Scaling energy system integration via a three-level Living Lab pathway

To reduce the European Union’s dependence on fossil fuels and diversify its energy supply before

2030, the REFORMERS project addresses the main problem of accelerating the transition to

decentralised, integrated energy systems. The project advances the concept of Renewable Energy

Valley (REVs): systems with high shares of renewable generation, storage technologies, and

intelligent management algorithms. By enabling the synergistic operation of multiple technologies

and energy carriers, REVs can become self-sufficient annually and provide a promising pathway

towards a more resilient and sustainable European energy system. A key enabling technology is

the digital twin, which supports the analysis, planning, optimisation, and control of renewable and

multi-energy assets. Within REFORMERS, these solutions are not only developed and implemented

in real-life settings but are also systematically scaled to support wider deployment across Europe.

The methods used to achieve this are organised through a three-level living lab methodology

designed for systematic scaling:

1. Level 1 (Controlled Testing): The Green Village is a small-scale living lab at Delft University

of Technology campus, offering high data coverage and extensive asset control for testing

and validation. It integrates residential and non-residential demand, PV, batteries, hydrogen

storage, and electricity, heat, and hydrogen networks. Its district heating network supports

thermal-flexibility experiments addressing grid congestion.

2. Level 2 (System-Level Demonstration): The Flagship REV in the Alkmaar–Heiloo region in

the Netherlands comprises more than 500 businesses and over 5,000 households and

integrates multiple energy hubs, short-term storage systems, and multi-energy carrier

infrastructures, including heat and hydrogen networks.

3. Level 3 (Transnational Replication): In six Replication Valleys across Europe, common

baseline assessments map energy systems, stakeholders, policy contexts and data

availability; workshops then match relevant Flagship Valley solutions to local needs and

define the required adaptations.This three-level setup (see Figure 1) enables a structured scaling pathway for energy system

integration solutions, progressing from controlled experimentation to system-level demonstration

and, ultimately, to transnational replication. The Green Village and the Flagship Valley are multi-

vector energy systems that combine renewable generation, short-term battery storage, and

hydrogen infrastructure, allowing solutions such as the digital twin to be validated in a controlled

setting and applied in a more complex real-life context that shares similar technological building

blocks. While The Green Village offers high observability and controllability at a small scale, the

flagship valley captures the complexity of a larger integrated energy ecosystem. For example, we

found that installing a 2 MWh battery addressed only part of the grid-congestion challenge;

collective grid contracts, coordinated control and rules for allocating scarce capacity are also

needed to enable multiple innovations and local businesses to operate.

and the Replication Valleys demonstrate how comparable solutions can be adapted to diverse

regional, climatic, and socio-economic contexts across Europe. The primary outcome of this

progression is the generation of technical, operational, and organisational insights embedded in

project-wide methods and implementation guidelines. In this way, the three-level scaling method

combines scientific rigour with practical relevance, accelerating the translation of local innovation

into transferable, widely deployable solutions for resilient and self-sufficient REVs across Europe.