Vanadium redox batteries are widely hailed as a strong contender for the long-duration storage requirements of the alternative energy market. This technology could potentially replace lead-acid batteries in UPS and other back-up uses, subject to competitive pricing of the vanadium-based electrolyte. The VRB market promises steady growth over the next few decades, constrained mainly by price volatility of vanadium in steel alloying as its primary application. It follows that the successful commercialisation of the VRB is contingent on access to low-cost vanadium from sources decoupled from the cyclical price and demand fluctuations of the construction industry globally.
The challenges with production of electrolyte are well described in this caption taken from the Cellenium Technologies website:
“Vanadium is commercially available as vanadium pentoxide (V2O5), or as ammonium vanadate (NH4VO3). In both these compounds the vanadium is in the oxidation state V5+. However, the electrolyte required for first filling vanadium regenerative fuel cells is acid vanadium sulfate with half the vanadium in the oxidation state V3+, and half in the state V4+. Unfortunately, vanadium pentoxide is only slightly soluble in sulfuric acid and water, and the methods used until now for preparing the acid vanadium electrolyte have been complex and costly chemical and electrochemical processes. The overall economics of vanadium fuel cells needs a better method of preparing the electrolyte from solid vanadium pentoxide.”
X GROUP has overcome this challenge through the use of ion-exchange as a platform technology to reduce unit costs of vanadium recovered from primary producer tailings and effluents as well as various secondary resources. X GROUP has developed and demonstrated viable process technologies for recovery of vanadium from alternative sources as illustrated below.
X GROUP has successfully piloted its novel flowsheet for the production of vanadium electrolyte solution directly off its simulated moving bed ion exchange (SMB IX) platform technology. SMB IX allows simultaneous isolation, purification, and concentration of vanadium from its associated impurities in alkaline or acidic leachates. The vanadium sulphate solution hereby obtained is in excess of 1.8M concentration and is of a high purity (≈99.9% metal oxide basis).
X GROUP Vanadium Solution
Further increasing the concentration of vanadium in our electrolyte will increase energy density above the 25Whkg−1 equivalent but above 2M vanadium sulphate solution is known to super-saturate causing precipitation at low temperatures of V2+, V3+ and V4+, or at elevated temperatures in the case of V5+. Current efforts are focussed on first correcting acid matrix and vanadium charge state to 3.5, whereafter further improvements to the stability of super-saturated vanadium solutions will be attempted, aiming for concentrations greater than 2M to be employed in 1st generation VRBs.
X GROUP recently acquired a ESP5 VRB previously constructed by Imergy Power Systems. The unit has a rated power output of 5kW with energy capacity of 25kWh which is well suited for evaluating X GROUP electrolyte in a real environment with both PV and power utility as alternative energy sources. The ESP5 unit requires some refurbishments including an upgrade to replace the chloride cell stack with a sulphate stack to match X GROUP requirements.
X GROUP Vanadium Redox Flow Battery
X GROUP will continue to leverage our experience in vanadium chemistry specifically and metallurgical processing generally to develop improvement patents using the ESP5 battery procured to fast-track testing of our electrolyte solutions. We have already reviewed much of the prior art to develop both defensive and offensive strategies around our core IP for vanadium recovery by SMB IX for production of VRB electrolyte. It is important to emphasise that barriers to entry will not only be built through formal IP.
There is a strong need both to secure the underlying resources (secondary vanadium in the form of waste product), and for business innovation to protect these resources against price rises which may stimulate competing interest from demand driven by the steel industry. We believe that the low-cost production of electrolyte from waste resources is a good approach and will continue to seek, on a project-by-project basis, to enter joint ventures with resource partners so that their upside is from the beneficiated electrolyte product, thus disincentivising price competition.