Design of an Optimum Battery Electric Fishing Vessel for Natuna Sea

Natuna Sea is one of the places in Indonesia, which has a high potency of fish up to one million ton per year. Fisherman in Indonesia relies too much on the fossil fuel, which has limited resources. The author wants to redesign the fishing vessel into the battery electric fishing vessel that can be recharge to reduce the use of fossil fuel and also to increasing the revenue of the fisherman. To minimize the capacity of the battery, the fishing activities concept is also change into centralized fishing activities which the activities is centralized in an open sea and has the offshore building as the fishing base that has power station to recharge the batteries and cold storage to collect all the fishes. As the object to redesign, it is used 10 GT purse seine fishing vessel. As the results of the calculation, it gets the total battery capacity 6000 Ah for operation 11 hours (4 hours travel time, 6.5 hours fishing activities, and 0.5 hours break). Based on the technical and economic analysis, it can be concluded that the battery electric fishing vessel has a better revenue and fewer expenses than the diesel-powered fishing vessel.

a high potency of catching fish. The potency of catching fish in the Natuna Sea nearly reached one million tons per year. There are three fishes with the high potency in Natuna which are, Small Pelagic fish with a potency of 621,500 tons per year, Demersal fish with a potency of 334,800 tons per year, and Big Pelagic fish with a potency of 66,100 tons per year [1].
The weather condition of the Natuna Sea has been categorized as "Slight Sea" by BMKG, where the wave height of Natuna Sea never gets higher than 1.25 meters. The average of the wave height of Natuna Sea is about 0.5 meters with the range of the wind speed is from 6 knots up to 20 knots. It makes sea around Natuna Island is a safe place for the fisherman to catch fish on there.
Natuna Sea does surround by islands which have the majority of the people works as a fisherman. Natuna Island is one of the islands that located in the north of Natuna Sea. In 2015, there are 7,066 families of fisherman from around 20,401 total families in Natuna Island [2]. It means almost 35% of the people in Natuna Island does depend on the outcome of the fisherman [3].
The life of the Fisherman is relying on the price and the availability of fuel oil as the main energy of their boat, either for a main engine or generator to produce electricity [4]. As today, the price of fuel is not being subsided again by the government and the availability also getting rare in the future, the fisherman activities got involved and their revenue is getting lower each day [5]. Therefore, a fishing boat without using any fuel is needed to help the life of the fisherman in Indonesia, especially in Natuna Island.
A Fishing boat or Fishing vessel that using rechargeable batteries as the source of power onboard is one of the answers to deny the using of fuel oil on the fishing vessel [6]. So the idea is, the batteries can be recharged or switch when the fisherman is on the power station. The location of power station can be located either on the sea or land or both.
Considering the weight and the price of the batteries used on the ship is getting heavy and expensive if the size of the batteries is getting larger, then the idea is to make a fishing activity which centralized in an area. Those areas will have like offshore building which consists of the energy station (produce energy), fish tanks (stored catching fish), guard tower (observe the area), and living or accommodation room for the crews. This offshore building or aquaculture or energy station on the sea is becoming a place for the fisherman to depart and arrive for fishing activities. Later, for once in 3 days or a week, a large fishing vessel which also as a supply vessel will come to collect all the fish to bring it to the shore. So, by that, the small battery electric fishing vessel won't have a long operation time.
The location and the design of the offshore building or aquaculture won't be discussed in this research. This research will focus on designing and calculating the battery capacity of the small battery electric fishing vessel. The fishing vessel used in this research is the existed fishing vessel design and will be redesigning the propulsion system into electrical propulsion.

A. Statement of Problem
This stage is an early stage to construct the research. In this stage, questions and problems are being prepared specifically in order to determine the specific objectives of this research. The content of the research is to overcome the statement of the problems mentioned earlier and it will be done by collecting some information about the problems. Therefore, the purpose of this research can be understood at this stage.

B. Literature Study
Right after the problems is raised, a literature study is performed. In this stage, literature will be used to connect the problems with existing theories and facts from various sources. Since this research research is an implementation of many aspects discipline, various literature topics are required to be constructed into one project. The study of literature is done by reading papers, journals, research, media and literature books that relate and able to support this research.

C. Collecting Data
After literature study, the next stage is collecting data. Data collection is done by gathering information about the existed design of fishing vessel equal to 10 GT, electrical equipment specifications and requirements such as Induction motor, purse seine winch, windlass, radio navigation, etc. and also the fishing activities profiles to know the operation time.

D. Resistance and Power Calculation
In calculating the resistance and power needed for the electric motor, Maxsurf software will be used with the efficiency of propeller between 40-55%. So after the data from the Maxsurf is out, it will be easier to select the Electric motor for the propulsion engine.

E. Determination of Operation Profile
In determining the operation profile, there will be some factors should be considered such as the radius of the fishing vessel will operate, time for setting and hauling the purse seine, time for searching the fish, and how many settings and hauling will be doing [7]. Those factors will be considered to choose the best operation profile, which has the long radius with many fishing activities and also operate in one day.

F. Arrangement of Electrical Load
Planning and arranging the electrical equipment will be doing at this stage. Besides planning the electrical equipment, there will be also the selection of the best electrical equipment which has the lowest electric consumption [8] . And if the equipment can be operated manually, then it will be selected, in order to minimize the electrical consumption on the fishing vessel, so that the battery capacity needed can be minimized.

G. Calculation of Electrical Load on Board
At this stage, all the equipment which consume electricity will be calculated to know how much electricity needed on board, so that the battery can be calculated [9] . This calculation stage collects all equipment on board and lists them on voltage, power, current, operation time, and the last is the ampere-hour to know the battery capacity needed on the board.

H. Calculation of Battery Capacity
On this stage, the calculation of battery capacity need to install is performed. The steps are collecting all the electrical loads on the fishing vessel and the time estimated of all the electrical load will be consumed, then find out the ampere consumption for all electrical load and multiply them with the time consumed to get the battery capacity in ampere-hour [10] . Last, adding some reserve capacity around 10% to 15% for the uncommon situation and for an emergency [11] .

I. Calculation of Payload
This stage is performing a calculation of payload to see if the battery is changing the payload or not. Calculating the payload will need some data such as weight displacement, construction weight, machinery weight except battery and DC motor, and moveable weight. These data will help to find the payload for each type of battery will select.

J. Economic Calculation
After knowing the battery capacity and types of battery that will be chosen, there will be an economic calculation to calculate the price to invest on the electrical propulsion and the operation cost of the electrical propulsion and diesel propulsion where later on will compare each other and showing which type of propulsion has the economic advantage [12] . Besides that, there will be also a break-even calculation of the electrical propulsion to show in which year the money to invest in the battery electric fishing vessel will be paid off.

K. Arrangement of Electric Propulsion on Fishing Vessel
In this stage, designing the wiring diagram of the electrical load is performed. Not only that, it is also doing an arrangement of battery room. In designing and planning the wiring there are several factors which should be considered such as voltage needed, current flow, type of the current, and etc. Planning battery room also cannot just put them in the room, but should also consider the space available to do the replacement or maintenance of the equipment there.

A. Fishing Vessel Principal Dimension
The fishing vessel used to redesign the propulsion system is a 10 GT fishing vessel with fishing equipment used is purse seine. The principal dimension of the fishing vessel can be seen on Table 1.

B. Resistance and Power Calculation
In calculating the resistance by Maxsurf software, the power propulsion is calculated based on overall efficiency set at 50%. It consists of propeller efficiency, transmission efficiency, and electrical efficiency. So the power describes on the Table 2 is the power of the electrical motor needed to produce thrust and accelerate the ship up to 7 knots. So the total operation time of the fishing vessel is 11 hours, and because the departure time is 7 AM then the time the fishing vessel finish or arrive again in aquaculture is at 6 PM.

D. Calculation of Electrical Load on the Board 1) Selection of Electric Motor
From the Table 2, it can be concluded that the power needed to speed up the fishing vessel up to 7 knots is 11,36 kW. Then, to select the electrical motor power, it just picks the motor which produces the power minimum 11,36 kW and the selected electric motor is AC motor VM 160L which produce power up to 12 2) Electrical Load on the Board The electrical load on board is a load of electricity needed to power up all devices and equipment which need electrical power to operate [14] . The devices and equipment which need electrical power to supply can be seen in the Table 3.  Table 3, the total power needed is 133,99 kWh to cover all the electrical load on board. So the battery will be selected with minimum capacity about 5973,90 Ah, which get from dividing the kWh with the battery voltage. Besides the capacity, in selecting the battery there will be other factors need to look up such as weight, dimensions, and price. Table  4 will show the batteries can be selected as the energy source on the fishing vessel. • Calculation of DWT Based on the early planning for the fishing vessel, it can be known that the DWT of the fishing vessel is 5,4 ton. The DWT is consist of Payload and Weight of the moveable items, where the payload itself is 3,9 ton and the rest is the weight of the moveable items.
The weight of the moveable items is consists of fresh waters, foods, crews and provisions, fuel oils, and the reserves.   Table 4.
So for the LWT variation result can be seen on Figure 1.

F. Economic Calculation
In calculation of economic, it will include some expenses such as, new build fishing vessel cost both use mechanical propulsion and electrical propulsion, operation cost both mechanical propulsion and electrical propulsion, and a comparison of both mechanical propulsion and electrical propulsion in the term of expenses each year up to 29 years to see which one is better or cheaper in expenses.

1) New Shipbuilding Cost
In calculating the shipbuilding cost, it uses an estimation where the estimation of new shipbuilding 9 109 using mechanical propulsion can be seen on the Table  5. For the new shipbuilding cost without mechanical propulsion, it can be determined by the same method of estimation but without using the mechanical propulsion. The calculation is described in the Table  6. 2) Electrical Propulsion Cost In calculating electrical propulsion cost, at first, it must be chosen which battery will be used as the electric source on the board. In choosing or selecting the battery, it comes to two factors which are the payload of the fishing vessel and the cost of the batteries. In the Table 7, it will display the battery total cost. So by comparing and analyzing the payload on the Figure 2 and the battery cost of the Table 7 for the six batteries, it will select the battery which has nearly the same or more payload with the previous design and has a lower cost among others.

3) Operation Costs
In calculating the operation cost of the fishing vessel either use diesel or electric propulsion, it should have the same operational profile, so that the comparison is valid. As mentioned on subchapter 4.3 about the operation time or profile, here the calculation of operation cost. Besides, the cost of propulsion, there are also others operation cost, such as food, ice, crew salary, and maintenance cost. Table 9 shows the total expenses for operation of diesel-powered fishing vessel and battery electric fishing vessel.

4) Loan Repayment
Beside all the expenses from the Table 9, actually there is additional cost need to pay which called loan repayments. Loan repayments is a cost need to pay through the loan activities which happened before, in this case is the loan to build the fishing vessel. Loan repayments value is depend on the amount of money borrowed, time to repay, and the interest. Table 10 will show the total loan repayment per year for the dieselpowered fishing vessel and the battery electric fishing vessel.

5) Expenses Comparison of Diesel-Powered and Battery Electric Fishing Vessel [2]
Based on all calculation above, it can be presented in a graph which shows the expenditure comparison between diesel-powered fishing vessel and battery electric fishing vessel each year for 29 years. The Figure 3 shows the expenditure comparison between diesel and electric propulsion. Based on Figure 3 also can be concluded that using an electric propulsion has a bigger investment than diesel propulsion, but in the end of fishing vessel lifetime, in this case, 29 years, the electric propulsion has a lower expense than diesel propulsion up to 3 billion Indonesian Rupiah (IDR). So, it can say that the electric propulsion use in this fishing vessel is better than diesel propulsion in the term of expenses.

6) BEP (Break Even Point) Analysis
Break Even Point is a point which has a condition of the total income and total expenses is the same or equal. This point has an important role in determining if the investment is a good investment or not, because this point tells about where the time when all the investment is getting paid off [13] .
In analyzing the Break Even Point, it is need to know the price to invest, cost for operating the fishing vessel and also needs to know the income from doing fishing. The Table 11 shows the total income from operating the diesel-powered fishing vessel and the battery electric fishing vessel. From the Table 5, 8, 9, 10, and 11, it can derive and make an accumulation of the income and expenses each year for 10 years as shown in the Table 12, Figure  4 and Figure 5.   As shown in the Figure 4 and 5, between income and expenses has an intersection on 4 th year of operation. So, it means that the investment of diesel-powered fishing vessel and battery electric fishing vessel will pay off in the 4th year of operation. In Figure 5, in the 10 th year, there is a sudden rise of expenses happened because of buying new batteries to replace the old one.

7) Internal Rate of Return (IRR) Analysis
Internal Rate of Return is the value that show the investor the annual growth rate of an investment. The value of IRR is related with the present value, because the goal of IRR is to find the rate that makes the present value of the sum of annual cash inflows equal to initial net cash outflow for the investment [15] .
By knowing the net cash flow which is calculated by subtracting the cash inflows and outflows each year, the value of Present value can be calculated by dividing the net cash flow with the sum of one and discount rate rise to the power of time period. The present value later on, will be used to calculate the IRR by using IRR formula in Microsoft excel.
The result of IRR for diesel-powered fishing vessel is 13,9% and for battery electric fishing vessel is 14,1%. It means, in the side of investor also, the battery electric fishing vessel is better to invest than diesel-powered fishing vessel. In the case of comparing it with the loan interest which is about 10%, this battery electric fishing vessel is a good investment project, because has higher value.

G. Arrangement of Electric Propulsion on Fishing Vessel
Electrical wiring on this fishing vessel is consist of two junctions which are AC junction and DC junction. AC junction consists of all equipment on the fishing vessel that required AC voltage to run such as propulsion motor and purse seine motor. DC junction consists of all equipment on the fishing vessel that required DC voltage to run such as radio navigation, navigation lamp, fish finder, and emergency lamp.
Each junction and the battery panel should be installed a good wiring that has the capability to deliver the electricity and also safe during the operation. In calculating the right wiring for each installation, it needs to calculate the nominal current. Nominal current can be calculated using these formulas: • For three phase AC current: After knowing the nominal current, the wiring can be selected by picking the value of nominal current as the minimum value of current the wiring should deliver.
Besides selecting the right wiring, it also needs to select the right busbar that can deliver the electricity safely. In order to select the right busbar, it needs to calculate the busbar current by using the formula below: Ibusbar = 4 x Inominal After knowing the busbar current, the busbar can be selected by picking the value of busbar current as the minimum value of current the busbar should deliver.
As for the complete wiring diagram and battery room layout can be seen in the attachment.

IV. CONCLUSION
The optimum battery for Natuna Sea electric fishing vessels 10 GT is 6000 Ah with the range of distance about 14 NM, speed service about 7 knots, and fishing activities about 6,5 hours.