Energy production from oceans Dr D. Missirlis SCHOOL OF SCIENCE & TECHNOLOGY Pagana Adamantia MSc in ICT Systems – October 2011.

Energy production from oceans

Dr D. Missirlis

SCHOOL OF SCIENCE & TECHNOLOGY

Pagana Adamantia

MSc in ICT Systems – October 2011

Introduction

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The aim of this work is to present methods which can be used for energy production from ocean power and to provide information about the development status and the trends in the technology of ocean energy systems.

This thesis is based on a detailed literature review.

Presentation Outline

In this work the four basic ways to reclaim energy from the ocean are presented and analyzed. These are the following:

• Ocean's high and low tides • Ocean's waves• Temperature differences in the water• Marine Wind

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Tidal Energy

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- Tidal power is extracted from the Earth's oceanic tides.- A tidal generator converts the energy of tidal flows into electricity.

Tidal Energy

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Principle of operation

An estuary or bay with a large natural tidal range is identified and then artificially enclosed with a barrier.

The electrical energy is produced by allowing water to flow from one side of the barrage, through turbines, to generate electricity.

Tidal Energy

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Single basin barrage

A combination of sluices which, when open, can allow water to flow relatively freely through the barrage, and gated turbines, the gates of which can be opened to allow water to flow through the turbines to generate electricity.

Ebb generation mode

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Double basin systems

Two-Way GenerationTwo-way generation on both ebb and flood (double effect cycle)

Tidal Energy

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Existing tidal energy plants

Tidal Energy

Wave Energy

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The energy that can be extracted form waves is a renewable type of energy called “Wave energy”. It is technically feasible to capture this energy in offshore locations.

Average annual wave power levels as kW/m of wave front

Wave Energy

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- Oscillating Water Column (OWC)

This device is based on the pressure of the enclosed air in a cavity (column of air).

Wave Energy

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- The Pelamis

Length = 120mDiameter = 3.5mOverall power rating = 0.75MWNominal wave power = 55kW/mAnnual power production = 2.7GWhWater depth = >50m

- The Wave Dragon

Width and length = 390x220mReservoir = 14,000 m3Rated power/unit = 11MWAnnual power production/unit = 35GWhWater depth = >30m

Wave Energy

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- The Archimedes Wave Swing (AWS)

The only moving part is an air-filled floater. Waves create an ‘up and down’ movement due to applied pressure on the floater which is located in a lower fixed cylinder.

Wave Energy

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- The McCabe Wave Pump

Hydraulic pumps attached between the center and end pontoons are activated as the waves force the end pontoons up and down.

- The PowerBuoyTM

Inside the buoy, a piston follows the movement of the waves’ rise and fall to output energy from the internal generator (immobile part).

Wave Energy

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- The AquaBuOYTM

The vertical movement of the buoy drives a broad, neutrally buoyant disk acting as a water piston contained in a long tube beneath the buoy.

Wave Energy

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There are plans for deploying a full scale, semi-commercial demonstration plant for fresh water and electricity production at the island of Amorgos in the South Aegean Sea, Greece.

- The case of Greece

Ocean Thermal Energy Conversion (OTEC)

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Ocean thermal energy conversion (OTEC) is a method which consists of extracting energy from the difference in temperature between shallow and deep waters by way of a heat engine.

Map of temperature difference between surface and depth of 1000m

Ocean Thermal Energy Conversion (OTEC)

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This cycle uses a working fluid (with a low boiling point) which is cooled down and heated up in a full cycle.

- Closed cycle OTEC

Ocean Thermal Energy Conversion (OTEC)

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- Open-cycle OTEC

The open-cycle process does not use an intermediate fluid like the closed-cycle but directly uses the sea water

Ocean Thermal Energy Conversion (OTEC)

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Block diagram of all applications from OTEC technology

Marine Wind Energy Conversion Systems

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Research on offshore wind technologies for shallow water, transitional depth, and deepwater

Marine Wind Energy Conversion Systems

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Marine wind turbines off the shores of

Copenhagen

The "Alpha Ventus" wind park, 45 kilometers (28 miles) north of the island of Borkum in the North Sea

Marine Wind Energy Conversion Systems

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Spar Platform Tension Leg Platform Semi-submersible platform.

Free Floating Platform (FFP) IDEOL

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TIDAL ENERGY

Tidal power incurs relatively high capital costs, and construction times can be several years for larger projects. Although plant lifetime can be very long (120 years for the barrage structure and 40 years for the equipment), the high capital costs and long construction time are considered to be a barrier for the construction of large tidal schemes.

OCEAN THERMAL ENERGY CONVERSION (OTEC)

OTEC has high capital costs. Economic analysis indicated the early market for OTEC to be islands and near-shore communities requiring 15 MW or less. Cost analyses showed that the closed cycle OTEC would be cost effective for only very large-sized plants (greater than 40 MW).

General Economics for the main ocean energy sources

General Economics for the main ocean energy sources

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WAVE ENERGY

It is difficult to estimate the unit costs of electrical energy produced from the waves, given that the few existing schemes are prototypes and there are additional costs incurred by such a preliminary stage of development.However, the estimated costs have shown a steady decrease with time, despite the little financial support received in recent years. It appears that several devices have already the potential to provide cheaper electrical energy for small islands and remote coastal communities that depend on expensive Diesel generation.

Conclusions

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Each system has its own advantages and disadvantages. Several common points to these four main technologies stand out.

The positive aspects of using ocean energy are:- Reduction in the dependence on fossil fuels.- Source of energy is free, renewable and clean.- Clean electricity is produced with no production of greenhouse gas or pollution (liquid or solid).-Energy produced is free once the initial costs are recovered.

The negative aspects of using ocean energy are:-At present, electricity produced would cost more than electricity generated from fossil fuels at their current costs.- Technologies are not fully developed.- Problems exist with the transport of electricity to onshore loads.

Thank you for your attention!

Energy production from oceans

Dr D. Missirlis

SCHOOL OF SCIENCE & TECHNOLOGY

Pagana Adamantia

MSc in ICT Systems – October 2011