The EU-funded Hihelios project is developing the TRL 7 innovative modular hybrid battery system to accelerate renewable energy integration and safe power supply.
European energy landscapes are changing strongly towards climate neutrality, leading to higher integration of renewable energy sources such as wind and solar power (PV). This transition requires the flexibility of the new grid to balance power consumption and production. Battery Energy Storage Systems (BESS) are a critical solution, but current technologies often force compromises in power and energy capacity. There is no single chemistry that provides both high power and high energy for long storage due to grid stability.
This is an issue that Horizon Europe Project Hihelios aims to solve. By pioneering innovative hybrid energy storage systems (HESS), the project develops a single integrated solution that combines the best of both storage technologies, targeting long storage times, estimated lifespans of over 5,000 cycles, and horizontal storage costs (LCOs) of less than 0.05 €/kWh by 2030.
The power of hybridization
Hihelios’ co-innovation lies in its hybrid design, combining two different types of energy storage technology.
High Energy Storage: For a long time, Hihelios utilizes a second-living nickel-manganese cobalt (NMC) battery module reused from electric vehicles (EVs). This provides cost-effective large storage while reducing the environmental impact of EV batteries by extending their lifespan. High Power Storage: To quickly handle grid services power explosions such as frequency adjustment, the system integrates lithium iron phosphate phosphate (LFP) batteries or supercapacitors. These components respond in milliseconds and provide the instant power needed to ensure grid stability.
This modular approach allows each Hihelios system to be precisely tailored to the needs of your application, optimizing performance, lifespan, and cost-effectiveness well beyond traditional single chemical systems.
Smart and Layered Control Architecture
Hihelios develops sophisticated multi-layered control architectures to allow high energy and high power systems to synergize. This hierarchical system consists of three main layers:
Energy Management Systems (EMS): EMS, which operates in the cloud, is a high-level strategist. Using advanced forecasts (weather and energy demand) and market prices, plan optimal charging and emission schedules over hours or days to maximize revenue and efficiency. Power Management System (PMS): Located on the site, PMS is a tactician. Transform strategic commands from EMS into real-time actions, making 2-second decisions on how to divide power between hybrid components and how to respond accurately to local grid conditions and service requests. Battery Management System (BMS): The BMS is a battery guardian. Continuously monitor the health, temperature, and state of charge of all battery cells, ensuring they operate safely and within limits. Provide such data upwards to the PMS.
This intelligent framework is enhanced by advanced battery models and “digital twins” for real-time diagnostics and predictive maintenance, further expanding the lifespan of the system.
Four diverse user cases in three countries
To prove its versatility, hihelios deploys Hess in four different use cases across Europe. Each is working on its own grid challenges for both short and long-term energy storage needs (Figure 1):

EV Fast Charging Support (Norway): In fast charging stations, manage the extreme power peaks caused by the simultaneously charging of multiple EVs, avoiding costly grid reinforcements and ensuring that they have enough energy to overstorage local PV production. Smart EV Charging and Grid Support (Belgium): Renovate existing battery systems to optimize EV charging, solar integration and flexibility services procurement and local energy community management with local grids. Weak Island Grid Support (Greece): Two Hess demonstrators will be deployed on Tyros. Supports the smart marina microgrid at the edge of the distributed grid antenna, increasing reliability of EV charging and local loads and avoiding crowding. The second Hess is part of a already existing, local hybrid power plant with Beth, wind and PV production, providing additional important stability services as a black start capacity to the island’s weak power system, increasing the energy storage capacity to shift renewable production daily into the consumption period.
From TRL 7 demonstrations to market-ready solutions
Hihelios is more than a research project. This is a direct path to commercialization. The main goal is to provide four complete operational demonstration participants at Technology Preparation Level (TRL) 7. In the project’s conclusion, these systems are maintained and provide a long-term real-world verification of performance, reliability and economic viability.
The project brings together 12 partners from six countries to ensure a direct path from R&D to market applications (Figure 2). We have already achieved TRL 9 and have built a concrete roadmap to prepare for industrial scale deployment.

Hihelios is actively seeking stakeholders, investors and industrial partners to develop technical or commercial partnerships and shape the future of resilient, sustainable and competitive European energy. Check out our website!
This article will also be featured in the 24th edition of Quarterly Publishing.
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