Performance and Reliability Analysis of an Off-Grid Hybrid Power System

Abstract

Small villages in remote locations of developing countries rarely have access to electricity and are highly dependent on burning fossil fuels for energy. In an effort to provide these villages with a quality power supply and to replace their current emissions-producing energy generation, we propose a Hybrid Power System (HPS) that uses small wind turbines and solar panels for power generation. The system manages the intermittency of the renewable power by storing excess energy during periods of low user demand (such as night time) and releasing that energy at demand peaks (times when people are using demanding appliances). The proposed storage method uses electrolysis, which is the separation of water molecules into hydrogen and oxygen by excess DC currents produced by the wind and solar. The hydrogen is then compressed and stored in metal hydride tanks and when demand exceeds wind and solar generation, power is provided using a Proton Exchange Membrane Fuel Cell (PEMFC), which is highly responsive in peak demand periods compared to other types of hydrogen fuel cells. A physics-based model of the HPS is constructed in order to improve its efficiency, and statistics-based reliability models are formed to evaluate its potential for loss of load. Efficiency of a HPS can be viewed as balancing the energy production with user consumption. For this purpose, accurate models of the subsystems (wind turbines, solar panels, an electrolyzer using metal hydride tanks for hydrogen storage, fuel cell stack) are created. Realistic models of the AC loads are also required; this includes models of a performance optimized data center (POD) and the power demanded by a small community. As to optimize the energy management of the entire system, a model of a main controller that utilizes closed-loop control systems to maintain power stability is designed. On the reliability side, analysis is performed to assess the system’s response to various failures over time. This work is aimed at examining the reliability of the power system; not the examination of failure data in order to improve the reliability of various components. Models for testing of performance are created on a MATLAB Simulink and SimPowerSystems platform.