SAMSUNG Energy Plant: All-in-One Solution for Floating Power Plants with Gas-fired Combined Cycle Gas Turbines

SAMSUNG Energy Plant: All-in-One Solution for Floating Power Plants with Gas-fired Combined Cycle Gas Turbines GASTECH 2017 4-7 April, 2017 Chiba, Tokyo, Japan Myung-Kwan Song 1, Yongseok Song 2, Jeong Oh Hwang 3, Changwoo Lee 4, Wonkyu Lee 5 1 Principal Engineer, Ph.D./P.E., Mechanical Systems Research, Central Research Institute, Samsung Heavy Industries Co., Ltd., Republic of Korea, Email: mgkn.song@samsung.com 2 Senior Engineer, Innovative Marine Solutions Research, Central Research Institute, Samsung Heavy Industries Co., Ltd., Republic of Kore 3 Senior Engineer, HSE Research, Central Research Institute, Samsung Heavy Industries Co., Ltd., Republic of Korea 4 Senior Engineer, Ph.D., Mechanical Systems Research, Central Research Institute, Samsung Heavy Industries Co., Ltd., Republic of Korea 5 Assistant Engineer, Offshore Engineering Research, Central Research Institute, Samsung Heavy Industries Co., Ltd., Republic of Korea

Abstract The 500MW-class floating gas power plant, developed by Samsung Heavy Industries (SHI), is introduced. It is called SEP-T500GC, which is the acronym of SAMSUNG Energy Plant of the 500MW-class floating power plant with fuel storage Tanks using Gas turbine Combined cycle. The all-in-one type floating power plant is composed of the power generation facilities, clean liquified natural gas (LNG) fuel supplying facilities, and LNG cargo containment system, etc. These facilities are integrated in a hull structure so that they can float on the water. The fuel supply process of natural gas devised for SEP is proposed. Structural Reliability of SEP is verified through various advanced computational analyses. Trim and stability calculation is conducted to check on floating stability. Cargo hold analysis is conducted to secure structural safety of a hull structure and structural analyses of topside structures are fulfilled. And, hydrodynamic analysis is carried out to verify the serviceability of gas turbines and to calculate the acceleration considered in the structural analysis of topside structures. The investigation results are presented to verify the applicability of membrane-type LNG containment system to SEP. Finally, the mooring arrangments for jetty mooring and ship-to-ship mooring are proposed as the position keeping methods. Keywords SAMSUNG Energy Plant, Floating Power Plant, Barge Mounted Power Plant, Gas-fired, Combined Cycle, Gas Turbine, Steam Turbine, OTSG, Power Transmission System, Mooring System 1. Introduction The floating power plant is the power generating plant topped on a floating vessel to supply the power electricity to power demand areas. Conceptually, the power plant can be integrated with the kinds of barge, oil tanker, LNGC (LNG carrier), and FSRU (floating storage regasification unit) to be floating power plants. The initial concept of floating power plants is the concept of barge mounted power plant, which is generally called BMPP. This BMPP has no its own fuel containment system on its own vessel. Most of the recently-developed floating power plants have fuel containment system on their own vessels. For example, some shipbuilders, engineering companies, and business developers such as Daewoo Shipbuilding and Marine Engineering (South Korea), Hyundai Heavy Industries (South Korea), SEVAN (Norway), Karadeniz (Turkey), Mitsubishi Heavy Industries (Japan), and Wison (China), have announced their own newly-developed floating power plants. Most of floating power plants to date are BMPP-type and powership-type ([7]). BMPP-type is installed and operated very close to coast powership-type has propulsion system and so it has excellent mobility function, because they are conversion vessles from bulk carriers, etc. As the fuel of power generation in floating power plants, heavy fuel oil has been mostly used in reciprocating engines and natural gas has been mostly used in heavy duty and aeroderivative gas turbines. As a result of the recent stringent environmental regulations following the Paris COP2021 global deal to tackle greenhouse gas emissions, it can be predicted that the consumed quantity of liquid fuel such as heavy fuel oil will decrease. Because the price of LNG and LPG is still high, it is difficult to predict that gas will completely replace liquid fuel. However, as shale gas starts to be mined in the United States and gas prices continue to decline, the use of gas also in floating power plants is expected to increase much more, and it is also well in line with environmental regulations ([3]). More than 60 floating power plants are operating globally, e.g. Caribbean, Africa, Southeast Asia, India, USA, etc. Gas-fired power generation is a peak power generation due to cost structure, but it is also used as base power generation in recent years. Gas and renewable energy are on the verge of increasing the share of electricity generation. US shale gas production is expected to surge, gas prices drop, and cost competitiveness compared to existing

liquid fuels. The floating LNG thermal power generation is in the early stage, and the main ordering party will be IPP (independent power producer), and service providers are expected to be vessel owners to operate FSRU and LNG carriers. State-owned power generation companies will focus on large-scale power generation facilities for business development and operation, and facilities with low capacity will likely be IPPs. If the floating power plant replaces the existing oil-based power plant in the Caribbean region, about 10GW market is expected to be formed. In particular, Southeastern Asia such as Indonesia, Philippines, and Malaysia, and Africa such as Angola, Ghana, and Nigeria, are the countries with lacking power infrastructures. The business of floating power plants requires business cooperation with business developers, vendors of main equipments (gas turbines, engines, etc.), suppliers, etc., and so firstly, SHI needed our own proprietary model to prepare for future business expansion. In this paper, the 500MW-class floating gas power plant, developed by SHI, is introduced. It is called SEP- T500GC, which is the acronym of SAMSUNG Energy Plant of the 500MW-class floating power plant with fuel storage Tanks using Gas turbine Combined cycle. It will be called shortly SEP in this paper. SEP, the all-in-one type floating power plant is composed of the power generation facilities, clean LNG fuel supplying facilities, and LNG cargo containment system, etc. These facilities are integrated in the hull structure so that they can float on the water. Floating power plants could be built to supply electricy to the powr demand area on behalf of onshore power plants. In addition, floaitng power plants are applicable to a wide variety of power generation related fields. Floating power plants may supply power electricity necessary to offshore and subsea facilities. Floating power plants located right near LNG production fields could generate and transmit the electricity from offshore to onshore. Floating power plants enable a reliable and flexible electricity supply to backup the disadvantages of renewable energy. 2. System Overview 2.1 System Outline SEP includes LNG containment systems, power generation blocks, compressor and machinery room, a regasification (re-gas) plant, electric and instrument building (E&I building), accommodation building, and gas combustion unit (GCU), etc. as shown in Figure 1. Power generation blocks are separated in two blocks and one block includes four gas turbines, four once through steam generators (OTSG), and one steam turbine. There is one electrical generator for each turbine. LNG containment system, in which LNG fuel is stored, is positioned inside a hull strcuture. Power generation blocks, compressor and machinery room, re-gas plant, E&I building, accommodation building, and GCU are located on the topside of the deck. LNG containment system is composed of four membrane-type tanks, pump towers, coffer dam, etc. For the mooring system, SEP is equipped with the auxiliaries such as fenders, windlasses, winches, and bollards. For the overhaul and maintenance of gas turbines, zip cranes can be installed on the platform of power generation blocks, otherwise, the barge equipped with crawler cranes can be dispatched to SEP. The zip crane can be also used to handle the cryogenic hoses connected to the manifolds of SEP for the loading operation of LNG. By using the installed overhead cranes, gas turbines can be transported to the touchdown area, in which gas turbines can be lifted by zip cranes. In E&I building, there are step-down transformers for on-board electrical distribution, gas insulated switch gear, and control panels, etc. Step-up transformers for power transmission to power consumption area or grid are placed near gas turbines and steam turbines outside the E&I building. Finally, Table 1 summarizes the general specification of SEP.

Figure 1. SAMSUNG Energy Plant: SEP-T500GC Table 1. Specification Model Name SEP-T500GC Power Capacity (MW) 604 LOA (m) 260 Breadth (m) 52 Depth (m) 32 Draught (m) 12 Power Generation System Gas Turbine / OTSG / Steam Turbine Power Distribution System Transformer / Switchboard LNG Containment System GTT Mark-III LNG Loading System Cryogenic Hose Fuel Supply System HP Pump / Vaporizer / LP Compressor 2.2 Layout SEP has the power capacity of 604MW (ISO condition) consisting of two power generation. The re-gas unit and E&I building are placed centrally in the longitudinal direction of SEP, and two power generation blocks are dividied on both sides of the re-gas unit and E&I building in the longitudinal direction of SEP. There are four gas turbines, four OTSGs, and one steam turbine in each power generation block as shown in Figure 2. The re-gas unit vaporizes LNG in storage tanks and supplies it to the gas turbines of power generation blocks through fuel supply system. E&I building transmit the electricity generated from power generation blocks to the power demand area. Because the re-gas unit is located between two power generation blocks, the route of pipeline connected to both power generation blocks will become short. Likewise, the route of electric cables of E&I building connected to both power generation blocks will also become short. This arrangement can save the cost of fuel handling pipes and electric cables and make it possible to effectively manage the maintenance work for main equipments in close proximity. More safety can be more secured by

isolating the main equipments from hazardous area. In addition, the main equipments of each power generation block are sequentially arranged to match the energy conversion procedure from fossil energy to electrical energy. The accommodation building is placed at the stern of SEP not to be overlapped with LNG containment system in order to avoid any and environmental hazards. Gas combustion unit is placed at the farthest stern of SEP not to be close to the accommodation building for the sake of people s safety. By increasing GCU height above accommodation building, the burnings from GCU cannot affect the safety and environmental condition in accommodation building. E&I building are located on the portside of SEP to transmit the generated electricity to onshore or destination area. Manifolds are located on the starboard of SEP to load LNG allowing easy and quick connection of loading systems such as cryogenic hoses between SEP and LNGC. The re-gas unit has an explosion-proof wall to prevent internal/external explosions/fires from spreading across the boundary. The explosion-proof wall is open to the starboard and the upper roof is open so that explosion pressure can be released. The re-gas unit, E&I building, and power generation blocks are installed on the platform deck as shown in Figure 3. The platform deck is supported by the stool on the upper deck of hull structures. Thus, the platform deck is placed on the upper deck, and LNG handling pipes and liquid domes are placed between the platform deck and upper deck. As a result, the ignition source of power generation plant blocks can be separated from the hazardous area of LNG containment system. Figure 2. Layout (Plan View) Figure 3. Layout (Elevation view)

3. Power Plant System Recently, gas-fired power plants are applied broadly from peak load to base load due to its technical performance improvement. While the simple cycle power plant with aeroderivative gas turbines is preferred to peaking application, the combined cycle power plant with industrial/heavy duty gas turbines is common for mid-merit and base load operation. Thus, SEP is designed as the combined cycle power plant to get high power generation efficiency. 3.1. Configuration The power generation blocks of SEP consist of two power blocks of 302MW (ISO condition) combined cycle power packages. The proposed 302MW power package consists of four industrial gas turbines and one steam turbine. Each gas turbine is connected with individual OTSG to recover the waste heat from the exhausted gas of a gas turbine. One example of industrial gas turbines, Siemens SGT-800 is shown in Figure 4. The restriction of the foot print of floating power plants is much severe than onshore power plants. OTSG, of which the required foot print is smaller than the conventional horizontal or vertical heat recovery steam generators, is a suitable solution for SEP. In addition, it has advantages on quick installation, easy maintenance, less complex system, and enhanced operating flexibility by removing HP drums in the conventional heat recovery steam generator and installing separators instead. Figure 4. Siemens SGT-800 of Industrial Gas Turbines 3.2. Heat and Mass Balance Figure 5 shows the heat and mass balance diagram for the one set of power generation block with 302MW under ISO condition. This diagram consists of four gas turbine generators with individual OTSG and one steam turbine generator. LNG with LHV=46,808 kj/kg is considered as fuel and the diagram is calculated under ISO condition. The power output amount of gas turbines is 207 MW and that of a steam turbine is 95MW. And, the gross electrical efficiency reaches approximately 56%. Two pressure steam lines of HP and LP are supplied from OTSG to a steam turbine. Seawater will be directly supplied to the steam condenser in the water / steam cycle.

Figure 5. Heat and Mass Balance for One Power Block of SEP 4. LNG Fuel Supply System The LNG fuel supply system is a system capable of regulating the temperature and pressure of the LNG in storage tanks so as to be used as the fuel of gas turbines, and to handle the BOG generated in storage tanks. The entire process of LNG supply and power generation system is shown in Figure 6. The LNG fuel supply system is composed of BOG handling & regasification system and seawater system. The former is main process to supply fuel gas from storage tanks into gas turbines, while the latter is utility process to regasify, heat up, and cool down. BOG handling & regasification system is made up of main/auxiliary LP compressors, main/auxiliary BOG recondensers. The combination of equipments depends on the operation mode, which are normal operation and loading operations. During normal operation, LNG is transferred from storage tanks to main BOG recondenser by LNG feed pumps. The BOG compressed by main LP BOG compressor is condensed by sub-cooled LNG in main BOG recondenser, which is direct contact type. LNG at main BOG recondenser including the condensed BOG, is pressured by LNG booster pumps and regasified at LNG vaporizers. Unlike normal operation, more excessive BOG is generated during the loading operation. To handle more excessive BOG, the auxiliary BOG handling system, e.g. auxiliary LP BOG compressor and auxiliary BOG recondenser, are also used. During loading operation, BOG is compressed by main and auxiliary LP compressors and then compressed BOG is transferred to main and auxiliary BOG recondenser to be recondensed. Operation at main BOG recondenser is the same as the normal operation, while compressed BOG is condensed at auxiliary BOG recondenser (heat exchanger type) by HP sub-cooled LNG, which is pressured by LNG booster pump. BOG condensed at auxiliary BOG recondenser is transferred to main BOG recondenser. Optionally, if BOG handling is not possible in the BOG recondensers due to excessive BOG generation, the excessive BOG is directly compressed and supplied to the gas turbines using HP BOG compressor. In SEP, a large amount of seawater is used for steam condensing after steam power generation. Since discharging of hot seawater directly into sea without proper action can cause great environmental problems, In SEP, the following two methods are applied to lower the temperature of discharged seawater and increase the heat exchange efficiency. Firstly, some of seawater heated at steam condenser is used with the heat source of LNG regasification. That is to say, by regasifying LNG in LNG vaporizer using high temperature seawater, it is possible to lower temperature of heated seawater and increase regasification efficiency. Secondly, the heated seawater is mixed with unheated seawater pumped by seawater mix pumps before discharging to lower temperature of seawater so that environmental rules or regulations can be satisfied. SEP is designed so that

the temperature of the seawater discharged does not exceed 7 C. The method of cooling down intake air can be used to improve the power efficiency of gas turbines. Inlet air cooler of gas turbines can be installed for this purpose. The temperature of the hot seawater is lowered almost near the freezing point in LNG vaporizer, and seawater is optionally used as the cooling source in inlet air coolers. The characteristics and advantages of SEP are summarized in Table 2. Figure 6. Entire Process: LNG Supply and Power Generation System Table 2. Characteristics and Advantages of SEP Characteristics Advantages Fuel-loss free All operational BOG are used as fuel, not vented Low OPEX & Eco-friendly Only re-gasified fuel gas Minimization for BOG handling equipment Easy loading operation Large BOG re-condensing capacity Maximization of power efficiency Improvement of regasification efficiency Eco-friendly seawater system BOG is not directly compressed to gas turbine. Cost for pumping and regasification is low than that for direct compressing. Low CAPEX & OPEX Optionally, additional direct BOG compressing is needed to direct compression. For handling of excess BOG during loading operation, LP equipment is added only. Loading operation of SEP is same as LNGC s, which is verified already. Stable BOG handling is provided. Loading time is fast or insulation thickness of CCS is thin. Power output is increased by cooling the inlet air using sub-cooled seawater. By regasifying LNG using heated seawater, it improves regeneration efficiency. Hot seawater is mixed with unheated seawater by Seawater Mix Pumps before discharging to lower temperature of seawater. Low CAPEX & OPEX High applicability & low OPEX High operability Low OPEX or low CAPEX High operability Low CAPEX Eco-friendly

5. LNG Containment System As SEP uses LNG as fuel, it needs a LNG Cargo Containment System (CCS) that can store nature gas at - 163 in liquefied state. According to IGC code, CCS is mainly classified as independent tanks and membrane tanks. While the independent tank is mounted to the hull after manufactured separately from a hull, the membrane tank is manufactured by assembling pieces of insulation to a hull. Comparing the price competitiveness of the independent tank and membrane tank, it can be changed depending on the size and material of CCS. It is confirmed that the price competitiveness of the membrane tank will be excellent in SEP by referring the FSRU and LNGC with the similar size and capacity. For this reason, the membrane tank such as GTT Mark-III system is applied to SEP. The most important issue in applying membrane tanks that the tank of SEP must have no limitation of filling ratio, i.e., any filling condition. This limitation results from the sloshing load induced by the wave height as well as the resonance phenomena caused by the coincidence of the natural period of the ship motion and the tank. The structural safety of CCS for the sloshing load is mainly verified by the model test due to the complicated phenomena. However, because it takes considerable time and cost in the early stages of the concept development, the sloshing assessment of CCS in this development is alternatively performed by using SLOPE 2D, which is computational fuild dynamics (CFD) software developed by ABS ([2]). It is difficult to obtain the same numerical results as the sloshing model test through CFD software due to some theoretical theoretical limitations, but, in the present stage, it is meaningful to compare the analysis results of SEP with those of the reference vessel. The reference vessel is LNGC with the storage tank of 174K. According to previous studies ([6],[10],[11]), the sloshing load is largest around 30% filling height(30%h) due to hydraulic jump or travelling bore. This sloshing load can be obtained through the wave scatter diagram and RAO (response amplitude operators) for LTR (long-term response) corresponding to 10-8 probability of exceedance level ([1]). For wave conditions, LNGC is designed under the harsh wave condition, i.e., IACS North Atlantic, while SEP is designed under the mild wave condition like the sheltered area. It is recommended to use 1-year and 40-year wave conditions for beam and head seas, and the two-parameter Bretschneider spectrum is used ([1]). The response of LNGC largely occurs due to the coincidence of the wave energy density and the peak RAO. In the case of SEP, the response can be negligibly small since the wave energy density and the roll peak RAO are far from each other. This means that LTR of LNGC is much larger than that of SEP. The sloshing occurs in the sloshing resonance range, which is defined from 70% to 130% of the tank natural period ([1]). Although the tank natural period of LNGC is somewhat closer to the peak value of its RAO than SEP, the motion of LNGC is seen to be very large due to the large LTR of LNGC as shown in Figure 7. LNGC has filling limits lower than 10%H and higher than 70%H, called standard filling level ([1]), since the sloshing load at the other filling level exceeds the structural capacity of CCS. The maximum sloshing load in the standard filling level of LNGC can be used as a criterion for the any filling condition of SEP in the comparative method. The sloshing loads obtained by SLOPE 2D are normalized by the maximum sloshing load generated at 30%H of LNGC for relative comparison as shown in Figure 8, of which the values were obtained by considering six degrees of freedom of the vessel. As mentioned above, Figure 8 shows the maximum sloshing load of the LNGC occurs at 30%H and sharply decreases at the higher filling levels. Motion of SEP produces the only hydrostatic pressure without sloshing and its value is also remarkably smaller than the criteria of the any filling condition. Therefore, it is reasonable to apply the membrane tank such as GTT Mk-III to SEP. As a future plan, the result will be finalized through the sloshing model test.

(a) LNGC Figure 7. Tank Motion at 30%H (b) SEP Figure 8. Normalized Sloshing Pressure of SEP and LNGC 6. Power Transmission System Most of power transmission systems are placed in the E&I building on the topside such as step-down transformers and gas insulated switchgear, etc. The step-up transformers are located near gas turbines and steam turbines. It is designed to be able to transit power electricity directly without additional transmission facilities such as substations onshore. The concept of transmission facility may be changed depending on the mooring system and the distance from the shore. According to the general concept of SEP, the power export cables pass through the gantry towers constructed in jetty structures, and connected to the grid on land. Otherwise, it is possible to use insulated power cables, which are continuously installed through the guideway on the jetty structures to the grid on the land. Figure 9 shows the key single line diagram of power system of SEP. The transmission line consists of two lines and each line allows transmission of 302MW. The step-up transformers consist of four 130MVA and two 110MVA transformers. 130MVA transformer is connected two gas turbine generators and the 110MVA transformer is connected to one steam turbine generator. There are two auxiliary step-down transformers for power consumption in SEP. The power for on-board power system is supplied from SEP s own produce

power. If power production of SEP is stopped due to failure of maintenance work, power for onboard is directly supplied from the grid. Even if one of two aux. transformers fails, the remaining one can cover all power transmission. The amount of the main power consumption is approximately 20MVA, which are mostly consumed in the power package system, cargo handling system, the re-gas system, and accommodation, control and operating station, etc. 7. Mooring System Figure 9. Key Single Line Diagram of Power System Mooring arrangements are proposed to secure the serviceability requirement of gas turbines and to keep the position of SEP in the given sea condition. SEP is normally moored at jetty structures and, only during the loading LNG from LNGC, SEP is additionaly moored by side-by-side mooring with LNGC. MOSES is used for the mooring analysis and quasi-static analysis ([12]). General arrangements of target vessels are depicted in Figure 10 and Table 3. Figure 10. Definition of Coordinate System for Mooring Analysis

Table 3. Main particulars of vessels Ships LOA (m) Breath (m) Draft (m) SEP 260 52.0 12 LNGC 293 45.8 11.8 Environmental conditions for mooring analysis are used in the assumption of sheltered area. The environmental condition with 100-year return period is used for the analysis of jetty mooring and 1-year return period for side-by-side mooring. Through the investigation of mooring analyses, mooring arrangements are proposed as shown in Figure 11. (a) Jetty Mooring (b) Side-by-side Mooring Figure 11. Mooring Arrangement for Jetty Mooring When the construction of jetty structure is not economical as it is located far from the shore, turret mooring system can be good solution. Turret mooring system is effective solution also in harsh environment for station keeping of the vessel as it provides weathervaning capability and minimizes environmental load. And, in this paper, several concept designs for turret mooring system are suggested to cope with various design requirements and they are shown in Table 4. Suggested models are designed for vessel which requires partial weathervaning system and in-line swivel or flexible cable and hoses were implemented instead of toroidal swivel system for cost reduction. Table 4. The Concept of Turret Mooring for SEP Configuration Electric Cable + Gas Line Electric Cable + Gas Line Electric Cable Drawing Weathervaning 120 Partial Power transfer Cable reel Cable reel Cable reel Gas transfer In-line swivel + Utility swivel Hose reel -

8. Structural Reliability 8.1 Structural Safety The width and depth of hull structure of SEP are determined taking into account the capacity of LNG and footprint of topside structures. SEP has inner structures of inner hull, side shell, hopper, cofferdam, deck and dome, etc. The forward and after parts of a hull are continuously added to hull structures surrounding four LNG tanks to place the accommodation building and compressor and machinery room, etc. Trim and stability calculations, mid-ship section assessment and cargo hold analysis were performed to evaluate the structural reliability of SEP. Trim and stability calculations were conducted by using the data of weight and center of gravity of hull structures, power plants, and machineries. In detail, the intact and damage stability for various load cases were respectively calculated according to IS and IGC code ([8],[9]). As a result, it was confirmed that the codes were satisfied for both stabilities. Nauticus of DNVGL was used to calculate the local scantling of mid-ship section and the results met the classification requirements properly. In addition, cargo hold analysis was carried out to calculate local scantling of transverse members in accordance with the related rules. Two tanks (= 1/2 tank + 1 tank + 1/2 tank) were modeled to analyze No.2 cargo hold tank and the supporting structures sustaining topside load from platform decks were modeled. Corrosion margin was considered and shell and beam elements were used to model cargo hold tanks and supporting structures. Various environmental loads mentioned in the related rules were applied to the cargo hold model. Scantling was determined to satisfy the allowable stress through iterative calculations and modifications as shown in Figure 12. The structural analysis was carried out to investigate the structural safety of supporting structures of gas turbines and steam turbines ([14]). The self-weight of turbines and supporters, wind force, and the acceleration of the floating vessel at the location of supports were considered in the analysis. And, the boundary condition of the supporter was conservatively defined as the fixed condition. The analysis results showed the value of unity check smaller than 1.0 ([4],[5]) as shown in Figure 13. (a) Analysis Model (b) Boundary Condition (c) Analysis Results (VM-stress) Figure 12. Cargo Hold analysis (a) Gas Turbine Supports (b) Steam Turbine Supports Figure 13. Analysis Results of Topside Structures

8.2 Serviceability of Gas Turbines As the main gas turbines of the power generation blocks installed on the deck of a floating vessel is affected by the motion of the vessel, it should be evaluated whether their serviceability requirements of the inclination and translational acceleration are satisfied or not. As heavy duty gas turbine is originally designed with fixed ground condition even though earthquake is considered, there are allowable requirements for the inclination and translational acceleration. While the heavy duty gas turbines have strict serviceability requirements, the industrial gas turbines have more margins on the serviceability requirements in the viewpoint of the inclination and translational acceleration. In addition, the concept of multiple gas turbines can effectively cope with partial load and the failure of some gas turbines by securing redundancy. To verify the applicability of gas turbines in the sea or water area, the vessel motion under assumed wave conditions was calculated by hydrodynamic analysis. The inclination angles and translational accelerations in the observation points are calculated from the vessel motion. The points are assigned to the farthest points of gas turbines from the center of gravity of the vessel as shown in Figure 14. The hydrodynamic analysis was performed by DNV WADAM and the post-processing was by POSTRESP ([16]). The operation condition was post-processed as long-term analysis by using the wave scatter diagram in a sheltered area. Two different transit routes were considered in this vefication. First transit route was assumed to be the heading for Philippine from South Korea. Second transit route was assumed the way to Angola from South Korea. The transit con dition is post-processed as short-term analysis. Table 5 shows the assessment results of the gas turbines for serviceability validation. For operation condition, the effects of the vessel motion are limited and the gas turbine has sufficient serviceability margin for all inclinations and translational accelerations. As the wave condition for the transit conditions is more severe, the results show less serviceability margin than the operation condition. Pitch motion has the minimum serviceability margin of 13%, the longitudinal acceleration the minimum serviceability margin of 80%, and the vertical acceleration has the minimum serviceability margin of 52%. Figure 14. Observation Points for the Verification of Gas Turbine's Applicability on the Water Table 5. Assessment Results of Serviceability Requirement of Gas Turbines Condition Operation Transit Serviceability Margin (%, percentage) Components of Motion Mooring Mooring No Mooring (ship-to-jetty) (ship-to-ship) Check Inclination Roll 95 31 89 OK Inclination Pitch 85 74 94 OK Acceleration X 85 78 93 OK Acceleration Y 91 85 94 OK Acceleration Z 80 77 91 OK Inclination Roll 39 - - OK Inclination Pitch 13 - - OK Acceleration X 80 - - OK Acceleration Y 56 - - OK Acceleration Z 52 - - OK

9. Concluding Remarks Through the market survey, it is confirmed that there is a potential market for floating power plants of 500MW or less in the future. The floating combined-cycle power plants can be used to provide power to areas where electric power infrastructure is scarce, or to provide alternative power to repower existing older generation power plants. In addition, the construction period can be shortened compared to onshore power plants. In addition, as the environmental regulations of the Paris COP2021 are strengthened, the power plant market using LNG as a clean fuel is expected to expand further. Also, as the application of renewable energy increases, the need for LNG power plants will continue to increase in order to backup the weakness of renewable energy such as flexibility. In this paper, SHI proposed the 500MW-class floating power plant of SEP, which integrates the combined cycle power plant, LNG cargo containment system, and fuel supply system, and floating structures, etc. The proprietary fuel supply process was developed. As a result, the LNG BOG handling and loading operation is optimized, the specification of the related equipments can be minimized, and GCU can be applied instead of flare towers. Therefore, it is predicted that CAPEX and OPEX can be minimized. It is also confirmed that it is possible to apply membrane-type fuel storage tank such as GTT MK-III. In addition, the reliability of the floating structures was verified through the trim and stability calculation, cargo hold analysis, and topside structure analysis. The serviceability of gas turbines was verified through hydrodynamics review. Finally, the mooring arrangements were proposed for the actual application of SEP. Comparing with the recent brand-new floating power plant concepts, the more detailed technical review has been carried out and, as a result, the technically more feasible and complete floating gas power plant was developed. Based on SHI s experience in developing 500MW class SEP (SEP-T500GC), SHI has developed the specifications of SEP-T50E, SEP-T100E, SEP-T150E, and SEP-T250GC, which are less than 500MWclass. Based on the line-up of SAMSUNG Energy Plants, SHI is trying to enter into the global power market. SHI will continuously do our best to find the detailed improvement items in viewpoint of the technical and commercial competitiveness. References [1] American Bureau of Shipping, Guidance Notes on Strength Assessment of Membrane-type LNG Containment Systems under Sloshing Loads, 2009 [2] American Bureau of Shipping, User Manual on ABS Slosh v4.1b, 2012 [3] A.M. Ferrer and H.A. Hadman, Floating Storage Regasification Unit(FSRU) the answer to locations with No Gas or No Gas Infrastructure : a gas-to-power application, Power-Gen International 2016, December 13~15, 2016, Orlando, FL USA [4] API RP 2A-WSD, Designing and Constructing Fixed Offshore Platforms-Working Stress Design, December 2000 [5] AISC, Specification for Structural Steel Buildings-Allowable Stress Design and Plastic Design 9th, June 1989 [6] DET NORSKE VERITAS, Sloshing Analysis of LNG Membrane Tanks, 2006 [7] G.H. Lee, J.H. Ha, and S.W. Park, Technological Status and Prospects of Floating Power Plant, KEIT PD Issure Report Vol 15-2, February 2015 [8] IGC Code, International Code for the Construction and Equipment of ships Carrying Liquefied Gases in

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