Tidal energy is produced by the surge of ocean waters during the rise and fall of tides. Tidal energy is a renewable source of energy. During the 20th century, engineers developed ways to use tidal movement to generate electricity in areas where there is a significant tidal range—the difference in area between high tide and low tide. All methods use special generators to convert tidal energy into electricity. Tidal energy production is still in its infancy. The amount of power produced so far has been small. There are very few commercial-sized tidal power plants operating in the world. The first was located in La Rance, France. The largest facility is the Sihwa Lake Tidal Power Station in South Korea. The United States has no tidal plants and only a few sites where tidal energy could be produced at a reasonable price. China, France, England, Canada, and Russia have much more potential to use this type of energy. In the United States, there are legal concerns about underwater land ownership and environmental impact. Investors are not enthusiastic about tidal energy because there is not a strong guarantee that it will make money or benefit consumers. Engineers are working to improve the technology of tidal energy generators to increase the amount of energy they produce, to decrease their impact on the environment, and to find a way to earn a profit for energy companies. Tidal Energy Generators There are currently three different ways to get tidal energy: tidal streams, barrages, and tidal lagoons. For most tidal energy generators, turbines are placed in tidal streams. A tidal stream is a fast-flowing body of water created by tides. A turbine is a machine that takes energy from a flow of fluid. That fluid can be air (wind) or liquid (water). Because water is much more dense than air, tidal energy is more powerful than wind energy. Unlike wind, tides are predictable and stable. Where tidal generators are used, they produce a steady, reliable stream of electricity. Placing turbines in tidal streams is complex, because the machines are large and disrupt the tide they are trying to harness. The environmental impact could be severe, depending on the size of the turbine and the site of the tidal stream. Turbines are most effective in shallow water. This produces more energy and allows ships to navigate around the turbines. A tidal generator's turbine blades also turn slowly, which helps marine life avoid getting caught in the system. The world's first tidal power station was constructed in 2007 at Strangford Lough in Northern Ireland. The turbines are placed in a narrow strait between the Strangford Lough inlet and the Irish Sea. The tide can move at 4 meters (13 feet) per second across the strait. Barrage Another type of tidal energy generator uses a large dam called a barrage. With a barrage, water can spill over the top or through turbines in the dam because the dam is low. Barrages can be constructed across tidal rivers, bays, and estuaries.

1. Energy Conversion System for Harvesting
Tidal energy, Wave Energy and Biofuels
Engr. Md. Rashidul Islam
Department of Electrical and Electronic Engineering (EEE)

2.  Tidal energy
 Methods of harvesting tidal energy
 Wave Energy Generator
 Biofuel
Contents

3.  Tidal energy : A form of hydro energy that converts the
energy obtained from tides into useful form of power mainly
electricity.
 Tides : Defined as the rise and fall of sea level caused by the
gravitational pull of the moon and the sun on the Earth.
 These tides are affected by a range of factors such as the sun
and moons alignment, the shape of the coastline and changes
in water depth.
 Tidal generator converts the energy of tidal flows into
electricity.
 Greater tidal variation and higher tidal current velocities can
dramatically increase the potential of a site for tidal electricity
generation.
Tidal Energy

4. Two types tidal energy can be extracted:
Kinetic energy of current of ocean between ebbing and
surging tides.
Potential energy from the difference in height between
high tide and low tide.
How tidal energy extract

5.  1.water moves in and out Pass the
turbine as tides ebb and flow.
 2. Turbine turn generator module
producing electricity.
 3.Electricity is pass through
Underwater cable.
How tidal energy works

6. Tidal stream generator
Tidal barrage
Dynamic tidal power
Tidal lagoon
 Tidal stream generator and Tidal barrage is the
advanced and widely used method of harvesting tidal
energy.
Methods of harvesting tidal energy

7. A machine that
extracts energy from moving
masses of water, in
particular tides.
Use kinetic energy of moving
current to turn turbine.
Amount of power Produced
dependent on Strength of the
water of current.
Tidal stream generator

8. Tidal stream generator was installed at Northern Ireland
in 2008
 Production:
1. 2 MW capacity, current of 2.4m/s

9. Advantage Disadvantage
Low cost
Smaller ecological effect
Grid connection
The pipes can be
dangerous for animal

10.  Same as HEPP.
 Use potential energy of sea water.
 Consists of turbine, sluice gate and basin to store water.
 During high tide the basin is filled through sluice gate.
Tidal barrage

11. Advantage Disadvantage
High predictability
Protection against flood
 High cost
 It effect ecology and water
level of separated area

12.  Dynamic tidal power:
 Promising technology that would exploit an interaction between potential and
kinetic energies in tidal flows.
 It proposes that very long dams (for example: 30–50 km length) be built from
coasts straight out into the sea or ocean, without enclosing an area.
 Tidal phase differences are introduced across the dam, leading to a significant
water-level differential in shallow coastal seas – featuring strong coast-parallel
oscillating tidal currents such as found in the UK, China, and Korea.
 Tidal lagoon:
 A new tidal energy design option is to construct circular retaining walls embedded
with turbines that can capture the potential energy of tides.
 The created reservoirs are similar to those of tidal barrages, except that the
location is artificial and does not contain a preexisting ecosystem.
 The lagoons can also be in double (or triple) format without pumping or with
pumping that will flatten out the power output.

13. • Biofuels are liquid and gaseous fuels produced from biomass – organic
matter derived from plants or animals.
• Global biofuel production would use limited farmland more efficiently if the
biomass were converted into electricity to power electric cars rather than
refined into ethanol, a new analysis finds.
• Nowadays, we can observe that global warming has increase due to the
emission Carbon Dioxide (CO2) gas to the atmosphere.
• Depletion of fossil fuels had become an influence for us to find a new source
of energy.
Biofuel

14.  Advanced biofuel technologies are conversion technologies which are still
in the research and development (R&D), pilot or demonstration phase,
commonly referred to as second- or third- generation.
 This category includes biofuels based on lignocellulosic biomass, such as
cellulosic-ethanol, biomass-to-liquids (BtL)-diesel and bio-synthetic gas
(bio-SG).
 The category also includes novel technologies that are mainly in the R&D
and pilot stage, such as algae-based biofuels and the conversion of sugar
into diesel-type biofuels using biological or chemical catalysts.
Advanced biofuel

15. Conversion Technologies
• Advanced biofuels (e.g., biobutanol and synthetic diesel) and other biofuels
derived from switchgrass, garbage, and algae are under development.
• New conversion technologies are expected to expand production potential by
allowing for the use of an array of non-food resources.
• Additionally, the energy input for agriculture and feedstock production could
be significantly reduced and the technologies are expected to be more
efficient as they will entail large-scale conversion operations.
• Biomass power technologies convert renewable biomass fuels to heat and
electricity using processes similar to those employed with fossil fuels.

16. Conversion Technologies

17. Wave Energy
 Wave power : Power drawn from waves of sea or oceans (Capture of energy of wind
waves to do useful work)
 Wave energy converter (WEC): A machine that exploits wave power.
 When wind blows across the sea surface , it transfers the energy to the waves.
 Wave power determined by wave speed , wave height, water density, and wave length.
 Wave height determined by wind speed, the duration of time the wind has been
blowing, fetch (the distance over which the wind excites the waves) and by the depth
and topography of the seafloor (which can focus or disperse the energy of the waves).
 In deep water, a few km off a coastline, with a wave height of 3 m and a wave
energy period of 8 seconds, meaning there are 36 kilowatts of power potential per
meter of wave crest.
 In major storms, the largest waves offshore are about 15 meters high and have a period
of about 15 seconds; such waves carry about 1.7 MW of power across each metre of
wavefront.

18. Tidal Energy : Captures the energy of the current caused by the gravitational pull
of the Sun and Moon
Wave Energy: Waves are generated by wind passing over the surface of the sea. As
long as the waves propagate slower than the wind speed just above the waves, there is
an energy transfer from the wind to the waves (Some of the kinetic energy in the
wind is transformed into waves once the wind hits the ocean surface).
Difference between Tidal Energy and Wave Energy

19.  Renewable source of energy.
To protect the environment for future generation.
To reduce the emissions of greenhouse gases and consumption of limited resources.
Environmentally nature friendly of electricity generation.
 Wave energy could play a major part in the world’s efforts to combat climate change.
Positive thinking on wave energy

20. Potential impact on the marine environment.
 Noise pollution
Lower efficiency: Waves generate about 2700 GW of power; Of those 2700 GW, only
about 500 GW can be captured with the current technology.
 Other biophysical impacts (flora and fauna, sediment regimes and water column
structure and flows) of scaling up the technology.
In terms of socio-economic challenges, wave farms can result in the displacement of
commercial and recreational fishermen from productive fishing grounds, can change the
pattern of beach sand nourishment, and may represent hazards to safe navigation.
Challenges of Wave Energy Conversion

21. Methods of Harvesting Wave Energy
Modern technology:
 Wave power devices are generally categorized by the method used to capture the
energy of the waves, by location and by the power take-off system.
 Locations are shoreline, nearshore and offshore. Types of power take-off
include: hydraulic ram, elastomeric hose pump, pump-to-shore, hydroelectric
turbine, air turbine, and linear electrical generator.
 When evaluating wave energy as a technology type, it is important to distinguish
between the four most common approaches: point absorber buoys, surface
attenuators, oscillating water columns, and overtopping devices.
 Three fundamental method: Wave Profile Devices (WPV), Oscillating Water
Columns (WCM), Wave Capture Devices ( WCD).

22.  This device floats on the surface of the water, held in place by cables connected to the
seabed.
 Buoys use the rise and fall of swells to generate electricity in various ways including
directly via linear generators, or via generators driven by mechanical linear-to-rotary
converters or hydraulic pumps.
 EMF generated by electrical transmission cables and acoustics of these devices may be
a concern for marine organisms.
 The presence of the buoys may affect fish, marine mammals, and birds as potential
minor collision risk and roosting sites.
 Potential also exists for entanglement in mooring lines.
 Energy removed from the waves may also affect the shoreline, resulting in a
recommendation that sites remain a considerable distance from the shore
Point Absorber Buoy

23. Wave Profile Devices
 Point absorber
 Linear absorber/ Wave Attenuator

24. Oscillating Water Column
 One way to harness wave energy is to bend or
focus the waves into a narrow channel
,increasing their power and size . The waves can
then be channeled into a catch basin or used
directly to spin turbines.
 As the water flows into and out of the basins it
either directly activates a generator or transfers
to a working fluid ,water , or air, which then
drives a turbine /generator
 Positioned onto or near to Rocks
 Partly submerged hollow chamber
 Constant ebbing and flowing enforced
air pressure to spin the turbine.
 Output capacity about 300 kW.

25. Wave Capture Device