ALTERNATIVE ELECTRICITY POWER SUPPLY SYSTEM

Alternative Electricity Power Supply System



Alternative Electricity Power Supply System

Introduction

Nowadays the development of clean energy systems, for both transportation and stationary applications, is recognized as mandatory to satisfy well-known environmental and regulatory requirements in terms of emissions and energy conversion efficiencies. Because of their high efficiencies and zero toxic emission levels, fuel cell systems are considered as one of the most attractive solutions in the automotive and power generation industry. Among the existing fuel cell technologies, the high-temperature fuel cells show a great promise due to their high energy conversion efficiency, fuel flexibility and high temperature of the exhaust heat which allows favorable co-generation and combination with other types of power generators such as heat engines

After the concept of fuel cell-heat engine hybrid systems was proposed at early 1990, a number of investigations have been carried out about the system performance from the energetic point of view. In a group of works, the cell performance was evaluated based on the operating curve interpolated from experimental test results. Some authors performed a parametric analysis to understand the effects of different operating conditions on the performance of a specified system. Most of the papers are dealing with the theoretical cycle analysis and simulation of the possible configurations of the hybrid systems.

Since it is difficult to experimentally quantify the interrelated parameters governing a hybrid system, theoretical modeling and numerical analysis become essential for the optimization of the system design and operating conditions. Therefore, the purpose of the present paper is to clarify these issues and present a general and fundamental analysis of the theoretical performance potential of a fuel cell-heat engine hybrid system.

Based on the simplifying assumptions derived from literature and performance data provided in, an irreversible thermodynamic modeling for a fuel cell-heat engine hybrid system is further carried out to simulate the system response to the changes in the operating conditions and design parameters through parametric study. The different sources of energy losses are specified and the performance characteristics of the system are investigated. In particular, both the heat-leak from the fuel cell to the environment and heat transfer between the fuel cell and the heat engine are considered. As a consequence, the performance of the hybrid system is optimized. These findings indicate which parts of the system deserve the greatest effort if one wants to improve the overall cycle efficiency.

An irreversible model of the fuel cell-heat engine hybrid systems

Although fuel cell technology has been studied extensively, the best way to employ fuel cell unites for the generation of electrical power remains to be determined. Optimal thermal management allows for effective use of the system's byproduct, heat, leading to substantial increases in the overall system efficiency. The heat generated in a fuel cell may be dissipated by convection, conduction or radiation. However, mostly the heat may be used to run a thermodynamic cycle, such as a heat engine, for additional power generation.

It is our opinion that initially a fuel cell-heat engine hybrid system has to be as simple ...