Towards Ocean Grazer's Modular Power Take-Off System Modeling:A Port-Hamiltonian Approach

This paper presents a modular modeling framework for the Ocean Grazer's Power Take-Off (PTO) system, which operates as an array of point-absorber type devices connected to a hydraulic system. The modeling is based on the port-Hamiltonian (PH) framework that enables energy-based analysis and control of the PTO system. Firstly, a modular model of a point-absorber hydraulic system, which represents the main building block of the PTO, is presented. The model consists of wave-mechanical and hydraulic subsystems that are interconnected with a transformer-type interconnection. Secondly, we show passivity of the point-absorber hydraulic element and the accumulation of potential energy, which is due to the novel pumping mechanism of the point-absorber. Finally, we illustrate these properties through simulation results

Revenue Optimization for the Ocean Grazer Wave Energy Converter through Storage Utilization

Increased penetration of renewable energy generation motivates a change of paradigm in the way power systems are structured and operated, as advocated by the smart grid concept. Accordingly, in this paper we investigate the lossless storage capabilities of the Ocean Grazer wave energy converter (WEC), which could facilitate the aforementioned paradigm shift. This specific WEC exhibits both adaptability with respect to the incoming waves and significant lossless storage capabilities. We propose a model predictive control (MPC) strategy based on a lumped dynamical model in order to mitigate power imbalances in the power grid and maximize the revenue of the WEC. Furthermore, we illustrate that the proposed strategy exploits the WEC energy storage capabilities and we show the economic benefits it brings. Lastly, the proposed strategy is compared with a heuristic approach and a setting without storage

Global impacts of European agricultural and biofuel policies

Food supply and food distribution have been and are important issues in the global political arena. The recent emergence of biofuel policies has increased the influence of the policy arena on agricultural production. In this paper we show the regional impact of changes in the European Common Agricultural Policy and biofuel policy. Shifting trade patterns, changes in agricultural production, and expansion of agricultural area or intensification of agriculture result in changes in land use and land use emissions. Higher prices for agricultural crops on the world market together with changing production raise agricultural income. Brazil is the region the most affected. The results show that arrangements or policies will be needed to avoid negative impacts in other regions of changing agricultural or biofuel policies in the European Union