The real-world lab project SoLAR in Allensbach at Lake Constance/Germany demonstrates the potential of intelligent energy sector coupling. With a real-time price system based on electric grid state variables, customers play an active role, sharing energy and using flexible appliances as “virtual batteries” for renewable energy integration. The approach minimizes cost of energy storage and grid extension whilst ensuring availability and resilience as well as low complexity of the energy system.

Citizens, engaging in climate protection, initiated the project. Renowned research institutes and companies implemented the project in a new residential development with 22 households in 12 semi-detached houses and 2 apartment buildings connected with an existing building with three households. It includes PV and smart control of a CHP unit, 12 heat pumps, several household appliances, charging units for electric vehicles and batteries. The complex has a private grid with tenant power supply as business case.

The project showed a raise in the CHP and PV electricity self-consumption rate from 55 to 73 %. In a next stage demonstration, the partners want to show how to scale the system to a whole distribution grid. In this context, they propose a new tariff system, including dynamic price components. This will maximise economic and individual benefits and aims to respond to existing EU regulatory requirements.

Project Information
City, Country
Allensbach, Germany
Duration (Start/End Dates)
Phase 1: 01.05.2018 – 30.04.2019, Phase 2: 16.07.2019 - 30.06.2022
Funding Source
Ministry for Environment, Climate und Energy Economy Baden-Württemberg
Project Lead (Organisation)
ISC Konstanz e.V.
Project Partners
EIFER EWIV, Kaufmann Bau GmbH, Easy Smart Grid GmbH, Energiedienst AG, Weider GmbH, BSH GmbH, Energiewerkstatt GmbH, Flotteladen GmbH, Stadtwerk Haßfurt, Stadtwerke Trier and others

No. of participants: 25 households (appr. 60 inh.)

Generation (kWp): 88 kWp PV, 21 kWel CHP

Storage (kWh):  virtual battery*: 564 kWh (real),

battery 41 kWh

Unit price ($/kWh): –

Project cost ($): 400.000 Euro (research funding)

  • The project demonstrates the activation and orchestration of flexibility of every type, power, energy consumption and availability to compensate volatile availability of renewable energy sources.
  • Dynamic tariffs provide financial incentive for flexibility, to activate and integrate customers as consumers and prosumers into the energy system. While conventional market approaches rely on negotiations and schedules for energy exchange in the future, the SoLAR technology deduces prices in real-time directly out of grid state. This way, correct prices to maintain balance and prevent grid congestion are derived at any time, while minimizing effort for market transactions.
  • The demonstrated technology represents a paradigm shift and has potential to boost the energy system transition. The technology is not only simple and cost effective, but solves upcoming problems of stability, resiliency, privacy and cyber security.
  • Goal of the project was to demonstrate the feasibility of the technology. Moreover, the partners worked on concepts, how to integrate the technology into the energy system and how a transition roadmap could look like.
  • What problem(s) does the case study aim to resolve?
  • What were the social objectives (if any)?
  • What were the environmental objectives (if any)?
  • To what degree were participants actively involved in design or operation?
  • Was participation financially or socially incentivised or both?
  • What degree of demand response flexibility was provided?
  • Provide images of, and participant quotes from the case study.

SoLAR aimed to show how customer flexibility can easily be activated to increase self-consumption of electric energy in a “grid cell” to integrate renewable energy.

  • The solution was designed to minimize effort of customers to participate in an energy market while maximizing financial benefits and provide high safety in regards to energy supply as well as data and cyber security.
  • The project is an essential part of the local climate protection activities and actively includes citizens in realization, preparing dynamic tariffs for local energy supply. It supports Allensbach’s commitment to reduce local carbon footprint.
  • The activation of demand (and generation) response flexibility was the main focus of the project. By shifting the operation time of heat pumps, EV chargers, household appliances and CHP the devices shall act as “virtual batteries” to provide flexibility with highest (financial) efficiency and lowest impact on environment and resources.

Main objective in the project was to coordinate all devices to increase the electricity self-consumption rate in the residential complex from some 50 to over 80%, while reducing grid load. It was expected that electricity cost is reduced by 4 to 6 cents/kWh.

Not all flexible devices were integrated into the system during the project duration. However, whenever a device was integrated, the behaviour was exactly as expected by the simulations done with the “Virtual Demonstrator” digital twin. So, based on the Virtual Demonstrator, following KPI have been derived in SoLAR:

The evaluation showed that – without the use of battery storage – self-consumption increases from 55 % to 73 %, which is less than expected. The contribution of household appliances and EV charging was below expectation. This can be explained by use of dryers mainly in the evening and the absence of vehicles during workdays, so that using PV power is limited. However, a strong reduction of load peeks on the grid by intelligent EV charging is proven. Assuming, all cars are charged during daytime, a self-consumption rate of 77 % is achieved after all. Applying the technology in larger grid cells, including wind power, is expected to increase self-consumption. A comparison with a schedule, calculated by an “omniscient solver”, showed that the system reached 90% of theoretically possible performance at 1-hour resolution.

As a consequence of the lower self-consumption rate (SCR) the reduction of energy cost is less than expected (about 3 ct/kWh). However, the principle of significantly decreasing energy cost by “virtual batteries” was successfully demonstrated.

For more information on the Case Study
Contact Person: Stefan Werner, Dr. Thomas Walter
Copyright Statement
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