Reducing the effects of co-ion transportation in the Acid-Base Flow Battery

Abstract

With the advent of the sustainable energy transition, the deployment of renewable energy sources is rapidly growing. One of the main problems for sustainable systems like wind and polar power is the fluctuating and intermittent behaviour of these sources. In order to make these systems more reliable energy storage is needed to compliment these systems. A multitude of different systems are now in development at different institutions and companies in order to fulfill this need, one of which being the Greenbattery under development at AquaBattery. The Greenbattery is an Acid Base Flow Battery (AB-FB), which is a further iteration of their original Concentration Gradient Flow Battery (CGFB or Bluebattery). The AB-FB shows promising market potential due to its low impact on the environment, relatively low cost and being easily scalable. Currently the AB-FB is on par in energy densities with systems such as Pumped Hydro Storage and Compressed Air Storage, while not being dependent on geological features or scale of size. However, the AB-FB still needs improvement as co-ion transportation degrades its potential energy density over time. In order to make this technology more viable parameters must be found in order to limit the co-ion transportation. During this thesis research is performed to identify any other potential losses, as well as testing the operational limits and behaviour of the membranes. After this the battery is subjugated to conditions simulating real life operation. During these tests the charge/discharge density, as well as depth of charge, is incrementally changed. By doing this insight is gained in the amount of co-ion transportation that is occurring and whether or not this improves the battery lifetime. The results show the battery can last up to twice as long before falling below 80 % of its original energy density. This is done by reducing the upper and lower limits of the state of charge. However, as a trade off, there is reduction in the energy density of the battery. Following this, research has been performed into the viability of resetting the system, which led to promising results. With this knowledge the operator gains insight whether he wants to put priority in higher energy density or longer lifetime, as well as when he should reset the system to keep it at maximum potential energy density. This gives flexibility to the AB-FB and hopefully help AquaBattery sell its product in the coming years.