1. Investigating The Opportunities For Wave Energy In The Aegean Sea
7th International Scientific Conference on “Energy and Climate Change”
8-10 October 2014 Athens, Greece
Investigating The Opportunities For Wave Energy In The Aegean Sea  
George Lavidas

2. Content 1. Introduction 2. Wave Energy Numerical Modelling
SWAN(Simulating Waves Nearshore)
3. Area of Investigation
Validation of Hindcast
4. Wave Energy Opportunities
Applications

3. 1.Introduction
Greece is a Mediterranean country with abundant Renewable Energy (RE) resource.
Currently Photovoltaic, solar thermal, onshore wind and hydro account for the RE penetration.
In 2012 almost 13.8% of energy production

5. Aegean Characteristics
Greece offers many coastline areas.
Number of naval infrastructure in existence in most locations.
Many island complexes.
Islands are isolated from the centralized grid.
Energy is comprised mostly by oil imports and thermal stations.
Increased cost of energy is subsidized by the State.
Greece is exposed to both the Aegean , the Ionian and the greater Mediterranean sea
Include many numbers of islands and complexes, that are usually classified are large, medium and small islands.
Major energy needs for the majority of the islands is covered by naval routes shipping oil products
Desalination purposes in islands are also operated by conventional stations
The increased cost of energy due to transportation of fuel and supply is provided by the State, leading to income State losses.

6. 2.Wave Energy
Waves pose a potential for the decentralization and energy production, in remote and island areas.
Resource assessment and identification of highly energetic areas is required.
Buoys offer some information of the wave environment.
Wave energy can be harnessed and used for contributing RE energy is remote location
Currently buoy, scattered through out the Aegean offer us a picture of the seasonal wave resource
Although a thorough resource identification and assessment has to be carried out
Identifying wave energy sites and predict energy production

7. Numerical Modelling
Most devices are to be located nearshore (depth <150m).
The absence and scarcity of buoys, make the assessment difficult.
Numerical wave models can substitute the procedure, if calibrated and set up correctly.
Currently numerical wave models can be used to assess and offers forecasts.
The proper physical terms and interactions included is of major importance for the proper performance of the model
Although buoys cannot be replaced, numerical models can help us identify promising wave energy locations
Proceed to proposed incorporation scenarios for wave energy

8. SWAN (Simulating Waves Nearshore)
Is a third generation numerical model, resolving the wave kinematic action balance equation in a implicit way.
Improved physical terms for nearshore applications.
Allows different spectra to be resolved.
Different numerical models are now available depending on the scale we want to obtain information on (WAM, WWIII, MIKE21).
Although based on some of the same principles, different approximations and solvers are used.
Input source terms include, triad interaction (shallow water only), quadruplets, dissipation - whitecapping, bottom friction, wave breaking, these can affect the final simulated waves in different ways
Smaller areas often require less computational resources, making more efficient in use, different models (explicit) require larger computational resources.

9. 3. Area of Investigation
A nested run was performed, Aegean Sea resolution is 0.025x0.025 degrees.
All shallow water physical terms activated and calibrated accordingly.
JONSWAP spectrum considered for wave generation and propagation.
Aegean Sea, hindcast 2010
Initial coarse run to provide boundary conditions, was performed for the 2010.
Mediterranean resolution 0.1x0.1, with no incoming boundaries only wind driven waves
JONSWAP spectrum suitable for short fetches was employed
Results are to be validated against buoy data and expanded if accuracy is deemed sufficient, for unknown areas.
Wave set up made, by taking into account the bathymetric and wind conditions dominant in the area, re-adjusting the physical terms of the model, to optimize performance

10. Validation of hindcast
Using multiple Indexes enhances the validation process.
Hindcsast was compared with 3-hr data buoy intervals.
High reliability of hindcast by SWAN
Athos
Pylos
Petrokaravo
Hs (m)
Tp (sec)
Tz (sec) R
0.77
0.91
0.96
0.93
0.97
0.88
MPI
0.98
0.89
0.78
0.82
Bias
-0.41
-0.31
-0.46
-0.33
-0.11
-0.26
+0.63
+0.27
RMSE
0.75
2.04
1.21
0.53
1.44
0.87
0.33
2.25
Components compared are Hs, Tp and Tz, which will offer the resource assessment for wave energy potential, with many statistical indexes
The hindcast yielded high accuracy results with MPI above 90% while the overall hindcast shows that a constant underestimation exist in the Hs, periods display similar results
The location of the buoy affect the statistical comparison, due to the location of the Athos buoy the hindcast showed the weakest results, this can be attributed to the physical shallow water interaction (triads and friction ) that are dominant in those areas

11. Significant wave height validation
Peak Period validation
The visual representation of two buoys, Athos (least accurate indexes) and Pylos (highest accurate Indexes)
Present the generation trend of the hindcast based on the physical terms
The calibration and hindcast of the models, can be used to examine and assess areas of wave resource interest.

12. 4. Opportunities for wave energy
Since waves are physically correlated by driven winds, it is expected that winter months present the most energetic resource.
Propagation of waves is following the dominant wind direction with a 50 degr (25 deg at each side) possibility of diversion.
Highest potential of wave energy can be identified through the results.
Summer months present the lowest power capacity.

13. Wave potential identification
From the hindcast it was established that the most energetic areas were located in the central Cycladic islands the South West of Peloponissous and the island of Crete.
The environment interacting at these locations, is enhanced by swells propagating from the West and South portion of the Mediterranean.
The complex bathymetry of the Aegean has a significant effect on the wave potential, the Central and North Aegean acts like a basin area, dissipating and diffracting the wave resource in higher degrees than the identified locations

14. Applications
Wave energy devices can be coupled with local RE sources and especially wind.
Due to the nature of the resource, waves and wind complement each other.
This can lead to multiple platforms utilization.
Employment and infrastructure opportunities.
Desalination plants can also benefit from wave devices.
Reduction of oil usage in island energy production.
Overall diversification of the energy mix.
Reduction of the economic cost for remote islands.
Assessment identification, is the first step, further investigation of proposed locations should be expanded upon
The dual capacity of local generation can be used to reduce the oil imports to the islands
Provide more RE alternatives based on local resource
Benefits on the development of local infrastructure such as harbours, which can benefit multiple sectors such as fisheries, tourism, naval etc.

15. THANK YOU Acknowledgments: EPSRC for the research grant
Dr. Vengatesan Venugopal
Dr. Daniel Friedrich