Design of a Wave Energy Converter

UNIVERSITÀ DEGLI STUDI DI PADOVA

DIPARTIMENTO DI INGEGNERIA CIVILE, EDILE E AMBIENTALE

Department Of Civil, Environmental and Architectural Engineering

Corso di Laurea Magistrale in Environmental Engineering

Curricula: Environment and Sustainability

Design of a Wave Energy Converter in Crete

Students Matriculation number

Maritato Mattia 2178706

Tanduo Giulia 2181520

Voltarel Nicolò 2198862

Summary

Summary .............................................................................................................................................. 1

1. Introduction .................................................................................................................................. 2

Waves’ characteristics

1.1. ........................................................................................................... 2

1.2. DEXA description ................................................................................................................. 3

2. Methods and Results ..................................................................................................................... 4

2.1. Energy converted ................................................................................................................... 4

2.2. Power converted .................................................................................................................... 5

2.3. Proceeds ................................................................................................................................ 7

2.4. Efficiency .............................................................................................................................. 9

2.5. Load Factor ......................................................................................................................... 12

2.6. Levelized cost of energy ..................................................................................................... 13

3. Conclusions ................................................................................................................................ 14

4. References .................................................................................................................................. 15

1

1. Introduction

The aim of this study is to determine the optimal length for a Wave Energy Converter (WEC). In this

case is considered the DEXA, that is a floating device that converts electricity from the movement of

the waves of the sea.

Waves’

1.1. characteristics

The location chosen for the DEXA is in the Mediterranean Sea, near the South-West coast of Crete

(Figure 1) having coordinates: 35° N 23° E. This place is 50 km from the western coast of Crete.

Figure 1: Location of the DEXA

The most frequent and constant winds are the Western and North-Western winds, which are primarily

responsible for the formation of long, regular waves. Another important factor is the very long fetch

in this direction that make the South-West coast of Crete an ideal location for positioning devices

such as the DEXA.

There are three main currents present in this area: the first one is a surface current that generally flows

from West to East and the second one is the Cretan Channel that acts like a funnel, making both winds

and currents move much faster. The last one is the upwelling of deep waters, which changes the water

density.

All of these factors make the coast of Crete an excellent location for a wave energy converter and in

this study the focus is on the DEXA device. The next step is to determine the optimal length for the

device to ensure the maximum converted energy. 2

The data that is used for the calculation of the optimal length is:

− the wave period T p

− the significant wave height H

s

− the frequency f, that is the number of times a wave with a certain height repeats in a period

− the water depth that is equal to 3000 m

1.2. DEXA description

The DEXA is a Wave Energy Converter (WEC) (Figure 2). It’s a floating device that converts

electricity from the movement of the waves of the sea. The DEXA device is classified as a wave

attenuator that is a long, floating device oriented to the parallel direction of the wave motion. The

structure consists of two symmetrical pontoons coupled by a central hinge. The mechanical

movement of the device activates some hydraulic cylinders that convert the wave energy into high

pressure fluid flow that drives a hydraulic motor and an electrical generator.

Figure 2: DEXA device

3

2. Methods and Results

2.1. Energy converted

The purpose of the study is to find the optimal length of the DEXA where we have the maximum

converted energy. The first thing to do is create a Matlab script where the inputs are the wave height

Hs, the average period T and the frequency, where waves of a certain height repeat in a period. As

p

outputs there are the energy converted by DEXA, the efficiency of the device and the proceeds.

The length of the DEXA can vary from 5 m to 100 m with interval of 5 m between each other. The

annual converted energy that is obtained is a specific energy for unit of length having measure unit

of kWh/m. After the calculation of the converted energy associated to each different length