FB potential and competitiveness in the soaring market of long duration energy storage

According to several analyses, Long Duration Energy Storage (LDES) is emerging a key paradigm in the transition to future decarbonized grids, powered by the intermittent and unpredictable energy generated by renewable energy sources. At the same time, flow batteries, or at least pure flow batteries (i.e., not hybrid architectures), are understood to present growing competitiveness in long discharge configurations, where the reduced impact of battery power components (stacks, pumps, power conditioning systems, …) results in lower unit capital expenditure (UCE) and levelized cost of storage (LCOS). On the other hand, also a number of different technologies are looking at LDES as the Holy Grail for their future success . In this framework, FB manufacturers should be interested in understanding what will be a realistic share of the LDES market for their products in the evolution toward the 2050 Net Zero targets, by clearly understanding which are strength and weakness of the competing technologies, so as to address conveniently the FB development. First of all, an unquestionable definition of LDES has to be adopted, regarding storage duration and discharge duration. A further major question consists in distinguishing technologies which are already available on the market at industrial level and those which are still at development level, whose effectiveness, reliability and profitability are still to be demonstrated. In addition, it is important to distinguish which technology are suitable to provide stationary energy storage to electrical grids and which not, since only the former are of interest in electricity decarbonization programs. Also, a distinction has to made between unidirectional and bidirectional energy storage systems, the former being able to hold energy for some time and leave it flow later always in a same direction. (i.e., from a source to an application), whilst the latter can reverse the power flow, thus performing both conversions, from electricity to storage and then from storage to electricity. Major examples of stationary unidirectional energy storage for grid application can be provided by impoundment hydro plants (IHPs) and high-temperature (280°C–600°C) molten-salt in concentrated solar plants (CSPs). Low-temperature (<100°C) water storage technologies are unidirectional and can reach very long storage times if properly insulated but are unsuitable for electricity generation. Conversely, examples of technologies for grid bidirectional energy storage are pumped-hydro energy storage (PHES), compressed air storage (CAES), hydrogen energy storage (HES), and a wide range of electrochemical energy storage (ECES) systems including conventional internal-storage batteries such as Li-ion, Na-X, Pb-A, metal-air chemistries (notably, Iron-air), and FBs. That given, effective and reliable assessments and comparison stand on the keen identification of key performance parameters (KPIs) of the different LDES technologies. They have been the object of recent work carried out by the Batteries Europe program for the EU R&D funding programs. FB manufacturers must be aware of such issues, when offering their systems on the EU market. Major KPIs which are considered in the comparison are: top power, top energy, discharge time at rated power, self-discharge rate, system round-trip efficiency, life cycles, calendar life, location/geographical versatility, recyclability, capital expenditure per unit energy, net present value, levelized cost of storage its simplified formulation.