# State of the Art of Renewable Energy and Energy Storage Systems Technologies in a Stand Alone Maritime

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## Energy Storage Systems Suitable for Stand-Alone Maritime Site

In this studied, an islanded site is considered. In such study case, both the load of the island and the renewable energy production will be highly intermittent. Therefore, balancing the production and the load on the gird presents a key feature. For these reasons, it is necessary to optimize the system behavior by associating an energy storage system to the renewable energy sources. In fact, energy storage systems can store electricity or transform electrical energy into other forms of energy and storing it in the process. Different energy storage systems can be applied to an islanded site. The more used ones will be presented in this part of the study.

### Pumped hydroelectric storage

Pumped hydroelectric storage (PHS) (fig.1.6) presents the largest energy storage capacity form for grid applications (about 95% of the total energy stored) [41, 42]. Such systems use the gravity potential energy of the water for storage purposes. In fact, at times of low demand, excess generation capacity is used to pump water from a lower reservoir into a higher one. When power is needed, water is released back into the lower reservoir threw a turbine, generating electricity [43]. The largest PHS station is the Bath country station in the U.S.A., with a production capacity of 3 GW [41, 42]. The energy stored in a PHS station is related to the volume V of water stored in the upper reservoir and the altitude difference h between the upper and lower reservoirs. In fact, the gravity potential energy respects the following equation: Ep = mgh (1.1) where, Ep is the gravity potential energy, m is the mass of the water stored in the upper reservoir, and g is gravitational constant. The mass of water is considered proportional to its volume, m = ⇢V (1.2) where ⇢ is the density of the water. Therefore, Ep = ⇢V gh (1.3) finally, by adding the efficiency of the PHS μphs EPHS = μphs⇢V gh (1.4) The PSH is the most developed between the different storage systems in this study. It scores a 9 TRL level [44]. PHS systems present also two key features: their long discharge time and their remarkable lifetime [43]. However, PHS systems present a low efficiency per volume unit since it needs two reservoirs, and each reservoir volume must be higher or equal to the one presented in equation (1.4), which presents a problem when applied in small
islanded sites.

#### Renewable Energy Systems Regulation

Renewable energy sources started to appear in considerable capacity on the international grid since the beginning of the 21st century [10, 11, 51–53]. In fact, according to reference [52], in 1990, the total wind-power world capacity was around 1 GW, and the solar photo-voltaic one presented values even smaller than 1 GW. After 1990, the renewable energy world capacity started increasing at an accelerating rate. By the year 2007, always according to the reference [52], the wind-power world capacity reached more then 90 GW, and the solar one reached more then 11 GW. More recent references [10, 11] present the recent evolution of these technologies, Figures 1.13 and 1.14
illustrate the renewable energy growth. In fact, according to the ’Renewables 2015 Global Status Report’, wind energy reached around 370 GW in 2017 and PV energy reached 177 GW of installed rated power. This recent increase in renewable energies on the grid is leading to new problems, particularly concerning the regulation and stability of the grid. In fact, renewable energies regulation and stability presents the following challenges:
• Most of renewable energy resources are not fully controllable. For example, when the load increases a diesel generator can increase the diesel combustion and produce more power; at the other hand, the wind can not be controlled at a faster value for a wind turbine to produce more power. Therefore, it is necessary to develop energy storage systems, in order to maintain the power stability on the grid [54].
• Many renewable energy resources are not yet fully mature. In fact, most renewable energy resources are still being researched and developed. Therefore, they can produce disturbances (counting voltage drop and frequency fluctuations) on the grid [55].
• Most renewable energy systems are connected to the grid via inverters. Knowing that inverters presents fast dynamics [56, 57], changes in the grid power can produce disturbances on the electrical signal.

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Abstract
Acknowledgements
Introduction
1 State of the Art of Renewable Energy and Energy Storage Systems Technologies in a Stand Alone Maritime
1.1 Introduction
1.2 Stand-Alone Maritime Site Suitable Renewable Energy Systems
1.2.1 Onshore wind turbine
1.2.2 Photovoltaic panel
1.2.3 Offshore wind turbine
1.2.4 Tidal turbine
1.2.5 Wave power
1.3 Energy Storage Systems Suitable for Stand-Alone Maritime Site
1.3.1 Pumped hydroelectric storage
1.3.2 Compressed air
1.3.3 Batteries
1.4 Offshore Energy transmission
1.5 Renewable Energy Systems Regulation
1.5.1 Vector Control
1.5.2 Observer-Based Control
1.6 Conclusion
2 Methodology of Analysis of the Energy Resource and the Energy Storage System for the Studied Stand-Alone Site
2.1 Introduction
2.2 Ouessant Island Energy Consumption
2.3 Wind Characteristics on the Island
2.3.1 Resource Characteristics
2.3.2 Turbine Properties
2.4 Tidal Characteristics in the Area Around the Island
2.4.1 Introduction
2.4.2 Existing measurements
2.4.3 Marine current velocity
2.4.4 Tidal energy and turbine properties
2.4.5 Turbine Properties
2.5 Solar Characteristics on the Island
2.6 Diesel Generators
2.7 Pumped Hydroelectric System
2.8 Conclusion
3 Sizing Method of a Hybrid Renewable-based System for a Stand- Alone Site
3.1 Introduction
3.2 Hybrid Renewable-based Farm Control Strategy
3.3 Sizing and Optimization Objectives
3.4 Simulation Results and Discussion
3.4.1 Results using fixed ESS, wind turbine, and tidal turbine models sizes
3.4.2 ESS sizes variation
3.4.3 Reducing wind turbine sizes
3.5 Conclusion
4 Design and Analysis of Inverter Control Methods for Micro-grid Applications in a Stand-Alone Site
4.1 Introduction
4.2 Design and Analysis of Single Inverter Regulation for Renewable Energy-based Systems
4.2.1 System Elements Description
4.2.2 P/Q Control Strategy
4.2.3 V/f Control Strategy
4.2.4 IVSG Control Strategy
4.2.5 Simulation Results
4.3 Design and Analysis of Inverter Control Methods in a Multi- Source Case
4.3.1 Traditional Droop Control Strategy
4.3.2 VSG Control Strategy
4.3.3 Simulation Results
4.3.4 Comparison and Discussion
4.4 Application to the Renewable Sources-based System for Ouessant Island
4.4.1 Introduction
4.4.2 System Elements Description
4.4.3 Simulation Results and System Performances Analysis
4.5 Conclusion
Conclusion and Perspectives
A Power Scheme of the Full System
B IVSG Block Diagram

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