Mohammed Jama

Prediction of Global Solar Radiation in Abu Dhabi

Mathematical expressions have been employed to estimate global solar radiation on horizontal from relative sunshine duration for two weather stations in the United Arab Emirates (UAE), which are Abu Dhabi and Al Ain. These expressions include the original Angstrom-Prescott regression function (linear), quadratic function, third-order function, single-term exponential function, power function, logarithmic, and linear-logarithmic function. The predicted values were compared to the measured values using number of statistical methods to validate the goodness of the fits, such as residual analysis and goodness of fit statistics. All the used mathematical models performed generally well in both cities of Abu Dhabi and Al Ain, with all values of the coefficient of determination (𝑅2) higher than 75%. Specifically, the linear Angstrom-Prescott model estimated the average monthly global radiation on horizontal best for the city of Abu Dhabi, providing the second lowest mean absolute percentage error (MAPE) of 1.89% and the highest value of 𝑅2, which is approximately 94%, while the third-order model proved to be the best estimator for the city of Al Ain, providing the lowest MAPE value (3.06%) and a corresponding 𝑅2 of 83%.

Self-tunable fuzzy logic controller for the optimization of heaving wave energy converters

This paper proposes a new suboptimal reactive control technique for controlling single body heaving wave energy converter (WEC). A self-tunable fuzzy logic controller is implemented to maximize the absorbed energy while respecting the physical limitations of the device. Particle swarm optimization (PSO) algorithm is utilized to carry out an on-line optimization process of the fuzzy membership functions (MFs) embedded in the fuzzy controller. The proposed PSO-FLC out-performed the conventional fuzzy logic controller (C-FLC) in terms of improving reference signal tracking accuracy, widening the device wave absorption bandwidth, and preserving a degree of robustness to model uncertainties.

Controlling heaving wave energy converter using function-based model predictive control technique

This paper proposes a new reactive control technique for controlling single body heaving wave energy converter (WEC). A function-based continuous model predictive controller (MPC) is implemented to maximize the absorbed energy while respecting the physical limitations of the device. Laguerre orthonormal functions are deployed to approximate the input variable trajectory, which reduces the computational burden associated with MPC. The developed control strategy is evaluated using both monochromatic and polychromatic sea states. The function-based mode predictive controller showed decent reference signal tracking capabilities, optimizing the control effort to achieve maximum power transfer, while respecting the actuators mechanical and electrical limitations. Also the controller provides means to alleviate the problem of excessive real/reactive power flows.

Fuzzy logic based reactive controller for heaving wave energy converters

This paper presents a new control strategy based on fuzzy logic for maximizing the absorbed energy of heaving wave energy converters (WEC). The fuzzy logic controller is responsible of minimizing the discrepancy between the optimal reference buoy velocity and the actual buoy velocity, hence maximizing the captured power for irregular sea environment. The proposed controller performed well compared to a conventional fixed reactive control strategy.

MATLAB - based modeling tool for designing, predicting and analyzing grid tied photovoltaic systems

Planning a photovoltaic (PV) system is complex. Many different factors must be taken into account such as site information, module type and inclination of the modules, level of irradiation, choice of the most suitable inverter, etc. To ease the planning process, computer based tools must be utilized. In this paper, a MATLAB-based modeling tool to design, predict and analyze grid - tied PV systems is presented. This software has a user friendly interface which requires a minimum of data in order to present your optimum system and examine its performance in a clear graphical form. The user can explore different combinations and scenarios to meet the proposed design requirements. Simplicity, accuracy and ability to adapt the designed tool to any updates in both site information and system components would probably make it an excellent tool for educational and research purposes.

Predicting the electrical behavior of grid-tied photovoltaic systems in Al Ain - UAE / model and case study

Technologies of solar energy offer a clean, renewable and domestic energy source, and are essential components of a sustainable energy future. Conventionally, PV modules used to be located over the roof, but presently and with the advances in photovoltaic technologies a new emerging field of application science the building integrated photovoltaic (BIPV) is taking place worldwide. In this newly emerging field PV cells are incorporated with horizontal and vertical elements of the building envelop such as windows and solar louvers. In this paper a computer modeling tool is developed to predict PV system power generation in typical housing of the United Arab Emirates (UAE). This MATLAB-based tool uses daily weather data for the location in UAE under investigation. A large database that includes various PV modules and inverters was built. Using this tool, 20 degree PV module tilt angle proved to produce the maximum power across the whole year in Al-Ain city - UAE. The results obtained were validated in comparison to other data collected from different cities. Moreover, this tool is flexible and can be easily adapted to changes in PV technologies and weather data.

Online Damping Strategy for Controlling Heaving Wave Energy Converters Using Three-Phase Bridge Boost Rectifier

One of the main research questions in the field of wave energy technologies concerns the development of an efficient control strategy that can enhance the economic competitiveness of these technologies. Numerous control strategies have been proposed in the past three decades of which only a few are deemed practical. This paper proposes a novel online damping control strategy that is based on the development of an explicit relation for controlling the damping force of a permanent magnet linear generator (PMLG) in real time. The strategy controls the duty cycle of a single-switch three-phase boost rectifier connected at the output terminals of the PMLG. Simulations were conducted to assess the performance of the wave energy converter after applying the proposed strategy under different operating conditions. The results showed satisfactory performances for different sea-state and electrical-loading conditions.

Function-Based Model Predictive Control Approach for Maximum Power Capture of Heaving Wave Energy Converters

This paper investigates the application of function based model predictive control (MPC) approach to control the movement of single-body heaving wave energy converter (WEC). The proposed controller is designed based on the principle of maximum power transfer, at which maximum power absorption is attained. In addition, the suggested MPC controller respects the physical and thermal limitations of the WEC. Also, the generalized architecture of the proposed controller allows for longer prediction horizons and permits to effectively tune the controller based on the surrounding wave environment. Simulations have been carried out to assess the performance of the proposed controller using realistic sea states. Results show that the proposed MPC controller has achieved satisfactory performance allowing the WEC to optimize energy absorption while respecting the system limitations.

Low Cost Controller for Wave Energy Converter

This study addresses a low computation cost controller for maximizing energy absorption of a point absorber in wave energy converters (WEC). The objective can be achieved by ensuring the perfect tracking between the buoy’s velocity and its reference. In particular, the sliding mode control (SMC) is proposed for achieving the maximum energy in WEC. The SMC is considered to be a low cost controller because it is a fixed controller and tuned offline. In order to prove the effectiveness of the SMC, a computer simulation is conducted using the actual polychromatic ocean wave. The proposed controller is tested under the nominal case and its perturbations. The perturbation scenario considers the un-model dynamic of the losses force and perturbation in the excitation force. For the sake of comparison, another low cost controller so called passive reactive controller is simulated under the same condition with the proposed SMC.

Perspectives on Damping Strategy for Heaving Wave Energy Converters

Damping strategies are cost-effective and easy-to-implement, and are used to mechanically load heaving wave energy converters (WECs) by utilizing the combination of a properly sized power take-off (PTO) system and an accompanying control algorithm. Compared with reactive-based control strategies, damping strategies have lower energy throughput, but they can be effective for small WEC systems. To the best of our knowledge, damping strategies have been generally discussed either within the mechanical or the electrical framework. Therefore, this paper is an attempt to bridge the two directly interacting sides of the problem. Furthermore, the effect of the wave characteristics and the operating conditions of the PTO system on the power capturing performance of WECs is examined. A criterion to properly select the required damping, considering not only the hydrodynamic forces but also the limitations present in the PTO system, is proposed. The simulation and experimental results of the investigated system are provided and discussed.