• Energy Research

Wind power is increasing rapidly and specially offshore wind. Offshore wind offers certain advantages as more constant wind and additional space without large restriction. However, deep-waters require floating technologies. A key drawback of offshore wind is the reduced windows for operation and maintenance. Therefore, the use of optimal control algorithms that ensure the correct operation of the wind farm is essential. Offshore wind farms are usually oriented towards a defined direction of wind flow, so upstream turbines tend to provide more active power, carrying higher fatigue load, which results in uneven distribution of fatigue across the wind farms. Loads must be distributed among the members of the farm, to extend the farm and turbines life and reduce possible maintenance or breakage costs. Taking into account wake effects as well as hydrodynamic impacts which add additional motion and stress to the system, this paper presents a wind farm Model Predictive Controller (MPC) in order to optimize the loads of each wind turbine for life-extension. The results of the control show how the power generation is met and the load distribution are better balanced reducing system stress. 

Wind power is increasing rapidly and specially offshore wind. Offshore wind offers certain advantages as more constant wind and additional space without large restriction. However, deep-waters require floating technologies. A key drawback of offshore wind is the reduced windows for operation and maintenance. Therefore, the use of optimal control algorithms that ensure the correct operation of the wind farm is essential. Offshore wind farms are usually oriented towards a defined direction of wind flow, so upstream turbines tend to provide more active power, carrying higher fatigue load, which results in uneven distribution of fatigue across the wind farms. Loads must be distributed among the members of the farm, to extend the farm and turbines life and reduce possible maintenance or breakage costs. Taking into account wake effects as well as hydrodynamic impacts which add additional motion and stress to the system, this paper presents a wind farm Model Predictive Controller (MPC) in order to optimize the loads of each wind turbine for life-extension. The results of the control show how the power generation is met and the load distribution are better balanced reducing system stress. 

Nowadays, offshore renewable energy is seen more and more as an attractive alternative to onshore energy thanks to less space limitations and usually better weather conditions. However, the higher costs in installation and maintenance demand a continuous search for higher conversion efficiency in order to achieve an economically viable electricity generation. In this line, the co-location of wind and wave power sources might serve to reduce the generation power variability and also to take advantage of using the same infrastructure and implementation area. Several studies have been carried out mainly focused on determining possible zones of implantation or developing new co-location concepts. However, the optimization and control of these new offshore energy conversion systems have not been extensively studied in the literature. This article presents a new optimal control strategy for co-located wind and wave farms in order to fulfill the operation and integration requirements demanded by power system operators. The proposed control scheme is evaluated in several realistic scenarios. The obtained results show that with adequate control strategies, it is possible to increase the electricity production of co-located wind-wave farms satisfying the frequency requirements of the network, even in adverse events, and also to increase the total power reserve of the system.

Nowadays, offshore renewable energy is seen more and more as an attractive alternative to onshore energy thanks to less space limitations and usually better weather conditions. However, the higher costs in installation and maintenance demand a continuous search for higher conversion efficiency in order to achieve an economically viable electricity generation. In this line, the co-location of wind and wave power sources might serve to reduce the generation power variability and also to take advantage of using the same infrastructure and implementation area. Several studies have been carried out mainly focused on determining possible zones of implantation or developing new co-location concepts. However, the optimization and control of these new offshore energy conversion systems have not been extensively studied in the literature. This article presents a new optimal control strategy for co-located wind and wave farms in order to fulfill the operation and integration requirements demanded by power system operators. The proposed control scheme is evaluated in several realistic scenarios. The obtained results show that with adequate control strategies, it is possible to increase the electricity production of co-located wind-wave farms satisfying the frequency requirements of the network, even in adverse events, and also to increase the total power reserve of the system.

The continuous dynamic motion of floating offshore wind turbines (FOWT) can introduce long-term fatigue and structural tensions, reinforcing the importance of structural control. Here, the novel proposed concept of collective structural control of waked floating wind farm by optimally de-loading the FOWTs with more motion, in order to avoid undesired tower-base bending-moment, long-term fatigue or increasing mooring tensions aims to be introduced. The study proposes a collective control strategy for distributing power set-points based on real-time assessment of the FOWT’s structural behavior by mitigating pitch motion and optimizing performance. To evaluate the effectiveness of this approach, a predictive controller is developed and tested on a spar-based wind farm. The results demonstrate that the adoption of a collective structural controller is more suitable for long-term operation of floating wind turbines compared to conventional power-oriented strategies, diminishing 7 times the standard deviation of the mean pitch values of the FOWTs in the array and thus, minimizing axial stress of the most upstream FOWTs. The impact of wave states on the behavior of the floating wind turbines within the array can be observed, influencing the effectiveness of the control strategy.

The continuous dynamic motion of floating offshore wind turbines (FOWT) can introduce long-term fatigue and structural tensions, reinforcing the importance of structural control. Here, the novel proposed concept of collective structural control of waked floating wind farm by optimally de-loading the FOWTs with more motion, in order to avoid undesired tower-base bending-moment, long-term fatigue or increasing mooring tensions aims to be introduced. The study proposes a collective control strategy for distributing power set-points based on real-time assessment of the FOWT’s structural behavior by mitigating pitch motion and optimizing performance. To evaluate the effectiveness of this approach, a predictive controller is developed and tested on a spar-based wind farm. The results demonstrate that the adoption of a collective structural controller is more suitable for long-term operation of floating wind turbines compared to conventional power-oriented strategies, diminishing 7 times the standard deviation of the mean pitch values of the FOWTs in the array and thus, minimizing axial stress of the most upstream FOWTs. The impact of wave states on the behavior of the floating wind turbines within the array can be observed, influencing the effectiveness of the control strategy.

Currently, reversible solid oxide cells (rSOC) are the only devices that allows a bidirectional conversion of H2O and H2, being able to operate as fuel cell and as electrolyzer. Thanks to the high-temperature operation, rSOC present a higher efficiency and additionally, provide a feasible solution for long-term energy storage in electrical systems. Experimental testing of rSOC have been mainly focused on cells characterization, thermal or degradation analysis, but the study of transition cycles has not been widely studied. The transitions between the operation as a solid oxide fuel cell (SOFC) and as a solid oxide electrolysis cell (SOEC) might have a significant impact on the rest of the electrical system in which the rSOC is integrated. This article analyzes experimentally the power responses of a rSOC stack, during each operating mode (SOEC-SOFC) and during transition between both modes. The results suggest that transition cycles can be achieved in less than 8 min and the total transition from SOEC rated power to SOFC rated power in less than 10 min, having a significant impact on microgrid operations, especially in islanded mode. The obtained results indicate that the most suitable role for rSOC in a microgrid is as grid-following. The grid-forming role is only possible if the rSOC operates along with a fast-response power source.