Matthias Leuthold

Overview of Nonelectrochemical Storage Technologies

In addition to electrochemical storage systems there are alternative technologies to store electric energy, which are based upon different physical principles. It is not sufficient to evaluate these storage technologies with respect to their technical parameters alone. In fact, an analysis of strengths, weaknesses, opportunities, and threats gives a good basis for the evaluation of a technology and its deployment potential. This chapter contains descriptions and evaluations of technically and operationally proven storage systems such as mechanical, electrical, and thermoelectric storage. Technologies that are still in the concept phase, are also briefly discussed.

Applications and Markets for Grid-Connected Storage Systems

Grid-connected storage systems can deliver a variety of services; ancillary services such as frequency control divided into instantaneous, primary, secondary, and tertiary reserve, black start capability, uninterruptible power supply (UPS), self-supply, peak shaving, load shifting, and others. For some of these applications markets already exist and for others it has yet to develop. In most cases the development of a market is not as much a technical question as a matter of technoeconomics. Today most grid services are provided by the conventional power system components—only a few as for example UPS, black start capability, and island systems are already established domains of storage system. The situation is expected to change with the increasing share of fluctuating renewable sources in the power system. With the diminishing share of dispatchable power generation the system services have to be sourced elsewhere. At the same time battery storage technologies have made enormous progress in cost reduction, mostly driven by the mobile communication and IT sector as well as more and more the electric mobility sector, which starts to drive the cost reduction further. At this situation many applications are being discussed and new business models are being developed. Even the nomenclature of applications is still developing and definitions still vary from one author to another. In this chapter a selection of the main groups of application is presented and discussed with respect to market situation, application characteristics, system requirements, and barriers to market entry.

Optimization of an off-grid hybrid power supply system based on battery aging models for different battery technologies

This paper presents an advanced simulation tool for optimizing an off-grid hybrid PV-wind-diesel system to supply the required electricity to a telecommunication base station. The suggested system investigates a combination of three different battery technologies: Lead-acid, Lithium-ion and Vanadium Redox-Flow batteries. An adequate strategy has been developed to control the energy flow among the system components and to decide which battery has to be charged or discharged according to the actual system state (e.g. power generated from the renewables, states of charge of the different batteries). Additionally, it controls the operation of the diesel generator. The management strategy operates each battery under consideration of the respective aging characteristics in order to increase the overall economics of the system. For each battery technology an aging model has been developed to consider the calendric and cyclic aging. This has a big effect on the total system costs through the replacement costs of the batteries. It correspondingly affects the choice of the suitable combination of battery technologies made by the optimization algorithm (Genetic Algorithm) to find the best solution with the minimal costs. In this work a comparison between the optimization results in two different countries is done (Aachen-Germany and Quneitra-Syria with an annual solar radiation of 950 kWh/kWp and 1850 kWh/kWp respectively). Moreover, a sensitivity analysis for different battery prices is done and the results are demonstrated.