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Back-Up Inverters for Safe Electricity Supply
M. Rothert, V. Wachenfeld, B. Engel
Storage, Strategy, Small Grid-Connected PV Systems, Backup
Components for PV Systems
Subtopic: Engineering and System Integration
Event: 24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany
Session: 4EP.1.5
3116 - 3120
ISBN: 3-936338-25-6
Paper DOI: 10.4229/24thEUPVSEC2009-4EP.1.5
0,00 EUR
Document(s): paper


According to a study authorized by European PV industry, the installed PV power in Germany will increase from 5.5 GW today up to nearly 80 GW in 2020. This figure is even higher than the maximum grid load at that time – following expert’s predictions. Due to today’s market situation, a significant share of the installed PV power will still be connected to the public low voltage grid. Thus provisions to guarantee grid stability cannot be limited to high voltage distribution and transportation grids. To unburden the public grid from massive upcoming transportation tasks, German government decided to implement a special incentive for direct utilization of PV generated energy into the clean energy act (EEG 2009). After reaching grid parity, meaning that the cost to generate electrical energy by PV is the same or higher than the price of energy for private households, a maximum share of direct utilization will be mandatory for an economic operation of PV systems. These preconditions cause new requirements for PV system technology: loads have to be switched on and off automatically, driven by the present availability of solar irradiation, tariff information of smart metering systems have to be evaluated, but not until the implementation of decentralized storage systems, an optimized adjustment of generation and consumption can be achieved. Today’s state of the art PV backup systems to bypass loss of mains situations already offer relevant parts of the expected requirement specification for tomorrow’s PV system technology: the integrated battery storage can optimize the share of direct utilization of the generated energy, but can also provide a guaranteed reserve power service for the public grid. Ancillary services like keeping the grid voltage stabile as well as controlling the power production and consumption depending on the state of charge of the battery or the available PV power can already be provided. PV backup systems offer more than a small step towards a stabile grid with a maximum share of renewable sources.