The development of a flow battery system for a wind farm in EU.
Objectives
- Development of redox flow-battery systems is gathering momentum due to their comparative advantages to the more established lithium-ion technology. These advantages are the ability to stay in charged state virtually indefinitely and decoupled power and energy. The term flow-battery comes from the fact that the electrolyte is made to flow through the stacks during charging and discharging of the battery.
- The testing of Lotte Chemical’s 25 kW / 50 kWh flow battery at PNDC is part of a 3-year project funded by the Korean government through the Korea Energy Technology Evaluation and Planning (KETEP) institute and looks at the development of Redox flow batteries for integration with distributed energy resources such as wind farms. Development of three systems rated at 25 kW / 50 kWh, 250 kW / 500 kWh and 750 kW / 1 MWh is foreseen.
Method
To test the functionality of the 25 kW / 50 kWh Zinc-Bromide redox flow battery from Lotte Chemicals at the Power Networks Demonstration Centre (PNDC), the system is repeatedly charged to 30 % state-of-charge (SoC) and discharged completely. The round-trip efficiency is measured by recording the energy flow at the terminals of the device in each case of charge and discharge.
Outcome
The Lotte flow-battery system has been tested up to SoC 30 % for 30 cycles, with each cycle consisting of charge and discharge parts. It has been found that the observations made during the charge part of the cycle are more consistent in terms of the energy consumed and the time taken to reach the SoC 30 %. However, the discharge part of the cycle has demonstrated less consistency for energy released and time to discharge, which has led to a wide range of round-trip efficiency results from as low as 46.85 % to 58.12 %. The wide range of efficiency results could potentially be attributed to the lack of automation in the control system which fails to maintain a balance between the stacks in order to discharge them at the same rate. Further work needs to be done before the system can be deployed for any real application.