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Increasing penetration of renewable power, alternative fuels and grid flexibility by cross-vector electrochemical processes

Periodic Reporting for period 2 - BALANCE (Increasing penetration of renewable power, alternative fuels and grid flexibility by cross-vector electrochemical processes)

Reporting period: 2018-06-01 to 2019-11-30

The growing problem that we address is the mismatch between the solar and wind electricity production and consumption patterns. A fundamental issue with the wind and solar electricity is the dependence of the production on the weather, while the electricity consumption is dictated by human activities. The matching between electricity production and consumption must be kept at all time to ensure grid reliability. In case of oversupply of electricity, some renewable resources need to be disconnected from the grid. In case of high electricity demand, renewable energy storages could be utilised instead of producing power from flexible fossil fuel power plants. Solving this issue is critical for the EU and our society in order to decrease the environmental footprint of our energy system, our security of energy supply and minimize the cost of energy.

We ambition to address this problem with the reversible high temperature electrolyser technology. High temperature steam electrolysers use electricity to produce hydrogen that can be used as a fuel or stored for a later time. A reversible electrolyser is capable of converting this hydrogen back into electricity, meaning it can store electrical energy in the form of a chemical fuel that can be easily stored for short or long periods. Since this technology is based on Reversible Solid Oxide Cells, it is referred to as rSOC. The technology is not yet mature in terms of performance and cost for market entry. The partners of the BALANCE project are joining their effort to develop this technology and to demonstrate its feasibility. Reversible electrolyser technology is expected to support the growth of wind and solar energy by providing grid-balancing services.

As a European Common Research and Innovation Agendas (ECRIA) project, BALANCE builds on significant achievements in national research programmes. A key outcome of BALANCE was the drafting of a European research agenda for the Reversible Solid Oxide Cell technology to coordinate the European R&D effort in order to accelerate technological development and deployment of rSOC.

Our technical objectives are to improve the technology at different scales - from electrode microstructure to system - and demonstrate it at system level in two locations. We aim to achieve 50 % efficiency in fuel cell mode and 90 % efficiency in electrolysis mode. The project should also investigate the most efficient and feasible downstream processing of the produced hydrogen into more conventional fuels.
Main results of the project include: 1. manufacturing of over 100 state-of-the-art cells by Technical University of Denmark and extensive characterisation campaign across the consortium along with a parallel development for novel material and microstructure (infiltrated oxygen electrode and doped strontium titanates for the fuel electrodes). In addition, the project delivered a so-called second-generation cell, integrating the latest electrode material development at DTU, which was also subjected to a wide campaign. The aim was to provide high performance, low area specific resistance and durable cells with upscalable production methods. These achievements are detailed in deliverable 5.3. 2. Four stacks manufactured by CEA and tested across the consortium, showing good repeatability of stack performance. In addition, for the first time, a segmented stack test was performed in rSOC at EPFL, giving insight into localised phenomena. 3. Stainless steel samples coated with four different protective layers, which were tested in high temperature exposure to analyse oxidation rate, change of area specific resistance and Chromium migration. The aim is to use low-cost steel material, while having suitable durability. 4. rSOC system prototyping and operation at VTT (2 stacks) and CEA (1 stack). The system prototypes show clearly that their different functionalities are achieved, but highest efficiency of 81% was achieved in electrolysis mode (AC to H2, LHV, excluding 150°C steam). However, there is a clear path to reach value of 90%, by better sizing of and improving the AC/DC convertor. Fuel cell efficiency was more limited with 26% from hydrogen to power, this value was limited with technical issue with the stack and previously the system has demonstrated efficiency at 50%. 5. An extensive techno-economic and business case analysis was performed giving insight on which process chain to select for which application in terms of economics (Deliverable 5.3). Project results were disseminated in 4 organized workshops, 17 scientific publications, and participation in 47 public events (conferences, workshops, summer schools).
In addition, European-wide survey on energy storage collected a significant number of answers that is open for consultation after data processing. This survey work was the basis for the drafting of an integrated European research agenda for rSOC technology. This public document presents the different research efforts and achievement obtained so far in the field and advise future development needs and needed support at the European level.
All public deliverables of the BALANCE project are available on the website: https://www.balance-project.org/
We build on synergies between the different achievements obtained in national programmes and elaborate an integrated European research Agenda covering the rSOC technology, which will accelerate European technological development.
During the project, we demonstrated rSOC at system level including all the relevant Balance-of-Plant components and using the unit cells manufactured by DTU and assembled into stacks by CEA, two of the BALANCE partners.
In addition, important developments were made at cell level (improved cell durability), at interconnect level (mapping of performance of different steal and coating combination in rSOC relevant atmosphere) and at stack level (optimisation for rSOC operation).
Such achievements have important implications in the capacity of the European Union to reach their energy targets, since rSOC technology support the introduction of renewable electricity sources by acting as an energy buffer by converting surplus power into chemical form (hydrogen for example) and converting it back into electricity when the power supply cannot keep up with the demand. In addition, rSOC bridges the electricity grid and chemical fuel production, which can increase the share of renewable in the transport fuel mix.
Schematic concept of the rSOC technology.