Environmental Science: Marine energy

Definitions and overall potential• Energy is a quantity that is often understood as the ability a physical system has to do work on other physical systems in physics • Marine energy

Group 7

1 Do Thi Ngoc Bich

2 Enkhbayar batsukh

3 Pham Thanh Huong

4 Do Thi Ngoc Khanh

5 Nguyen Hanh Mai

6 Tran Thu Trang

7 Trinh Thi Thu Trang

Introduction to Environmental Science

Prof : Nguyen Xuan Cu

Marine energy

Company Logo

Some kinds of marine energy

3

Potential

of Vietnam

Definitions and overall potential

I Definitions and overall potential

• Energy is a quantity that is often understood as

the ability a physical system has to do work on other physical systems ( in physics )

• Marine energy ( marine power /ocean energy /

ocean power) refers to the energy carried by

ocean waves, tides, salinity, and ocean

temperature differences ( Wikipedia )

• Larger conception : Energy that belongs to

the ocean

• The oceans have a tremendous amount of energy and are close to most concentrated populations Many researches show that ocean energy has the potential of providing for a substantial amount of new renewable energy around the world

II Some kinds of marine energy

1.Wave energy

a General view

•. Waves are generated by wind passing over the surface of the

sea, there is an energy transfer from the wind to the waves.

• Wave power is the transport of energy by

ocean surface waves, and the capture of that energy to do useful work (electricity generation , water desalination, or the pumping of water )

• In general, larger waves are more powerful but wave power is also determined by wave speed, wavelength, and water density.

Wave power devices can be categorized

in terms of

b Some examples

• Salter’s Duck ( Nodding Duck )

• The Pelamis Wave Energy

Converter

The machine is made up of

connected sections which flex and bend as waves pass; it is this

motion which is used to generate electricity.

• Oyster is a wave-powered pump which pushes high pressure water to drive an onshore hydro-electric turbine.

• Aquamarine Power’s Oyster

technology captures energy in

nearshore waves and converts it

into clean sustainable electricity

LIMPET (Land Installed

Marine Power Energy Transmitter )

• Can produce a great deal of energy.

• Waves that are caused by winds can

• Western seaboard of Europe

• the northern coast of the UK

• the Pacific coastlines of North and South America

• Southern Africa

• Australia, and New Zealand

The north and south temperate

zones have the best sites for

capturing wave power (the

prevailing westerlies in these

zones blow strongest in winter)

d Locations with the most potential

2 Tidal energy

a General view

•. Tides are the rise and fall of sea levels caused by the combined

effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.

•. Tidal power / tidal energy, is a form of hydropower that converts

the energy of tides into electricity or other useful forms of power

b Three main kinds of tidal energy

• Tidal barrage is a dam-like structure used to

capture the energy from Masses of water moving

in and out of a flight or river due to Tidal forces.

• Tidal stream generator

 A tidal stream generator/ tidal energy converter (TEC) is

a machine designed to extract energy from run of river or tidal estuarine sites

turbines, and are

thus often referred

to as tidal turbines.

• Dynamic tidal power (DTP) is a new and

untested method of tidal power generation It would involve creating large dam-like of 30 to 60

km forming a large 'T' shape.

DTP would interfere

with coast-parallel

oscillating tidal waves

which run along the

coasts of continental

shelves, containing

powerful hydraulic

currents (common

in e.g China ,Korea,

and the UK).

c Advantages vs Disadvantages

• Tidal energy is renewable

• It is free once the dam is

built and the

maintenance costs

associated with running a

tidal station are relatively

inexpensive

• Tides are easy to predict

• Tidal power is not currently economically feasible (costs of building a dam) except kinds using tidal turbines

• affect the aquatic ecosystems, transport

or fishery

3 Current energy

a What is ocean current ?

• The ocean currents are driven by wind and solar heating

of the waters near the equator, though some ocean

currents result from density and salinity variations of

water

• These currents are relatively constant and flow in one direction only

b Some examples

Submerged water turbines

similar to wind turbines Shroud turbines

( concentrators )

 Systems could be sited on river beds or

suspended in the ocean

c Challenges

• The costs is still high , especially the maintenance costs

• Marine growth buildup

4.Ocean thermal energy

a Potential

b Ocean Thermal Conversion (OTC)

• Method : uses the difference between

cooler deep

ocean waters

warmer shallow or surface

 run a heat engine + produce useful work

( electricity , freshwater … )

• Larger difference greater efficiency

Therefore , the tropical ocean (20oC to 25oC) offers the greatest possibilities.

•How it works

 The most commonly used heat cycle for OTEC is the

Rankine cycle using a low-pressure turbine.

 Systems may be either closed-cycle or open-cycle.

Closed-cycle engines use working fluids that are

typically thought of as refrigerants such as ammonia or

R-134a

Open-cycle engines use vapour from the seawater itself

as the working fluid.

Hybrit is the combination of the two above

Diagram of a closed cycle OTEC plant

Diagram of an open cycle OTEC plant

Hybrit cycle

A hybrid cycle combines the features of the closed- and

open-cycle systems

 warm seawater enters a vacuum chamber and is

flash-evaporated (similar to the open-cycle evaporation process )

 The steam vaporizes the working fluid (NH3 )of a cycle loop on the other side of an ammonia vaporizer

closed- The vaporized fluid then drives a turbine to produce

electricity

 The steam condenses within the heat exchanger and

provides desalinated water

c Advantages vs Disadvantages

• OTEC has the potential to offer huge

amounts of clean energy

• OTEC plants can operate continuously

providing a base load supply for an

electrical power generation system

• OTEC can also supply quantities of cold

water as a by-product

 Used for air conditioning and

refrigeration and the fertile deep ocean

water can feed biological technologies

• It is expensive to plan, design, and build such power

generation plants (also wide diameter pipes needed)

• the costly maintenance of these pipes other equipment since the corrosion

• organic materials like plankton and algae often get sucked

• Ocean weather may also create problems ( tropical storms or hurricanes )

5 Salinity energy

• Osmosis is the flow of a

solvent (water) through

• As a result of the osmotic

pressure difference between

both solutions, the water from

solution B thus will diffuse

through the membrane in order

to dilute the solution A The

pressure drives the turbines and

power the generator that

produces the electrical energy.

• Osmotic power or salinity gradient power is the energy available from the

difference in the salt concentration between seawater and river water

b A promising example

The Norwegian company Statkraft opens the world’s first facility for osmotic power generation Statkraft says a full-scale commercial osmotic power plant

could be ready by 2015

They says osmotic power

could produce up to 1,600–

1,700 terawatt hours

worldwide – the equivalent of

half of the energy generated

in the EU today.

c Challenges

• Osmotic power is expensive to run

• Another challenge is technical Ex : The membrane needs to be made five times more efficient than it is today

• Possible negative environmental impact

The main waste product of salinity gradient

technology is brackish water This will cause salinity

fluctuations that may result in low densities of both animals and plants due to intolerance of sudden severe salinity drops or spikes

6 Petroleum and gas

a General view

• Petroleum is a mixture of several compounds of carbon and is found deep within the earth’s crust

• Petroleum wells occur between layers on non-porous, impervious rocks

• Oil deposits are found with water, dust particles, rocks, salt and sand

Wherever there is such a well, natural gas is also found accumulated in

pockets of spaces within rocks.

• Petroleum is formed due to decomposition of microorganisms which got

buried under the sea over millions of years ago Dead marine micro

organisms got buried under sand and the effects of pressure, heat and bacteria got them converted into oily liquids The decomposition took

place in the absence of air or oxygen Petroleum wells are generally found

under the sea surface

b Exploitation method

• Wells are drilled into oil reservoirs to extract the crude oil and gas

• "Natural lift" production methods that rely on the natural pressure

which is sufficient over a long time

• The natural pressure in many reservoirs can dissipates Then the oil

must be pumped out using “artificial lift” created by mechanical

pumps powered by gas or electricity.

• A common secondary method is “waterflood” or injection of water

into the reservoir to increase pressure and force the oil up

• "tertiary" or "enhanced" oil recovery methods may be used to

increase the oil's flow characteristics by injecting steam, carbon dioxide and other gases or chemicals into the reservoir

• Extracting oil from oil/tar sand and oil shale deposits

requires mining the sand or shale and heating it in a vessel

or retort, or using “in-situ” methods of injecting heated

liquids into the deposit and then pumping out the

oil-saturated liquid

• The refining petroleum is done by

fractional distillation Each

hydrocarbon component with its

own boiling point separates out

neatly when the petroleum is

heated

• Some by-products after processes

such as cracking,cyclisation

,oxidation , halogenation ( Methyl

alcohol , ethyl alcohol , ethylene ,

benzene, toluene, D.D.T )

c Environmental impacts

• Global Warming When burned, petroleum and gas release

carbon dioxide; a greenhouse gas

surrounding marine environment

• Oil spills Crude oil and refined fuel spills

from tanker ship accidents have damaged natural ecosystems.

• A tarball is a blob

of petroleum which has been

weathered after floating in the

ocean Tarballs are an

aquatic pollutant in most

environments, although they can

occur naturally and as such are not

always associated with oil spills

7 Wind farm offshore

a General view

• Wind power is the conversion

of wind energy into a useful form of energy, such as using wind turbines to make electricity, wind mills for mechanical power, wind pumps for pumping water or drainage , or sails to propel ships

• A wind farm is a group of wind turbines in the same location

used for production of electric power

• A large wind farm may consist of several hundred individual

wind turbines, and cover an extended area of hundreds of

square miles

• Offshore wind power

->Offshore wind farm + solar energy +OTEC =>

‘energy island’

Some examples of

offshore wind

turbine’s base

<-b Differences from land based ones

passes Out to sea, the surface is perfectly flat and there's much less friction, so you get faster winds.

farm.

• Wind turbines will take the space away from other

applications.

• Wind turbines can be built larger offshore than their

land based counterparts

c Advantages vs Disadvantages

• No Pollution /Global Warming

Effects and Fuel Cost

• Low costs of maintenance

• Wind Energy has become a

mainstream source of energy and

a large industrial base already

exists

• No Noise Pollution

(unlike in land )

• They are located in the Ocean

where birds don’t fly frequently.

• High construction costs

• They need to withstand rough weather

8 Bio- Energy

Bioenergy or in narrow sense Biofuel is renewable energy

made available from biological sources.

b Examples

-First use was an illuminant in

lamps and as candle wax

-Then in 1700s it was used in

Petroleum Industry as it burns with bright and clear glow , emitting no odor.

-Fortunately , since 1930’s there is strict Control on hunting waves ,Market for Whale oil is now almost disappeared.

• Oil from sperm whale

• Algae for Biofuel

Algae Biofuel is primarily used in the process of

producing biodiesel fuel

Process of making biodiesel is stable and not nearly hazardous as the process of petro-

diesel.

c Main advantages

• The potential of using algae to produce biomass for heating

homes or running transport

food to fuel production like soybeans , sunflower

• Unlike terrestrial biomass, it is not be limited by freshwater

III Potential of Vietnam

approximately 1 million km2 of marine area

• More than 3000 km in coastal length

• More than 3000 islands , especially , 2 archipelagos – Hoang

Sa and Truong Sa

• Vietnam has tropical monsoon climate

• It is evaluated that Vietnam has big potential to develop

marine energy , particularly , wind and wave power.

• Wave energy along the coast is abundant (15 to 30 kW/m)

Ex : Ha Long , Quang Ninh , Ganh Rai , Ba Ria- Vung Tau

• Wave energy in Truong Sa islands zone perhaps the most

• Vietnam outstrips countries in areas for Wind energy

potential ( Thailand , Laos, Cambodia ) with strong winds

•Currently , our nation’s marine energy accounts for just about 1% in electricity energy We estimate that renewable energy will occupy 4% by 2020.

• At the present , Vietnam has

to import technology but tend to create our own equipment

• There’re also some researches and models of institutes and universities

• It’s estimated that Vietnam has the total reserve

including 10 billion tons of petroleum and 1000 billion m³ gas

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