Black sea waves, energy source.

Samoilescu, Gheorghe ; Sergiu, Nicolae ; Dorian, Marin 等

1. INTRODUCTION

West side of the Black Sea is baric disturbance more subjected than other areas as the meteorological data reveals. The cyclone and anticyclone genesis high frequency is the real reason (Bologa 1998).

The storm conditions are frequently created in the cold season when low pressure atmosphere mass is coming over worm waters. Air stratification is not stable and this generates vertical and horizontal high wind gradients.

Wave height increasing is also the consequence of constant wind flow, stable in time and direction. Six hours at a 9 m/s wind speed produces a 0.9 to 1.2 meters height increase and from 15 to 28 meters in length. In areas more than 40 meters water depth creating waves time is 20-200 minutes depending on wind speed. The extinguish time in this case is between 2 and 5 hours. (Iulian 1990)

Black Sea currents regime also depends on river water volume contribution, water density gradient and sea floor. Measurements from Constanta reveals: 36.6% S currents, 22.6% N and 40.8% SV-SSE.

2. IRREGULAR WAVE CHARACTERISTICS

Natural waves are irregular, with different periods and amplitudes (Bondar 1998), (Bondar1992). The analysis will use statistics and probabilistic techniques. Wave parameters are presented in figures 1 and 2:

--[xi]--sea surface instant displacement from reference position;

-[[xi].aub.a]--relative wave amplitude (distance from reference position to wave comb);

--[h.sub.w]--relative wave height (vertical distance between two combs or two gaps);

--[T.sub.4]--relative period at zero intersection (time between two consecutive zero displacement [xi](t) with ascendant trend);

--[T.sub.3]--relative period between two wave combs;

If [xi] displacement depends on x we shall define:

--[([L.sub.w]).sub.4]--relative wave length at zero level considering a positive trend (distance between two zero values in movement way);

--[([L.sub.w]).sub.3]--relative wave length between two successive combs (horizontal distance between two combs in movement way);

--[[bar.h].sub.w]--average irregular wave height (arithmetic average in a sea specific point, excepting values lower than 0.1 m).

[FIGURE 1 OMITTED]

The results are:

--average wave period, corresponding to [xi](t) = 0

[[bar.T].sub.4] = [T.sub.44]/[N.sub.10] = 86/125 = 0.688s; (1)

--average wave period, corresponding to combs

[[bar.T].sub.3] = [T.sub.53]/[N.sub.20] = 120.2/127 = 0.94s; (2)

--average wave period

[[bar.T].sub.0] = [T.sub.t]/[N.sub.01] + [N.sub.02] = 206.2/252 = 0.81s. (3)

For average wave length the same pattern must be used. Calculus must be done for all sea levels from table 1.

Processing a great number of measured values in a long time period is the key for right results.

Measurements revealed a stationary character of irregular wave. This opens the way for statistic processing of measurements.

We offer a calculus sample in tables 1 and 2.

In order to obtain the characteristics of wave, short time measurements are the advantage of statistic processing.

Elaborated by Meteorology and Hydrology Institute of Bucharest, Black Sea wave specter has the general form

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (4)

[FIGURE 2 OMITTED]

In equation (4)

--E = [rho]g[H.sup.2]/8 is the average specific energy of waves, in [kJ/[m.sup.2]],

--[bar.[omega]] = 2[pi]/[bar.T] is the average pulse, in[rad/s],

--[omega] is the wind pulse, in [rad/s],

--[rho] is the water density and

--H is the height of the wave, in[m].

Specific energy from 1994 to 2007 had values between 0.05 to 4.46 [kJ/[m.sup.2]], 88.9% from it being in 0.7-3.7 [kJ/[m.sup.2]] limits.

Wave characteristics are subjected to a significantly change over a year and from one year to another due to a great gradient of wind.

We will consider a Gauss distribution of the relative height and a Rayleigh one for amplitudes. Five energy values will be taken into consideration for the above mentioned interval 0.7-1.4 -2.1-2.8-3.6 [kJ/[m.sup.2]].

Average heights will be calculated for this energy values.

A micro power station is proposed to work with Black Sea waves. It will be designed according to 3.3 s wave period and 0.65 m average height.

3. HYDRO PNEUMATIC POWER STATION MODEL

A micro power station using wave energy is the aim of present research. It will work in an insular regime using the hydro pneumatic principle.

The caisson is made from steel and orientated to open sea. This particular orientation was chosen in order to use all types of wave. The generator module is placed into a cylindrical column fixed in caisson's ceiling. One way turbine and an electric generator are generator's main components. Cylindrical column is vertically fixed over the caisson. At a safe level, where waves cannot reach, it has a hole for air circulation.

One way turbine requires a special attention. The concept takes into consideration a variable geometry turbine. Overload turbine protection use a centrifugal device.

The whole installation is sustained by concrete embedded columns. This is able to ensure the necessary stability when the installation is placed on the sea floor.

4. CONVERSION SYSTEM CHARACTERISTICS

We will present assemble main components most important characteristics.

Micro power station characteristics are:

--nominal power of micro station 3 kW

--system length 5 m

--system height 7.4 m

--system width 5 m

--micro power station global output 0.329

The turbine characteristics are:

--type one-way

--pale aerodynamic profile NCA 0012

--nominal power 3.5 kW

--spinning 3000 rot/min

--air speed at turbine nominal power 53.7 m/s

--turbine diameter 0.42 m

--estimated output 0.5

Generator characteristics are:

--type vertical, synchronic

--nominal power3 kW

--spinning 3000 rot/min

--estimated output 0.91

5. CONCLUSIONS

Waves are wind generated. Black Sea wave regime is highly unpredictable regarding direction, height and period.

The most important aspect in wave creation is the relation between wind speed and wave dimensions.

The micro power station will be designed according to particular characteristics of the Black Sea.

6. REFERENCES

Bologa, A.S. (1998). I.R.C.M. Contract no. 31/1998, Regional Research and Management Development in the Black Sea, Constanta

Bondar, C. (1992). Contribution at Profile, Deformation and Breaking of the Waves in the Coastal Region, Meteorology Institute of Bucharest, Bucharest.

Bondar, C. (1998). Regarding of Energetic Specter Aspects of Waves in Romanian Sea Shore of the Black Sea, Meteorology Institute of Bucharest, Bucharest.

Iulian, C. (1990). Waves Energy Exploit, Technical Publishing House, Bucharest

*** (2007). Hydro pneumatic power plant using waves, Contract 21-001, National Center for Programs Management CNMP, Bucharest.

Tab. 1. Wave characteristics

 No. Cumulated
[h.sub.w] of wave
(m) waves % numbers 1 x 2

1 2 3 4 5
2.0 4 4 4 8
2.25 40 39 44 90
2.5 31 30 75 77.5
2.75 25 25 150 68.5
3.0 2 2 102 6
[summation] 102 100 -- 250.25

 Average wave height 1 x 2
[h.sub.w]
(m) [[bar.h].sub.w] ([[bar.h]
 .sub.w]).sub.1/3]

1 6 7
2.0 8 --
2.25 90 --
2.5 77.5 17.5 = (2.5 x
2.75 68.75 68.75
3.0 6 6
[summation] 250.25 92.25

 Average wave height 1 x 2
[h.sub.w]
(m) ([[bar.h].sub.w]) ([[bar.h].sub.w])
 .sub./1] .sub.1/10]

1 8 9
2.0 -- --
2.25 -- --
2.5 -- --
2.75 22 = 2.7 x 8 --
3.0 6 3
[summation] 28 3

Tab. 2. Wave characteristics

 T4 between Periods [T.sub.3] Periods
 two values number between number
[zeta](t)=0, from two combs, from
 (s) column 1 (s) column 3

 1 2 3 4
 0.5 20 0.6 21

 0.7 40 0.8 42

 0.9 30 1.0 28

 1.1 10 1.2 12

 1.2 25 1.4 24

[summation] [N.sub.10]=125 -- [N.sub.20]=127

 T4 between 1 x 2 3 x 4 5 + 6
 two values
[zeta](t)=0,
 (s)

 1 5 6 7
 0.5 10 12.6 22.6

 0.7 28 33.6 61.6

 0.9 27 28 55.0

 1.1 11 14.4 35.4

 1.2 30 33.6 63.6

[summation] [T.sub.44]=8 [T.sub.33] = 120.2 [T.sub.0] = 206.2