Motivation & Objectives

Power-to-Gas (P2G) is a promising solution for long-term Electrical Energy Storage of the intermittent power generated by Renewable Energy Sources as well as a smart solution for decarbonizing the transport sector and energy-intensive industries. P2G solutions are based on using intermittent power to produce green hydrogen.

The efficiency of the whole conversion process is mostly determined by the electrolysis step, typically representing more than half of the price of the final product. Therefore, it is a must (and an opportunity) to develop highly performing and cost-efficient electrolysis cells that ensure a competitive P2G technology.

Among the different types of electrolysis systems, those based on high temperature Solid Oxide Electrolysis Cells (SOECs) are, by far, the most efficient ones. Solid Oxide Cells (SOCs) can operate efficiently in both electrolysis and fuel cell modes opening the way for a more advanced novel storage solution, the so-called Reversible Solid Oxide Cells that extend the P2G concept to standalone “Power-to-Power” (P2P) solutions suitable for new markets. Despite the potential for revolutionizing the storage sector, SOCs present several drawbacks related to their high T operation, slow start times (of several hours) and challenging operation under pressure, all intrinsically related to their ceramic nature. These issues make them not usable for direct coupling with intermittent renewable energy sources or relevant applications like off-shore electrical energy storage or transportation, for which no suitable lightweight and small solution is available today.

Besides, the state-of-the-art SOCs involve the use of big amounts of critical raw materials or materials with high supply risk such as rare-earth elements or cobalt, which will hinder their full deployment. Improving reversible SOCs while downscaling their size and reducing the critical raw materials content can only be achieved through breakthroughs in materials and disruptive architectures that allow high energy density features, superior thermomechanical response and outstanding performance and durability at low costs. In this regard, advanced thin films and integration technologies will foster this revolution enabling the implementation of novel concepts and materials with superior performance while involving low amounts of raw material and the smallest possible footprint.

Therefore, the EPISTORE project aims to deliver efficient electrical energy storage by using advanced thin film SOCs with fast response and extremely low contents of critical raw materials. Using novel nanoscale concepts and developing never explored materials, revolutionary rSOCs will give rise to radically new ultracompact and fast response P2G and P2P storage solutions directly coupled to renewable energy sources and applicable to forbidden scenarios such as off-shore power generation and new markets like transportation.

The main goal of EPISTORE is to develop a new family of superior performing ultrathin Reversible Solid Oxide Cells (<1μm in thickness) using “Silicon-on-Nothing” techniques, in such a way that ultrathin devices deposited on Si skins will be transferred to flexible low-cost metallic substrates for final stacking. The rSOC functioning as a SOEC will be able to produce hydrogen at high current densities of 3 A/cm2 (1.3V) at low temperatures (T<500˚C) and under pressure (5 bar). EPISTORE will release kW-range “pocket-sized” rSOC stack modules (3x3x3cm3) with exceptional SOEC capabilities that will multiply x30 the current H2 production per unit volume (>10000kg/hm3) and x5 the specific power densities of SOFCs (>2.5 kW/kg).

The thin film nature of the EPISTORE cells will enable the implementation of major breakthroughs, from emerging fields such nanoionics or nanocatalysis and new materials like High Entropy Oxides (HEO), while paving the way for cost-effective and scalable energy storage with a reduction of >99% in the use of critical raw and high supply risk materials (vs. conventional SOCs).