Large scale photovoltaic array deployment for
lacustrine and marine environments: A critical review.
ENGR 6116 E – Seminar Series
Kim Trapani
Research Supervisor: Prof. Dean Millar
Introduction
Advances in renewable energy have resulted in large scale offshore
deployment of renewable technologies, exploiting wind, tidal and
wave energy. Water covers almost 71% of the earth’s surface; hence a
great proportion of the solar resource is not exploitable using
traditional onshore photovoltaic (PV) arrays and configurations.
Offshore PVs
An offshore PV array
would consist of floating
PV panels.
In large scale application
this could consist of a
number of standard size
devices or of a scaled up
version.
Far Niente, California
Current Offshore Technologies
WIND
TIDAL
WAVE
North Hoyle, 60MW
La Rance, 240MW
Aguçadoura, 2.25MW
Thanet, 300MW
Strangford Lough, 1.2MW
Oahu, 40kW
Strangford Lough, 1.2MW
North Hoyle, 60MW
Far Niente, 110kW
Aguçadoura, 2.25MW
La Rance, 240MW
Thanet, 300MW
Oahu, 40kW
Wind Resource
Where the power extracted is:
P = ½ρAv3
Example of a typical wind rose
and power output from a wind farm
On average a typical wind
turbine site is intermittent,
that is at 0m/s for 3-4% of
the time.
Horns Rev, Denmark
80 x V80
Turbine spacing is 7D x 7D
Wind Technology
Advantages:
• Developed technology
• Low physical footprint
Disadvantages:
• Wake effects
• Visual impacts
• Cut in/Cut out speed
Typical spacing for
offshore wind farms:
>7D
Horns Rev, Denmark
GLOBAL INSTALLED CAPACITY – 2056MW
Tidal Barrage
(Boyle, 2004)
Advantages:
• Developed technology
• Predictable and controlled power output
Disadvantages:
• Major environmental impacts
• Requires large catchment area
• Visual impacts
TIDAL BARRAGE
Marine Current Turbines (MCTs)
Typical spacing MCTs is 5 – 8D
Retrieved from http://green-tide.org/technology/
MCTs
Advantages:
• Predictable
• Minimal impacts
Disadvantages:
• Subject to wake effects
• Minor visual impacts
Attenuating WECs
Advantages:
• Sector leader (has
sold 4 units!)
Attenuator – the energy absorber is of comparable
magnitude to the wavelength of incident waves and
aligned parallel to the wave propagation direction.
Disadvantages:
• Device complexity
• Need for maintenance
• Scales only with more
devices
ATTENUATING WECs
Utilisation of biodegradable hydraulic
and transformer fluids.
Point Absorber WECs
Advantages:
• Higher density
installed capacity
Point absorber – the energy absorber is very small
with respect to the wavelength of incident waves.
Disadvantages:
• Submerged
components
POINT ABSORBER WECs
Retrieved from www.oceanpowertechnologies.com
Spacing requirements for
OPTs Powerbuoys is 5D*
* According to proposal from Coos Bay Wave Park
Terminating Absorber WECs
Advantages:
• High absorption
efficiency
Terminator – the energy absorber is of comparable
magnitude to the wavelength of incident waves and
aligned perpendicular to the wave propagation
direction.
Disadvantages:
• Requires large
catchment area
• Arms fall off!
• Moorings
TERMINATING ABSORBER
WECs
Retrieved from http://www.wavedragon.net
Offshore Case Studies
Device
North Hoyle
Type
Wind
Horns Rev
Wind
Turbine
2002
€
272.00M $ 403.05M $
531.72M
20
160.00 MW 20.00km²
39.0%
Thanet
Wind
Turbine
2010
£
780.00M $1,388.47M $
1,388.47M
20
300.00 MW 35.00km²
35.0%
La Rance
Strangford
Lough
Aguçadoura
Tidal
Barrage
1967
Fr. 640.00 M $ 139.83M $
665.26M
30
240.00 MW 22.00km²
25.7%
Tidal
TCT
2008
£
8.50M $
16.71M $
15.15M
15
1.20 MW
0.01km²
40.0%
Wave
Pelamis
2006
$
8.20M $
9.30M $
9.71M
15
2.25 MW
0.22km²
25.0%
HL Crystalline Offshore PV
Crystalline
Proposal
$
350.00M $ 350.00M $
350.00M
20
224.00 MW 2.00km²
12.2%
HL Thin Film
Offshore PV
Thin Film
Proposal
$
330.00M $ 330.00M $
330.00M
20
224.00 MW 3.00km²
12.5%
ML Crystalline Offshore PV
Crystalline
Proposal
$
350.00M $ 350.00M $
350.00M
20
224.00 MW 2.00km²
14.9%
ML Thin Film
Thin Film
Proposal
$
330.00M $ 330.00M $
330.00M
20
224.00 MW 3.00km²
15.3%
Discount Rate
7.50%
Offshore PV
Technology Installation
Turbine
2003
£
CAPEX
CAPEX* 2009/10 - CAPEX Design Life Capacity Footprint Capacity Factor
86.00M $ 196.36M $
255.12M
20
60.00 MW 10.00km²
36.3%
*CAD $
Yield Production
Wind
1,339 kWh/kW
3,180 kWh/kW
1,304 kWh/kW
1,071 kWh/kW
3,416 kWh/kW
Footprint Capacity (MW) Capacity Factor Yield (MWh)
10.00km²
60.00 MW
36.3%
190793
20.00km² 160.00 MW
39.0%
546624
35.00km² 300.00 MW
35.0%
919800
22.00km² 240.00 MW
25.7%
540317
0.01km²
1.20 MW
40.0%
4205
kWh/kW
kWh/m² W/m²
3,180 kWh/kW 19.1
6.0
3,416 kWh/kW 27.3
8.0
3,066 kWh/kW 26.3
8.6
2,251 kWh/kW 24.6
10.9
3,504 kWh/kW 525.6 150.0
Agucadoura
0.22km²
2.25 MW
25.0%
4928
2,190 kWh/kW
22.4
10.2
HL Crystalline
HL Thin Film
ML Crystalline
ML Thin Film
2.00km²
3.00km²
2.00km²
3.00km²
224.00 MW
224.00 MW
224.00 MW
224.00 MW
12.2%
12.5%
14.9%
15.3%
240000
246000
292000
300000
1,071 kWh/kW
1,098 kWh/kW
1,304 kWh/kW
1,339 kWh/kW
120.0
82.0
146.0
100.0
112.0
74.7
112.0
74.7
kWh/kW
3,066 kWh/kW
Offshore PV
2,190 kWh/kW
Wave Tidal
1,098 kWh/kW
Device
North Hoyle
Horns Rev
Thanet
La Rance
Strangford Lough
3,504 kWh/kW
1000.0
160.0
900.0
140.0
800.0
120.0
700.0
600.0
100.0
500.0
80.0
400.0
60.0
300.0
40.0
200.0
20.0
100.0
0.0
0.0
North
Hoyle
Horns Rev
Thanet
La Rance
Strangford Agucadoura
HL
Lough
Crystalline
kWh/m²
W/m²
HL Thin
Film
ML
Crystalline
ML Thin
Film
Installed Capacity per m²
Production Yield per m²
2,251 kWh/kW
Economics
40.00 c/kWh
35.00 c/kWh
30.00 c/kWh
25.00 c/kWh
20.00 c/kWh
15.00 c/kWh
10.00 c/kWh
5.00 c/kWh
0.00 c/kWh
North Hoyle
Horns Rev
Thanet
La Rance
Strangford
Lough
Levelised Investment
Agucadoura HL Crystalline HL Thin Film
ML
ML Thin Film
Crystalline
O&M Costs
Data compiled from case studies and EWEA, 2009
Albedo Effect
The increase in diffuse lighting from the water surface, could be as much
as 60% higher depending on the angle of incidence. Similar increases in
diffused lighting could be expected from surfaces with snow/ice.
PV Technologies: Review
There are two main PV technology types in the market:
• Crystalline solar cells
• Amorphous solar cells
Crystalline Cells
Mono-Crystalline Cells
Amorphous Cells
η = 9 – 11%
η = 14 – 15%
~ 0.140 kWp/m2
~ CAN $ 2.50/Wp
Poly-Crystalline Cells
η = 13 – 14%
~ 0.140 kWp/m2
~ CAN $ 2.00/Wp
~ 0.080 kWp/m2
~CAN $ 1.00/Wp
Waste Heat in PVs
When PV panels are exposed to direct sunlight only a fraction of the rays
is converted into electricity, the rest is converted into waste heat – this is
what determines the efficiency of a PV panel.
PV panels only converts light of a
certain wavelength according to the
panel’s band gap. It though still
absorbs most of the solar spectrum
(apart from that which is reflected at
the PV surface), and what is not
converted into electricity is given out
as waste heat.
Effect of Efficiency with Heat
“Temperature coefficients provide the rate of
change (derivative) with respect to temperature
of different photovoltaic performance
parameters”
(King, Kratochvil, & Boyson, 1997)
STC Standard Temperature and
Conditions:
Temp. = 25°C
Irradiance = 1000W/m2
Air Reference Mass = 1.5
Temperature
coefficient is
-0.4342%/K for
tested PV panel
at STC.
↓ η ∝ ↑heat
Heat Transfer
In ground mounted PV arrays this heat would have to be extracted
through radiation, convection and conduction using air as the medium.
Radiation:
Convection:
Conduction:
P = eσA(T4 – Tc4)
∆Q = hA∆T
∆Q = -kA∆T/l
P – net radiated power
e – emissivity
σ – Stefan’s constant
A – radiating area
T – temp. of radiator
Tc – temp. of medium
∆Q – heat transfer
h – convective heat transfer coefficient
A – surface area
∆T – temperature gradient
∆Q – heat transfer
k – thermal conductivity
A – surface area
∆T – temperature gradient
l – length
Heat Transfer
In ground mounted PV arrays this heat would have to be extracted
through radiation, convection and conduction using air as the medium.
Radiation:
Convection:
Conduction:
P = eσA(T4 – Tc4)
∆Q = hA∆T
∆Q = -kA∆T/l
P – net radiated power
e – emissivity
σ – Stefan’s constant
A – radiating area
T – temp. of radiator
Tc – temp. of medium
∆Q – heat transfer
h – convective heat transfer coefficient
A – surface area
∆T – temperature gradient
∆Q – heat transfer
k – thermal conductivity
A – surface area
∆T – temperature gradient
l – length
Hence the heat
extracted depends
on the temperature
and thermal
conductivity of the
medium.
Since h is a factor of k
↑ Efficiency with ↓ Temp.
Hence at lower air to water temperatures the efficiency of the PV panels
would be higher – thus giving a higher power output.
Thus at -55°C the efficiency of the
PV panel would be ~ 19%
compared to the 14% at STC
Thermal Conductivities (Water vs. Air)
Medium
Thermal Conductivity
(W/mK)
Temperature
(K)
Density
(kg/m3 )
Air
0.025
293
1.29
Water
0.6
293
1000
Ice
2.1
293
917
(Hukseflux, 2010)
The change of fluid medium from air to water would imply a
significantly higher thermal conductivity. Hence the fraction of heat
extracted through conduction would be higher, since the heat
extracted is directly proportional to the thermal conductivity.
This will though require testing in order to determine the increase in
efficiency of the PV due to the enhanced heat conduction medium.
∆Q = -kA∆T/l
↑ η ∝ ↑heat extracted ∝ k
PV Reliability
• PV has no moving part
• Minimal maintenance (other
than maintaining surfaces
clean)
• Conventional technologies rely
on mechanical movement
With moored devices
the scenario is slightly
different since the
reliability of the whole
structure relies on the
device maintaining its
moored position.
WECs have a mooring failure
rate of 0.555/annum*.
*Thies, Flinn, & Smith, 2009
Self Cleaning Surface
↑PV Reliability implies ↓Lower Failure Rate
Land Competition
↑Population ∝ ↑Agricultural land requirement
United Nations, 2004
Land Cover
Percentage
Urban
0.30%
Ice/Cold Desert
5.90%
Coastal Fringes
3.20%
Irrigated Cropland
3.00%
Wetland
0.70%
Cropland
8.30%
Desert/Barren Land
20.90%
Grassland
13.60%
Mosaics inc. Cropland
8.40%
Woodland
14.50%
Forest
21.20%
IIASA Data 2000
Floating PV Devices: Review
(TTi, 2008)
• First floating PV array installation.
• Tilted at the optimal solar gain angle.
• Floating on pontoons.
• Gaps between panel arrays for
cleaning access and avoiding panels
shading.
(Faenza-Lugo, 2009)
• Laid almost horizontal over a support
structure.
• Fixed structure.
• 7-8% output reduction due to being
horizontal.
• Cleaning access available.
Design Concepts
• Modular unit
• Central buoy – for dry cable
coupling
• Electrodes/heating elements
• Flexible to deform according
to oncoming waves
• Transparent to minimise
blocking of sunlight with the
water column
• Scalable device
• Central buoy – heating PCM
• Slightly raised for a gradient
• Articulating according to
oncoming waves
Research Outline
Design Criteria
• Self-cleaning
• Anti-fouling protection
• Modular or scalable for large scale application
• PVs cooled to allow enhanced yields
• Heating element incorporation to ensure maximal availability in
lacustrine environments (freezing and snowed waters)
• Easily deployed
• Materials with least environmental impacts or which mitigate the
impacts
• Modules connection according to required voltage output
• Electrical safe connections, and availability for eventual access to
electrical systems during operation phase
• Mooring configuration which allows the higher installation packing
Device Loadings
The design should account for the loading forces,
depending on the site’s environment, to ensure that the
device remains in place during its operational periods
and also that it produces the optimal power output.
POTENTIAL IMPACTS
Environmental Impacts:
• Sunlight blocking of
the water column
• Reduction of oxygen
levels
• Electro magnetic fields
from the cables
Social Impacts:
• Fishing and leisure
exclusion zone
• Collision risk
Simulation Stage
Simulation work is required to estimate the yield which could be
expected from a floating PV device, since the tilt at which the rays
would be incident to are continuously changing according to the
movement of the device.
Time dependent
wave simulation
modelling of the
device
Time dependent
numerical modelling for
the device at the
simulated orientation
Net yield estimation
for particular device
Wave Simulation Modelling
Both SWAN and OrcaFlex are capable of producing a time dependent
motion study, based upon a specified wave model.
Retrieved from www.orcina.com
SWAN is a geometrical model
based which defines the wave
spectrum according to the
characteristics of the region’s
bathymetry.
OrcaFlex is a dynamic analysis
simulation software which allows
evaluation of entire offshore
systems.
Irradiance Numerical Modelling
R is the ratio between the
horizontal and the tilted plane
for the various irradiance
factors (i.e. direct, diffused
and reflected)
Hence by applying the
inclination factor derived
from the wave simulation,
the yield will be estimated.
Testing and Large Scale Application
A small scale model will be deployed, to investigate the performance
of the offshore device and conclude discrepancies with the estimated
yield.
PERFORMANCE
Actual power
output
COMPARISON
Tested estimation
for large scale
offshore PV
installations
Estimated
power output
Conclusion
Photovoltaic devices floating on the water is a
relatively new concept, which needs to be developed
further if it is to be considered as another renewable
offshore technology.
Compared to other offshore technologies, offshore
PVs have the potential to be cost competitive – with
predictable power outputs. When considering large
scale ground mounted structures it has the potential
to be more efficient and could essentially produce a
better yield per m2.
Research Partners
1. Mining Innovation, Rehabilitation and Applied Research Corporation
(MIRARCO), Sudbury, Northern Ontario, Canada (Lead Partner). Key contact:
Prof. Dean Millar.
2. Laurentian University, Sudbury, Northern Ontario, Canada. Cooperative
Freshwater Ecology Unit/Department of Biology. Collaborating contact: Prof.
Charles Ramcharan.
3. CANMET Energy Technology Centre,
Collaborating contact: Dr. Sophie Pelland.
Varennes,
Québec,
Canada.
4. Loughborough University, Leicestershire, UK. Applied Photovoltaics Research
Group. Collaborating contact: Prof. Ralph Gottschlag, Head of Group.
5. University of Exeter, Cornwall Campus, UK. Peninsula Research Institute for
Marine Renewable Energy (PRIMaRE). Collaborating contact: Dr. Lars
Johanning, Head of PRIMaRE.
References
Andre, H. (1978). Ten Years of Experience at the "La Rance" Tidal Power Plant. Ocean
Management , 4, 165 - 178.
Budikova,
D.
(2010).
Albedo.
http://www.eoearth.org/article/Albedo
Retrieved
from
The
Encyclopaedia
of
Earth:
Boyle, G. (2004). Renewable Energy: Power for a Sustainable Future. Oxford University Press.
Brook, B. (2009). TCASE 5: Ocean Power I - Pelamis. Retrieved from Brave New Climate:
http://bravenewclimate.com/2009/10/25/tcase5/
Krohn, S. Ed. (2009). The Economics of Wind Energy. European Wind Energy Association
(EWEA), Belgium.
Faenza-Lugo. (2009). Energia sull'acqua. Il Resto del Carlino (Anno 123, No. 287) , 12.
Hukseflux. (2010). Thermal Conductivities Measurements. Retrieved from Hukseflux Thermal
Sensors: http://www.hukseflux.com/thermalScience/thermalConductivity.html
King, D. L., Kratochvil, J. A., & Boyson, W. E. (1997). Temperature coefficient for PV modules and
arrays: Measurement methods, difficulties and results. 26th IEEE Photovoltaic Specialists
Conference. California: Sandia National Laboratories.
References
Natural Resources Canada. (2010). RETScreen International . Retrieved from Retscreen :
http://www.retscreen.net/ang/home.php
Overton, J., & Lemming, J. (2006). Offshore wind energy development in the North European
Seas. DTI.
Power-Technology. (2006). Pelamis, World’s First Commercial Wave Energy Project, Aguçadoura ,
Portugal. Retrieved from Power-Technology: http://www.power-technology.com/projects/pelamis/
SunElectronics. (2010). Solar Panel and Inverter Price Comparison. Retrieved from Sun
Electronics: http://sunelec.com/
Thies, P. R., Flinn, J., & Smith, G. H. (2009). Is it a showstopper? Reliability assessment and
criticality analysis for wave energy converters. Proceedings of the 8th European Wave and Tidal
Energy Conference. Uppsala, Sweden.
TTi, (. T. (2008). Moving Energy Forward - Floatovoltaics Spec Sheet. Novato, CA: TTi.
Vattenfall.
(2005).
Kentish
Flats
Facts.
http://www.kentishflats.co.uk/page.dsp?area=1414
Retrieved
Vattenfall.
(2010).
Thanet
Offshore
Wind
Farm.
http://www.vattenfall.co.uk/en/thanet-offshore-wind-farm.htm
from
Retrieved
Kentish
from
Flats:
Vattenfall:
THANK YOU
ANY QUESTIONS?