where,
Δ BHP; the added brake horse power[kW]
f(v); Rayleigh wind speed distribution
B(v); the added brake horse power characteristic by the air resistance[kW]
Vm; the relative maximum wind speed[m/s]
The added brake horse power characteristic by the air resistance was calculated by the equation.
where,
B(v); the added brake horse power characteristic by the air resistance[kW]
Ra; the air resistance[N]
Vs; the ship speed[m/s]
ηp; the propulsive efficiency, It is 64[%].
The air resistance was calculated by the equation.
When relative wind speed is from 0[m/s] to cut in wind speed and over cut out wind speed.
Ra = 9.8・2・ 0.0064・Sr・ Aw・ V2・cosθ (5)
When relative wind speed is from cut in wind speed to cut out wind speed.
Ra = 9.8・0.0064・Aw- V2 cosθ (6)
where,
Ra; the air resistance[N]
Sr; solidity ratio, It is 0.04.
Aw; the expanded area of the blade[m2]
V; the relative wind speed[m/s]
θ; the angle of the relative wind direction from the head of the ship
As the result of calculation, when the relative wind speed was 19.5[m/s] and the relative wind direction was from the head of the ship, the maximum value of added brake horse power was 4.1 [kWh]. In case of that, the wind energy was 8.2[kWh] and the total fuel consumption decreased by 0.8[kg/h].
2.3 Reduction of Fuel Consumption and NOx and SOx Emission
The fuel consumption and NOx and SOx emission of the designed electric power generating system with those of the present electric power generating system were compared. They are shown in Table 1.
Table 1. The fuel consumption and NOx and SOx emission
3. ELECTRIC POWER GENERATING SYSTEM WITH WIND ENERGY GENERATION SYSTEM OF LARGE SHIP
3.1 Outline of Large Ship
The large ship is a coal cargo ship of NYK line CO., Ltd.. The coal cargo ship having the length of 239.8[m], the breadth of 43.0[m], and the gross tonnage of 58013.0[t], shuttles among Japan, North America, and Australia, and takes about twenty-four days for a voyage. The subject navigation of this paper was from February 21 in 1998 to March 3 in 1999, which totals to two hundred and eighty days.
The present electric power generating system of the coal cargo ship has three sets of diesel engine generators having the capacity of 530[kW] and one set of diesel engine generator having the capacity of 100[kW] for an emergency.
The maximum value of electric energy consumption is 383[kWh], the minimum one is 259[kWh], the average one is 320[kWh]. During the navigation, one diesel engine generator is operated and provides the electric power.
3.2 Design of New Hybrid Electric Power Generating System of Large Ship
3.2.1 Analysis of Wind Data and Operation of Wind Turbine
From the daily average data of true wind direction, true wind speed, relative wind direction, and ship speed those were measured every hour and recorded in deck and engine abstract log, relative wind speed was calculated.
From the data of relative wind speed, the distribution of it was obtained. The distribution of relative wind speed is shown in Fig.4. According to Rayleigh wind speed distribution (average wind spped is 8[m/s]) that is similar to the distribution of relative wind speed and the distribution of wind energy, the operating wind speed of setting wind turbine was decided as follows; cut in wind speed was 4[m/s]. Cut out wind speed was 25[m/s]. Rated wind speed was 13[m/s].
Fig.4. The distribution of relative wind speed
3.2.2 Setting Place and Dimensions of Wind Turbine
From the general arrangement of the ship, the setting place and dimensions of wind turbine were decided.
Twelve wind turbines were set between the hatches on the deck; each turbine has a rotor of 6[m] in diameter, two blades upwind, and a blade tower 7[m] in height. The setting place of the wind turbines is shown in Fig.5.
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