We propose unification of various geometric design approaches, available in the open literatures and published research papers, for profile of star rotor used in rotary piston machines type hydrostatic units, namely pumps and motors. The star rotor profile has cycloidal root. We consider three basic approaches. These approaches are otherwise self-sufficient for profile selection purpose although the end formulae are different in relation to the common parametric terms. A closer scrutiny reveals that the initial selection of co-ordinate systems, profile generating centrode pairs and the location of the generating point lead to such differences. Our unification provides infusion and integration of three different paradigms that we have considered. This investigation is aimed at helping researchers develop a better understanding design approaches of such machines.

In the present study, the leakage of fluid due to gap generation at the contact points is eliminated by introducing interference between the rotor and the stator of an Orbit motor. Interference is incorporated in the system by modifying the roller radius, the chordal thickness, and the pitch circle radius. In an Orbit motor of interference-fit type, the contact points and the rotor center deviate from their original positions as found in an Orbit motor of perfect-fit type. A corrective technique based on minimization of the potential energy of the system is used to obtain the rotor center of an interference-fit motor. The rotor profile is initially generated around the geometrically obtained center of a perfect-fit motor. It is then shifted in the direction of decreasing potential energy, until the rotor center corresponding to minimum energy is attained. The main drawback of introducing interference is the generation of an unbalanced torque which affects the output torque of the motor. Thus, optimization of interference parameters using genetic algorithm is carried out to determine a system for which no gap is generated at the contacts and simultaneously it is ensured that the unbalanced torque ripple amplitude is minimum.

Intermittency characteristic of renewable energy sources can be resolved using an energy storage technology. The function of the energy storage system is to store the excess energy that is produced from various renewable energy sources during the off‐peak hours and releases the same energy during the peak hours. The energy that is produced from the renewable energy sources can be stored in different forms such as Mechanical, Electrical, Electrochemical, Thermal, Chemical energy etc. Among all these forms of stored energy, a CAES technology under the Mechanical form of energy is the most cost effective for the bulk energy storage purpose. It involves a combined operation of various components such as Compressor/Expander, Gas turbine, combustion chambers, heat exchangers, generator unit, and underground compressed air storage. This article focuses to review the detail of various CAES systems such as D‐CAES, A‐CAES, I‐CAES etc. Additionally, it presents various technologies that are used to improve the energy efficiency and applicability of the CAES system. It is found that a maximum RTE of the C‐CAES, A‐CAES, and I‐CAES are 54%, 71%, and 80%, respectively. In addition, the RTE of the modified CAES systems such as LP‐CAES, PH‐CAES, and SC‐CAES are about 90%, 80%, and 60 to 80%, respectively.

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