Therefore, grid-tied solar systems are generally cheaper and simpler to install. Moreover, home solar panels often generate more electricity than what is typically consumed. With net metering, homeowners can place this excess electricity in the utility grid, and utility companies purchase electricity from homeowners at the same rate they sell it themselves.

C. Technical Hindrances i. Lightning strikes may damage electronic components. Diodes, which are mounted on the termination box under each panel, may either crack or short circuit under high humidity and heat conditions. Monitoring systems in solar power plants can easily determine the faults, whereas, the government can develop a program to train those who wish to use the home solar system about its basic operation, maintenance, and management. ii. Building capacity is vital to producing a workforce for the successful implementation of PV systems. Training and producing a competent workforce to drive industry growth and PV diffusion is yet another challenge that this industry faces. A focused, collaborative, and goal-oriented workforce is required to achieve technological leadership in PV. To generate Sustainability 2018, 10, 1822 11 of 23

a competent workforce, the government can develop a program to train those wishing to use the home solar energy system about its basic operation, maintenance, and management. iii. The increasing distance between solar power plants and homes increases costs and complicates the industry’s risk management of transmission technologies. Establishing a systematic approach to maximize the use of existing network assets is, therefore, important. In locations where solar power plants are small and dispersed over the low voltage grid (e.g., rooftop solar PVs), managing the interface between the high voltage transmission network and low voltage local networks is a priority. Careful planning and analysis also help reach optimal solutions. Moreover, enhancing intra-industry cooperation is needed for expanding the PV supply chain and motivating technical knowledge sharing through conferences and workshops.

D. Ecological and Social Impacts After the complete life cycle of solar modules (20–30 years), safety, environmental, and health concerns arise because the disposal of the modules is another challenge [45,46]. Most estimates of life cycle emissions for PV systems are between 0.07 and 0.18 pounds of CO2 per kWh [26]. Thus, the disposing of the large quantities of modules in a single landfill can cause potential risks to humans and biota (i.e., animal and plant life of an area during a time period). Harmful chemicals can seep into these landfills and contaminate local ground and surface water. The future solar market is assessed to be fairly large. Thus, now is the perfect time to plan the management of future solar waste, as any delay may result in the tedious task of attending to tons of waste. Various toxic materials are utilized in the manufacturing process of solar modules, especially in the extraction of solar cells. Cadmium (Cd) is a toxic element that is utilized in the thin film of solar cells as a semiconductor converting solar energy into electrical energy. According to the National Institute of Occupational Safety & Health, Cd dust and vapors can cause severe diseases, such as cancer. Many other harmful chemicals are also used as solvents for cleaning dust and dirt from PV modules. Upon seeing their harmful effects, the European Union prohibited the use of Cd, Pb, Hg, and other harmful compounds as per the regulations of the Restriction of Hazardous Substances Directive [45]. This prohibition emphasizes that research on new materials is crucial for this industry. Solar power plant projects require relatively large areas for deployment and last 15–20 years or more, thereby preventing land usage for any other purpose. Utility-scale PV systems commonly require approximately 3.5–10 acres per megawatt [26]. This requirement is a serious concern as several current issues relate to this problem, such as the population explosion that has already resulted in the occupation of several useful lands. Moreover, the removal of trees and bushes may be required to produce the optimum solar site if they happen to block sunrays, thereby adversely affecting wildlife. The Korean government has, therefore, resorted to establishing floating solar power plants since 2014. Establishing such power plants also allows the government to avoid social costs, especially on-land requisition problems. E. Performance Limitations PV panels offer a rather low efficiency at 4–12% for thin film panels and under 22% for crystalline panels [25,26]. In addition, dirt, dust, tree debris, moss, sap, water spots, snow, and mold significantly affect the performance of PV panels and may, thus, cause further reduction in the overall efficiency. Fortunately, efficiency may be improved through a dual-axis tracking system that allows wind, rain, and gravity to remove most debris and dust. Moreover, the dual-axis tracking system can increase the total amount of energy produced by a PV system by approximately 20–30% [23,47].

4. Wind Energy South Korea declared its plan to reduce its greenhouse gas emissions by 30% by 2020 to the international community by deploying renewable energy systems, especially wind energy conversion systems [31]. This section investigates the opportunities and feasibility of wind energy, as well as the Sustainability 2018, 10, 1822 12 of 23 prospects and challenges. In addition, wind directions in summer and winter seasons are discussed; Sustainabilityand a wind 2018 energy, 10, x FOR analysis PEER REVIEW for different cities of South Korea is provided. 12 of 23

4.1.4.1. Opportunities Opportunities and and Potential Potential of of Wind Wind Energy Energy WindWind energy energy is is another another free free available available energy energy source source that that can can be be converted converted to to electricity. electricity. AccordingAccording to to wind wind speed speed data data obtained obtained from from both both the the KMA KMA [14,30] [14,30 ]and and National National Institute Institute of of MeteorologicalMeteorological Science Science (NIMS) (NIMS) [17], [17 the], theannual annual aver averageage wind wind speed speed of South of Korea South is Korea 4.0 m/s, is varying 4.0 m/s, betweenvarying 3.5 between m/s in 3.5September m/s in and September 4.6 m/s in and March, 4.6 m/s as shown in March, in Figure as shown 9. In summer, in Figure the9. wind In summer, speed evidentlythe wind and speed considerably evidently anddecreases considerably compared decreases with that compared in winter. with This that seasonal in winter. variation This of seasonal wind speedvariation is deeply of wind related speed with is deeply the atmospheric related with pressure the atmospheric and wind pressure direction and in South wind directionKorea. Figure in South 10 depictsKorea. the Figure wind 10 monsoondepicts the trend wind that monsoon affects Sout trendh thatKorea affects in winter South and Korea summer. in winter In summer, and summer. the NorthIn summer, Pacific the atmospheric North Paciﬁc pressure atmospheric is directed pressure south isof directed South Korea south an ofd Southaffects Korea every andregion affects in South every Korea.region This in South condition Korea. directs This condition the wind directs in summer the wind considerably in summer southeast considerably or southwest. southeast orBy southwest.contrast, theBy main contrast, wind the direction main wind in directionwinter is innorthwest winter is in northwest most areas, in most and areas,northeast and wind northeast appears wind in appears some partsin some of the parts southwestern of the southwestern and southern and southern coasts of coasts Gyeongnam. of Gyeongnam. In addition, In addition, southwestern southwestern winds winds can becan seen be seenin Gangwon in Gangwon Province. Province. The The distribution distribution of ofwind wind direction direction reflects reﬂects the the northwestern northwestern wind wind systemsystem due due to to the the Siberian Siberian high high pressure pressure duri duringng winter winter in in the the northern northern part part of of Korea. Korea. TheThe change change of of wind wind direction direction when when season season changes changes is is one one of of the the weak weak points points of of using using wind wind energyenergy in in South South Korea. Korea. However, However, wind wind speed speed varies varies per per province. province. According According to to the the resource resource ‘Maps’ ‘Maps’ inin NIMS NIMS [17] [17 ]shown shown in in Figure Figure 11,11 ,most most of of inland inland areas areas have have low low wind wind speed speed at at less less than than 5.0 5.0 m/s. m/s. However,However, wind wind speed speed above above 7.5 7.5 m/s m/s can can be be observed observed in in the the mountainous mountainous regions regions of of the the nearby nearby east east coastcoast (Mt. (Mt. Seorak, Seorak, Mt. Mt. Odaesan, Odaesan, Mt. Mt.Taebaek, Taebaek, and Mt. and Deogyu), Mt. Deogyu), the southeastern the southeastern coast, and coast, Jeju and Island Jeju locatedIsland below located the below peninsula. the peninsula. In case of In offshore case of wind offshore, wind wind, velocity wind of velocity 6.5–7.0 m/s of 6.5–7.0 appears m/s in the appears east westin the coasts east of west Gangwon-do, coasts of Gangwon-do, and strong wind and strongspeed of wind 7.5 m/s speed or ofmore 7.5 is m/s observed or more on is the observed southern on coast.the southern Moreover, coast. the Moreover, average top the averagewind in topwinter wind of in more winter than of more8.5 m/ than s appear 8.5 m/ sin appear Jeju Island, in Jeju Gyeongnam’sIsland, Gyeongnam’s east coast, east and coast, Ga andngwon Gangwon Province Province mountainous mountainous areas areas (Mt. (Mt. Seorak, Seorak, Odaesan, Odaesan, and and Taebaek)Taebaek) in December. InIn January,January, stronger stronger than than 8.5 8.5 m/s m/s winds winds appear appear on on the the east east coast coast of Pohangof Pohang and andUljin, Uljin, along along the southwest the southwest coast ofcoast Jeju of Island Jeju andIsland Mokpo. and StrongerMokpo. Stronger than 8.5 m/sthan wind 8.5 m/s in February wind in is Februaryobserved is in observed Gangwon-do’s in Gangwon-do’s mountainous mountain area. In Gangwon-do,ous area. In Gangwon-do, the mountainous the areasmountainous in Gangwon-do areas inhave Gangwon-do winds of over have 8.5 winds m/s, andof over strong 8.5 winds m/s, and areobserved strong winds in the are east observed coast of Gyeongnam in the east Province,coast of Gyeongnamthe southwest Province, coast of the South southwest Jeonnam, coast and of Jeju South Island. Jeonnam, and Jeju Island.

2 Wind speed (m\s) 1

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

FigureFigure 9. 9. AverageAverage monthly monthly wind wind sp speedeed of of South South Korea Korea [17]. [17]. Sustainability 2018, 10, 1822 13 of 23 Sustainability 2018, 10, x FOR PEER REVIEW 13 of 23

(a) Summer

(b) Winter

Figure 10. Wind monsoonmonsoon trendtrend inin SouthSouth KoreaKorea inin winterwinter andand summersummer seasonsseasons [[8].8]. Sustainability 2018, 10, 1822 14 of 23 Sustainability 2018, 10, x FOR PEER REVIEW 14 of 23

Sustainability 2018, 10, x FOR PEER REVIEW 14 of 23

Figure 11. Meteorological map of wind speeds in South Korea [[17].17]. Figure 11. Meteorological map of wind speeds in South Korea [17]. Figure 12 shows the monthly average of wind speed for Seoul city (capital) over 37 years (1 Figure 12 shows the monthly average of wind speed for Seoul city (capital) over 37 years JanuaryFigure 1981 12 to shows 31 December the monthly 2017), average according of windto an speedhourly for solar Seoul radiation city (capital) data that over obtained 37 years from (1 (1 January 1981 to 31 December 2017), according to an hourly solar radiation data that obtained theJanuary Korea 1981 Meteorological to 31 December Administration 2017), according (KMA) to [30].an hourly solar radiation data that obtained from fromthe Korea the Korea Meteorological Meteorological Administration Administration (KMA) (KMA) [30]. [30].

Figure 12. Monthly average of wind speed in Seoul city over 37 years. Figure 12. Monthly average of wind speed in Seoul city over 37 years. Figure 12. Monthly average of wind speed in Seoul city over 37 years. Figure 12 reveals that the highest average value of wind speed was 2.85 m/s in March; whereas Figure 12 reveals that the highest average value of wind speed was 2.85 m/s in March; whereas the lower adjacent was 2.13 m/s and the upper adjacent was 3.52 m/s. While, the lowest average value the lowerFigure adjacent 12 reveals was that 2.13 the m/s highest and the average upper value adjace ofnt wind was 3.52 speed m/s. was While, 2.85 m/s the lowest in March; average whereas value the of wind speed was 2.0 m/s in September with lower adjacent was 1.35 m/s and upper adjacent was lowerof wind adjacent speed waswas 2.132.0 m/s m/s in and September the upper with adjacent lower adjacent was 3.52 was m/s. 1.35 While, m/s theand lowestupper averageadjacent valuewas 2.51 m/s. In a nutshell, use of wind energy in Seoul city is not recommended. of2.51 wind m/s. speed In a nutshell, was 2.0 m/suse of in wind September energy with in Seoul lower city adjacent is not recommended. was 1.35 m/s and upper adjacent was 2.51 m/s. In a nutshell, use of wind energy in Seoul city is not recommended. 4.2. Statistical Analysis and Comparisons 4.2. Statistical Analysis and Comparisons 4.2. StatisticalEvaluation Analysis of the andwind Comparisons power and energy per unit area is important in the assessment of the Evaluation of the wind power and energy per unit area is important in the assessment of the windwindEvaluation powerpower project.project. of the AA wind wind powerturbine and (WT) energy producesproduces per unit energyenergy area byby is convertingconverting important the inthe theflowing flowing assessment wind wind speed ofspeed the windintointo mechanical mechanical power project. energyenergy A windandand then turbine to electricity. (WT) produces WindWind powerpower energy isis bydetermined determined converting by by thethe the ﬂowingsize size of of rotor rotor wind blades, blades, speed windwind velocity,velocity, andand airair density. Moreover, the theoreticaltheoretical powerpower inin movingmoving air air is is the the flow flow rate rate of of kinetickinetic energyenergy perper secondsecond by a WT and is given byby thethe equationequation [48–50] [48–50] Sustainability 2018, 10, 1822 15 of 23 into mechanical energy and then to electricity. Wind power is determined by the size of rotor blades, wind velocity, and air density. Moreover, the theoretical power in moving air is the ﬂow rate of kinetic energySustainability per 2018 second, 10, xby FOR a PEER WT and REVIEW is given by the equation [48–50] 15 of 23

1 1 3 P = P =ρ AVρAV3 Cp Cp (3) 2 2 (3) where V is the monthlymonthly windwind speedspeed (m/s),(m/s), and and CpCp isis the the coefficient coefficient by Betz limit, which can achieve the maximummaximum valuevalue ofof 59%59% for for all all types types of of WTs. WTs.A Ais is the the swept swept area area (π D(π2D/4,2/4,D Dis is the the rotor rotor diameter diameter in min2 mand2 andπ =π3.1416), = 3.1416), and andρ is ρthe is the corrected corrected monthly monthly air densityair density (kg/m (kg/m3), which3), which can can be estimatedbe estimated by theby followingthe following equation equation [48– [48–50],50], P ρ =P , (4) ρ = RT, RT (4) 2 where PP isis thethe monthlymonthly mean mean air air pressure pressure (N/m (N/m);2);T Tis is the the monthly monthly mean mean air air temperature temperature (K); (K); and andR isR theis the specific specific gas gas constant constant for for air air (287 (287 J/kg J/kg K). K). 2 As shown in Equation (3), if the rotor area in m2 is fixed fixed and the air density is fixedfixed for a givengiven location, then the energy containedcontained in windwind isis onlyonly dependentdependent onon thethe windwind speed.speed. Then, we can 3 simplify the aforementionedaforementioned equation to obtain K.V3,, where where K K is is a fixedfixed constantconstant representing the combined fixedfixed rotor blade area, air mass,mass, andand efficiencyefficiency ofof thethe turbine.turbine. Thus, the “available wind energy is proportional to the cube of the wind speed”speed” or wind velocity. This statement is important because a small change in wind speed resultsresults inin aa hugehuge changechange inin thethe powerpower containedcontained withinwithin it.it. The power output from WT to anotheranother varies due toto differentdifferent manufacturingmanufacturing factors besides wind speed. In our case, choosing a suitable wind turbine for low wind speed and considering wind energy potential for different regions, where the performance of wind energy generator increases in open areas are are important. important. The The Skys Skystreamtream 3.7 3.7 WT WT model model is considered is considered in this in this study study to investigate to investigate the thepossibility possibility of using of using WTs WTs for for residential residential consumptio consumptionn (private (private use). use). The The Skystream Skystream 3.7 3.7 WT WT model, model, designed for homes and businesses, paved the way as the firstfirst compact, all-inclusive personal wind generator (with(with built-inbuilt-in controls controls and and inverter) inverter) designed designed to workto work in very in very low winds.low winds. More More details details about theabout electrical the electrical and mechanical and mechanical characteristics characteristics of the Skystream of the Skystream 3.7 WT are3.7 providedWT are provided in [51]. Figure in [51]. 13 showsFigure the13 shows estimation the estimation of annual of energy annual output energy for ou varioustput for wind various speeds wind that speeds represents that represents all possible all areaspossible of Southareas of Korea. South InKorea. addition, In addition, Figure Figure12 illustrates 12 illustrates that wind that wind energy energy production production is much is much less thanless than that ofthat solar of energy,solar energy, which explainswhich explains why the wh usey ofthe wind use generatorsof wind generators is uncommon is uncommon in residential in consumptionresidential consumption (home systems). (home systems).

Figure 13. Estimated annual energy production for various wind speeds of the Skystream 3.7 WT model for residential use.

However, wind farms (stations) in open areas that include a set of WTs achieve positive results. A total of 51 wind farms are installed in South Korea. Moreover, the Korean government plans to invest approximately $7.5 billion into wind farms to increase the total capacity to 2.5 GW by 2019 [31]. Details are provided in the following section.

Sustainability 2018, 10, 1822 16 of 23

4.3.Sustainability Current Status 2018, 10 and, x FOR Prospects PEER REVIEW 16 of 23 4.3.This Current section Status highlights and Prospects details about the cumulative wind energy production over the last decade (2007–2016),This section the location highlights and details capacity about of the cumulative current wind wind farms, energy and production the government’s over the last strategies decade and future(2007–2016), plans. the location and capacity of the current wind farms, and the government’s strategies and futureFigure plans. 14 shows the cumulative production of wind power in South Korea over the last decade. Evidently,Figure the 14 power shows the output cumulative increases production annually, of wind which power reflects in South the Korea high over interest the last of decade. the Korean governmentEvidently, to the shift power toward output green increases energy annually, and reduce which the significantreflects the economichigh interest and of ecological the Korean influence of energygovernment provided to shift by fossiltoward fuels green in the energy coming and years reduce [52 ].the The significant cumulative economic wind powerand ecological was 1089 MW in 2016influence from of 51 energy installed provided sites andby fossil 345 unitsfuels in [53 the], incoming which years the cumulative[52]. The cumulative wind power wind increasedpower by was 1089 MW in 2016 from 51 installed sites and 345 units [53], in which the cumulative wind power 20.20% compared with that in 2015 (869 MW) [54]. The highest cumulative wind power produced increased by 20.20% compared with that in 2015 (869 MW) [54]. The highest cumulative wind power wasproduced in Gangwon, was in which Gangwon, was 189,140which was kW 189,140 from 11kW sites from and 11 sites 113 units,and 113 whereas, units, whereas, the lowest the lowest wind power producedwind power was inproduced Busan’s was wind in Busan’s farm, whichwind farm, was whic 750 kWh was from 750 kW one from site andone site one and unit one [53 unit]. In [53]. addition, theIn cumulative addition, the wind cumulative power generated wind power by generated Jeju’s wind by farmsJeju’s wind was 128,150farms was kW. 128,150 Figure kW. 15 summarizesFigure 15 the locationsummarizes and capacity the location of the and installed capacity wind of the farminstalled in South wind farm Korea. in South Korea.

1200 1089

1000 869

800 612 560 600 488 425 351 382 400 304 Total capacity (MW) Total capacity 196 200

0 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

FigureFigure14. 14. CumulativeCumulative wind wind power power capacity capacity in South in South Korea Korea [54]. [54].

MostMost wind wind farms farms areare inin Gangwon Province Province and and JejuJeju Island Island due to due the tostrong the strongwinds in winds winter in ofwinter more than 9 m/s that appeared in Jeju Island, Gyeongnam’s east coast, and Gangwon Province of more than 9 m/s that appeared in Jeju Island, Gyeongnam’s east coast, and Gangwon Province mountainous areas (Mt. Seorak, Odaesan, and Taebaek) in December. In January, stronger than 9 m/s mountainouswinds appeared areas on (Mt. the Seorak, east coast Odaesan, of Pohang and and Taebaek) Uljin and in along December. the southwest In January, coast stronger of Jeju Island than 9 m/s windsand appeared Mokpo. Stronger on the eastthan coast 9 m/s of of Pohang wind was and ob Uljinserved and in alongin Gangwon-do’s the southwest mountainous coast of Jeju area Island in and Mokpo.February. Stronger In Gangwon-do, than 9 m/s the of windmoun wastainous observed areas have in in widespread Gangwon-do’s winds mountainous stronger than area9 m/s, in and February. In Gangwon-do,strong winds can the be mountainous seen in the east areas coast have of Gy widespreadeongnam Province, winds southwest stronger than coast 9 of m/s, South and Jeonnam, strong winds canand be seenJeju Island in the [17]. east coast of Gyeongnam Province, southwest coast of South Jeonnam, and Jeju Island [17Jeju]. Island is a major island off the southern end of the South Korea, where the construction of anJeju offshore Island wind is a majorfarm is islandplanned off based the southern on the ex endcellent of thewind South energy Korea, resources. where In the1992, construction a wind of turbine with a 250 kW capacity was installed near Jeju Island. This was the first wind turbine an offshore wind farm is planned based on the excellent wind energy resources. In 1992, a wind turbine connected to the national grid in the country [31]. After that, the construction of wind energy farms with a 250 kW capacity was installed near Jeju Island. This was the ﬁrst wind turbine connected to the rapidly increased due to the highly increasing demand of electricity. In the sea off of Gujwa-eup, 2- nationalMW and grid 3-MW in the wind country power [31 generators]. After that, were the installed construction as a test, of whereas wind energy 30-MW, farms 100-MW, rapidly and increased84- MW commercial wind farms are planned in the sea off of Hangyeong-myeon, Hanlim-eup, and Daejeong-eup of Jeju Island, respectively [55,56]. Sustainability 2018, 10, 1822 17 of 23 due to the highly increasing demand of electricity. In the sea off of Gujwa-eup, 2-MW and 3-MW wind power generators were installed as a test, whereas 30-MW, 100-MW, and 84-MW commercial wind farms are planned in the sea off of Hangyeong-myeon, Hanlim-eup, and Daejeong-eup of Jeju Island, Sustainability 2018, 10, x FOR PEER REVIEW 17 of 23 respectively [55,56].

Figure 15. Locations and capacity of wind farms in South Korea [53]. Figure 15. Locations and capacity of wind farms in South Korea [53].

Moreover,Moreover, several several studies studies [[57,58]57,58] have have been been conducted conducted to assess to assess the possibility the possibility of installing of installing off- off-shoreshore wind wind farmsfarms in different places places of of South South Korea. Korea. Kim Kim and and Kim Kim [59] [ 59assessed] assessed the wind the wind energy energy resourcesresources of the of Yulchonthe Yulchon district district in in Korea Korea and and conducted conducted aa comparativecomparative economic economic analysis analysis in inorder order to to determine the feasibility of establishing a 30 MW capacity wind farm. They shortlisted three wind determine the feasibility of establishing a 30 MW capacity wind farm. They shortlisted three wind turbines as potential candidates and conducted a techno-economic analysis to determine the turbinesoptimum as potential wind turbine candidates for the and Yulchon conducted district. a techno-economicThey shortlisted six analysis different to wind determine turbines the which optimum windare turbine best suited for the for Yulchon the development district. Theyof the shortlistedwind farm sixand different also estimated wind turbinestheir annual which energy are best suitedproductions for the development (AEP) and ofcapacity the wind factors. farm The and study, also estimatedconductedtheir by Kim annual et al energy. [58], focused productions on the (AEP) and capacityselection of factors. an optimal The candidate study, conducted site around by the Kim Korean et al. Peninsula [58], focused through on an the economic selection evaluation of an optimal candidatefor the site development around the of Korea’s Korean first Peninsula large-size through off-shore an wind economic farm. They evaluation used different for the criteria development to of Korea’sselect optimum first large-size site(s) which off-shore include wind the farm. expected They B/ usedC (benefit/cost) different criteriaratio, the to possible select optimuminstallation site(s) whichcapacity include of the the expectedwind farm, B/C the (benefit/cost)convenience of ratio, grid connection, the possible and installation so on. They capacity found that of the there wind are farm, the conveniencemultiple locations of grid around connection, the Korean and soPeninsula on. They best found suited that for therelarge-scale are multiple off-shore locations wind farms. around A the similar study was also conducted by Oh et al. [60] in order to assess the wind energy potential around Korean Peninsula best suited for large-scale off-shore wind farms. A similar study was also conducted the Korean Peninsula, and also to determine the feasibility of a 100 MW class off-shore wind farm. by OhLee et et al. al. [60 [61]] in conducted order to assessa feasibility the wind study energy to assess potential the wind around potential the of Korean the Younggwang Peninsula, district and also to determinein South the Korea, feasibility which of isa a100 candidate MW class site for off-shore the development wind farm. of Leean off-shore et al. [61 wind] conducted farm, which a feasibility is planned to be constructed by 2019. Sustainability 2018, 10, 1822 18 of 23 study to assess the wind potential of the Younggwang district in South Korea, which is a candidate site for the development of an off-shore wind farm, which is planned to be constructed by 2019. Wind farms play a decisive role in meeting energy demands and achieving a climate-friendly environment.Sustainability The2018, 10 Korean, x FOR PEER government REVIEW plans to invest approximately $7.5 billion in wind 18 farmsof 23 to increase the total capacity to 2.5 GW by 2019 [31]. Furthermore, the Korean government seeks to develop theWind solar farms and play wind a decisive power sectorrole in as meeting major alternativeenergy demands energy and resources, achieving which a climate-friendly will account for 11.0%environment. of total energy The production Korean government by 2035[ 31plans]. Wind to inve powerst approximately will play an $7.5 important billion in role wind in thefarms long-term to increase the total capacity to 2.5 GW by 2019 [31]. Furthermore, the Korean government seeks to deployment plan, where wind farms will supply 18.2% of total energy by 2035 [11]. develop the solar and wind power sector as major alternative energy resources, which will account 4.4. Challengesfor 11.0% of and total Potential energy production Solutions by 2035 [31]. Wind power will play an important role in the long- term deployment plan, where wind farms will supply 18.2% of total energy by 2035 [11]. Despite the huge potential and numerous benefits of wind energy, many challenges which may4.4. affect Challenges the future and Potential of wind Solutions energy should be considered. The main barriers and challenges are summarizedDespite as follows: the huge potential and numerous benefits of wind energy, many challenges which may affect the future of wind energy should be considered. The main barriers and challenges are A. Cost summarized as follows: FigureA. Cost 16 LCOE, O&M, and fuel costs for the baseload technologies of electricity generation with various scenarios of wind technologies at 3% discount rate. The LCOE for onshore wind Figure 16 LCOE, O&M, and fuel costs for the baseload technologies of electricity generation with and offshore wind are US$ 111.64/MWh (US$ 0.112/kWh = 122.08 South Korean Won) and various scenarios of wind technologies at 3% discount rate. The LCOE for onshore wind and offshore US$ 214.47/MWh (US$ 0.214/kWh = 233.26 Won), respectively. Meanwhile, the LCOE for conventional wind are US$ 111.64/MWh (US$ 0.112/kWh = 122.08 South Korean Won) and US$ 214.47/MWh (US$ energy0.214/kWh technologies = 233.26 coal-pc800 Won), respectively. is US$ 77.66/MWh Meanwhile, (US$the LCOE 0.078/kWh for conventional = 85.02 won),energy US$ technologies 74.30/MWh (US$coal-pc800 0.074/kWh is US$ = 80.66 77.66/MWh Won) for (US$ coal-pc1000, 0.078/kWh and= 85.02 US$ won), 121.82/MWh US$ 74.30/MWh (US$ (US$ 0.122/kWh 0.074/kWh = 132.98 = 80.66 Won) for CCGTWon) [for38 ].coal-pc1000, Despite the and general US$ 121.82/MWh sustained (US$ decrease 0.122/kWh in the = cost132.98 of Won) renewable for CCGT energy [38]. Despite for the past years,the the general LCOE sustained of wind decrease energy technologyin the cost ofis rene stillwable higher energy than for that the ofpast conventional years, the LCOE technologies of wind for electricityenergy generation. technology is The still mainhigher reason than that for of the conv increaseentional intechnologies the LCOE for of electricity wind energy generation. technology The is the significantmain reason variation for the increase in capital in costs,the LCOE which of wind accounts energy for technology more than is 80% the significant of LCOE forvariation wind energyin technology.capital costs, However, which theaccounts fact thatfor more positive than externality80% of LCOE that for wind green energy energy technology. technology However, (wind the energy) fact that positive externality that green energy technology (wind energy) does not rely on fuel, which does not rely on fuel, which is subject to significant price fluctuations and associated risks, should be is subject to significant price fluctuations and associated risks, should be considered. In addition, considered. In addition, using green energy technology may lead to reduced CO2 and other pollutant using green energy technology may lead to reduced CO2 and other pollutant emissions, decreased emissions,need for decreased other generation need for capacity, other generationand potentially capacity, reduced and need potentially for grid usage reduced and associated need for gridlosses usage and associated[34]. losses [34].

FigureFigure 16. LCOE, 16. LCOE, O&M, O&M, and and fuel fuel costs costs for forbaseload baseload techno technologieslogies of of electricity electricity generation generation with with various various scenarios of wind technologies. scenarios of wind technologies. Sustainability 2018, 10, 1822 19 of 23

Most wind turbine systems were supplied by local turbine manufacturers since 2011. However, one of the leading turbine manufacturers (Vestas) has 42.2% market share in the Korean wind energy industry, and many wind farm owners are not fully satisfied with Vestas’ service due to its high cost [53]. Increasing the independence of manufacturers and reliance on local turbine manufacturers may considerably reduce costs (replacement and maintenance). Nevertheless, local turbine manufacturers should enhance the size, length, cost, reliability, and efficiency of wind turbines. B. Energy Source Wind sources are intermittent and unpredictable. To ensure uninterrupted power supply, wind energy systems should be coupled with other energy sources (public electrical grid). In addition, competent short- and long-term forecasting and careful planning and analysis would help reach an optimal solution. C. Technical Hindrances i. Local turbine manufacturers should enhance the size, length, cost, reliability, and efficiency of wind turbines. Numerous manufacturing issues must be addressed because wind turbine components undergo excessive forces and tremendous joint stresses and failures. For instance, blades, towers, and casings must be able to withstand heat, cold, rain, and ice and adapt to changing wind speeds. Blades must also be constructed with a high strength-to-weight ratio, and thus research into new materials is crucial. ii. The increasing distance between offshore wind farms and destinations makes the costs and risk management of transmission technologies an even more complex challenge to the industry. Careful planning and analysis would help reach optimal solutions. iii. Turbines might cause noise due to turbine blades. However, this problem is resolved or greatly reduced through technological development and by choosing the locations of wind plants properly.

D. Environmental Factors Another barrier to using wind turbines is lightning activity—strikes by lightning and damage to the electronic components. However, this problem may be considerably reduced through technological developments and monitoring systems and through periodic maintenance that increases system performance.

5. Conclusions and Recommendations This paper discussed the opportunities, prospects, and challenges of solar and wind energy in South Korea. The findings of this study can help the decision of policy makers to frame strong policies by understanding the overall perspective of implementing solar and wind energy, considering the strength, weakness, opportunities, and challenges associated with it. Furthermore, the findings revealed that the opportunities and strengths of solar and wind energy are much stronger than their weaknesses and challenges. Hence, the present study strongly recommends the adoption, deployment, growth, and installation of solar and wind energy technology and related projects for a sustainable future in South Korea. Note that the results obtained are in the context of South Korea but more or less can be generalized to neighboring countries, because strengths, weaknesses, and opportunities are common attributes selected in research. Herein, some recommendations are suggested that can help in the decision-making process of policy makers to frame strong policies to efficiently develop and ensure sustainability with improved planning to provide clean energy.

• The southeastern coastal area, including Jeju Island, is considered a suitable place to establish solar power plants due to these locations having a high radiation rate of over 5 kWh/m2. In addition, Sustainability 2018, 10, 1822 20 of 23

using a dual-axis tracking system for the PV array increase the total amount of energy produced by a PV system by approximately 20% to 30%, and dual-axis tracking system also allows wind, rain, and gravity to remove most debris and dust. On the other hand, it is necessary to consider the area that will be uses for installation of solar power plants. Solar power plants floating on top of the water near these islands is recommended, thereby promoting land use to accommodate potential population growth in the future without any obstacles. • Jeju Island, Gyeongnam’s east coast, Gangwon Province mountainous areas (Mt. Seorak, Odaesan, Taebaek), the southwest coast of south Jeonnam, and the eastern coasts of Pohang and Uljin are a suitable places to use energy acquired from wind power. Moreover, the government should support and encourage local turbine manufacturers. The local turbine manufacturers need to make wind turbines larger, taller, less expensive, more reliable, and more efficient. • The infrastructure of transmission systems requires particular attention and care from officials to reduce transmission and distribution losses as much as possible. Careful planning and analysis would help reach the optimal solution. • Generally, renewable energy markets have experienced phenomenal growth in South Korea in the last decade because of significant technological improvements and government policies that support the development and utilization of renewable energy, thereby leading to a reduction in cost. Despite the huge technical potential, the development and large-scale deployment of renewable energy technologies in South Korea must overcome technical, financial, regulatory, and institutional barriers. The continued support through policies may be necessary to maintain and enhance the growth of renewable energy. In addition, the cooperation between the government and NGOs should be strengthened by devising an improved financing infrastructure to boost renewable energy technology and its products. • Excess energy of homes’ installed solar power systems can be added to the public electrical grid, and utility companies can buy electricity from homeowners at the same rate as they sell it themselves. • Competent forecasting and careful planning and analysis of solar radiation and wind speed would help achieve an optimal long term system.

In this study, we extensively reviewed the opportunities and prospects of solar and wind energy, as well as its present challenges and potential solutions. One of the most crucial challenges that solar and wind energy systems face is their energy source (i.e., solar radiation and wind, respectively) which is extremely variable. Such variability may increase risk and uncertainty levels in expected solar and wind energy generation, which is considered an inhibiting factor toward energy security. Thus, our future research will focus on the long-term prediction of mean hourly wind speeds and solar radiation values in a region. Such prediction is feasible through the application of a combination of different approaches to minimize the risk of failure within the energy system and to forecast its reliability by modeling or simulating future scenarios in line with the vision of the government.

Author Contributions: As the first author, M.H.A. wrote the main parts and the first draft of this paper as well as reviewed the literature on sustainable power supply. J.H.K. conducted a study on the locations and capacity of solar power plants in South Korea, and wrote Section 3.3 (current status and prospects of the solar power plants). J.K. revised the final version of paper. Acknowledgments: This work was supported by the Human Resources Development of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korean Ministry of Trade, Industry & Energy (no. 20164030201340). Conflicts of Interest: The authors declare that they have no competing interests. Sustainability 2018, 10, 1822 21 of 23

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