Summary of mechanical engineering and engineering mechanics doctoral thesis: Research on the mechanical model and calculating design of an electrical generator for sea wave energy

Objective of the thesis For the purpose of building a model of electrical generator for sea wave energy, the device operates efficient and in suitable to Vietnam''s sea condition; determining the optimal damping coefficient of the generating motor, model parameters to received the maximum output power; design, fabrication of the electrical generator with the output voltages are 12 VDC, 220 VAC frequency 50 Hz and pure sine wave.

MINISTRY OF EDUCATION VIETNAM ACADEMY AND TRAINING OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY Nguyen Van Hai RESEARCH ON THE MECHANICAL MODEL AND CALCULATING DESIGN OF AN ELECTRICAL GENERATOR FOR SEA WAVE ENERGY Major: Engineering Mechanics Code: 52 01 01 SUMMARY OF MECHANICAL ENGINEERING AND ENGINEERING MECHANICS DOCTORAL THESIS HANOI – 2019 The thesis has been completed at: Graduate University of Science and Technology - Vietnam Academy of Science and Technology Supervisor: Prof DrSc Nguyen Dong Anh Reviewer 1: Reviewer 2: Reviewer 3: Thesis is defended at Graduate University of Science and Technology - Vietnam Academy of Science and Technology at…, on date…month…2019 Hardcopy of the thesis be found at: - Library of Graduate University of Science and Technology - Vietnam National Library INTRODUCTION Reasons for choosing the topic According to calculations by scientists, the received energy from fossil fuels will become gradually exhausted, and now therefore looking for new energy sources is requisite For Vietnam, the 2020 target is to become a country in which marine economics will constitute over 50% of GDP Therefore, the energy demand supplying for general economics and particular marine economics is very important The research and fabrication of electrical generators for sea wave energy are necessary Moreover, the electrical energy received from sea wave energy conversion is friendly to environment, almost endless and is a clean energy source The sea wave energy is an important energy source of the world as well as Vietnam in the future In addition, Vietnam has the advantage of being a country with a coastline stretching over 3260 km, with more than 3000 islands and over one million km2 of sea surface, it indicates that the energy source from the sea is huge In order to exploit the vast energy resources of the sea, the author proposes a research of thesis of building a device model to convert from sea wave energy to electricity Objective of the thesis For the purpose of building a model of electrical generator for sea wave energy, the device operates efficient and in suitable to Vietnam's sea condition; Determining the optimal damping coefficient of the generating motor, model parameters to received the maximum output power; Design, fabrication of the electrical generator with the output voltages are 12 VDC, 220 VAC frequency 50 Hz and pure sine wave Research method The thesis uses analytical method, combining of the numerical simulation and experiment for calculation, being specifically described as follows: - Determining the optimal damping coefficient of the generating motor and model parameters by the analytical method - Using fourth-order Runge-Kutta and Simpson methods in numerical simulation calculations, to determine the output power of the device received from the sea wave energy and survey the device's operation according to the sea wave conditions - Calculation, design, fabrication and experiment of the electrical generator operates in sea Scientific and practical significance - The thesis brings the electrical generator model for sea wave energy, with the process of making the electrical generator device from research to fabrication, the device operates effectively and suitable to the actual conditions of Vietnam sea - The electrical generator can be used for signal buoys of seaway and can supply the electrical power for lighthouses Structure of the thesis The contents of the thesis include the introduction, chapters, the conclusion and proposition CHAPTER OVERVIEW OF RESEARCHES ON THE ELECTRICAL GENERATOR FOR SEA WAVE ENERGY AND APPLICABILITY IN VIETNAM 1.1 Overview of researches on the electrical generator in the world In the world, the research and fabrication of the electrical generator devices for sea wave energy source have been considered for a long time The received electrical energy source for wave energy conversion has met some demands of society Up to now, the electrical generators from sea wave energy have been investigated and fabricated in many countries, for example, Britain, Canada, Denmark, France, Ireland, Japan, Norway, Spain, Sweden, South Korea, the United States,… The models are researched in various forms such as the on-shore device, the device fixed on the bottom of the sea, and the floating device on the sea surface [1-19] The analyses of models show that the electrical generator devices have been researched and fabricated in many ways In device models, the generating motor is designed to operate in a rotational motion or in a vertical up-down motion Each device has different advantages and disadvantages, depending on the fabrication capabilities of each unit so that the research and fabrication devices operate effectively and suitable to the actual use 1.2 Overview of researches on the electrical generator in Vietnam In Vietnam, several research institutions have fabricated electrical generators for sea wave energy At National Research Institute of Mechanical Engineering, the researchers have calculated device model with Pelamis type, the device has been experimented in Hon Dau - Haiphong sea and supplied the electrical power to the border guards on the island to use [24]; At Vietnam National University, the researchers have fabricated linear electrical generators that operate and float on the sea surface in vertical direction The device has been tested in sea with the received output power still limited [26,27]; At Institute of Energy Science - VAST has fabricated an electrical generator device from sea wave energy, the device is fixed on the sea surface The fabricated device used the vertical axis hydropower generator with 60 W power, the device has been tested in sea with the output power received 50.92 W [28]; At Institute of Mechanics - VAST has carried out researches on surveying the energy characteristics of floating wave energy converters, to propose the design, calculation and fabrication of energy conversion devices [30] Moreover, since 2013, in the professional work, the author has calculated a numerical simulation of the electrical generator model from sea wave energy The device model is calculated with the linear electrical generator, directly generating electricity and fixed on the seabed [31] And more, the author has leaded the project "Study, design and fabrication of the electrical power system from the renewable energy sources, project’s code: VAST 02.04/11-12" [32] The project has designed and fabricated a power generation system with input energy sources from solar panel, wind energy and sea wave energy In which, the input source from sea wave energy has been calculated and designed to be integrated with the electrical generator for sea wave energy will be studied and fabricated in the thesis 1.3 Research on the ability to apply the electrical generator in Vietnam and research orientation of the thesis Vietnam is a country with a coastline stretching over 3260 km, a marine space of over million km2, accounting for 29% of the area of the East Sea, with nearly 3000 large and small islands, it indicates that the energy source from the sea is huge From the monitoring and survey data show that the average sea wave height at the near coast is about 0.5÷1.2 m with the wave period from 2÷8 seconds, offshore wave height is about 1.2÷2 m with a wave period from 6÷8 seconds Especially, when the rough sea, the coastal wave height reaches about 3.5÷5 m, offshore reaches about 6÷9 m [34-37] This is an abundant energy source, which is very suitable for the electrical generator devices from sea wave energy to be with small and medium power Moreover, the demand for electricity to provide for the marine economics, electricity for national security in the protection of sea and island sovereignty is an urgent task, while Vietnam’s National electricity Network can not reach Therefore, the research and fabrication of the electrical generator devices for sea wave energy to meet the actual needs is necessary Research orientation of the thesis: The purpose of the thesis is research, calculate and design a device to generate electricity from sea wave energy The device is efficient operation, and suitable for processing ability in Vietnam The power source of device generates at two voltage levels are 12 VDC and 220 VAC frequency 50 Hz, with voltage quality is pure sine wave and according to Vietnam’s National grid Standard Especially, the electrical generator can be used for signal buoys of seaway and can supply the electrical power for lighthouses Conclusions of chapter Chapter presents an overview of the electrical generators in the world, especially, the models mounted on the seabed and vertical direction operation Having pointed out that domestic units have been realizing research and fabrication of the electrical generator with detailed analysises for each type of device model The characteristics of sea wave energy have been collected and analyzed, with data on wave energy flux, wave height and wave period to along the Vietnam coast stretching over 3260 km In which, the average sea wave height at the near coast is about 0.5÷1.2 m with the wave period from 2÷8 seconds, offshore wave height is about 1.2÷2 m with a wave period from ÷ seconds Especially, when the rough sea, the coastal wave height reaches about 3.5÷5 m, offshore reaches about 6÷9 m Having indicated that the necessity and application capability of device model in Vietnam Having shown out the structure of the electrical generator model for sea wave energy, and orient the research contents of the thesis, the device operates effectively and suitable to the actual conditions of Vietnam sea CHAPTER RESEARCH ON THE MECHANICAL MODEL AND OPTIMIZATION OF THE ELECTRICAL GENERATOR FOR SEA WAVE ENERGY 2.1 Building a model of the electrical generator for sea wave energy The electrical generator device is fabricated for converting sea wave energy into electrical energy This requires a system that can convert the vertical slow motion of buoy to a high speed rotating motion at the input of generating motor The main structures of device include a circular cylinder-shaped buoy, a rope, a piston-rack, a gearbox, a generating motor, a block of 12 VDC voltage stabilizer, a DC-AC inverter and a protection system with the generating voltage being 220 VAC frequency 50 Hz and pure sine wave, as shown in Fig 2.1 zS(t) m z(t) k a Illustration of device model [33] γ b Mechanical model Figure 2.1 The schematic illustration of an electrical generator for sea wave energy The governing equation of buoy associated with piston-rack, as shown in Fig 2.1, can be written as follows: m d z dt  gSb ( z s  z )  mg   dz em dt  k L( z  z0 )  k N ( z  z0 ) , (2.7) where m is total mass of the buoy and the piston-rack, z= z(t) is the vertical coordinate describing the position of the buoy at time t; ρ is the water density, g is the acceleration of gravity, Sb is the bottom area of the buoy, zs is the vertical coordinate describing the height of sea wave from the seabed; the damping constant γ = γf +γem , in which the damping coefficient of fluid, γf, is assumed to be very small in comparison with the damping coefficient of generating motor γem [44,45], and can be neglected; kL is the linear spring coefficient, kN is the nonlinear spring coefficient, z0 is the rest position The average of the power Pgm extracted from the wave by the converter taken over the time interval [0,τ] is given by [15,20,38-41]: Pgm  1   em z (t ) dt  (2.8) 2.2 Oscillating survey in nonlinear case From the motion equation (2.7), performing the variable transformation z – z0 = x, the equation (2.7) is rewritten as: d 2x dx k L x  k N x (2.22) dt dt The wave equation used here is z s  A cos(t )  z m  gS b ( z s  z  x)  mg   em Use symbols  ,  , c and B In case of near resonance      , performing the calculation, the author gets equation: 11   m gSb A  k L  gSb  2   em  The mechanical power of the device received from the sea wave energy in a period is determined: Pgm    em (gSb A) 2 k  gS  m L b 2   em2 (2.56) The maximum spring force is determined: FL_max = kLHmax (2.57) The maximum Acsimet force of buoy: FAcs_max = ρgπa2h (2.58) The device model is researched and fabricated with the selection of Hon Dau - Hai Phong sea to test and exploit in the actual operation At Hon Dau sea, the sea wave conditions have a period to change in the range of 3.5÷4.5 seconds and the wave height of 0.5÷1.4 m [36], so the moving velocity in the vertical direction reaches from 0.29÷0.62 m/s In the thesis, the model is determined with the smallest mechanical power level of device to reach 270 W, the oscillating range of the model is 0.45 m From the expressions (2.57), (2.58) combining the wave data in Hon Dau sea, the model parameters are determined kL = 2100 N/m, the buoy is circular cylinder-shaped with a height of 0.42 m and radius of 0.4 m Figure 2.4 shows the graph of the mechanical power levels of the device according to the damping coefficient γem at the wave wave periods 3.5 seconds, 4.0 seconds, 4.26 seconds, 4.5 seconds in a wave amplitude of 0.5 m In the thesis, the selected generating motor has a damping coefficient of 3400 Ns/m, corresponding to the mechanical power of the device is obtained maximum 12 Survey of the mechanical power according to the buoy size: In survey calculation, the buoy radius varies from 0.35÷0.55 m Calculation results given a comprehensive picture of the mechanical power levels of device received from sea wave energy In figure 2.8 is a graph of the mechanical power of the device received from sea wave energy according to the buoy radii at sea wave periods Figure 2.4 The power versus damping coefficient Figure 2.8 The power versus radius of buoy 2.4 Building a numerical simulation program and survey the operation of device to converte from sea wave energy to mechanical energy Building a numerical simulation program: The motion equation (2.7) is solved by the fourth-order Runge Kutta method, applying the Simpson method to calculate the numerical integral and determine the mechanical power level of the device The numerical simulation program is programmed on Matlab software, to investigate the operation of the device with the effect of the nonlinear spring when the device operates at m wave height or higher 13 Algorithm flowchart of numerical simulation program: Bigin Inputs t0, Z0, Δt, tmax, ps Calculation: k1 = f(ti, Zi, ps) k2 = f(ti+ ti:= ti+1 t t k3 = f(ti+ , Z(i) + , Z(i) + t t k1, ps) k2, ps) k4 = f(ti+Δt, Z(i) + Δtk3, ps) Z (i 1) No Z (i ) ti+1:= ti + Δt  ( k1  2k  2k3  k ) t / Integral (2.8) by Simpson method: ti+1≥ tmax n 1 Yes Output results ( j) ( j) Z1  Z1 ; Z  Z kq1   Q ( Z 2( j ) , p s ) j 1, 3, n2 kq   j  , , ( j) Q ( Z , ps )  Q ( Z (0) , ps )  Q ( Z (n) , ps )  t 2  P  gm  3  kq1  kq   End Figure 2.9 Flowchart of the numerical simulation program In the survey calculation, the author has performed in two cases that is the first-order wave (linear wave) in the expression (2.41) and Stockes's second-order wave is given by [38,51,52]: zs  A sin(t )  A k cosh(kz0 ) sinh ( kz0 ) [  cosh(2 kz0 )] sin( 2t )  z0 (2.59) 14 Numerical simulation calculation of the device's operation: From the calculating results are shown that the operation of the device depends on both the amplitude and frequency of the sea waves In the case, with the first-order wave, the oscillating buoy is delayed in phase compared with the sea wave about 33.60 (Fig 2.11) The Figure 2.16 illustrates the relationship between velocity and displacement of the buoy motion in the case of the second-order wave It shows that the phase orbit of buoy motion is stable and varies in the frequency and amplitude components of the secondorder sea wave 0.5 6.2 Buoy displacement Sea wave displacement 0.4 0.3 5.8 Velocity (m/s) Amplitude (m) 5.6 5.4 0.2 0.1 -0.1 -0.2 5.2 -0.3 Time (s) 10 12 Figure 2.11 The displacement of buoy and the sea wave elevation level versus time 5.2 5.3 5.4 5.5 5.6 Displacement (m) 5.7 Figure 2.16 The phase orbit of buoy motion Figure 2.20 shows the characteristic curves of mechanical power according to the sea wave amplitudes, at the wave frequency appears continuous when testing the device in sea that received 1.47 rad/s Figure 2.21 is the motion of the buoy according to the sea wave amplitude with Stockes's second-order wave function The results are calculated at wave amplitude A = 0.5 m, the difference of power between the two cases when considering linear system (kN = 0) and nonlinear (with kN = 1680 N/m3) is 4.4% For wave amplitude A = 1.5 m, the difference is 17.1%, respectively 15 Figure 2.20 The characteristic curves of power versus sea wave amplitude Figure 2.21 The displacement of buoy versus sea wave amplitude Conclusions of chapter In chapter two, the author has built the detailed schema of the electrical generator for sea wave energy, and set up the nonlinear motion equation of the model The average method of nonlinear mechanics has been applied in the resonance phenomenon survey to obtained the graph of amplitude-frequency resonance curves, and indicated the device's stable and unstable operation area Providing the ability to fabricate operattion device at nonlinear region used in sea with large wave amplitude With the damping coefficient of the generating motor, the stiffness of the spring, and the buoy size of the device have been determined optimization from actual sea wave data The author has selected the generating motor of Windbluepower Power Company with stable generating power can grow to 1500W Writing a program to calculate the numerical simulation Surveying the nonlinearity and the vibration amplitude of model according to the sea wave amplitudes, determining the phase orbit of the buoy motion and device's mechanical power level receives from the wave energy Results of chapter are published in [3], [4] and [5] 16 CHAPTER CALCULATING DESIGN AND FABRICATING DEVICE 3.1 Structure of the electrical generator for sea wave energy In the model, the device is added the solar panel to install on the buoy The aim is to create an efficient generation system, the solar panel is also an extra energy source to assure that the signal lamp at the top of buoy always operates for the time at which the sea is calm Figure 3.1 Structural schema of the electrical generator for sea wave energy 3.2 Calculating design of the mechanical part The drawings are calculated and designed on Solidworks and AutoCad software packages The detailed drawings, function blocks and inner mechanical structures are calculated and installed appropriately in the device 17 In the device model, the buoy is designed a circular cylindershaped with height of 420 mm and a diameter of 800 mm, the casing of device is diameter of 500 mm and 750 mm in height Figure 3.3 Inner of the electrical generator Figure 3.5 The casing of electrical generator Table Main structural components of the electrical generator Parameters Value Piston casing length (mm) 400 Piston rod length (mm) 450 With parameters: Rack length (mm) 450 h1 = 250 mm Pinion diameter (mm) 60 Gearbox ratio 1:30 h2 = 750 mm h3 = 750 mm l = 1634 mm 3.3 Calculating design of the electrical part The electrical part in the device is calculated using a generating motor that it is the AC three-phase type permanent magnet motor, and the 12 VDC voltage stabilizer with the input voltage received from AC three-phase voltage of the generating motor These 18 equipments were imported from WindBlue Power Company The output voltage from the 12 VDC voltage stabilizer is connected to the input of DC-AC inverter In the thesis, the DC-AC converter is designed with a 2000 W power, and according to Vietnam’s National grid Standard The protection circuit block is built to control the operating device according to conditions of overload, high heat level and weak voltage to protect the operating system [39,61] 2 13 VSS U5 COM VCC + SHDN DB102 C13 D11 10uF 104 HO 2.2R D19 LO D12 22R D4 22R Q13 40N60 R29 3.3K 4148 R28 L1 294SN D14 22R D26 R21 22R C22 104 T13 + 12 HIN VS LIN VCC R10 R DIODE Q10 IRF140 RA1 RB0/INT D18 22R 16F716 VDK Q18 40N60 R39 3.3K 4148 R38 R18 R R37 3.3K 4148 R36 R47 10K 18 GND T14 TRANSFORMER ISOLATED Q17 40N60 RB2 10 11 12 914 RB3 RB4 D17 VDD U10 U9 2.1 ( Chữ in đậm, 11, Times New Roman) R Q16 40N60 R35 3.3K C20 105 4148 R34 R49 10K RB1 OSC1/CLKIN C19 225 C18 225 22R R48 RA0 16 22n C17 C1 0.1uF RB5 13 D30 D31 RB6 RB7 Y 20M DIODE RA2 RA3 R43 OSC2/CLKOUT MCLR VCC C16 22n RA4/TOCKI 15 D10 R42 17 R17 22R D16 1K 1K R45 R16 R R46 D9 1K 1K U7 Q9 IRF140 1K T11 CHƯƠNG …… R D33 LO R33 3.3K 4148 R32 R51 330R 22R R50 521 22R 521 DD 2.1.1 (Chữ in đậm, nghiêng, 11, Times new Roman) R56 5.6K 14 18k C28 393 C27 103 13 IN1+ IN1IN2+ IN2- CT RT VREF Q20 V 12 C1 C2 E1 E2 11 4148 2.2K R54 1M 12 + Q21 COMP DTC OC VCC - TL494C A1013 20M U19A U12A + - 11 R55 C26 33 D32 LM324 D34 LM324 4148 ( Chữ thường, Times New Roman, 11) TIP41CQ19 LS2 10 VCC5 R58 470R R10-E1Y2-V52 5VDC 12VDC 4.7u C25 33 5VDC 10 2.1.1.1 (Chữ thường, nghiêng, 11, Times New Roman) C28 Y2 A1013 12VDC AQ Sensor7 + U21A LM339 - RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 VDD VSS RD7 RD6 RD5 RD4 RC7 RC6 RC5 RC4 RD3 RD2 12 Ap chuan RE3 RA0 RA1 RA2 RA3 RA4 RA5 RE0 RE1 PIC16LC74/FP RE2 VDD VSS RA7OSC1 RA6OSC2 RC0 RC1 RC2 RC3 RD0 RD1 R57 10K R58 U20 16 15 R59 1.8K 11 10u C29 220V AC 225 C14 D29 R12 R R15 D28 10uF 104 3 Q6 IRF140 R 2.2R C15 HO VCC 30VDC R11 COM 13 VSS Q5 IRF140 R VB 11 IR2110 SHDN R9 330uF C23 Q15 40N60 C2 ( Chữ thường, Times New Roman, 11) T10 D15 10 + D7 D20 C24 104 R41 U8 R8 R C3 330uF 1 150K Q4 IRF140 R R19 L 220uH 3.3K D27 VDD R7 R52 VCC 150K R6 R R D8 DIODE 330uF 10K + 3.3K R44 + R22 R20 S R31 3.3K 4148 2 0.15R 1.1.1.1 (Chữ thường, nghiêng, 11, Times New Roman) R23 DD Q14 40N60 R30 D5 D13 L2 294SN T9 C10 104 470uF D6 Q3 IRF140 C11 + C7 104 R5 C6 470uF D25 + 330uF C5 10K D24 R4 R R VCC GND VCC Q2 IRF140 DSCHG C4 R3 + THR IR4427 TRG R2 R 30VDC OUT Q1 IRF140 R CV RST Q12 40N60 R27 3.3K C21 105 4148 R26 U1 S R1 R25 3.3K 4148 R24 DIODE OUT 7805 Q11 40N60 C12 - D3 VB IR2110 D23 VS LIN 1 T8 R40 HIN Q8 IRF140 11 GND IN 330 VDC VCC R14 R D21 D22 3 U4 10 12 R13 R GND 7815 V 12 VDD IN D2 + Q7 IRF140 D1 C8 104 OUT U6 C9 2200uF + T7 G ……… U11 5VDC Figure 3.8 Schematic illustration of DC-AC inverter and protection system 19 3.4 Device fabrication The electrical generator is fabricated and assembled including the core of device, mechanical structures and the protective frame of device when the actual experiment in sea as follows: Figure 3.17 The core of device Conclusions of chapter Figure 3.18 The electrical generator device Results obtained in this chapter are as follows: Having built the total structure of the electrical generator for sea wave energy and showing the function blocks in the device The mechanical structures have been detailed calculated and designed for device Having calculated the electrical part with DC-AC converter to convert from 12 VDC voltage to 220 VAC voltage frequency 50 Hz and pure sine acording to Vietnam's National grid Standard, and the protection system for the operating device All parts of the device have been fabricated and complete assembly of device, checking the operation of device in the laboratory Results of chapter are published in [2] and [6] 20 CHAPTER EXPERIMENT AND ASSESSING THE PERFORMANCE OF THE OPERATING DEVICE IN SEA 4.1 Experiment of the electrical generator in sea Figure 4.1 demonstrates several pictures of field experiments of the electrical generator for sea wave energy in the Hon Dau sea, Haiphong province, Vietnam [33,40] Figure 4.1 The transport of device on the HQ1788 Ship and experiment in sea Sea wave period: The received results are shown that the period of wave appears more and continuously at period of 4.26 seconds, corresponding to the frequency 1.47 rad/s The data are obtained from DASIM measurement equipment with Futek pressure sensor of America The received average pressure value is about 0.31 psi (i.e 0.021 atm in SI unit) and maximum value is 0.74 psi (i.e 0.05 atm) The obtained pressure values will be used for the purpose of fabricating buoy and device casing Output voltage of device: Table 4.2 shows the average values of the received voltage and current from the generating motor of device at the tested load levels (excluding the power from solar pannel) and DC-AC converter performance 21 Table 4.2 Output average power according to the tested loads Performance Load Voltage Current Voltage Current power UDC IDC (A) UAC IAC (A) ηdc-ac (%) Pe (W) (VDC) (VAC) 100 12 9,92 224 0,45 84,67 140 12 13,47 223 0,61 84,15 200 12 20,33 223 0,92 84,09 300 12 29,5 221 1,35 84,27 4.2 Analyzing the voltage quality of the device The output voltage waveform of the device is measured and analyzed by the Picoscope USB Oscilloscope 2204A of England, and the voltage spectrum analysis software is written by the author in Matlab It is showed that the output voltage wave on the load in time and in frequency is received at 220 VAC ± 1.25% frequency 50 Hz ± 0.06% and is a pure sine wave Therefore, the author found that the output voltage quality of the electrical generator has met according to Vietnam's National grid Standard [71] 4.3 Analyzing the performance of the device operating in sea From data in table 4.2, the received average performance of the DC-AC inverter is determined as follows:  dc  ac  84,67  84,15  84,09  84, 27  84,3% (4.2) With the output electrical power Pe of the device has emitted and operated stably at 200 W during the experiment, the numerical simulation power value of device has received in chapter is 295.8 W The energy conversion performance η of the electrical generator is determined by the expression: 22  P 200 e 100%  100%  67% Pgm 295,8 (4.3) In which the performance of the mechanical energy transmission from the received buoy to the generating motor is 88%, the performance of the electrical part is 75.8% The obtained results have showed the reasonableness between theoretical and experimental research Conclusions of chapter In present chapter, the author has experimented the operating device in Hon Dau sea, Haiphong province, Vietnam The device works in the vertical direction and fixed on the bottom of the sea, the buoy of device floats on the sea surface The output voltage sources of device are 12 VDC, 220 VAC frequency 50 Hz and pure sine according to Vietnam's National grid Standard The conversion performance from the mechanical energy of the received buoy to the electrical energy is 67% The power of device has generated up to 300 W and operated stably at 200 W during the experiment in sea Results of chapter are published in [1], [2], [3] and [4] CONCLUSION AND PROPOSITION Conclusion of thesis General conclusions This thesis presents the author's research results on building mechanical model and calculating design of the electrical generator for sea wave energy In the dissertation, the research approach has been started from surveying the actual conditions of sea wave, and then building the mechanical model, calculating the design, 23 fabricating and experimenting the device in sea The new contributions of the thesis are as follows: - Having collected and analyzed the sea wave characteristics of period and wave height in Vietnam sea - Having built the mechanical model and set up the nonlinear motion equation of the model The average method of nonlinear mechanics has been applied in the resonance phenomenon survey, and indicated the device's stable and unstable operation region Showing the ability to fabricate the operating device at nonlinear region used in sea with large wave amplitude The analytic method has used for the linear model calculation, the fourth-order RungeKutta and Simpson methods used for nonlinear model calculation and numerical integration The damping coefficient of the generating motor has been determined optimization for selecting the generating motor of device, and the power level of device received from the sea wave energy according to the model parameters and suitable to the actual conditions of Vietnam sea - The electrical generator for sea wave energy has been fabricated and experimented in Hon Dau sea, Haiphong province, Vietnam The output power has operated stable at 200 W load during the experiment in sea, the conversion performance from the mechanical energy of the received buoy to the electrical energy is 67% New contributions of the thesis - The author has proposed and built a model of high-efficient electrical generator, suitable to the actual sea wave conditions and fabricating capability in Vietnam - The author has established the nonlinear motion equation of the device, calculated the optimal damping coefficient of the generating 24 motor, the received mechanical power level of device from the sea wave energy according to the parameters of model and the actual sea wave conditions - A model of electrical generator for sea wave energy is fabricated The author's device does not overlap with the devices already exist in Vietnam and in the world The device has been tested in Hon Dau sea, Haiphong province, Vietnam The output power of the device has operated stable at 200 W load during the experiment in sea - The output voltage quality of device is reached of 220 VAC 220 VAC ± 1,52% frequency 50 Hz ± 0.06% and pure sine according to Vietnam’s National grid Standard The electrical generator can be used for signal buoys of seaway and can supply the electrical power for lighthouses Proposition From the initial results of the thesis has been achieved, the author found that it is necessary to continue the next studies, to create a capable device of using in practice: - Research on the fabricating material of device casing, to ensure the long-term operation device and stable in the sea's actual condition - Research on expand the problem of multi-level interaction between the electrical generator and the buoy under the action of sea wave - Continue to improve the model to increase the performance and the output power of the electrical generator - Continue to test the operating device in sea for a long time to inspect the operating device, as well as the ability to transfer the electrical generator to the using units LIST OF THE AUTHOR’S PUBLICATIONS Nguyen Van Hai, Nguyen Dong Anh, Performance analysis of the electrical generator for sea wave energy, Hội nghị Cơ học toàn quốc lần thứ X, Hà Nội (8-9/12/2017), Tập Động lực học Điều khiển; Cơ học Máy, 2018, 102-109 Nguyen Van Hai, Nguyen Dong Anh, Nguyen Nhu Hieu, Fabrication and experiment of an electrical generator for sea wave energy, Vietnam Journal of Science and Technology, VAST, 2017, 55 (6), 780-792 Nguyen Van Hai, Nguyen Dong Anh, Nguyen Nhu Hieu, Numerical simulation of an electrical generator for sea wave energy (JMEST), 2017, (9), 8104-8110 Nguyen Dong Anh, Nguyen Van Hai, The research and experiment of a linear electrical generator from sea wave energy, Journal of Marine Science and Technology, VAST, 2017, 17 (1), 44-54 Nguyen Van Hai, Nguyen Dong Anh, Nguyen Nhu Hieu, Study and calculate the small power electrical generator from sea wave energy, Proceedings of the 2nd National Conference on Mechanical Engineering and Automation, Oct 7-8, 2016, Hanoi University of Science and Technology, Hanoi, 2017, 216-219 Nguyen Van Hai, Study, design and fabrication of the intelligent DC-AC inverter to satisfy the charging equipment from renewable energy sources, Proceedings of the 2012 International Conference on Advanced Technologies for Communications (ATC/REV 2012), Hanoi, 2012, 125-129 ... and suitable to the actual conditions of Vietnam sea 7 CHAPTER RESEARCH ON THE MECHANICAL MODEL AND OPTIMIZATION OF THE ELECTRICAL GENERATOR FOR SEA WAVE ENERGY 2.1 Building a model of the electrical. .. [3] and [4] CONCLUSION AND PROPOSITION Conclusion of thesis General conclusions This thesis presents the author's research results on building mechanical model and calculating design of the electrical. .. GENERATOR FOR SEA WAVE ENERGY AND APPLICABILITY IN VIETNAM 1.1 Overview of researches on the electrical generator in the world In the world, the research and fabrication of the electrical generator