14. Tidal Turbines (MCT Seagen)
750 kW – 1.5 MW
15 – 20 m rotors
3 m monopile
10 – 20 RPM
Deployed in multi-unit
farms or arrays
Like a wind farm, but
Water 800x denser than air
Smaller rotors
More closely spaced
MCT Seagen Pile
14
http://www.marineturbines.com/technical.htm
15. Tidal Turbines (Swanturbines)
Direct drive to generator
Gravity base
Versus a bored foundation
Fixed pitch turbine blades
http://www.darvill.clara.net/altenerg/tidal.htm
No gearboxes
Improved reliability
But trades off efficiency
15
16. Deeper Water Current Turbine
16
Boyle, Renewable Energy, Oxford University Press (2004)
17. Oscillating Tidal Turbine
Oscillates up and down
150 kW prototype
operational (2003)
Plans for 3 – 5 MW
prototypes
http://www.engb.com
17
Boyle, Renewable Energy, Oxford University Press (2004)
18. Polo Tidal Turbine
Vertical turbine blades
Rotates under a
tethered ring
50 m in diameter
20 m deep
600 tonnes
Max power 12 MW
18
Boyle, Renewable Energy, Oxford University Press (2004)
19. Power from Land Tides (!)
http://www.geocities.com/newideasfromtelewise/tidalpowerplant.htm
19
20. Advantages of Tidal Turbines
Low Visual Impact
Low Noise Pollution
Sound levels transmitted are very low
High Predictability
Mainly, if not totally submerged.
Tides predicted years in advance, unlike wind
High Power Density
Much smaller turbines than wind turbines for the
same power
http://ee4.swan.ac.uk/egormeja/index.htm
20
21. Disadvantages of Tidal Turbines
High maintenance costs
High power distribution costs
Somewhat limited upside capacity
Intermittent power generation
21
23. Definitions
Barrage
Flood
An artificial dam to increase the depth of water for
use in irrigation or navigation, or in this case,
generating electricity.
The rise of the tide toward land (rising tide)
Ebb
The return of the tide to the sea (falling tide)
23
24. Potential Tidal Barrage Sites
Only about 20 sites in the world have been identified as possible tidal barrage stations
24
Boyle, Renewable Energy, Oxford University Press (2004)
25. Schematic of Tidal Barrage
25
Boyle, Renewable Energy, Oxford University Press (2004)
26. Cross Section of a Tidal Barrage
http://europa.eu.int/comm/energy_transport/atlas/htmlu/tidal.html
26
30. La Rance Tidal Power Barrage
Rance River estuary, Brittany (France)
Largest in world
Completed in 1966
24×10 MW bulb turbines (240 MW)
5.4 meter diameter
Capacity factor of ~40%
Maximum annual energy: 2.1 TWh
Realized annual energy: 840 GWh
Electric cost: 3.7¢/kWh
30
Boyle, Renewable Energy, Oxford University Press (2004)
Tester et al., Sustainable Energy, MIT Press, 2005
31. La Rance Tidal Power Barrage
http://www.stacey.peak-media.co.uk/Brittany2003/Rance/Rance.htm
31
36. Tidal Barrage Energy Calculations
R = range (height) of tide (in m)
A = area of tidal pool (in km2)
m = mass of water
g = 9.81 m/s2 = gravitational constant
ρ = 1025 kg/m3 = density of seawater
η ≅ 0.33 = capacity factor (20-35%)
E = ηmgR / 2 = η ( ρAR) gR / 2
E = 1397ηR A kWh per tidal cycle
2
Assuming 706 tidal cycles per year (12 hrs 24 min per cycle)
E yr = 0.997 ×10 6ηR 2 A
36
Tester et al., Sustainable Energy, MIT Press, 2005
37. La Rance Barrage Example
η = 33%
R = 8.5 m
A = 22 km2
E yr = 0.997 ×106ηR 2 A
E yr = 0.997 ×10 (0.33)(8.5 )(22)
6
2
E yr = 517 GWh/yr
37
Tester et al., Sustainable Energy, MIT Press, 2005
38. Proposed Severn Barrage (1989)
Never constructed, but instructive
38
Boyle, Renewable Energy, Oxford University Press (2004)
39. Proposed Severn Barrage (1989)
Severn River estuary
Border between Wales and England
216 × 40 MW turbine generators (9.0m dia)
8,640 MW total capacity
17 TWh average energy output
Ebb generation with flow pumping
16 km (9.6 mi) total barrage length
£8.2 ($15) billion estimated cost (1988)
39
47. Tidal Fence
Array of vertical axis tidal
turbines
No effect on tide levels
Less environmental impact
than a barrage
1000 MW peak (600 MW
average) fences soon
47
Boyle, Renewable Energy, Oxford University Press (2004)
48. Promising Tidal Energy Sites
Country
Location
TWh/yr
GW
Canada
Fundy Bay
17
4.3
Cumberland
4
1.1
Alaska
6.5
2.3
Passamaquody
2.1
1
Argentina
San Jose Gulf
9.5
5
Russia
Orkhotsk Sea
125
44
India
Camby
15
7.6
Kutch
1.6
0.6
USA
Korea
10
Australia
5.7
http://europa.eu.int/comm/energy_transport/atlas/htmlu/tidalsites.html
1.9
48
49. Tidal Barrage Environmental Factors
Changes in estuary ecosystems
Less turbidity – clearer water
More light, more life
Accumulation of silt
Less variation in tidal range
Fewer mud flats
Concentration of pollution in silt
Visual clutter
49
50. Advantages of Tidal Barrages
High predictability
Similar to low-head dams
Tides predicted years in advance, unlike wind
Known technology
Protection against floods
Benefits for transportation (bridge)
Some environmental benefits
http://ee4.swan.ac.uk/egormeja/index.htm
50
51. Disadvantages of Tidal Turbines
High capital costs
Few attractive tidal power sites worldwide
Intermittent power generation
Silt accumulation behind barrage
Accumulation of pollutants in mud
Changes to estuary ecosystem
51
54. Wave Frequency and Amplitude
54
Boyle, Renewable Energy, Oxford University Press (2004)
55. Wave Patterns over Time
55
Boyle, Renewable Energy, Oxford University Press (2004)
56. Wave Power Calculations
Hs2 = Significant wave height – 4x rms water elevation (m)
Te = avg time between upward movements across mean (s)
P = Power in kW per meter of wave crest length
2
s e
H T
P=
2
Example: Hs2 = 3m and Te = 10s
H T 3 ×10
kW
P=
=
= 45
2
2
m
2
s e
2
56
57. Global Wave Energy Averages
Average wave energy (est.) in kW/m (kW per meter of wave length)
http://www.wavedragon.net/technology/wave-energy.htm
57
58. Wave Energy Potential
Potential of 1,500 – 7,500 TWh/year
200,000 MW installed wave and tidal energy power
forecast by 2050
10 and 50% of the world’s yearly electricity demand
IEA (International Energy Agency)
Power production of 6 TWh/y
Load factor of 0.35
DTI and Carbon Trust (UK)
“Independent of the different estimates the potential
for a pollution free energy generation is enormous.”
http://www.wavedragon.net/technology/wave-energy.htm
58
67. Turbines for Wave Energy
Turbine used in Mighty Whale
67
Boyle, Renewable Energy, Oxford University Press (2004)
http://www.jamstec.go.jp/jamstec/MTD/Whale/
70. Wave Dragon
Wave Dragon
Copenhagen, Denmark
http://www.WaveDragon.net
Click Picture for Video
http://www.wavedragon.net/technology/wave-energy.htm
70
71. Wave Dragon Energy Output
in a 24kW/m wave climate = 12 GWh/year
in a 36kW/m wave climate = 20 GWh/year
in a 48kW/m wave climate = 35 GWh/year
in a 60kW/m wave climate = 43 GWh/year
in a 72kW/m wave climate = 52 GWh/year.
http://www.wavedragon.net/technology/wave-energy.htm
71
72. Declining Wave Energy Costs
72
Boyle, Renewable Energy, Oxford University Press (2004)
73. Wave Energy Power Distribution
73
Boyle, Renewable Energy, Oxford University Press (2004)
74. Wave Energy Supply vs. Electric Demand
74
Boyle, Renewable Energy, Oxford University Press (2004)
76. Wave Energy Environmental Impact
Little chemical pollution
Little visual impact
Some hazard to shipping
No problem for migrating fish, marine life
Extract small fraction of overall wave energy
Little impact on coastlines
Release little CO2, SO2, and NOx
11g, 0.03g, and 0.05g / kWh respectively
76
Boyle, Renewable Energy, Oxford University Press (2004)
78. Wave Power Advantages
Onshore wave energy systems can be incorporated
into harbor walls and coastal protection
Create calm sea space behind wave energy
systems
Reduce/share system costs
Providing dual use
Development of mariculture
Other commercial and recreational uses;
Long-term operational life time of plant
Non-polluting and inexhaustible supply of energy
http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
78
79. Wave Power Disadvantages
High capital costs for initial construction
High maintenance costs
Wave energy is an intermittent resource
Requires favorable wave climate.
Investment of power transmission cables to shore
Degradation of scenic ocean front views
Interference with other uses of coastal and offshore
areas
navigation, fishing, and recreation if not properly sited
Reduced wave heights may affect beach processes
in the littoral zone
http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
79
80. Wave Energy Summary
Potential as significant power supply (1 TW)
Intermittence problems mitigated by
integration with general energy supply
system
Many different alternative designs
Complimentary to other renewable and
conventional energy technologies
http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
80
82. World Oceanic Energy Potentials (GW)
Source
Tides
Waves
Currents
OTEC1
Salinity
World electric2
World hydro
Temperature gradients
2
As of 1998
1
Potential (est)
2,500 GW
2,7003
5,000
200,000
1,000,000
3
4,000
Along coastlines
4
Practical (est)
20 GW
500
50
40
NPA4
2,800
550
Not presently available
82
Tester et al., Sustainable Energy, MIT Press, 2005
83. Solar Power – Next Week
83
http://www.c-a-b.org.uk/projects/tech1.jpg
Hinweis der Redaktion
Marine current turbines work, in principle, much like submerged windmills, but driven by flowing water rather than air. They can be installed in the sea at places with high tidal current velocities, or in a few places with fast enough continuous ocean currents, to take out energy from these huge volumes of flowing water. These flows have the major advantage of being an energy resource which is mostly as predictable as the tides that cause them, unlike wind or wave energy which respond to the more random quirks of the weather system. The technology under development by MCT consists of twin axial flow rotors of 15m to 20m in diameter, each driving a generator via a gearbox much like a hydro-electric turbine or a wind turbine. The twin power units of each system are mounted on wing-like extensions either side of a tubular steel monopile some 3m in diameter which is set into a hole drilled into the seabed.
The submerged turbines, which will generally be rated at from 750 to 1500kW per unit (depending on the local flow pattern and peak velocity), will be grouped in arrays or "farms" under the sea, at places with high currents, in much the same way that wind turbines in a wind farm are set out in rows to catch the wind. The main difference is that marine current turbines of a given power rating are smaller, (because water is 800 times denser than air) and they can be packed closer together (because tidal streams are normally bi-directional whereas wind tends to be multi-directional).
Environmental Impact Analyses completed by independent consultants have confirmed our belief that the technology does not offer any serious threat to fish or marine mammals. The rotors turn slowly (10 to 20 rpm) (a ship's propeller, by comparison, typically runs 10 times as fast and moreover our rotors stay in one place whereas some ships move much faster than sea creatures can swim). The risk of impact from our rotor blades is extremely small bearing in mind that virtually all marine creatures that choose to swim in areas with strong currents have excellent perceptive powers and agility, giving them the ability to successfully avoid collisions with static or slow-moving underwater obstructions.
The "Swanturbines" design is different to other devices in a number of ways. The most significant is that it is direct drive, where the blades are connected directly to the electrical generator without a gearbox between. This is more efficient and there is no gearbox to go wrong. Another difference is that it uses a "gravity base", a large concrete block to hold it to the seabed, rather than drilling into the seabed. Finally, the blades are fixed pitch, rather than actively controlled, this is again to design out components that could be unreliable.
http://www.darvill.clara.net/altenerg/tidal.htm
Stingray is designed to extract energy from water that flows due to tidal effects - tidal stream energy. It consists of a hydroplane which has its attack angle relative to the approaching water stream varied by a simple mechanism. This causes the supporting arm to oscillate which in turn forces hydraulic cylinders to extend and retract. This produces high pressure oil which is used to drive a generator.
http://www.engb.com
From http://www.geocities.com/newideasfromtelewise/tidalpowerplant.htm
The tidal activity in land is much smaller than that of in the sea because of its less flexibility and high density. With the help of a hydraulic system, it is possible to extract energy from land tidal activity. When the tide occur, the top surface of the Earth will move up and down and the body structure of the mechanism fixed on the top surface will also move up and down (see diagrams below). But there occurs a relative motion between the top surface of the Earth and the bottom of the supporting stand because of the density difference between the top and bottom (density will be less on the top surface), flexibility (elasticity) difference between the top and bottom (flexibility will be more on the top surface). The large two-way head piston is rigidly connected to the strong rigid-supporting stand and which is rigidly fixed in the bottom of the deep well.
During the upward motion of the cylinder (assume that the relative movement between the top and bottom is about 1cm), as the large two- way head piston is remaining stationary related to the bottom, the inside volume of lower chamber will decrease and the fluid in it will experience a high pressure, that causes the fluid in it with a volume of 0.0824m3 to escape through the 32.3cm diameter cylinder (Sc4 - see.fig) provided on the body structure. Since there is a small piston 4(Sp4) which can slide through its small cylinder, the fluid will push this piston in 1meter and the one way piston 2 (Lp2) connected on the other end will also moves 1meter. Since the diameter of the one way cylinder2 (Lc2) is 1meter then, the volume of the displaced fluid by Lp2 will be 0.785m3 and this fluid will escape through 37.7 cm diameter cylinder 3 (Sc3). This causes, the small piston 3 (Sp3) and the small piston 2 (Sp2) with the rack slides through the small cylinder 2(Sc2) and small cylinder 3 (Sc3) in 7meter. As the rack is meshing with the pinions P1 & P2, it will rotate and through the gear train of the required gear ratio the power will be transferred to the rotor of the generator; and by its rotation, electricity will be produced.
Similarly, during the down ward motion of the cylinder, in the tidal-fall, the inside volume of upper chamber will decrease and the fluid in it will experience a high pressure that causes the fluid in it with a volume of 0.1m3 to escape through the 35.6cm diameter cylinder (Sc1 - see.fig) provided on the body structure. Since there is a small piston 1(Sp1) which can slide through its small cylinder, the fluid will push this piston in 1meter and the one way piston 1 (Lp1) connected on the other end will also moves 1meter. Since the diameter of the one way cylinder1 (Lc1) is 1meter then, the volume of the displaced fluid by Lp1 will be 0.785m3 and this fluid will escape through 37.7 cm diameter cylinder 2(Sc2). This causes the small piston 2 (Sp2) and small piston 3 (Sp3) with the rack, slides through the small cylinder 2(Sc2) and small cylinder 3 (Sc3) in 7meter. As the rack is meshing with the pinions P1 & P2, it will rotate and through the gear train of the required gear ratio the power will be transferred to the rotor of the generator and by its rotation, electricity will be produced.
The construction of this barrage began in 1960. The system used consists of a dam 330m long and a 22km2 basin with a tidal range of 8m, it incorporates a lock to allow passage for small craft. During construction, two temporary dams were built on either side of the barrage to ensure that it would be dry, this was for safety and convenience. The work was completed in 1967 when 24, 5.4m diameter Bulb turbines, rated at 10MW were connected to the 225kV French Transmission network.
Blue Energy Power System - For large scale power production, multiple turbines are linked in series to create a tidal fence across an ocean passage or inlet. These are large scale, site specific, custom engineered energy installations which will vary in size and output by location. These structures have the added benefit as a transportation solution.
Mega Power System - A scaled-up version of the Blue Energy Power System, the mega class is a tidal fence capable of producing thousands of megawatts of power. These tidal fences can be many kilometers long and can operate in depths of up to 70 metres.
http://www.bluenergy.com/technology.html
The potential energy of a set of waves is proportional to wave height squared times wave period (the time between wave crests). Longer period waves have relatively longer wavelengths and move faster. The potential energy is equal to the kinetic energy (that can be expended). Wave power is expressed in kilowatts per meter (at a location such as a shoreline).
The formula below shows how wave power can be calculated. Excluding waves created by major storms, the largest waves are about 15 meters high and have a period of about 15 seconds. According to the formula, such waves carry about 1700 kilowatts of potential power across each meter of wavefront. A good wave power location will have an average flux much less than this: perhaps about 50 kw/m.
Formula: Power (in kw/m) = k H2 T ~ 0.5 H2 T,
where k = constant, H = wave height (crest to trough) in meters, and T = wave period (crest to crest) in seconds.
Potential world-wide wave energy contribution to the production of electricity is estimated by IEA (International Energy Agency) to be between 10 and 50% of the world’s yearly electricity demand of 15,000 TWh
A recent study by the DTI and Carbon Trust in UK is stating some 200,000 MW installed wave and tidal energy power by 2050 which with a load factor of 0.35 is resulting in a power production of 6 TWh/y. Independent of the different estimates the potential for a pollution free energy generation is enormous
http://www.wavedragon.net/technology/wave-energy.htm
Another promising type of wave energy power plant is a shoreline-based system called the Tapered Channel (Tapchan). The principle here is capital intensive yet has potential due to its ruggedness and simplicity. A tapering collector funnels incoming incoming waves in a channel. As the wave travels down the narrowing channel it increases in height till the water spills into an elevated reservoir. The water trapped in the reservoir can be released back to the sea similar to conventional hydroelectric power plants to generate electricity [1]. The advantage of this particular system lies in its ability to buffer storage which dampens the irregularity of the waves. However, the Tapchan system does require a low tidal range and suitable shoreline topography -limiting its application world-wide. A demonstration prototype of this design has been running since 1985 and plans are under consideration to build a commercial scale plant in Java [8].
http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
The Oscillating Water Column generates electricity in a two step process. As a wave enters the column, it forces the air in the column up the closed column past a turbine, and increases the pressure within the column. As the wave retreats, the air is drawn back past the turbine due to the reduced air pressure on the ocean side of turbine.
Much research is occurring internationally to develop oscillating water columns which require less stringent siting conditions, including the OSPREY and floating columns, such as the Japanese Mighty Whale
Another notable example of an OWC is the “Mighty Whale.” It is the world’s largest offshore floating OWC and was launched in July 1998 by the Japan Marine Science and Technology Center. This prototype, moored facing the predominant wave direction, has a displacement of 4,400 tons and measures 50m long. The Mighty Whale has three air chambers that convert wave energy into pneumatic energy. Wave action causes the internal water level in each chamber to rise and fall, forcing a bi-directional flow over an air-turbine to generate energy. The resulting electricity is supplied mainly to the nearby coastal areas. Storage batteries onboard ensure that electricity is available even during periods of reduced wave activity. It is projected that a row of such devices could be used to supply energy to fish farms in the calm waters behind the devices, and aeration/purification of seawater [7].
http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html
This technology builds upon SARA's pioneering Ocean Wave Energy Conversion system, awarded US Patent 5,136,173; 1992. Unlike alternative concepts that make use of cumbersome intermediate mechanical stages, SARA's approach uses direct conversion of mechanical fluid energy into electricity, via a highly efficient magnetohydrodynamics (MHD) process.
Product:
Rapidly-deployable Wave-powered MHD Electric Generator for the US Navy
Low-cost commercial power for coastal communities.
Benefits:
Almost no moving parts. No gears, no levers, no turbines, no drive belts, no bearings, etc.
Direct, local, and efficient conversion of fluid motion into electricity, with no intermediate mechanical stages.
Highly-compatible with very-strong, but slow-moving, driving forces (ocean waves, for example).
High capital costs for initial construction [9] to resist exposure to strong wave forces, storms, and corrosion [10];
Wave energy is an intermittent resource [2];
Requires favorable wave climate. The highest concentration of wave energy occurs between the latitudes 40° and 60° in each hemisphere, which is where the winds blow most strongly. Latitudes of around 30° of the equator due to the regular trade winds may also be suitable for exploitation of wave energy [11];
Offshore wave energy systems require investment power transmission cables for electrical connections to shore [11];
Degradation of scenic ocean front views from wave energy devices located near or on the shore, and from onshore overhead electric transmission lines [10];
Potential interference with other uses of coastal and offshore areas such as navigation, fishing, and recreation if not properly sited [2];
By reducing the height of waves they may affect beach processes in the littoral zone [2].
Ocean waves have the potential to contribute up to one TW to the global energy supply.
The problems associated with the intermittence of wave energy can be smoothed by integration with the general energy supply system.
Many different wave power plants, some of them multi-purpose, have been proposed, assessed, and cost-estimated
With the development of large-scale demonstration and commercial power plants underway, wave energy will begin to play an increasing role in complementing other renewable and conventional energy technologies to meet global needs.