The EU’s renewable energy directive requires that 20 per cent of the energy used by its member states comes from renewable sources by 2020. Malta must also do its part and we are seeing some renewable energy initiatives taking root on the island.
The major renewable energy resources in Malta are solar energy, wind energy and energy from waste. Since Malta is a small and densely-populated country there are only small possibilities for large scale electricity generation from solar or wind energy. Three sites are being seriously considered for wind farms in Malta: Hal Far, Baħrija and Sikka l-Bajda. Despite Malta having large territorial waters, only Sikka l-Bajda is being seriously considered for an offshore wind farm since to date wind farms have been erected only in shallow waters (up to about 30 metres deep). Sikka l-Bajda is the only shallow water site of considerable size and sufficiently distant from the shore for an offshore wind farm.
The research I have been conducting at the University of Malta for my Masters of Science in Engineering course was dedicated to offshore wind energy generation in Maltese deep waters. The project was undertaken within the Department of Mechanical Engineering under the supervision of Tonio Sant and Martin Muscat. A large offshore site with a depth varying from 50 to 70 metres is situated to the southeast of Malta. The area includes Hurd Bank and could accommodate an offshore wind farm with a capacity of around 400 Megawatts.
However, technology for installing offshore wind turbines at such sea depths is still in research and development stage. The increased depth is expected to increase the costs related to the supporting structures and installation. On the other hand, most offshore wind turbine developments to date have been conducted in the North Sea. It is expected that the more benign wind and wave conditions in the Mediterranean would reduce the load bearing demand on the support structures and facilitate the installation and maintenance activities.
My research project focused on the design of a support structure for an offshore wind turbine that could be constructed in waters up to 70 metres deep in the southeast of Malta, covering Hurd Bank. At such depths, bottom-mounted structures are used. On the other hand, floating structures are considered to be more appropriate for deeper waters, typically in depths exceeding 90 metres. Floating structures were beyond the scope of this project.
The support structure of an offshore wind turbine is responsible for holding the turbine fixed in its position during its whole lifetime. There are various different types of support structures for an offshore wind turbine that can be used. One of the first steps in the design process is to select the type that is to be used. Following a selection process the bottom-mounted jacket type structure was selected for the area under consideration. The jacket type support structure was designed in more detail using state-of-the-art software tools and according to international design guidelines. A comparison between the designed support structures for Maltese conditions and a similar one that had been designed for Scottish waters showed that, under Maltese conditions, a lighter support structure may be used. This resulted from the less extreme wind and wave conditions in the Mediterranean and the better bearing capacity of the seabed.
This research was funded by STEPS (Strategic educational pathways) scholarship part-financed by the EU European Social Fund.