The “Blue Acid/Base Battery” (BAoBaB), stores electrical energy using pH and salinity differences in water. The principle of BAoBaB is altering the acid-base balance by means of an excess of available electricity to obtain an acid and base from its corresponding salt solution. When electricity is needed, acid and base are recombined into their corresponding salt solution again while obtaining electrical work from the entropy and enthalpy gain. Our goal is to develop this totally new, environment-friendly, cost-competitive, scalable, water-based electrical energy storage system from TRL3 to TRL5. Our objectives are: 1. to establish and extend the potential of BAoBaB to become a reliable and environmentally friendly way of storing (renewable) electricity at kWh-MWh scale for application at user premises or at substation level. 2. to understand and enhance mass transfer in round-trip conversion techniques and hence to improve the energy conversion efficiencies of the BAoBaB system, aiming an efficiency >80% and >10 times higher energy density than in Pumped Hydropower Storage. 3. to validate under accepted utility use conditions an automatically operated BAoBaB system (with corresponding battery management) at a scale of 1 kW power and 7 kWh energy storage. 4. To pave the road for cost competitive energy storage with attention to life-cycle cost and performance, aiming at <0.05 €/kWh/cycle. BAoBaB operates at a timescale of hours to days, and hence will enable a larger penetration degree of distributed and intermittent renewable energy sources. Not only the storage capacities are huge (kWh to MWh), resources are plentiful (salt and water) and environmental risks are minimal. Together with the location independence and non-toxic nature, penetration rate can be high within the EU and outside, providing the EU export opportunities.

The concept is based on the generation of electricity from salinity gradient using Reverse Electrodialysis with artificial saline solutions operating in a closed-loop. The original salinity gradient is regenerated by a separation step that uses heat at 40 - 100 C. The regenerated solutions can be stored at very low costs and the stack can react within seconds, providing flexibility to the power system. It is a quiet technology operating under normal pressures and temperatures imposing no risks. The industrial partners ensures the MRL will be kept aligned with the advances in TRL. The overall objective is to prove this revolutionary concept, develop the necessary materials, components and know-how for bringing it to the level of a lab prototype generating electricity from low-grade heat at higher efficiencies and lower costs than ever achieved to date. Specific objectives: Select the most suitable technologies for the regeneration process and the combinations of salts and solvents that can maximise the system performance. Create new knowledge for developing: membranes for the selected solutions; membrane manufacturing concepts that can be scaled-up for high volume and low-cost production; efficient stacks suitable for this application; energy efficient regeneration processes. Implement and validate a process simulation tool to analyse the performance under different configurations and operating conditions. Evaluate and improve the performance of the overall system through tests on a lab-prototype, identifying potential up-scaling and operational issues (System efficiencies reaching 15% and power densities of 25 W/m2 of cell pair). Define a development roadmap, taking into account environmental, social and regulatory issues, leading to levelised cost of electricity below 0.03 Euro/kWh by 2025 to 2030. Involve target group representatives to the Advisory Board and communicate the key results in order to initiate a dialogue and facilitate the engagement of key actors.

Shortage of fresh water has become one of the major challenges for societies all over the world. Water desalination offers an opportunity to significantly increase the freshwater supply for drinking, industrial use and irrigation. All current desalination technologies require significant electrical or thermal energy, with today's Reverse Osmosis (RO) desalination units consuming electric energy of at least 3 kWh/m3 – in extensive tests about ten years ago, the Affordable Desalination Collaboration (ADC) in California measured 1.6 kWh/m3 for RO power consumption on the best commercially available membranes, and total plant energy about twice as high. To overcome thermodynamical limitations of RO, which point to 1.09 kwh/m3 for seawater at 50 % recovery, Microbial Desalination Cells (MDC) concurrently treat wastewater and generate energy to achieve desalination. MDCs can produce around 1.8 kWh of bioelectricity from the handling of 1 m3 of wastewater. Such energy can be directly used to i) totally remove the salt content in seawater without external energy input, or ii) partially reduce the salinity to lower substantially the amount of energy for a subsequent desalination treatment. MIDES aims to develop the World’s largest demonstrator of an innovative and low-energy technology for drinking water production, using MDC technology either as stand-alone or as pre-treatment step for RO. The project will focus on overcoming the current limitations of MDC technology such as low desalination rate, high manufacturing cost, biofouling and scaling problems on membranes, optimization of the microbial-electrochemical process, system scaling up and economic feasibility of the technology. This will be achieved via innovation in nanostructured electrodes, antifouling membranes (using nanoparticles with biocide activity), electrochemical reactor design and optimization, microbial electrochemistry and physiology expertise, and process engineering and control.