Many homeowners generate electricity with their photovoltaic system and feed it into the public grid. Anyone wishing to be energy self-sufficient and consume the power themselves is faced with the same challenges that apply to all volatile forms of energy: the electrical energy needs to be stored.
The variety of home storage systems available on the market has increased accordingly. Furthermore, falling prices have raised the number of KfW grant applications. According to the German Solar Industry Federation (BSW-Solar), there are currently approximately 25,000 solar power storage units in use. This led to an increase in public interest in lithium ion-based batteries in the last year. In standardization circles it was acknowledged that there is an urgent need to define rules for connection conditions and for the testing of cells, batteries and storage units. At the national level, VDE application guides were therefore developed with the aim of increasing the safety of the storage systems.
The VDE application guide "Stationary electrical energy storage systems intended for connection to the low-voltage grid" includes the safety requirements for the planning, construction, operation, disassembly and disposal of these energy storage systems for fixed connection to local electrical installations connected to the low-voltage network. It takes into account various hazards that can arise from switching between different parallel or isolated network operating modes.
This VDE application guide also includes complete energy storage systems and is aimed above all at installers. It was published in September 2015.
The second VDE application guide "Stationary energy storage systems with lithium batteries - safety requirements" only applies for battery energy storage systems (BESS) with batteries consisting of lithium-ion cells or other lithium-based cell chemistry such as lithium-polymer cells.
It focuses primarily on safety requirements for batteries and battery components of energy storage systems as well as related testing and acceptance conditions for lithium batteries. It contains requirements designed to ensure the safety of the storage units throughout their life cycle - warehousing, transport, installation, operation, repairs, disassembly and recycling.
The scope is confined to residential and small-scale commercial use. The aim is to increase safety levels for users of storage units. This document is at the draft stage and is currently undergoing intensive revision. Both issues will be incorporated into international IEC standardization on the basis of these VDE application guides.