CONSIDERATIONS ON THE POWER SYSTEM RECONFIGURATION FOR A VERY LARGE CRUDE CARRIERS TANKER SHIP [301555]

CONSIDERATIONS ON THE POWER SYSTEM RECONFIGURATION FOR A [anonimizat]. Univ. Dr. Ing. Iordan Novac

Constantza Maritime University

ABSTRACT

The concept of energy efficiency (or energy optimization) [anonimizat], one of the main concerns of humanity to the whole world.

[anonimizat], [anonimizat], [anonimizat] a reduction in the amount of CO2 released to the atmosphere.

Main ideea of this paper is to improve the energy performance of a crude oil super tanker ship of 305000 dwt, by studying the possibility of introducing alternative energy sources onboard.

Keywords: [anonimizat], [anonimizat]

1. INTRODUCTION

This paper consist in concepts modernization of a very large crude carriers of 305000 dwt.

[anonimizat], [anonimizat].

Initialy, [anonimizat], [anonimizat].

2. CURRENT STATUS OF ALTERNATIVE ENERGY DEVELOPMENT ONBOARD OF SHIPS

One of the main problems of ship industry is to reduce CO2 emission.

Several alternatives are proposed to reduce or replace fossil fuels onboad ships like: sails, kites, [anonimizat], [anonimizat].

[anonimizat], hybrid systems for power generation onboard a ship. These are systems for generating energy that is actually green renewable.

Along time is been developing several concepts of eco ships.

One of the projects is Aquarius MRE System which use a lot of rigid sails and solar panels to form a vessel based on a system of renewable energy. On large vessels can be installed up to 20 [anonimizat] (figure 1).

Aquarius MRE system is not intended to be the main source of propulsion of ships. Instead, [anonimizat] 20% and emissions of toxic gases.

[anonimizat] 500 kW or more.

Figure 1 Aquarius MRE concept

Another concept is Fery Medaka Solar ([anonimizat] 2).

Eco Marine Power is leading a project to develop an eco ship designed to operate as a ferryboat for urban areas.

Medaka is a ferryboat that not only uses solar power as a [anonimizat] a range of other features that will be more softly with environment than traditional models of existing ferries.

[anonimizat] a [anonimizat] a lower cost than diesel.

Figure 2 Solar Medaka ferryboat

Finally, a [anonimizat] E / S Orcell (figure 3), produced by Wallenius Wilhelmsen.

Orcelle will have an optimal cargo loading capacity of 85000 m2, equivalent to 14 football fields. This represents a 50% [anonimizat]g able to carry 6500 vehicles.

Figure 3 Orcell eco ship

3. ESSENTIAL CONSIDERATIONS ON POWER SYSTEM RECONFIGURATION FOR A VERY LARGE CRUDE CARRIERS OF 305000 DWT.

In first state the ship is not equipped with innovative technologies to enhance energy efficiency. This is why on I will propose some measures to equip the ship with innovative technology, like: one shaft generator, five wind turbines and photovoltaic pannels.

3.1.Power system reconfiguration using a shaft generator

There are two type of operating modes for the energy system of the ship equiped with shaft generators.

1.Power Take Off Operation

In power take-off (PTO) operation, the shaft generator operates as a generator. The shaft generator drive can operate in island mode (single generator) or in parallel mode with other auxiliary generators.

Shaft generator drive uses droop control to adjust voltage and frequency when operating parallel with other generators. The shaft generator drive is seen as one of the generators in the system.

In addition to basic features, the shaft generator drive includes extra functionality. The shaft generator drive can compensate unbalanced loads in the grid and also provides reactive power compensation.

Figure 4 Power Take Off Operation

2.Power Take In Operation

In power take-in (PTI) operation mode, the shaft generator functions as a motor. The power is taken from auxiliary generators and the shaft generator drive operates the motor.

The take-me-home feature can be used if the main engine has malfunctioned. The main engine can be decoupled from the shaft line so that the shaft generator can operate independently, allowing the main engine to be repaired.

The motoring power of the shaft generator can be used to boost main engine power. The shaft generator drive can drive the shaft generator/motor in synchronization with main engine.

Figure 5 Power Take In Operation

There are three type of shaft generators if we refer to frecvency.

To illustrate the variation, the electric power diagrams are shown for the CFE (constant frecvency electrical), RCF (renk constant frecvency) and GCR (gear constant ratio) principles. The diagrams are shown for basic layouts, but it is important to note that other shaft generator layout ranges based on a particular engine load profile could be selected to ensure that the electric power from the shaft generator is available for most preferred main engine load conditions.

Figure 6 Electric power vs main engine power

Analyzing above, for the reference ship, we will choose a shaft generator CFE type, because of its constant frecvency electrical functioning.

PTO shaft type generator / CFE (figure 7) is able to produce constant frequency electricity with changes of main engine speed. If this type of generator uses a speed reducer, the alternator may have an embedded electronic converter, which provides correction for various speed of main engine, and therefore correction the speed of the alternator. As an alternative solution, and very usual one, electricity is produced with variable frequency and after is converted into electrical energy with constant frequency by thyristors.

CFE shaft generators are capable of operating in parallel mode with other generators when the main engine power is between 75 % and 100 %. Between 40 % and 75 % of main engine power, electric power produced by the generator is reduced in proportion to main engine load. Such generators are commonly used than those directly fitted on the engine because there is no limitation on the installation onboard.

Overall efficiency of such a system is between 84 % and 88%.

Figure 7 CFE type shaft generator

For reference ship we choose a Cumins HCM 6 type shaft generator (figure 8).

Figure 8 Cummins type shaft generator

Main parameters of HCM6 shaft generator are:

-power:

-nominal voltage:

-speed:

-frecvency:

-phase number:

-power factor:

The shaft generator HCM6 is CFE type and reaches rated power when the main engine has a load between 40% and 110 %. Because of during the ship voyage the turbogenerator is operating at more than 50 % main engine load, and because we want as much fuel economy, the shaft generator is a very good solution.

Figure 9 CFE type shaft generator

Also, during the ship voyage it can be used in paralel mode, both, turbogenerator and shaft generator.

From the experience of voyages, ship needs no more than 900 kW of electrical power, so, a shaft generator power of a 976 kW is a good choosen.

Finally, we have the ship electric power system configuration:

-two diesel generators YANMAR type, of 1700 kW each,

-one turbogenerator of 1100 kW,

-one emergency generator of 620 kW,

-a shaft generator of 976 kW.

3.2.Power system reconfiguration using photovoltaic pannels

The new solar cells with spherical shape and narrow dimensions, could revolutionize the field of photovoltaic solar energy application.

Japan, leader in photovoltaic technology, has developed new solar cells with tiny spherical shape between 1 mm and 1.5 mm diameter as opposed to the traditional 72 mm flat cells.

A negative electrode and a positive one, opposite each other, are positioned in the center of the surface "p" type and " n" type (figure 10).

This positioning of the electrodes makes the cell to be non – directed and may occur even distribution of the generated amperage. Sensitive cell which can take light from any direction is called three-dimensional light capture.

Figure 10 Spheral cell

We will study the possibility of placing solar onboard reference ship.

The panels are formed of spherical cells with PV module witch comprise a number of 12 spheral cells. Spheral cells can be conected in paralel or series to produce voltage power and high amperage. Lights is concentrated four times more with a hight efficiency.

Depending on available ship space,we calculate the number of solar modules, the number of photovoltaic pannels and the hence area to be located.

Figure 11 Pannels with spheral cell

We put solar panels on port and starboard platforms uppon bridge. We calculated the areas of location and got the following results as shown in figure 12:

– we have two areas, on top, of 52 squere meters each, making a total area of 104 square meters for placement of solar panels,

– we have two areas, on the bow, of 50 square meters each, making a total area of 100 square meters for placement of solar panels,

– on the aft area we have two of 50 square meters each, making a total area of 100 square meters for placement of solar panels,

Finally, we have a total of 304 square meters for placement of solar panels

Figure 12 Areea for placement of solar panels

A modul area:

S = 24 x 15 mm = 360 mmp = 0.00036 m2 (1)

Number of modules:

Nm = 304 / 0.00036 = 844444 pieces (2)

Number of cells:

Nm = 844000 pieces = 844000 x 12 =10128000 cells (3)

We put cells on photovoltaic pannels as to supply batteries of 48 V. So, we will have 126600 cells in paralel mode and 80 cells în series mode.

Total electric voltage:

(4)

Total electric amperage:

(5)

Total electric power:

(6)

Figure 13 Series mode of cells

Figure 14 Paralel mode of cells

3.3.Power system reconfiguration using wind turbines

The wind turbine is device that converts kinetic energy from wind in mechanical energy. If the mechanical energy is used to produce electricity, the device may be called wind generator.

Advantages of vertical axis wind turbine against horizontaly one:

-they are easier to maintain because moving equipment are placed closer to the ground platform,

-propeller blades are vertical, so there is no need a rudder for the propeller orientation,

– vertical turbines have increased aerodynamic efficiency at high and low pressure,

-for the same diameter of the propeller blades vwrtical turbine has a larger diameter than the turbine with horizontal axis,

-vertical turbines are more efficient in areas with wind turbulence because the propeller blades are placed close to the ground,

– propeller blades have a lower rotational speed, so can resist stronger winds than horizontal-axis turbines,

Lentz wind turbines have type cup blades which provides efficiency at low wind speed, safe operation and low noise. It is recommended to operate in parallel with photovoltaic panels thereby ensuring greater energy security.

For reference ship we choose a Lentz wind turbines with dimensions below.

Table 1. Wind turbines dimensions

Figure 15 Lentz wind turbine dimensions

The ship will be equipped with five turbines wind turbines, with a total power of 250 kW.

Figure 16 Ship equiped with wind turbines

4. OPERATIONAL COMPARATION BETWEEN FIRST AND RECONFIGURATED POWER SYSTEM

In table below we have real operation parameters for very large crude carriers of 305000 dwt.

This is a operation comparation between first power system (auxiliary engines and turbogenerator) and reconfigurated system (auxiliary engines, turbo generator, shaft generator, wind turbines, photovoltaic pannels).

We can observe that reconfigurated system cover required ship energy only if the main engine has a load bigger than aproximatly 30%.

The table coprise different speed of ship and different load of main engine.

Also, we can amphasize that inovative energy cover energy required by the ship in 95% of cases from table.

This things also means a fuel economy.

Maximum power produced by inovative technlogy onboard is 981 kW witch means o very good efficiency.

Table 2 Comparation between first ship power system and reconfigurated power system (real operation parameters)

Table legend:

ME- main engine

AE – auxiliary engine

TG – turbo generator

SG – shaft gennerator

WT – wind turbine

PP – photovoltaic pannels

5. CONCLUSIONS

Refference ship economic speed is 15 knots. If during a voyage the ship operate at economic speed, result that auxiliary engines are not used and required electrical power will be covered only by the inovative technology system.

Also, fuel consumed will be only heavy fuel oil by the main engine.

This paper treat not only theoretical aspects but also real operational parameters for power systems onboard.

6. REFERENCES

[1] NOVAC, I., Ship theory and construction, Part 2 – Ship hydrodynamics, Universitatea Maritimă, Constanța, 2013.

[2] TAIRA, K., NAKATA J. Sphelar cell array module, Japan, 2013.

[3]MUSCATO, D., GANDE E.BAUER Z., Photovoltaic Technology in the Shipping Industry A feasibility study on the use of solar energy for diesel abatement in Handymax class cargo vessels, Japan, 2011.

[4] MAN Diesel Ltd., Shaft Generators for Low Speed Main Engines, 2011.

[5] FAITAR C. Concepte de modernizare energetică a unui VLCC de 305000 tdw. Calculul și proiectarea sistemelor energetice auxiliare. Universitatea Maritimă Constanța, 2014.

[6] www.pveducation.org/pvcdrom/modules/module-circuit-design, accessed at 22.11.2015