Paper

Expert System for Component Selection of Selfsufficient and Regenerative Electricity Supply Systems with Hydrogen Storage
Maike Stark, Matthias Hausmann & Gerhard Krost, IEEE
El. Power Systems Institute University of Duisburg-Essen Duisburg, Germany maike.stark@uni-due.de

Abstract—Decentralized small scale electricity generation based on renewable energy sources usually necessitatesdecoupling of volatile power generation and consumption by means of energy storage. Hydrogen has proven as an eligible storage medium for mid- and long-term range, which – when indicated – can be reasonably complemented by accumulator short term storage. The selection of appropriate system components – sources, storage devices and the appertaining peripherals – is a demanding task which affords a highdegree of freedom but, on the other hand, has to account for various operational dependencies and restrictions of system components, as well as for conduct of load and generation. This paper delineates a most recently developed part of a design tool where the primary selection of system components is based on an expert system which takes into account the characteristics and performance of relevantrenewable power sources, load shapes, storage systems and safety rules, and also covers economic as well as ecological aspects. In particular it allows for optimal, comprehensible and transparent selection of appropriate power supply components for applications such as telecommunication relay stations, residential buildings or farms in remote rural areas. Accumulator, Component Selection,Decentralized Power Supply, Expert System, Hydrogen Storage, Photovoltaic, Renewable Energy

I. INTRODUCTION Small autonomous energy supply systems based on renewables such as solar and wind power can significantly contribute for saving fossil energy resources as well as CO2 emission reduction; on the other hand, heavy fluctuations caused by solar day/night cycles and/or weather dependent irradiation aswell as wind volatility complicate proper and continuous operation. According to the particular load demand, this implies the necessity to provide short and/or long term energy storage. The selection of appropriate storage types and sizes finally depends on the renewable energy source chosen, the expected energy harvest profile, as well as load demand characteristics.

Various principalconfigurations are supposable for autonomous, decentralized and renewables based systems for the electric supply of, for instance, • remotely located telecommunication base stations (up to 2.5 kW) [1], [2]; • solitary buildings such as alpine huts, summer residences or small farms (up to 5 kW) [3], [4]; • farms and small settlements in developing countries (above 5 kW) [5]. To assure effectiveness inpractical operation, appropriate selection and dimensioning of the particular components is indispensable. This requires collection of comprehensive knowledge and experience from various domains such as electrical, process and chemical engineering, and is therefore a complex and time consuming task. A tool being able to prudently and flexibly master this task is still missing; such tool must rely onthe knowledge of above mentioned domains, comprising the characteristics and specifics of available system components, their applicable variants (e.g., pressurized vs. metal-hydride hydrogen storage), and the operational interactions and restrictions between all system components involved. In the frame of a current research project such tool is under development. It provides three successive stepsof plant layout: • expert system based selection of components; • numerical simulation based dimensioning of devices; • simulation based derivation of appropriate operation strategy. In the following the initial part-system of the design tool, the expert system based components selection which has been elaborated most recently, will be reported. In particular an expert system was chosen for this...