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Blue Acid/Base Battery: Storage and recovery of renewable electrical energy by reversible salt water dissociation

Periodic Reporting for period 3 - BAoBaB (Blue Acid/Base Battery: Storage and recovery of renewable electrical energy by reversible salt water dissociation)

Reporting period: 2019-11-01 to 2021-07-31

The need of electric energy storage for our society has drastically increased in the last years. New technological solutions must be developed, in order to provide a safe and sustainable availability of electric energy.
The BAoBaB project (Blue Acid/Base Battery) aims to develop a new, environment-friendly, and cost-competitive battery for stationary electrical energy storage, and to apply this system in the existing electricity grid.
The BAoBaB technology is based on the so-called "acid-base flow battery", where electric energy can be stored by using special membranes able to generate acid and base solutions. In this way, electric energy can be stored by using only salt and water, thus providing a cost-effective, safe, and sustainable energy storage system.

Specific objectives of the BAoBaB project are:
1) to establish the market potential for the BAoBaB technology as reliable energy storage technology at kWh-MWh scale and different application levels (user premises or substation level)
2) to optimize the performance of the battery under controlled laboratory conditions, aiming to enhance round-trip efficiency
3) to develop novel components (including pH-resistant monopolar and bipolar membranes) tailored for acid-base flow battery applications
4) to upscale and demonstrate the technology at pilot scale in real environment, at a scale of 1 kW power and 7 kWh energy storage
5) to pave the road for cost competitive energy storage with attention to life-cycle cost and performance.
The BAoBaB project has been executed between May 2017 - July 2021. All the partners have contributed to the development of new components and the feasibility assessment of the BAoBaB technology. In particular, Wetsus, AquaBattery and University of Palermo have been actively involved in laboratory and modeling activities, to optimize the battery design and operating conditions at laboratory scale. Fujifilm has developed novel pH-resistant monopolar and bipolar membranes, especially optimized for the BAoBaB operational conditions (e.g. using highly concentrated acid and base solutions). Finally, a demonstration plant with four battery units has been installed at the power plant on Pantelleria island (Italy). The pilot has a nominal installed capacity of 1 kW / 7 kWh, and has been tested for nine months (November 2020-July 2021). After the end of the project, the containerized pilot has been revamped by AquaBattery and will be used for further demonstration phase in the Netherlands.
The BAoBaB storage technology represents a completely new concept in the field of energy storage systems, and therefore it will enlarge the portfolio of available battery technologies in the near future. The scalability of this technology, including affordable small systems, allows to use the BAoBaB in a wide range of capacities and for different purposes. In particular, thanks to cheap and widely available storage solutions (water and salt), the BAoBaB system can be applied for kWh- to MWh-scale systems.
The cost per storage capacity for BAoBaB is expected to be lower than for chemical storage, since no expensive material is used (i.e. water and salt instead of rare metals or chemicals), thus minimizing the environmental impact. Our model predictions estimated a levelized cost of storage of <0.20 €/kWh/cycle, thus showing the potential of the technology as novel energy storage system. Moreover, the BAoBaB system has also potentially lower costs and higher performance compared to mechanical electric storage systems (e.g. PHS, or Compressed Air Energy Storage), since no high-pressure equipment are needed. Further R&D activities are currently ongoing to upscale the technology at 100 kW scale, and bring the acid-base flow battery to the market.
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