Deutsche Version  ACT
Electrical Storage
System concept 27.2.2015

Asssembly of inverter
© Sunways AG

Store PV-electricity economical

To use electricity generated by photovoltaic systems efficiently, an intelligent management of storage, on site consumption and feeding to the grid is necessary. Sunways, Akasol and Fraunhofer ISE partnered in order to develop such highly efficient PV-battery-system with intelligent communication and control.

Project status Project finished
Representative system size / energy 2,5 to 7,5 kWh
Representative system size / power 6 kW
Representative cycle time 6 hours
Application residential
Project duration July 2012 until December 2014

Battery is supposed to work at 350 Volts to enable direct connection to one of the inverter’s intermediate direct current links. This design allows to omit electronic parts necessary in current systems. Substantial cost savings can be expected. Energy management is supposed to optimize ratios of immediate on site electricity consumption, storage and feeding to the grid with respect to grid service and battery lifetime. Laboratory samples are built up and running, prototypes are in preparation, final step are field tests.

Use PV-electricity efficiency

The system efficiency will be high because charging/discharging of battery is conducted directly from/to intermediate direct current link of the feed in inverter without further transformation.
The system will be cost efficient at the same time because of the reduced number and complexity of electronic parts realized by this direct connection. High voltage battery system is meeting all requirements of safety and performance at optimized cost because of customized thermo- and electricity management with levelled conditions of all battery cells. Information on battery status is monitored by energy management of the system and charging cycles are optimized with respect to battery lifetime.

Up to date communication technology and intelligent control algorithms are providing flexibility to meet requirements and regulations for efficient and effective deployment of the storage capacity. Integration of smart meters allows for optimization of on site electricity consumption as well as integration into a smart grid environment.
The HeiPhoSS system is supposed to substantially contribute to the overall development of a smart grid which draws maximum benefit from PV generated electricity as well for the economic aim of the owner as for the macroeconomic aim of optimal utilization, security and stability of the grid.

Inverter, battery and energy management

Aims of inverter development
The inverter developed within the HeiPhoSS project in connection with the high voltage battery system will contain several advantages compared to current storage systems:

  • Battery can be connected directly to intermediate direct current circuit without additional converter devices which allows for higher system efficiency.
  • Battery voltage is supposed to be about 350 Volts, PV generator may range between 350 and 1000 Volts.
  • Levelling of electricity between battery and PV generator is achieved simply by means of inverter circuit design.
  • Electric actuators are only working only when bias between voltages runs out of range therefore keeping system efficiency up during normal conditions.
  • System layout works with one phase and three phase environment.

Aims of battery development
The battery developed within the HeiPhoSS project is supposed to contain several new features integrated into a validated and tested battery system.

  • Identification of most suitable cell technology currently available at reasonable pricing.
  • Development of control electronic for management of battery
  • Development of housing for battery which provides protection for cells and connectivity to thermal and electrical system
  • Maximum security for residential owners
  • Design and implementation of battery management software including interfaces to power electronic system
  • Assembly, testing and validation of prototypes

Aims of Energy management system development
The energy management system developed within the HeiPhoSS project primarily aims at exploring and assessing new advantageous management regimes for PV-battery-systems. Prerequisite is an advanced communication network between the electrical and the control components. Control protocols are to be developed in order to provide a platform for algorithms for optimization according to different criteria. First focus is local management of the system, but possibility for future management according to grid requisition will be implemented. Technical and economic benefits will be evaluated and fed back into specification of platform.

Simulation of optimization algorithms as well as specification and field testing are expected to result in an energy management system which adds benefit to the PV-battery-system.

Supported by: The Federal Government on the basis of a decision by the German Bundestag


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Research funding

The information system EnArgus provides information on research funding, including on this project (German only).