The paper presents a mathematical model for Polymer Electrolyte Membrane "PEM" fuel cell and an Equivalent Electrical Model for a PEM Electrolyzer. The performance both of the fuel cell and the electrolyzer, depending on the developed model and taking all the losses as well as the double layer charging effect into account, is studied by varying the different operating parameters to evaluate their effect on the systems. In the fuel cell case, this will help in the development of regulation of the control or/and controlling systems to improve its performance. As for the electrolyzer, it will help in increasing the hydrogen production.

The following paper presents a comparative study between different types of the collection network configurations. The primary interest lies in the identification of the most cost effective farm configurations with the lowest cost profile. Different configurations based around small clusters of turbines that are controlled by a single power converter for both AC and DC technologies are discussed and compared to conventional configurations. In addition, the possible coupling of variable speed WTs into clusters with a collective rotational speed are more thoroughly considered.

This paper outlines the advantages and the disadvantages of the most commonly generator used in Wind Energy Conversion Systems (WECS). The state of art on wind turbine technology is established by comparison of each type. Doubly Fed Induction Generators (DFIG), Squirrel Cage Induction generators (SCIG) are the two types of induction generators commonly used for geared operation in WECS in variable speeds and fixed speeds, while the Permanent Magnet Synchronous generators (PMSG) can operate gearless. Due to higher demand of power from wind energy, off shore installations are becoming more popular and new wind turbine designs are being expected in the near future, with the development of the improved generators and converter designs.

Increasing worldwide demand for energy has made wind energy a forerunner as a renewable energy resource. Due to this, and due to the intermittent nature of wind, Wind Turbines (WT) reliability should be considered. Improving the reliability of a WT translates into reduced operation and maintenance cost. This highlights the aim of this paper which is a technical review on WTs critical failures as well as an update on recent progress in fault diagnosis and condition monitoring methods used.

In this paper, an electrical equivalent circuit for a proton exchange membrane (PEM) electrolyzer is used to develop a Simulink block diagram. The I-V characteristic for a single PEM electrolyzer cell is modeled under a steady-state and elaborated using an electrical equivalent circuit. Hydrogen production rates characteristics are developed with respect to the input current and power. It is clearly seen that the electrolytic hydrogen production rate increases with the input current in a linear fashion and the variation of hydrogen production rate with the input electrical power is non-linear (i.e. logarithmic). These characteristics are simulated using the developed Simulink/Matlab model of PEM electrolyzer cell. The parameters of the developed model can also be defined by taking into account temperature and pressure effects.

This paper examines the problem of longevity in pacemaker batteries. A mathematical model is elaborated. Several variations of stimulus currents and time are imposed and their results are studied. The given simulations show the effect of the current pulses on the charge consumption and the battery longevity. The range of values which assure the best system performance and the best battery protection from wear and depreciation is also discussed.