ZERO FEED-IN

An increasing number of firms with high electricity requirements are looking to cover as much of this demand as possible from their own PV installations or other renewable energy sources, for both economic and environmental reasons. Because of limits set on the maximum amount that can be fed in, in many cases the only option is a less powerful PV installation, which will at no point produce enough excess to risk overloading the grid with high feed-in levels. However, these installations can also never cover a firm’s own requirements, leading to high additional costs for drawing electricity from the public utility grid.

The solution: An SG-ready (smart grid-ready) battery storage system with intelligent inverter and storage system configured for zero feed-in usage. The system ensures that excess photovoltaic energy is not fed into the utility grid when the battery storage system is fully charged. This technology allows firms in areas with a weak grid infrastructure to meet their high demand from their own electricity supply.

• Large PV installations can be operated anywhere, irrespective of the local utility grid
• High cost savings, with demand covered by self-consumption
• Optimum efficiency for the PV installation when combined with forecast-based charging, leading to quick amortization
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WITHOUT STORAGE SYSTEM 

While the PV installation is producing electricity, the VAS Energy Manager (or Home Manager for the TS 48V) regulates the flow to the consumer and battery storage system. Once storage systems are fully charged, excess electricity from the PV installation not required by consumers would normally feed into the public utility grid. Negative load variations such as these occur abruptly, for example when consumers are switched off, and need to be curtailed just as abruptly. Here the measurement unit alerts the inverter which then limits the flow from the PV modules accordingly. For this process, the target response time of three seconds poses a challenge to the system’s control speed. The VAS storage systems are up to this challenge.

The public utility grid needs to be protected from overloading as a result of feed-in from large PV installations. Depending on the capacity of an area’s utility grid infrastructure, this means that systems with certain power ratings cannot be installed if they cannot utilise a zero feed-in concept. The requirements for a concept like this are clearly set out in normative FNN (Network Technology/Network Operation Forum) guidelines: the excess power created must be 90% curtailed within a maximum of three seconds, and 100% curtailed within 10 seconds at most.