DKE project - DIN-Connect

Project period

2017 to 2018

Project management

DGS - LV Berlin Brandenburg e.V.

Funding organisations

Federal Ministry for Economic Affairs and Energy (BMWi)

German Institute for Standardisation (DIN)

Project description

The DGS has been working on the topic of electrical energy storage for photovoltaic systems for several years. A simple comparison of storage systems with one another and a precise analysis of performance based on simulations are hardly possible. There is a lack of sufficient data for an economic efficiency analysis based on this analysis. This leads to major uncertainties and barriers to investment in this important area of the energy transition.

Various characteristic values influence each other in battery storage systems. For example, the storage capacity must always be considered in conjunction with the permissible depth of discharge, which determines the effective usable storage capacity. The depth of discharge also influences the number of charge cycles that can be achieved. Studies of storage systems have revealed a not inconsiderable standby consumption of many systems, for which only a few manufacturers currently provide information in the data sheet, although it can have a strong influence on performance and cost-effectiveness. The data sheets often only state the battery efficiency, with values of over 97%. However, these values are not achieved in practice because the surrounding power electronics often operate in the partial load range, in which the overall efficiency is significantly lower. The customer is led to believe that a maximum of 3% of the stored energy is lost during storage. In practice, the energy loss over a longer observation period is more in the range of 10% to 30%. There is no corresponding information in the data sheets. The layman or installer may not even be aware of critical points that an expert may still scrutinise.

The less detailed memory may therefore appear more favourable than it is according to the data sheet. In contrast, the memory of a supplier who publishes very precise data sheet information is unjustifiably rated lower. This problem can be remedied with the help of a clear data sheet standard.

The data sheet standard thus protects the user from unprofitable investments and at the same time supports the honest manufacturer.

For photovoltaic modules, for example, DIN EN 50380 „Data sheet and nameplate data of photovoltaic modules“ provides a sufficient database for simulating the modules. This means that the annual yield of PV modules can be determined with sufficient accuracy and then used for economic analyses. Something similar is urgently needed for storage systems.

Previous standardisation projects on electrical energy storage systems have mainly focused on the safety of the systems and professional planning and installation. These are, for example, the VDE-AR-E 2510-2 application rule: 2015-09 „Stationary electrical energy storage systems intended for connection to the low-voltage grid“ or the E VDE-AR-E 2510-50 application rule: 2014-11 „Stationary energy storage systems with lithium batteries“.

The aim of the DIN-Connect pre-standardisation project „Data sheet specifications of storage systems“ is to develop the basis for a data sheet standard for electrical energy storage systems for photovoltaic systems. The aim is to work out which characteristic values should be specified in the data sheet for a quick rough comparison of storage systems and which values are required in the data sheet for a detailed comparison in the context of computer-aided simulations of storage systems with regard to the economic and technical suitability for a specific project. In addition, a precise definition of the corresponding characteristic values is to be provided and a draft standard is to be developed in dialogue with various players in the storage sector.

The results will then be incorporated directly into the work of the DKE and the VDE. They can later be submitted as international standardisation proposals at CENELEC and IEC level. The standards would promote the economic development of storage system providers, the skilled trades and the renewable energy sector.

The increasing spread of storage systems has an essential positive influence on grid stability in an electricity grid with an ever-increasing proportion of fluctuating power sources. A data sheet standard in turn has an influence on the successful dissemination of storage systems.

The pre-standardisation project takes on the task of bringing together various stakeholders such as manufacturers, installers and users as well as the regulatory level (authorities) and agreeing on binding data sheet specifications.