The FlexHub project delivered a blockchain‑based prototype called FlexChain that supports the trading of flexible energy resources in a market setting. FlexChain is built on the Quorum variant of the Ethereum protocol, which replaces a central database with a distributed ledger of redundant nodes. Smart contracts on the ledger encode the matching logic that pairs supply offers from distributed energy resources with demand requests from distribution network operators. The ledger’s notarisation feature records all input data and matching results, ensuring immutability and traceability. Because the contracts are visible to all validator nodes, the outcomes are auditable and the system is resistant to single points of failure. Consensus guarantees are provided by either Raft or Istanbul BFT; the network tolerates the loss of up to 50 % of validators in Raft mode or up to 33 % malicious nodes in Istanbul BFT mode without loss of integrity.

Performance testing of the prototype revealed that the matching algorithm, implemented in Solidity, consumes significant computational resources and introduces latency. The current implementation is limited by the expressiveness of Solidity, which hampers optimisation. A proposed improvement is to move the matching logic off the chain into a conventional programming language such as Python or Java, trading off some transparency for speed. Another optimisation path involves the use of proxy contracts that forward calls to newer contract versions, allowing seamless upgrades without redeploying the entire system. To control transaction volume and protect against denial‑of‑service attacks, the design includes a token called FlexCoin. Each transaction must pay gas in FlexCoin, and validators receive transaction fees, thereby limiting the number of operations a client can submit per unit time.

Identity management is addressed by allowing all market participants—flexibility providers, demand requests, and network operators—to sign their data with cryptographic key pairs. This enables the creation of verifiable credentials that bind an asset to its creator, ensuring non‑repudiation and tamper‑resistance. The architecture also supports the integration of existing IoT devices, smart meters, and cloud services through standardized communication protocols, as outlined in the Smart Grid Architecture Model framework.

The project was carried out by a consortium of industry and research partners. EnergyDock GmbH led the development of the FlexChain prototype and performed the pilot study in collaboration with Green Planet Energy, a regional electricity supplier, during spring 2022. Other consortium members contributed expertise in blockchain governance, user interface design, and regulatory compliance. The consortium operated under a flexible governance model that allows new validators to join or leave the network, with decisions made through consensus voting. The FlexHub initiative was funded by a European research grant aimed at accelerating the deployment of smart grid technologies, with a project duration spanning from early 2022 to late 2024.

In summary, FlexChain demonstrates that a permissioned blockchain can provide a secure, transparent, and resilient platform for trading flexible energy resources. The prototype’s key technical achievements include a distributed ledger that eliminates central points of failure, smart contracts that enforce market rules, and mechanisms for identity verification and transaction throttling. While the current implementation faces performance bottlenecks in the on‑chain matching logic, the proposed off‑chain and proxy contract solutions offer clear paths to scalability. The collaborative effort, backed by industry partners and a European research fund, has produced a testbed that can be expanded to support broader market participation and integration with existing grid management systems.