Conceptual design of floating storage and regasification unit (FSRU) for Eastern Part Indonesia

Liquefied Natural Gas (LNG) can be used as an alternative fuel with environmentally friendly solutions. In general, the domestic distribution of natural gas in LNG is more cost-effective than transporting gas through underwater pipelines considering Indonesia as archipelagic country. According to Indonesia’s Minister of Energy and Mineral Resources Regulation Number 13 of 2020, the government supports converting 52 power plants to LNG. However, the current challenge in the LNG industry is the lack of supporting facilities. Storage and regasification facilities are among the infrastructure that requires optimization. Floating Storage and Regasification Unit (FSRU) are viable options for energy distribution that offer opportunities and competitiveness compared to onshore terminals. Small and medium-scale FSRU can serve as an alternative solution due to their relatively fast, flexible, and affordable development process. Therefore, this research will develop a small-medium FSRU design with a capacity of 60 MW − 70 MW in Eastern Indonesia. FSRU design should consist of four segments including location considerations and environmental conditions, powerplants gas requirements, LNG storage tank sizing and LNG regasification process. Calculations for various supporting FSRU components, seakeeping analysis, loading-offloading processes, 3D modelling and the integration of solar panels were discussed. The results obtained include the principal dimension, technical aspects of FSRU design, and the technology for LNG regasification processes used.


Introduction
With the massive increase in the industrial development of Indonesia, the country needs more energy supply including electricity [1].In general, the domestic distribution of natural gas in LNG is more costeffective than transporting gas through underwater pipelines.LNG has several advantages of emitting less than 10% of particulate matter compared to other sources [2].Using LNG for power generation can achieve 50% reduction in greenhouse gas emissions compared to coal [3].In maritime transport, utilizing gas-fueled engines instead of heavy fuel oil can lead to emission reductions of up to 21% [4].Additionally, imported natural gas in LNG form can contribute to balancing fluctuations in electricity generation from renewable sources and meeting peak electricity demands [5].
According to DJMigas data as of January 2017, the natural gas reserves in Indonesia reached 142.72 TSCF, with 100.36 TSCF being proven reserves and 42.36 TSCF being potential reserves [6].The 1239 (2023) 012015 IOP Publishing doi:10.1088/1755-1315/1239/1/012015 2 government of Indonesia is dedicated to increasing the consumption of natural gas through the construction of 52 power plants.It aims to increase consumption as outlined in the Regulation of the Minister of Energy and Mineral Resources Number 13 of 2020 concerning the conversion of power plants to LNG Fuel.This conversion will result in a total installed capacity of 1697 MW and will require 166.98 billion BTU (British thermal units) of natural gas per day.The Asia Pacific Energy Research Center report on APEC Energy Supply-Demand Outlook 2019 forecasts that Indonesian gas demand will rise to meet both domestic and export requirements, reaching 60.9 Mtoe by 2040.Gas consumption in the power sector will remain significant, accounting for 30% in 2020 and growing to 40% of the total gas demand.
At present, Indonesia possesses significant gas potential.However, the locations of several gas power plants in Indonesia are scattered.The need for infrastructure capable of supplying LNG to end users is expected to increase in accordance with the electricity demand.One of the most critical infrastructures is the storage and regasification terminal.FSRU serves the purpose of storing LNG and converting it into its gaseous form.These units have gained significant popularity over the past two decades and currently constitute 6.3% of the global LNG fleet [1].The development of FSRU is particularly needed in Eastern Indonesia, given its challenging geography as shown as figure above.Compared to western Indonesia, the distribution of LNG in eastern Indonesia is limited due to challenging geographical conditions.The existing pipeline infrastructure is also significantly underdeveloped.To address these challenges, the concept of utilizing small-scale LNG and regasification terminals has emerged as a promising alternative for transporting natural gas for power generation, replacing the use of diesel oil.FSRU can provide greater operational flexibility and an efficient solution in cases where land transportation is not feasible.
Decision-making in the analysis of selecting a medium-scale LNG regasification terminal using real options analysis has been conducted.The concept of FSRU is chosen as the most suitable configuration compared to FRU, FSU, and onshore regasification terminals in Indonesia [7].According to research conducted by Bulte, FSRU terminals are mentioned to be cheaper than onshore terminals in terms of price and cost, but more expensive than natural gas pipelines.Regarding construction time, new FSRU vessels are typically completed within 27 to 36 months, and the conversion of conventional vessels for LNG transportation to FSRU vessels can be even faster, taking place between 18 to 24 months [8].In Kelle's study, if the construction of an onshore LNG terminal is not feasible FSRU becomes a viable alternative [9].Meanwhile, according to Jovanović et al., underwater pipelines are characterized by long-term investments with a relatively slower payback period.Additionally, the implementation of FSRU receiving terminals is one of the fastest-growing segments in the LNG industry due to numerous advantages over land-based terminals [10].Ramos et al. (2014) compared the environmental risks of onshore LNG terminals and FSRU.This comparison supports FSRU because the distance to the population is greater, resulting in lower environmental and social risks [11].Artana has conducted a study on utilizing multiple criteria decision-making to choose the location of FSRU in Bali.FSRU is considered an alternative choice to replace onshore LNG receiving terminals [12].Research on the conceptual design of a simple mini FSRU has been conducted by Putra et al [13].However, in the design, several technical considerations and detailed system components have not been included.
The current issue faced is that the available FSRU designs mostly cater to large-scale LNG distribution, while the demand in Indonesia is relatively small ranging from 0.42 BBTUD (Billion British Thermal Units per day) at the lowest to 14.64 BBTUD at the highest.This design, however, does not seem feasible for the eastern part with geography issues.One alternative is the implementation and development of a small-scale FSRU concept, which offers many advantages, including rapid LNG distribution, reduce capital cost, and lower environmental risks.This concept is believed to fulfill the gas requirements of consumers which not connected to gas pipelines or require smaller gas volumes, such as small-capacity power plants and small regasification terminals.
This paper presents a conceptual design of a small to medium-scale floating storage and regasification unit (FSRU) with a capacity of 60 MW to 70 MW and investigates its technical feasibility by considering critical design requirements.As a case study, Eastern Parts Indonesia is carried out by analyzing environmental conditions, estimating the required LNG consumption, determining the hull structure, and anticipating the design cases, and several technical considerations by relevant regulations.

Small to Medium Scale FSRU
Currently, most FSRU designs have large capacities ranging from 100.000 cubic meters to over 200.000 cubic meters.This design of large FSRU, however, does not seem feasible for small demands which are scattered in the eastern part of Indonesia with challenging geography.One alternative is small to medium-scale FSRU, which is similar to large FSRU.To build and operate FSRU several design requirements should be satisfied.It is important to emphasize that three design criteria including safety, economics, and principal functions are related to each other.For example, structural integrity of hull against environmental loads.Loads due to wave and tides are the dimensioning factors, although LNG transfer operations have been conducted successfully, they are still limited to calm area condition.Selecting location of FSRU should considering environmental condition for safety factors.Cost of fabrication and installation will be significantly affected by these considerations.This study suggests that the small to medium FSRU considered for small powerplants capacities should consist of four segments: location considerations and environmental conditions, powerplants gas requirements, storage tank LNG sizing and deck arrangements, and regasification LNG process.Figure 2 shows a schematic diagram of the small to medium FSRU design considerations.

Conceptual Design Proposed
This section presents a conceptual design that addresses some of the issues regarding the design considerations.FSRU design process is shown in figure 3. Existing FSRU database is used to compare and reference the design.Several regulations related to FSRU design are International Maritime Organization (IMO) documents, including SOLAS 1974 and IGC Code, Class Rules, and other regulations related to LNG design.The parametric design phase holds significant importance throughout the design process as it establishes the key ship characteristics by defining the design parameters.Statistical design methods typically rely on regression formulas to determine these design parameters.Additionally, numerical programs are employed to gather data on the hydrodynamic characteristics.Utilizing existing FSRU designs to determine the initial size.The initial design stage focuses on determining the hull form.Calculations for various supporting FSRU components, general arrangements, 3D modeling, loadingoffloading processes and the integration of solar panels also discussed.

FSRU Location Considerations and Power Plant Gas Requirements
Selecting an appropriate site for an FSRU project is crucial, and it involves conducting metocean and oceanographic studies to ensure the terminal can operate safely in the selected location.By analyzing historical data on weather and marine conditions, including factors like wind speed, wind direction, wave height, tides, and more, the project can gain insights into extreme conditions and the frequency of different weather and marine conditions at the proposed site.This analysis reduces uncertainties in the terminal specifications and improves safety, operational efficiency, and reliability.
The conceptual design of Eastern Part Indonesia was carried out as a case study.The data in Table 1 were derived from European Centre For Medium-Range Weather Forecast (ECMWF) by 2013-2022 every hour.The location of the FSRU should be chosen with care to dispense LNG efficiently and not interrupt other ships traffic.The freeboard and deck height of the FSRU should be designed by taking the wave height into account.The structural integrity of the hull structure is strongly affected by wave height, wind speed, tide level, etc.All environmental conditions are important factors in selecting the site and type of hull structure.They also affect the LNG transfer operation and motion.Therefore, the FSRU design will be placed near Jayapura power plants with sea depth 20 meters.This location consideration also takes into account the environmental data around the mooring location.Environment data is gathered on an hourly basis, subsequently analysed with the results of significant wave height (Hs), zero crossing wave period (Tz), and peak wave period (Tp) outcomes represented in Table 1.The data have been collected and averaged on every five years basis.The maximum significant wave height (Hsmax) observed over the past 10 years are 1.66 m.
Initially, most terminals were designed for seasonal demand, but FSRU have proven to be reliable and capable of providing continuous regasification for base load requirements.Table 2 shows power plants capacity in Eastern powerplant Indonesia.Based on the distance matrix from the LNG source to each power plant, it can be determined the round trip of the LNG carrier (LNGC).Assuming LNG will be transferred using small LNG carrier (SLNGC) from The Tangguh LNG plants, with a service speed approximately 12 knots.Regasification and storage system will take place at the FSRU, and then it will be transferred to the onshore receiving facility (ORF) and other gas-fired power plants where gas metering or further gas heating take places.
LNG loading unloading timeline is divided in three stages: before, during and after loading unloading.The time limit for the loading unloading ratio is set to approximately 12 hours before entering port or before ship to ship (STS) operations, while the loading unloading time is approximately 12 hours, depending on the LNG pump capacity.The round-trip time for the SLNGC vessel from the Tangguh refinery to the FSRU in Jayapura is 15.4 days, which includes sailing time, loading-unloading time, and idle or slack time.The capacity of the SLNGC tank is determined by multiplying the gas demand (m 3 /day) by the total round trip time plus the safety stock.This ensures a continuous supply of gas.The total storage tank capacity of the LNG vessel around 14.518 m 3 .assuming a safety stock of 3 days for the power plants.Therefore.the planned volume of LNG to be accommodated by the FSRU is 15.000 m 3 .The FSRU design is planned to use 2 tanks with capacity of 2x7500 m 3 .Barge is chosen as the hull form to facilitate operability and initial fabrication construction.Barge or flat-bottomed vessel is chosen as it is suitable for shallow waters conditions.Based on the power plant capacity, LNGC hull ratio, and the appropriate selection of hull form.the principal dimensions of the FSRU can be determined as shown in Table 3 above.Alternative LNG supply chain with the assumption LNG source -LNG plant (liquefaction) -LNG shuttle -FSRU -Gas pipeline -Power plant 1/ Power plant 2 -End user.LNG is transported from the LNG source to the FSRU using LNG shuttle.Here, the LNG which has been converted into gas is transferred to the power plants using a gas pipeline.The gas sent to the power plants is used as fuel to generate electricity.The gas pipeline enables the delivery of natural gas not only to one power plant but also to several power plants.This supply chain scheme is particularly useful when truck transportation is not feasible due to land transportation limitations and delivery access constraints.To implement this alternative scheme.environmental conditions such as geography conditions need to be considered, as well as the planned location of the gas pipelines.
The analysis of sea-keeping is a critical aspect of FSRU design and has a significant impact on the availability of the FSRU.Even if the unloading of LNG from an LNG carrier is temporarily not possible due to weather conditions, the FSRU operation can still be maintained.As long as the availability of unloading is typically above 95%, the operation of the FSRU will remain unaffected.Minimizing the motions and accelerations of the FSRU is important for the comfort and efficiency of the crew.Seakeeping analysis has been conducted for the designed FSRU, focusing on pitch, roll, and combined pitch and roll motions.Response Amplitude Operator (RAO) which is a transfer function used to determine the effects of sea conditions on the motion of a marine structure is shown in figure 4(a) -(f).It helps determine whether a marine structure requires design modifications to improve stability.The use of RAO in this design phase enables the identification of necessary design modifications to meet safety criteria and enhance the performance of the vessel.RAO indicates the motion trend of a ship in relation to waves.Based on the seakeeping RAO analysis, it can be determined that the FSRU encounters the highest environmental load at a 90° direction.Therefore, in order to minimize the load on the FSRU and achieve effective mooring tension, the FSRU should be oriented in the 90° direction.
The maximum pitch moment is influenced by waves approaching from the bow or aft direction.In the case of moored FSRU with fixed positioning, where waves approach perpendicular to the longitudinal centerline, no pitching is expected.However, for moored carriers capable of weathervaning, pitching can occur for wavelengths longer than twice the ship's length.Since the waves are shorter compared to the ship's length, little to no pitching is anticipated.

Deck Arrangements.
For the LNG storage tank, cylindrical LNG tank (IMO type C) will be used to contain LNG.There are two cylindrical LNG tank connected to the LNG pump at the same time.One of them is in stand-by mode.This choice is based on the consideration that LNG tank type C can withstand pressures of ≤ 10 bar, allowing for longer Boil Off Gas (BOG) storage time without being affected by sloshing and prevents the occurrence of local stress.The double bottom of FSRU (H) is calculated with the formula 1 following guidance from DNV part 3.1.6.where B is breadth of the FSRU. =  20 (1) The inert gas requirement is determined by DNV Part 5.3.11.which states that the inert gas system must supply at least 125% of the maximum flow rate out of the storage tank (reduced volume from the storage tank).Inert gas generator chosen based on the natural gas send out capacity and gas expansion ratio.Gas expansion ratio assumed to be 581.47m 3 NG/ m 3 LNG.
From the calculation, double bottom FSRU is designed 1.35 m minimal height and the inert gas capacity is 126.5 m 3 /h.According to DNV GL Chapter 2. Section 9. 3.5.the water spray system which functions to prevent fires should be supplied to several areas: including exposed storage tank domes, visible parts of storage tanks, storage vessels on the open deck, liquid and gas discharge and loading manifolds, boundaries of the FSRU structure, and the gas pre-treatment area.The determination of the emergency fire pump capacity on the FSRU complies with SOLAS Chapter II-2.2.2.4.2.2004.which states that the number of installed pumps exceeds the minimum required, the capacity of the pump should be at least 25 m 3 /h and capable of supplying 2 fire nozzles simultaneously.

𝑣 = 𝑄 𝜋 𝑥 𝑑 2 4
(2) The diameter of the emergency fire pump pipe is adjusted to the main firefighting pipeline diameter.which is 8 inches.The flow rate of seawater in the firefighting pipeline can be calculated by the following formula 2.Where v is seawater flow rates, Q is pump flow rate, and d is internal pipe diameter.Based on the calculation, the water velocity in the fire-fighting pipeline when using the emergency fire pump is 780.5 m/h or 0.217 m/s.

Heating Medium Regasification Capacity. For the regasification unit, this research uses
Intermediate Fluid Vaporizer (IFV).Several advantages of using IFV are it can be used both open loop or closed loop, design LNG pressure 10 to 150 barg, free from freezing problems of seawater by not contacting the LNG with sea water, reducing weight and size, and free from propane leakage.The minimum LNG regasification capacity is 17 mmscfd or 2 x n (vaporizer).PFD of regasification LNG process using IFV is shown in figure 5. Black lines are normal operation system, red lines are intermediate discharge and re-discharge system (only for overhaul maintenance) and blue line is cooling system for LNG tube sheet if quick start is required.While in normal operation, specifically in holding mode without loading, the boil-off gas (BOG) produced from the LNG stored in the tanks is typically around 0.10-0.15%by weight per day, equivalent to approximately 3-5 t/h (tons per hour), varying based on the FSRU age.Modern FSRU with improved insulation exhibit lower BOG rates, approaching 0.1%.

Pipe Diameter.
The determination of the main gas pipe diameter in the FSRU consists of three types: LNG liquid header pipe in the loading system, natural gas header pipe for BOG, and gas pipe for power plants.Natural gas header pipe diameter depends on the performance of the LNG pump.Diameter of the LNG liquid header (Di) is calculated with formula 3.Where Q is LNG flowrate and v is the velocity of LNG with maximum velocity for stainless steel is 3 m/s.Referring to the pump specifications.which have a capacity of 1000 m 3 /h.the diameter of the LNG liquid header pipe is 450 mm.According to the minimum thickness standard stated in DNV Part 4.6.9. it should be at least 4 mm.

𝐷𝑖 = √ 4 𝑥 𝑄 𝑣 𝑥 𝜋 (3)
For the natural gas header pipe diameter is based on the maximum allowed gas flow velocity.which is 20 m/s.Therefore.the minimum diameter of the NG header pipe is 114 mm.For the gas pipe diameter to the power plants consists of the high-pressure line and the low-pressure line.as different types of engines are used in the power plants.The high-pressure line is responsible for meeting the gas demand for gas turbine power plants with a gas capacity of 14.8 t/h or equivalent to 20.000 m 3 gas/hour at peak load conditions.Meanwhile.the low-pressure line is responsible for meeting the gas demand for the Jayapura Peaker and Jayapura Load Follower power plants, both using Wartsila dual fuel diesel engines, with a total gas capacity of 15.3 t/h or equivalent to 20.630 m 3 gas/hour at peak load conditions.Based on the calculations.the diameter of the natural gas low-pressure line pipe is 0.58 m, and the diameter of the natural gas high-pressure line pipe is 0.57 m.

Tank Capacity.
There are three tanks to be considered: ballast tanks, bilge tanks, and freshwater tanks.The ballast system in the FSRU has purpose to maintain stability and to keep the FSRU in an even keel condition caused by the regasified LNG which reduces the weight of the tanks.Bilge and ballast pumps will be combined as general service to reduce investment costs.The capacity of the ballast pump depends on the required de-ballasting time.The ballast pump capacity is assumed to be 0.035 m 3 /s.Minimum diameter main pipe is 4.79 inches.
Table 4 show ballast tank capacity of FSRU design.The use of freshwater in the FSRU is divided into two categories: consumable and non-consumable needs.Consumable needs include drinking and cooking water with minimum of 2.5 litres/person per day is required for cleaning and sanitation needs.It requires 60-200 kg of clean water per crew member per day.The amount of crew is 15 persons.Therefore, the calculation for freshwater is 2070 kg/day or 2.070 m 3 /day, and the freshwater requirement for engine cooling is 0.12 m 3 per engine.But in the FSRU it is provided twice the amount to cover at least one full requirement.

Conceptual Design FSRU in Eastern Indonesia
The FSRU is designed with two cranes for loading and unloading process.Flexible hoses are used to transfer LNG from the LNGC storage tank to the FSRU.The FSRU manifold is planned to have a total of 5 manifolds: including two manifolds for the liquid phase, two manifolds for the vapor phase, and one transfer pipe to the power plant on each portside and starboard of the FSRU.The manifold planning refers to OCIMF standards.The engine room is located at the front, on the lower deck of the accommodation area.Cargo control room, meeting room, and office are situated on the accommodation deck.Each FSRU tank is equipped with two low-pressure pumps which are submersible hydraulic pumps located below the LNG tank.Each tank is also equipped with inlets and outlets for the regasification facility, vent mast, metering unit, pressure control, and temperature control.The pressure control functions as an automatic system to control the operation conditions of the centrifugal pump to achieve the required pressure, while the temperature control ensures that the NG outlet temperature does not drop below 18°C during the gasification process.Additionally, emergency shutdown (ESD) valves and gas metering units are installed at the pump outlet and NG delivery outlet to automatically cut off the liquid and gas phases.In case of leakage or fire, an alarm will be triggered.and the water spray system will be activated on top of the equipment.The regasification facilities are located between the tanks to facilitate LNG handling.The BOG from each tank will be directed to the BOG management system, which is positioned near the regasification facilities above the LNG tanks.The BOG will then be routed to the generators and some of the natural gas will be supplied to the power plant.

The Use of Solar Panel in FSRU
The generator used has an output power of 920 kW.When summed up, the highest total load occurs during the night-time and loading conditions due to the fire-fighting pump operation during LNG loading on the FSRU.Optimization of the available area on the FSRU for the placement of solar panels is conducted.From the optimization results.the areas utilized for solar panel placement are on the accommodation deck and additional platform with areas of 359.93 m 2 and 145.41 m 2 , respectively.
The number of solar panels required to continuously supply the lighting load on the FSRU is 144 panels.The power calculation prioritizes the electrical load requirement for the lighting system on the FSRU which is 45.2 kW.Considering the average sunlight duration in Indonesia is 12 hours with a maximum assumed sunlight duration of 5 hours per day, the total power generated is 543 kWh per day.

Technical Loading and Unloading Process of FSRU
Liquefied Natural Gas (LNG) will be loaded onto the LNG Carrier (LNGC) with a cargo tank capacity of 15.000 m 3 .The LNGC will transfer LNG to FSRU using the Ship-To-Ship (STS) transfer method.During the unloading operation from the LNG Carrier to the FSRU, excessive Boil-Off Gas (BOG) will be controlled by sending it to the power plant using the compressors on the ship.Some of the BOG will be returned to the cargo tank of the LNG Carrier through free flow to maintain a positive tank pressure (0.10 ~ 0.15 BarG) as the amount of LNG in the cargo tank decreases.Figure 7 shows PFD for loading unloading LNG from LNGC to FSRU storage tank.The regasification process involves converting LNG from a liquid phase to a gas phase.Initially, natural gas is cooled to a temperature of -160 °C and a pressure of 1 atm to form liquid LNG (Liquid Natural Gas).Changing the phase from gas to liquid facilitates transportation and storage processes.LNG undergoes regasification in the Regasification Unit of the FSRU to convert it back to gas.Once the BOG in the FSRU tank reaches a certain pressure (approximately 0.15 -0.25 Mpa), the LNG is pressurized (0.8 -1.0 Mpa) by centrifugal pumps in each tank and then transferred to the LNG gasifier process.In this process, it is heated and gasified by water-ethylene glycol.resulting in natural gas at a specific pressure (0.8-1.0 Mpa) and a temperature of -50℃ before entering the gas heater.Inside the LNG gas heater.It undergoes further heating by water-ethylene glycol to reach the required temperature (around 18℃) and pressure (0.8-1.0 Mpa) before being transferred to the power plant.
3.6.Safety and Economical Analysis of FSRU 3.6.1 Safety Analysis of FSRU.When conducting a risk assessment for an FSRU, it is essential to consider several factors, including the FSRU itself, incoming LNG carriers, other coastal infrastructure, the terminal location, oceanographic conditions, and the traffic in the surrounding waters.The risk assessment is influenced by four categories of factors: first, location and specific local conditions.This includes factors such as the importance of LNG imports for the region, potential threats, possible accidents, and critical coastal infrastructure, as well as the FSRU ship and incoming LNG carrier.Second, risk management objectives: this involves identifying the consequences to be avoided, such as injuries or property damage, and the significance of ensuring LNG supply.Third, Protective mechanisms: this category encompasses safety measures, warning and alarm systems, and reaction measures in case of accidents.Last, regular evaluation is hazardous projects like liquefied natural gas imports need to be regularly re-evaluated to assess the adequacy of applied safeguards due to changing conditions.This includes changes in facilities, coastal infrastructure, emerging threats, and shifts in risk management objectives, among others.
In the risk assessment process, specific information related to the FSRU facility should be identified, including the location, local conditions, environmental and oceanographic conditions, and cargo operations.Factors to consider include the proximity to neighbouring areas and facilities, prevailing weather conditions, and the specifics of cargo operations, such as the size and design of the FSRU ship, regasification capacity, and required LNG supply.When identifying potential hazards and threats, both unexpected accidents and intentionally caused incidents should be considered.Potential accident scenarios involve leakage from tanks or pipelines, tank or pipeline ruptures, collisions with incoming LNG tankers, hull damage leading to oil spills, incidents with the ballast system, onboard accidents, fires, explosions, and disruptions due to severe weather conditions.It is important to note that when the FSRU ship operates as an LNG terminal, there is no risk of ballast water pollution in the marine environment, as LNG carrier arrive with full cargo and do not discharge ballast water into local waters.
The flammability of cargoes is a significant risk in the liquefied gas industry.Preventing the formation of flammable mixtures is crucial, and this is achieved through strategies like containing the gas, removing ignition sources, and ensuring an inert atmosphere.In the case of FSRU, where storage tanks and various equipment are located, extensive fire detection equipment is installed.Fire detectors are categorized as heat, smoke, or flame detectors, selected based on the materials that could potentially burn in specific areas.Examples of typical locations for fire detectors include electrical control rooms, BOG compressor houses, and all cargo pumps.
Several systems install in FSRU including the Emergency Shutdown (ESD).ESD system plays a crucial role in halting all cargo processes in the event of an emergency.The primary purpose of the system is to activate automatically in emergency situations to prevent adverse consequences.Factors triggering system activation include exceeding pressure limits in cargo tanks, pipelines, or pumps, fire detection on the FSRU or LNG ship, interruption of synchronization, and power outages.Before cargo reloading begins, a thorough check of the entire system ensures readiness and successful synchronization.Second, pressure Control and Exhaust Valve System.It establishes minimum and maximum allowable pressure values.In case of pressure increase above the upper limit, gas is released through vent valves to reduce pressure, while a decrease below the lower limit allows additional gas to 1239 (2023) 012015 IOP Publishing doi:10.1088/1755-1315/1239/1/01201513 enter, causing pressure to rise.This prevents potential damage to tanks and pipelines due to excessively high or low pressures.Each tank is connected to a vent mast, and evaporated gas is collected in a main vent tank before being discharged through the main vent mast.Nitrogen is constantly used to treat the vents, creating an inert atmosphere that prevents flammability.A valve at the bottom of each vent mast regulates the release of nitrogen into the vent line to mitigate the risk of ignition when gas leaves the vent mast.Last, PERC System.The Powered Emergency Release Coupling (PERC) system swiftly and effectively halts cargo transhipment processes in emergency situations.It releases all transhipment pipes using specially designed safety hooks located at the junction of the terminal pipeline and the cargo LNG pipeline of the ship.The system can also release mooring ropes to quickly move the ship to a safe distance using its own propulsion or with the assistance of tugs.This applies to both the LNG transhipment vessel and the FSRU.

Economical Analysis of FSRU.
The capital cost of an FSRU terminal is typically 50-60% lower compared to an onshore terminal of similar capacity.This cost advantage is attributed to the FSRU's compact size and efficient shipyard costs, in contrast to the larger land area and significant civil engineering required for onshore terminals.The reduced capital expenditure and improved cash flow significantly enhance the project economics.As a point of consideration, a study has been conducted to compare the economic analysis of FSRU and onshore LNG terminals.The findings, presented in Table 5, indicate a lower total CAPEX for FSRU.Currently, the cost of constructing a new FSRU with a capacity of 173,000 m3 falls within the price range of $240-$280 million.The lower CAPEX can be attributed to the significant impact of the smaller size of the FSRU.Additionally, FSRU terminals offer a shorter delivery schedule for the first gas, which further improves cash flow and project economics.The ability to commence gas delivery more quickly also enhances the competitiveness of the project.Most FSRU are leased, as the vessel is owned by a shipping company and can be reassigned once the project is completed.This leasing arrangement offers advantages over onshore terminals, where the construction cost is considered a sunk cost.Leasing improves cash flow and project economics, particularly for shorter-term projects.However, for longerterm projects like those spanning 20 years, outright purchase may be more cost-effective.Some recent FSRU contracts provide this option.

Conclusion
The conceptual design of an FSRU intended to provide power plants in Eastern Indonesia with a capacity from 60 MW to 70 MW has been conducted.The design encompasses various aspects.including determining the FSRU's location.considering principal dimensions and hull form.establishing the general arrangement of the FSRU.outlining the loading and unloading procedures for LNG and the regasification unit.addressing technical considerations related to deck arrangements.and exploring the innovative utilization of solar panels.These design elements are thoroughly examined and discussed in detail within this paper.

Figure 1 .
Figure 1.Distribution of LNG Plants and FSRU in Indonesia.

Table 2 .
Plant Capacity

Table 4 .
Tank Capacity

Table 5 .
CAPEX Comparison for Onshore LNG Terminal and FSRU []