Feasibility of Tidal Energy
on the Irish Grid system
Dr. Garth Bryans
Supervised by:
Queen’s University Belfast
• Dr. B Fox,
• Prof. M O’Malley
• Prof. P Crossley
• Prof. T J T Whittaker
Electricity Research Centre,
University College Dublin
Summary
• Incentives for Tidal Energy
• Method of resource assessment
• Systems in development
• Feasible areas
• System operations & efficiency
• Cost of grid connection
• Conclusions
1. Incentives for Tidal Energy
There is a need to develop and integrate
renewables into the grid to comply with emissions
targets and system security.
The benefits of tidal energy include:
•Predictability
•Minimal environmental impact
•Utilization of technologies developed by the
wind industry
1. Incentives for Tidal Energy
T Whittaker, P L Fraenkel, A Bell & L
Lugg (2003) The Potential for the use
of Marine Current Energy in Northern
Ireland. DTI.
2. Method of Resource Assessment
Testing the resource against the viable limits of TEDs
Tidal range
Sea bed slope
Max. wave height in 50 years
Distance from Ireland
Sea bed depth
Maximum spring velocity
3. Systems
Class A: Marine Current Turbines, Seaflow project
http://www.
marineturbines
.com
4. Feasible areas
2.2m/s, 20 to 40m,
MCT TED
4. Feasible areas
Power output with relation to blade diameter and current speed
4. Feasible areas
1.8m/s, 20 to 50m,
MCT TED
4. Feasible tidal generation around Ireland
Energy extractable around Ireland up to 15km from
the coast of Ireland assuming a 40% efficiency,
and a row spacing of 15 blade diameters (40% of
sites removed).
5. System operations & efficiency
•Evaluating the methods of controlling effect of tidal
generation:
•Electrical down rating of turbines, serves to reduce capital
cost and the effect on the system.
•Locating TEDs at opposing times of high water to cancel
daily variation.
•Effect of tidal generation on net system ramp rates.
•Effect on the demand profile.
•Capacity / availability factors.
•Effect of tidal energy on net system emissions.
•Inertial response from tidal generation.
5.1 Installed electrical down rating (IEDR)
IEDR of one turbine by 50% of the maximum energy extractable from
the tidal steam resource
5.1 Methods of controlling the effect of tidal
generation
Power output from one site
1.5
Power (MW)
Power (MW)
1.5
1
0.5
0
0
1
0.5
10
20
Time (Days)
0
0
30
Three sites 2.1 hours apart
2.5
1.5
Power (MW)
Power (MW)
2
Two sites 3.1 hours apart
10
20
Time (Days)
30
Four sites 1.6 hours apart
2
1.5
1
0.5
0
0
1
0.5
10
20
Time (Days)
30
0
0
10
20
Time (Days)
30
5.1 Methods of controlling the effect of tidal
generation
Total power output of a system with
tidal superposition following EDR
15
50% IEDR
applied to TEDs
Power output (MW)
No EDR
50% OEDR
applied to TEDs
10
5
0
5
10
Time (Days)
15
20
Simplification of spiking
5. System operations & efficiency
•Evaluating the methods of controlling effect of
tidal generation:
•Effect of tidal generation on net system ramp
rates.
•Effect on the demand profile.
•Capacity / availability factors.
•Effect of tidal energy on net system emissions.
•Inertial response from tidal generation.
5.2 Effect on system ramp rates
Ramp rate (MW / min)
The maximum system ramp rates
with and without TG for each season
25
20
15
10
5
0
-5
-10
-15
Autumn
Winter
Summer
Spring
Additional ramp rate caused by 100MW (average) TG
System ramp rate with no TG on the system
5. System operations & efficiency
•Evaluating the methods of controlling effect of
tidal generation:
•Effect of tidal generation on net system ramp
rates.
•Effect on the demand profile.
•Capacity / availability factors.
•Effect of tidal energy on net system emissions.
•Inertial response from tidal generation.
5.3 Effect
on
system
demand
profile
The average energy delivered in each 15min period during a day, over a year, with an
average of 100MW (511MW installed) of tidal generation.
Average tidal energy production in a year over a day
Average tidal energy generated
in 1 year (MWh)
30
25
20
15
10
5
0
0
2
4
6
8
10
12
14
Time (hours)
16
18
20
22
5.3 Effect on system demand profile
The average demand profile for each season in 2006, with an average of 100MW
(511MW installed) of tidal generation during a spring tide and during a neap tide.
Winter
Demand (MW)
Demand (MW)
Autumn
Time (days)
Spring
Summer
Demand (MW)
Demand (MW)
Time (days)
Time (days)
Time (days)
5. System operations & efficiency
•Evaluating the methods of controlling effect of
tidal generation:
•Effect of tidal generation on net system ramp
rates.
•Effect on the demand profile.
•Capacity / availability factors.
•Effect of tidal energy on net system emissions.
•Inertial response from tidal generation.
5.4 Capacity / availability factors
Availablitiy factor profile
1
0.9
Availability Factor
0.8
0.7
0.6
0.5
0.4
0.3
0.2
One turbine
2 TED areas 3.1h apart under IEDR
2 TED areas 3.1h apart under OEDR
0.1
0
0
20
40
60
Percentage EDR from Max power (%)
80
100
5. System operations & efficiency
•Evaluating the methods of controlling effect of
tidal generation:
•Effect of tidal generation on net system ramp
rates.
•Effect on the demand profile.
•Capacity / availability factors.
•Effect of tidal energy on net system emissions.
•Inertial response from tidal generation.
5.6 Effect on net system emissions
Determined from the 2007 all-island system modelled in PLEXOS
5.6 Effect on net system emissions
Determined from the 2007 all-island system modelled in PLEXOS
5.6 Effect on net system emissions
Determined from the 2007 all-island system modelled in PLEXOS
5. System operations & efficiency
•Evaluating the methods of controlling effect of
tidal generation:
•Effect of tidal generation on net system ramp
rates.
•Effect on the demand profile.
•Capacity / availability factors.
•Effect of tidal energy on net system emissions.
•Inertial response from tidal generation.
5.7 Inertial response from tidal generation
•A tidal turbine can have a radius of down to
~25% that of a wind turbine (depending on
location).
•A tidal turbine (~10 rpm) has a lower rotational
speed than a wind turbine (20-25rpm).
•The blades on a tidal turbine are heavier and
stiffer than on a wind turbine.
5.7 Inertial response from tidal generation
50.1
No tidal generation
Tidal using induction generators
Tidal using DFIG
Tidal using DFIG with SCL
50
Frequency (Hz)
49.9
49.8
49.7
49.6
49.5
49.4
49.3
0
2
4
6
8
10
12
Time (s)
14
16
18
20
Frequency trace following a loss of 422 MW of generation on the system during the
summer night valley with 500MW of tidal generation on the system.
6. Cost of grid connection
• The gird connection limits were tested using a PSSE
load flow model.
•The cost of grid re-enforcements was based on 2006
prices.
7. Conclusions
• With current technology tidal generation could only
provide about 2% of the annual Irish electricity demand.
• The proposed levels of tidal generation do not have a
serious effect on system operations. However methods
to control these effects have been identified.
• Tidal generation is more efficient in terms of installed
at reducing CO2 and NOx emissions than wind
generation and will offer similar saving in SO2 as wind
generation.
8. Acknowledgements
•The Department of Enterprise Trade and Investment
(Northern Ireland)
•Sustainable Management of Assets and Renewable
Technology
•Sustainable Energy Ireland
•The Danish Hydrographic Institute
•Kirk, McClure and Morton
•Northern Ireland Electricity
•British Oceanographic Data Centre
•Airtricity