Fornybar energi del 3 - Marin fornybar energi

Fornybar energi del 3 - Marin fornybar energi

Ny fornybar energi – del 3:
Marin fornybar energi
Prof Peter M Haugan, Geofysisk institutt, basert på materiale fra
Prof II Finn Gunnar Nielsen, Geofysisk Institutt
Outline
•  General. Marine renewables
•  Wind energy
•  General
•  Offshore wind
•  Tidal energy
•  Wave energy
•  Thermal and salinity gradients
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Marine renewable energy
Source: European Science Foundation. Marine Board. Vision
document on Marine Renewable Energy, 2010
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The potential exceeds the demands.
Source: IPCC SRREN, 2011
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Onshore wind farms
Wind Farm, Kern
County,Tehachapi, CA. 1996
Midtfjellet vindpark, Fitjar
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Energy in the wind
•  Questions:
•  What kind of energy is a wind turbine
utilizing?
•  How much energy or power is available
for the wind turbine?
1
PAvail = ρ AV 3
2
•  How much power can be extracted?
Pmax
16 1
=
⋅ ρ AV 3
27 2
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A
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Offshore wind farms – Example Sheringham Shoal, UK
Facts:
• 315 MW of capacity • Located off the coast of Norfolk, England • 88 wind turbines, each 3.6 MW,
• Turbine blade length 52 meters
• Turbine tower height 80 meters
• Placed on foundations on the seabed Source:http://www.statoil.com/en/TechnologyInnovation/NewEnergy/
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Size of wind turbines
Source: EWEA
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Wind energy potential – World
Annual average wind speed at 10 m from NCEP,
:http//www.windatlas.dk/World/Index.htm
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Wind variation with height
A power law may approximate the increase of wind
speed with altitude for neutral atmospheric conditions
⎛ z
u ( z ) = u ( zref ) ⎜
⎜ zref
⎝
zref = 10m
α
⎞
⎟⎟
⎠
⎧ 0.1 open sea
⎪
α = ⎨ 0.15 flat land
⎪0.4 urban area
⎩
Source: Stull,R. B., An Introduction to Boundary Layer Meteorology, 1997
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The standard wind turbine
Source: http://www.alternative-energy-news.info/technology/wind-power/wind-turbines/
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Wind energy potential – Norway
http://www.nve.no/Global/Publikasjoner/Publikasjoner%202009/Oppdragsrapport%20A%202009/oppdragsrapportA9-09.pdf
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Hywind utenfor Karmøy

Turbines, two basic principles: HAWT VAWT
Horizontal Axis
Vertical Axis
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Costs
Wind power - On the move from land to deep water
Jackets
Monopiles
Water depth
Floaters
Floating wind will compete with conventional bottom fixed solutions in a mature market
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Power curve of a wind turbine (HAWT)
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Yearly production – capacity factor
Capacity factor:
AEP
Cp =
Prated 365* 24
AEP: Annual Energy Production (MWh)
Typical ranges:
“Full load hours”:
Onshore: 0.25 – 0.35
Offshore: 0.35 - 0.45
AEP
T=
Prated
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Competitive prices
euenergypost.eu
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Summary Wind
• 
• 
• 
• 
• 
Huge resource potential.
Maximum «capacity factor» 59%.
Turbine sizes increases.
Costs at grid parity at several locations.
The industry moves offshore.
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Tidal energy – Main principles.
Tidal barrage
P = CP ρ gQh
Tidal stream
P = CP
1
2 ρ AV
3
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Tidal range
Source: IPCC SRREN 2011
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The Rance barrage (North Brittany) , 1967
Up to 13.5 meters height difference
22km2 reservoir
24 turbines, D= 5.3m, 10 MW each
600 GWh/y (average capacity factor of 0.29).
Coastal & river device
(peak flow > 10 times river flow)
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Shihwa Lake Tidal Power Station, South Korea
254 MW / 552 GWh/yr (capacity factor 0.25),
Operating from 2011
Average tidal range 5.6m
30km2 lake
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Challenge: Power from La Rance.
•  Compute the yearly average
power production from La
Rance
•  Optimum operation?
P = CP ρ gQh
Q
depends upon h
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Tidal stream. Kvalsundet, Hammerfest, 2003
Max flow velocity 2.5 m/sec (mean 1.8 m/sec)
0.3 MW turbine (Test version)
Diameter : 20m
0.7 GWh/y (average capacity factor of 0.27)
1 MW unit installed in Scotland, Orkney, Dec. 2011.
HS300, installed in Kvalsundet
Prototype support structure
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Summary Tidal
•  Need large average current speed / large tidal
differences
•  Limited number of relevant locations
•  Predictable
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Ocean waves
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Ocean waves
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Resources Waves
Average energy densities:
20 – 100 kW/m wave front
Source: World Energy Council
Example: 50 kW/m, 30% efficiency:
130 MWh/ym
100TWh/y: 760km
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Key principle for extracting wave energy
Energy absorption requires a force
working together with a velocity
•  Work: Force*distance
•  Power: Force*velocity
Falnes: “In order for an
oscillating system to be a
good wave absorber it should
be a good wave generator’’.
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Wave energy - main principles
Source: Bedard(2006) «Overview: EPRI Ocean Energy Program» Presented to Duke Univerisity Global Change Centre.
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Wave power converters. Installations in full / reduced scale
Fred Olsen, “Buldra”. (Norway 2004-)
•  Array of heaving buoys. Semisubmersible
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The TapChan concept (Toftestallen, 1985).
Wave focusing plus overtopping
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Relative motion attenuator – Pelamis (750 kW device)
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Summary, wave energy
• 
• 
• 
• 
Large energy potential
A large number of principles proposed
“To extract energy you must generate waves”
Survivability drives costs
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Ocean Thermal Energy Converter (OTEC)
Utilizes difference in water temperature.
Largest differences in tropical areas.
Temperature difference at 20 and
1000m sea depth.
Source: NREL 2014
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OTEC – working principle
Maximum fraction of
energy available for work
(Carnot cycle)
η = 1−
= 1−
TC
TH
273 + 4
= 0.067
273 + 24
38
Possible layouts
Source: OTEC Corporation
Floating OTEC plant
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New OTEC installed in August 2015.
More, see e.g. OTEC overview, by L.A. Vega, Ph.D., http://www.otecnews.org/portal/otec-articles/ocean-thermalenergy-conversion-otec-by-l-a-vega-ph-d/#engineering
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Salinity gradient, Pressure Retarded Osmosis (PRO)
see IRENA (2014), NREL (2012)
Key principle: Utilizes difference in salt concentration in two fluids.
Creates a pressure difference over a membrane.
Up to 26 bar pressure difference
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Salinity gradient: Reverse Electro Dialysis (RED)
Principle: Salt ions move through the membrane and creates an electrical potential.
Use a stack of alternating cathodes and anodes.
Source: Gert Jan Euverink, Wetsus Pieter Hack, REDstack
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Salinity gradients – potentials (IRENA 2014)
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Summary Thermal and salinity gradients
Thermal gradients:
• 
• 
• 
Relevant in tropical regions only
Small scale testing ongoing
Low efficiencies.
Salinity gradients:
• 
• 
• 
• 
Two principles:
•  Generate pressure difference
•  Generate electrical potential difference.
Few sites world wide
Tested in small scale
Challenges in up-scaling (membrane)
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