Deutsche Version  ACT
Electrical Storage
Power-heat systems 12.4.2017

Laboratory installation of the INE-VES concept (CHP plus thermal storage and control) at Vaillant GmbH
© Vaillant GmbH

Network storage with hybrid photovoltaic system

Researchers develop new strategies for the operation of hybrid photovoltaic systems in residential buildings and small businesses. Small electric energy storage will cooperate with the thermal storages, which supply the building with heat. For this purpose, the scientists optimize the operation management by simulations and laboratory measurements in the project INE-VES. The optimized operations management will increase the benefit of the system for the power grid, as well as for the owner.

Project status Project completed
Typical system size (Energy) 4 bis 12 kWh
Typical system size (Output) 3 bis 10 kW
Volumetric energy density 20,54 Wh/l
Gravimetric energy 47,05 Wh/kg
Efficiency AC/AC 85 bis 90% (incl. BMS and inverter)
Storage loss 6%/d (BMS consumption)
Cycle durability 4.000 bis 7.000 Zyklen (depending on charging current)
Service life of the system 1 Zyklus/d
Typical period between storage and withdrawal 6 bis 12 h
Example application areas Grid supporting PV self-consumption, market oriented operation, load management
Project duration October 2013 until March 2017

INE-VES is a joint project focusing on the integration of combined power and heat storage systems into the local energy supply of small residential and business buildings as well as on the system integration to the distribution grid. In the course of the project, smart energy management strategies are developed, optimized and implemented.
The performance of the integrated system and the energy management strategies are determined via simulations and laboratory measurements. Benefits for the power-heat-storage system operator and the impact on the distribution grid are analyzed for various use-cases. Significant contributions to the economic operation of power-heat-storage systems are delivered with the combined use of an improved methodology for system design and sizing tools. Another focus of INE-VES is the analysis of innovative storage technologies and applicability of large virtual storage systems in the distribution grid.

  • BMWi INE-VES 1 Konzept ENG © Fraunhofer IWES
  • Overview over different scenarios and use cases from different stakeholder perspectives (end customer – scenario I, II, III; utility / distribution system operator – scenario IV,V) © Fraunhofer IWES
  • Approach for system configuration and component sizing for different control strategies © Fraunhofer IWES
  • Laboratory installation of the INE-VES concept (CHP plus thermal storage and control) at Vaillant GmbH © Vaillant GmbH
  • Laboratory testing of battery inverter Sunny-Island in combination with Saft Li-batteries and inverter communication to battery system © SMA Solar Technology AG

Networked storage in combination with PV and CHP systems

To enable an intelligent integration of fluctuating renewable energy sources into the energy system (i.e., grid and market) the energy concept of the German government demands for approaches and storage technologies to consolidate the electricity and the heat sector. This holds especially for the integration of photovoltaics (PV) into the energy system. The INE-VES research contributes to this goal by improving the economics of small scale installations power-heat-storage systems through the combination of optimized system design and smart energy management strategies. Innovative, integrated energy storage in combination with PV and CHP systems will positively contribute towards realizing the transformation of the energy system's infrastructure. The project partners are Fraunhofer IWES, SAFT Batteries, SMA Solar Technology AG and Vaillant GmbH.

The project pursues the following scientific goals to achieve a holistic evaluation of power-heat-storage systems:

  • Assessment of different use cases and control strategies for power-heat-storage systems under changing technical, economic and regulatory conditions
  • Analysis of interdependencies between use cases, control strategies and system design
  • Further development of a simulation platform for power-heat-storage systems
  • Development and implementation of intelligent control strategies and energy management applications for such systems, which allow for individual and interconnected cluster control
  • Higher-order control for establishing virtual large-scale storages in low voltage networks
  • Development of a monitoring concept for power-heat-storage systems
  • Modular and holistic laboratory testing to evaluate systems' performance

Applications respective requirements

Starting point for all investigations are various use cases for PV-CHP-storage system based on different potential scenarios. The use case evaluation takes the requirements of different stakeholders such as system operators, end customers and utilities into account. The interaction among stakeholders will be gradually increased from scenario to scenario. Self-consumption and market-oriented as well as grid-supporting control strategies for power-heat-storage systems will be developed and further evaluated. Additionally, an economic optimization of system sizing and configuration is performed depending on the individual stakeholder and the related control strategy.
In laboratory tests, the system performance will be evaluated. New testing procedures are developed to coherently assess the different system integrations and their performance. The analysis of new business models for power-heat-storage systems, a coherent control strategy and system sizing allows improving the economics of the investigated systems


Market and technology analysis:

  • Definition of technical, market and regulatory framework and use cases for power-heat-storage systems

Development of control strategies, modelling and simulative system assessment:

  • Implementation of detailed component models of power-heat-storage systems
  • Development of optimal control strategies for such systems for local and clustered operation in low voltage networks
  • Techno-economic assessment of different use cases and related control strategies
  • Implementation of control and energy management strategies:
  • Implementation of developed control strategies using the Fraunhofer IWES OGEMA platform
  • Specification of component interfaces to demonstrate local and clustered system operation

System testing and demonstration:

  • Development of performance testing procedure for power-heat-storage systems
  • Realization of power and energy related performance testing of single components and the integrated systems
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).