# Design Parameters Analysis of Point Absorber WEC via an evolutionary-algorithm-based Dimensioning Tool

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

**Figure 1.**Project Development Stages Flow-Chart Scheme Example of a R&D WEC Development Project [10].

## 2. Parametric Analysis Definition

#### 2.1. Reference Case Definition

- (a)
- Generation plant with a single grid-connected WEC.
- (b)
- (c)
- The sea site for the commissioning and testing is located at PLOCAN.
- (d)
- The WEC is a point absorber, which is one of the most suitable topologies for the installation of a direct-driven generator [29].
- (e)
- (f)

Acronym | Description | Value |
---|---|---|

P_{nom} | Rated Electric Power | 220 kW (peak power) |

F_{nom} | Maximum Force | 220 kN |

V_{nom} | Rated Speed | 1 m/s |

S_{nom} | Maximum Stroke | 4 m |

#### 2.2. Parametric Analysis Set-up

Parametric Analysis Cases | Analysis 1 | Analysis 2 | Analysis 3 | Analysis 4 | Analysis 5 |
---|---|---|---|---|---|

Peak-Power Frequency Matching (f) | Location (c) | WEC (d) | PTO Force (b) | Control (e) | |

Reference Case | Two-Body Peak-Power Frequency Matching | PLOCAN | 2-body WEC | 220 kN | Reactive Control |

Parametric Analysis | Maximum Peak-Power Frequency | SANTOÑA | 1-body WEC | (37–660) kN | Damping Control |

No Peak-Power Matching | IPS buoy |

**Figure 4.**Point Absorber Configurations to Heave Energy Extraction: (

**a**) 1-Body Point Absorber; (

**b**) IPS Buoy; (

**c**) 2-Body Point Absorber.

_{PTO}). Due to the particular characteristics of the selected PTO (SRLG), there is scalability in terms of force, whereas a new electromagnetic design would be required to scale the speed. Nine different cases are included in the analysis, comprising values from 37 to 660 kN. In this paper, the analysis of this factor does not consider the extra costs related with the PTO modifications (the aim of the analysis is only to understand the relationship of the PTO rated force in the WEC dimensioning process). Thus, the prime mover (the part of the WEC that interacts with the ocean waves) costs, but not the WEC global cost (prime mover + PTO), are considered in the analysis of the objective functions.

## 3. Preliminary Dimensioning Algorithm

#### 3.1. Optimization Problem Algorithm

#### Multi-Objective Differential Evolution Algorithm

- (1)
- In each iteration (generation), the DE algorithm generates a new set (population) of candidate solutions (child population, Q
_{t}) from the initial set of solutions (parent population, P_{t}). The definition of the new set of solutions implies the specification of the particular values of the search space variables (see Section 3.3.1 for more information). The main differential characteristic of the DE algorithm, compared with other bio-inspired algorithms, is the definition of a new set of candidate solutions where each one is obtained from mutation of two randomly chosen candidate solutions by the sum of the weighted differences between them. - (2)
- In a second iteration step, the candidate solutions (Q
_{t}) are evaluated, calculating their objective function values (described in Section 3.3.2) and restricted values (described in Section 3.3.3) by means of a WEC mathematical model (described in Section 3.2) characterized for some particular values of the search space. - (3)
- The third iteration step evaluates and compares Q
_{t}together with P_{t}in order to determine the initial population of the following iteration (P_{t+1}). Subsequently, a joint set of solutions (R_{t}), from P_{t}and Q_{t}, is ordered in terms of the multi-objective function values (dominance between solutions) by means of a non-dominated sorting algorithm based on NSGA-II. Besides, R_{t}is sorted in terms of restrictions accomplishing Deb’s rules. In this way, an order is established based on feasibility, when the solution accomplishes all the restrictions, and dominance, when the solution gets better values in both objective functions. Finally, P_{t+1}is composed by the best solutions of R_{t}.

^{®}) runs in Intel I7-2600 PC (16 GB RAM) is executed in approximately 200 min.

#### 3.2. Mathematical Model of a WEC

#### 3.2.1. Location and Operation States

_{p}) and significant height (H

_{s}) is obtained by means of a least-square approximation for both locations.

_{s}= K

_{T-H}·T

_{p}

^{2}; K

_{T-H_PLOCAN}= 0.0223; K

_{T-H_SANTOÑA}= 0.0146

_{T-H}is the relationship coefficient between H

_{s}and T

_{p}.

_{reg}is the regular equivalent wave height; T

_{−1,0}is the energy period; T

_{reg}is the regular equivalent wave period; S(f) is the energy wave spectrum and c

_{g}is the group velocity.

_{−1,0}or T

_{p}is related bi-univocally with a value of H

_{s}according to Equation (1), and each pair (T

_{p}, H

_{s}) has an equivalent regular representation (T

_{reg}, H

_{reg}) according to Equations (2) and (3).

_{min}(period of waves with sufficient energy to be worth activating the WEC) and T

_{max}(period of waves so energetic that they could damage the WEC) according to the following statement: The operation range, defined by T

_{min}and T

_{max}, must contain 90% of the total sea state occurrence.

**Figure 6.**Four Operation Ranges of Renewable Power Plants particularized for ocean wave energy. The WEC generated power profile is represented for the pairs (H

_{s},T

_{p}) of the most representative sea states of a particular location.

_{Pmin}is defined as the period in which the rated power is reached. Thus, T

_{min}, T

_{Pmin}and T

_{max}determine the 4 operational WEC ranges as depicted in Figure 6: Range I in which the WEC remains in a standby mode; Range II in which the PTO extracts the maximum power from the waves (resonance mode); Range III in which the PTO works restricted by its rated power (saturated mode); and Range IV in which the WEC remains in a survival mode Table 3 summarizes these period values for both locations.

Acronym | Name | PLOCAN | Santoña |
---|---|---|---|

Value | Value | ||

T_{min} | Minimum Wave Period (of the operation range) | 6 s | 7 s |

T_{max} | Maximum Wave Period (of the operation range) | 14 s | 18 s |

T_{r} | Maximum Occurrence Wave Period | 8 s | 10 s |

#### 3.2.2. Point Absorber Dynamic Model

_{mec_1}is the electric resistance equivalent to the mechanical damper D

_{mec_1}, that consists of the mechanical losses associated with the PTO; R

_{r11}is the electric resistance equivalent to the radiation term D

_{r11}; C

_{1}is the capacitance equivalent to the inverse of the stiffness coefficient S

_{1}; L

_{1}is the inductance equivalent to the device mass m

_{1}; L

_{ad11}is the inductance equivalent to the added mass term m

_{ad11}; U

_{e,1}is the voltage equivalent to the wave excitation force F

_{e,1}; U

_{PTO}is the voltage equivalent to the PTO force F

_{PTO}; I

_{1}is the current equivalent to the velocity v

_{1}and Z

_{11}is the total impedance of the mechanical system.

_{mec}) in terms of U

_{PTO}:

*****denotes the conjugate of the complex variable y and Re(y) denotes the real part of the complex variable y.

_{mec_i}is the mechanical equivalent resistance of the body i (where the sub-index “i” takes the value “1” for the floating body and “2” for the semi-submerged body); R

_{rij}is the radiation hydrodynamic resistance of the body i produced by the movement of the body j; C

_{i}is the capacity associated with the stiffness coefficient of the body i; L

_{i}is the inductance associated with the mass of the body i; L

_{adij}is the added mass inductance of the body i produced by the movement of the body j; U

_{e,i}is the excitation voltage of the body i; U

_{PTO}is the voltage that represents the PTO force; I

_{i}is the current that represents the velocity of the body i; Z

_{11}is the body 1 total impedance; Z

_{22}is the body 2 total impedance; and Z

_{12}and Z

_{21}are the mutual impedances.

_{TH}) and Thevenin equivalent impedance (Z

_{TH}) (corresponding to U

_{e,1}y Z

_{11}in the circuit diagram of Figure 7a) are shown in Equations (10) and (11) respectively. The same simplify result can be obtain from the analysis of the dynamics Equations (7)–(9) as presented in [45]:

_{TH}= (Z

_{11}·Z

_{22}− Z

_{12}

^{2})/(Z

_{1}1 + Z

_{22}+ 2·Z

_{12}) =…

…=(Z

_{11}·Z

_{22}− Z

_{12}

^{2})·(Z

*****

_{11}+ Z

*****

_{22}+ 2·Z

*****

_{12})/|(Z

_{11}+ Z

_{22}+ 2·Z

_{12})|

^{2}

_{TH}= ((Z

_{11}+ Z

_{12})·U

_{e,1}− (Z

_{22}+ Z

_{12})·U

_{e,2})/(Z

_{11}+ Z

_{22}+ 2·Z

_{12}))

#### 3.2.3. PTO Power Loss Model

_{mec}presented previously in Equation (6):

_{elec}is the PTO electric power output; P

_{loss}is the power losses (winding losses); F

_{PTO}is the PTO exerted force (named U

_{PTO}in the equivalent electric circuit); v

_{PTO}is the relative velocity between stator and translator of the SRLG-PTO (named I

_{1}, in 1-body WEC case, or I

_{r}, in IPS or 2-body WEC cases, in the equivalent electric circuit ); R

_{PTO_cu}is the PTO electric resistance; |I

_{PTO}| is the amplitude of the PTO electric current phasor and R’

_{PTO_cu}is the proportional coefficient to calculate the winding losses from F

_{PTO}values.

_{NOM}) in order to analyze the effect of the PTO rated characteristics in the design. In this regard, expressions for PTO scalability are defined based on two premises: The PTO volume is proportional to its rated force, and PTO efficiency is independent from its rated force (efficiency remains constant and its value is independent of the rated force). These assumptions imply that PTO scalability is based on variations of the electric configuration instead of on modifications of the current values. It means that, instead of basing the scalability in modifications of voltage and current rated values (and consequently magnetic and electric modifications), the scalability is based on the selection of the number of sub-machines (minimum independent and functional machine unit).

_{NOM}, see Table 2) which results are presented in the Section 4.4:

_{PTO}value of the reference case. Significant PTO modifications and complex scalability expressions are needed for F

_{PTO}values far from rated values. An accurate cost and complex scalability model implies to take into account the magnetic materials, the magnetic circuit design (rate between number of poles in stator and translator, shape of the poles, topology, etc.), the electric design (coils configurations and characteristic, conductors section, current density, etc.), the mechanical design (linear bearings selection, maximum stroke, etc.), etc.

#### 3.2.4. PTO Control Strategy

_{elect}) Equation (14) is firstly expressed in terms of the module and phase of the phasor PTO force (F

_{PTO}), based on the expression of mechanic extracted power P

_{mec}Equation (6) and in the SRLG power loss model Equation (12). P

_{elec}is presented in terms of F

_{PTO}module and angle to ease the calculation of the optimum values by means of Lagrange multipliers:

_{elec}= (1/|Z

_{th}|)·[|F

_{TH}·F

_{PTO}|·cos(θ

_{F_PTO}+ θ

_{Z_TH}) − (|F

_{PTO}|

^{2}·cos(θ

_{Z_TH})] − Rꞌ

_{PTO_cu}·|F

_{PTO}|

^{2}

_{F_PTO}and θ

_{Z_th}are the phases of the complex variable F

_{PTO}and Z

_{TH}respectively.

_{elec}maximization with restrictions in the module of F

_{PTO}to the SRLG rated value F

_{NOM}(see Table 1). The Lagrange multipliers theory Equation (15) is applied to solve it. The expressions Equations (16) and (17) show the F

_{PTO}module and phase values that maximize P

_{elec}. The restriction in the PTO force module does not affect the optimum PTO phase value Equation (17):

_{elec}− λ(F

_{PTO}− F

_{NOM})]

_{PTO}| = max([F

_{NOM}, |F

_{th}·Z

_{th}*/(2·R

_{th}+ 2·Rꞌ

_{PTO_cu}·|Z

_{th}|

^{2})|])

_{F_PTO}= angle(F

_{th}·Z

_{th}

*****/(2·R

_{th}+ 2·R’

_{PTO_cu}·|Z

_{th}|

^{2})|)

_{NOM}

_{,}is the PTO rated force value and λ is the Lagrange multiplier included to take into account the PTO maximum force restriction.

_{elec}) Equation (18) is firstly expressed in terms of the mechanical impedance (Z

_{PTO}) representing the PTO force, based on Equations (6) and (12). P

_{elec}is presented in terms of Z

_{PTO}to ease the optimum values calculation:

_{elec}= F

_{PTO}·v

_{PTO}* − Rꞌ·|F

_{PTO}|

^{2}= Z

_{PTO}·|v

_{PTO}|

^{2}− Rꞌ

_{PTO_cu}·|F

_{PTO}|

^{2}

_{PTO}is the mechanical impedance imposed by the PTO when it exerts the force according to a certain control strategy.

_{elec}) taking into account that Z

_{PTO}may be real, and the Z

_{PTO}value has to constrain the PTO force maximum value to its rated value. The expression of the Z

_{PTO}optimal value, obtained again by applying the Lagrange multipliers theory, is shown in Equation (19):

_{TH}and R

_{PTO}are the real parts of the Thevenin impedance (Z

_{TH}) and PTO impedance (Z

_{PTO}).

#### 3.3. Optimization Problem Definition

#### 3.3.1. Search Space

_{1}, R

_{2}, d

_{1}, d

_{2}and d

_{3}), the search space of the 1-body point absorber is composed of two dimensions (R

_{1}and d

_{1}) and the search space of the IPS point absorber is composed of six dimensions (R

_{1}, d

_{1}, d

_{2}, d

_{3}, l

_{1}and l

_{2}). It is important to notice that the variable R

_{3}represents the radius of the PTO housing.

**Figure 8.**(

**a**) 1-Body Point Absorber Search Space Variables; (

**b**) IPS Buoy Search Space Variables; (

**c**) 2-Body Point Absorber Search Space Variables.

#### 3.3.2. Objective Functions

_{1})

^{2}− (R

_{3})

^{2}]·d1 + π·(R

_{3})

^{2}·d

_{3}+ π·(R

_{2})

^{2}·d

_{2}

_{elec}, calculated according to Equations (6) and (12), by the occurrence sea state probability (p

_{wave}). The resultant summation is finally multiplied by the hours in one year. The expression is shown in Equation (21):

_{elec}[W·h] = Σ[P

_{elec}(H

_{s,}T

_{p})·p

_{wave}(H

_{s},T

_{p})]·(365·24 h/year)

_{elec}is the PTO annual energy extracted and p

_{wave}is the occurrence probability of a certain sea state (characterized by its H

_{s}and its T

_{p}) according to the annual occurrence scatter diagrams shown in Figure 5.

#### 3.3.3. Restrictions

- (a)
- Minimum PTO electric extracted power in WEC operational Range III. The power extracted values of the profile should exceed the minimum value of the PTO rated power (P
_{NOM}, defined in Table 1) multiplied by a certain coefficient. - (b)
- Maximum PTO relative velocity in WEC operational Ranges II and III. The power extracted values of the profile should exceed the maximum value of the PTO rated velocity (v
_{NOM}, defined in Table 1) multiplied by a certain coefficient - (c)
- Maximum PTO relative displacement in WEC operational Ranges II and III. This restriction is applied over the amplitude of the relative movement (between 2 bodies in the case of IPS and 2-body devices; between the floating body and the sea floor in the case of 1-body WEC). It ensures that the relative movement amplitude does not reach the maximum value of the PTO maximum stroke S
_{NOM}(see Table 1), which should be limited by protections such as end stop springs or similar devices. - (d)
- (e)
- Anti-Slamming [55] restriction in WEC operational Ranges II and III. This restriction ensures that the floating-body oscillatory-movement amplitude is less than its own draft (d
_{1}). The distance between the mass center of body 1 (floating body) and the sea water surface is restricted to the maximum value of the floating body draft multiplied by a certain coefficient.

_{NOM}, v

_{NOM}and s

_{NOM}, respectively (see Table 1). This approach considers as non-feasible solutions the WEC geometries with a dynamic behavior profiles which exceed the PTO rated values. These restrictions ensure the WEC suitability for the PTO. The anti-slamming restriction, (e), is considered to avoid dangerous situations for the WEC survivability.

_{r}. The variable T

_{r}is defined in Section 3.2.1 as the period of the sea state with the maximum annual hours of occurrence, as seen in the scatter diagrams, Figure 5. These WEC peak-power frequencies are evaluated by calculating the zero-crossing values of the impedance Z

_{th}frequency-profile (see Section 3.2.2) [31]. A graphical representation of the restriction is shown in Figure 9.

_{TH}expression Equation (10), taking into account that the numerator has three zeros respect to the variable ω (since it is raised to the third power). Indeed, if the imaginary part of the Z

_{TH}(in a particular WEC solution) would be plotted, three zero-crossing could be appreciated (as show, for the sake of example, in the blue profile in Figure 9):

- (a)
- The first (ω
_{r2}= 2π (T_{r2}^{−1})) produces the maximization of the oscillation amplitude in the submerged body. This peak-power frequency is related with the natural resonance frequency of body 2. It is usually sufficiently high to be out of the WEC operational Ranges II and III, due to the fact that the stiffness of the body 2 is small compared with its mass. - (b)
- The second (ω
_{r1}= 2π (T_{r1}^{−1})) produces the maximization of the oscillation amplitude in the floating-body. This peak-power frequency is related with the natural resonance frequency of body 1. It is usually within the WEC operational Ranges II and III. - (c)
- The third (ω
_{r12}= 2π (T_{r12}^{−1})) appears by the effect of the PTO and in a well-tuned device. It produces a peak in the power extraction frequency profile characterized by individual and relative velocities relatively manageable. The value of this frequency is usually between ω_{r1}and ω_{r2}[31,32,45]. This frequency, not usually considered a resonance frequency, is in the neighborhood of the resonance frequency of the two rigidly connected bodies [31,45].

**Figure 9.**Graphical Representation of the WEC Peak-Power Frequency Matching Restriction. The forbidden zone, no Z

_{th}zero-crossing, is represented by a red dashed area. Red Z

_{th}profile belongs to a non-feasible candidate solution and blue Z

_{th}profile belongs to a feasible one.

_{r1}, associated with the body 1 resonance frequency (floating-body). In the case of an IPS point absorber, there are two peak-power frequencies, ω

_{r1}and ω

_{r12,}being the peak-power associated with the natural resonance frequency ω

_{r2}(a) negligible due to its small submerged body stiffness coefficient.

## 4. Discussion of the Parametric Analysis Results

_{1}and R

_{2}) for a 2-body point absorber and the radius and draft of the floating body (R

_{1}and d

_{1}) for the case of a 1-body point absorber and IPS buoy.

#### 4.1. Parametric Analysis 1: Peak-Power Frequency Matching Restriction

**Figure 10.**Pareto Frontiers Comparison for the Parametric Analysis of the Peak-Power Frequency Restriction presented in terms of objective functions.

^{3}) and extracted energy when compared to PF2 and similar results are obtained compared to PF1. It should be recalled that the peak-power frequency related with the two bodies relative displacement (ω

_{r12}) has a lower value than the resonant frequency of body 1 (ω

_{r1}), so ω

_{r1}resonance searching (PF2 solutions) ensures that ω

_{r1}value is around 1/T

_{r}and ω

_{r12}searching (in PF3 solutions) ensures that ω

_{r1}value exceed 1/T

_{r}value. Taking into account that ratio between the stiffness coefficient and the mass of the body 1 is directly related with its resonance frequency (ω

_{r1}), the ω

_{r1}resonance searching imposes a lower body 1 stiffness-mass ratio in the body 1 than the ω

_{r12}searching. Furthermore, the ω

_{r1}resonance searching implies greater body 1 excursions at its resonance frequency [14]. These two factors have an influence on the observed behavior at the Pareto frontiers PF2 and PF3. On one hand, the first factor (low ratio stiffness-mass) could lead PF2 to higher volume solutions. On the other hand, the low volume WEC solutions tend to have low draft and low mass, thus they have great sensitivity to maximum stroke and anti-slamming restrictions. In addition, the second factor (grater excursions) could emphasize this sensibility, reducing the number of feasible solutions in the low volume zone.

_{r12}, and the inherent high PTO damping value [31] what leads to high electrical losses), so volume changes do not lead to an equivalent compensation in energy extraction. This effect could be the reason of getting better PF solutions in high volume for non-resonant devices.

#### 4.2. Parametric Analysis 2: Location

_{r1}(magenta) and with the restriction only of ω

_{r12}(cyan) are shown (Section 3.3.3). The Pareto frontier is presented in green.

**Figure 11.**Comparison of the Pareto frontiers for the two locations considered. (

**a**) Pareto Frontiers presented in terms of the Objective Functions; (

**b**) Pareto Frontiers presented in terms of the Search Space Variables R

_{1}and R

_{2}.

_{r1}and for ω

_{r12}). This means that these solutions have a large amount of annual operation hours in the Range III of the PTO (see Figure 6), where the peak-power matching becomes important in order to minimize the reactive mechanical energy needed for tuning the system. The large number of hours in Range III responds to the fact that a more energetic swell represents a higher excitation force and therefore a higher need of PTO force (see Equations (16) and (17)).

_{1}and R

_{2}. In this graph it can be seen that both the design trends and the space of feasible solutions change in the new location. Not only these variables present lower values but the values must also be different to fit the different wave periods.

#### 4.3. Parametric Analysis 3: WEC Concept

_{1}can be different to R

_{2}, whereas in the WEC IPS, R

_{1}and R

_{2}are not allowed to be different (Figure 8a,c) so it is possible that the elimination of this degree of freedom goes against the IPS device design.

**Figure 12.**Comparison of Pareto frontiers for the Parametric Analysis of the WEC Concept (2-Body Point Absorber vs. IPS buoy and 1-Body Point Absorber). (

**a**) The Pareto frontiers are presented in terms of the Objective Functions; (

**b**) The Pareto Frontiers are presented in terms of the Search Space Variables R

_{1}and d

_{1}.

_{r1}and ω

_{r12}). Also, working with relatively large inertias produces a decrease in the absorption bandwidth of the device. It is noteworthy that 1-body WEC have several inherent disadvantages such as the need to use the seabed as a “second body” which limits these kind of devices to moderated depths, or the need for tides compensation [57].

_{1}and d

_{1}(the dimensions of the floating body). It is remarkable how the areas corresponding to the feasible solutions (respect to R

_{1}and d

_{1}) are very similar for the three cases, almost overlapping for the case of WEC ISP with low values for these design-variables. Thus, the Pareto frontiers (with respect to R

_{1}and d

_{1}) in the 1-body and 2-body cases are composed of similar dimension of the floating body, being slightly higher in the case of two bodies, and also the dimensions of the floating body for the frontier in the ISP case are somewhat greater than the other two. The reduction of the feasible area for low values of R

_{1}and d

_{1}in the case of WEC ISP may be due to the fact that of R

_{1}and R

_{2}have the same value since small radii of the floating body impose small radii on the submerged body.

#### 4.4. Parametric Analysis 4: PTO Rated Force

_{1}) and the radius of the submerged body (R

_{2}).

**Figure 13.**Comparison of the Pareto frontiers for the Parametric Analysis of the PTO Rated Force. (

**a**) The Pareto frontiers are presented in terms of the Objective Functions; (

**b**) The Pareto frontiers are presented in terms of the Search Space Variables R

_{1}and R

_{2}.

_{PTO-nom}) has a direct impact on the power extracted by the WEC. Pareto frontiers solutions with greater energy extracted are obtained when the ability of the PTO to develop force increases, since although the ability to extract energy is tied to the volume of WEC device, such capacity cannot be fully exploited if the characteristics of the PTO do not allow it. It is also noted that the frontiers tend to converge to solutions of small volumes and small energy extracted regardless of the rated force represented. This can be explained by taking into account that, for these solutions it is prioritizing the adequacy of the WEC to the location over the adequacy to the PTO, so the rated force of the PTO is not fully exploited. This graph also represents, in dashed black line, the case of non-limited rated force and optimal control [3]. It can be noted how this case seems to mark the upper limit of the Pareto frontiers where the low volume solutions converge.

#### 4.5. Parametric Analysis 5: Energy Extraction Control Strategy

**Figure 14.**Comparison of the Pareto frontiers for the Parametric Analysis of the Energy Extraction Strategy. The Pareto Frontiers are presented in terms of the Objective Functions (

**a**) with the peak-power matching restriction activated; (

**b**) with the peak-power matching restriction deactivated.

## 5. Discussion and Future Work

## 6. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

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**MDPI and ACS Style**

Blanco, M.; Moreno-Torres, P.; Lafoz, M.; Ramírez, D. Design Parameters Analysis of Point Absorber WEC via an evolutionary-algorithm-based Dimensioning Tool. *Energies* **2015**, *8*, 11203-11233.
https://doi.org/10.3390/en81011203

**AMA Style**

Blanco M, Moreno-Torres P, Lafoz M, Ramírez D. Design Parameters Analysis of Point Absorber WEC via an evolutionary-algorithm-based Dimensioning Tool. *Energies*. 2015; 8(10):11203-11233.
https://doi.org/10.3390/en81011203

**Chicago/Turabian Style**

Blanco, Marcos, Pablo Moreno-Torres, Marcos Lafoz, and Dionisio Ramírez. 2015. "Design Parameters Analysis of Point Absorber WEC via an evolutionary-algorithm-based Dimensioning Tool" *Energies* 8, no. 10: 11203-11233.
https://doi.org/10.3390/en81011203