Maritime Technology and Engineering 5 Volume 2

Proceedings of the 5th International Conference on Maritime Technology and Engineering (MARTECH 2020), November 16-19, 2020, Lisbon, Portugal

Carlos Guedes Soares, Carlos Guedes Soares

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000459081
• Edition: 1
• Topic: Tecnología e ingeniería
• Subtopic: Ciencia y tecnología militares

This set of two volumes comprises the collection of the papers presented at the 5th International Conference on Maritime Technology and Engineering (MARTECH 2020) that was held in Lisbon, Portugal, from 16 to 19 November 2020. The Conference has evolved from the series of biennial national conferences in Portugal, which have become an international event, and which reflect the internationalization of the maritime sector and its activities. MARTECH 2020 is the fifth of this new series of biennial conferences. The set comprises 180 contributions that were reviewed by an International Scientific Committee.

Volume 2 is dedicated to ship performance and hydrodynamics, including CFD, maneuvering, seakeeping, moorings and resistance. In addition, it includes sections on ship machinery, renewable energy, fishing and aquaculture, coastal structures, and waves and currents.

Renewable energy

Wave energy assessment in the São Roque do Pico island for OWC installation

G. Anastas

Portuguese Foundation for Science and Technology, Lisbon, Portugal

J.A. Santos

ISEL – Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, Portugal Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal

L.V. Pinheiro & C.J.E.M. Fortes

National Laboratory of Civil Engineering, Lisbon, Portugal

DOI: 10.1201/9781003216599-54

ABSTRACT: This paper aims to determine the wave energy exploitable for two potential sites, located above the breakwaters of both São Roque do Pico and Madalena city harbors. For that purpose, the third-generation wave model SWAN is used to estimate the sea-wave conditions over the last 40 years. Boundary conditions of the sea states and wind fields are provided by the climate reanalysis datasets (ERA5). Using those results as inputs to the SWAN model, the sea-states were propagated shoreward, in order to estimate and analyze the wave climate conditions in the region of interest. By combining the average energy flux per unit-length of wave front and the probability of occurrence of each sea state, the average exploitable annual energy per unit length of wave crest can be computed. The variability of this energy flux is described, since it is of fundamental importance for the efficiency of the Wave Energy Converters (WEC).

1 Introduction

In the last decades, the increase in the need for renewable energy sources has led to a steep increase in the research and development of the Wave Energy Converters (WEC) with the aim of satisfying the growing demand for clean and renewable energies.

Its predictability, seasonal stability, low visual impact, and the overall high energy carried by ocean waves (Clément et al. 2002) make the possibilities for this energy exploitation exceeding the expectation in wind or solar energy for electrical production. Wave energy is not only more predictable than wind or solar energy, but it has also a higher energetic density allowing extraction of more energy in smaller areas. In island environments, the importance of implementing such energy extraction systems is enhanced by the fact that they can contribute to the energetic autonomy of the local communities. For the exploitation of this wave energy resource, various technological solutions exist. In this study we are considering the introduction of an Oscillating Water Column (OWC) within the trunk of a breakwater. The design and construction of the structure are the most critical issues (not considering the air turbine technology), in matter of efficiency, environmental impact and financial viability for the OWC technology, which uses waves to compress and expand air so as to rotate an air turbine, which in turn produces electricity.

Most WEC have been conceived as offshore devices, where the highest wave energy densities are found. The installation of WEC in the nearshore has often been dismissed due to the lower gross energy densities without further consideration of the differences between the characteristics of offshore and nearshore wave energy resources. However, a simple scaling of the wave climate inadequately describes the nearshore wave climate. A better representation is required to correctly assess the nearshore wave energy resource potential. With the integration of the plant structure into a breakwater comes several advantages like the fact that constructional costs are shared, that the access for construction, operation and maintenance are simplified, and that it doesn’t produce extra environmental impact. Although, since these fixtures aren’t omni-directional and installed in fixed positions, it can be easily understood that the amount of energy exploitable is influenced by its own orientation and the relative incident wave directions (Folley & Whittaker 2009). As a consequence, wave directions are also to be considered through wave energy estimated flux, in order to obtain a proper assessment. This approach was applied by Electric Power Research Institute Group to determine the available and recoverable wave energy resource on the United States coastline (Electric Power Research Institute 2011). To reach the objective of this p...