Details

Autor(en) / Beteiligte

• König, S.
• Suriyah, M.R.
• Leibfried, T.

Titel

Innovative model-based flow rate optimization for vanadium redox flow batteries

Ist Teil von

• Journal of power sources, 2016-11, Vol.333, p.134-144

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• In this paper, an innovative approach is presented to optimize the flow rate of a 6-kW vanadium redox flow battery with realistic stack dimensions. Efficiency is derived using a multi-physics battery model and a newly proposed instantaneous efficiency determination technique. An optimization algorithm is applied to identify optimal flow rates for operation points defined by state-of-charge (SoC) and current. The proposed method is evaluated against the conventional approach of applying Faraday's first law of electrolysis, scaled to the so-called flow factor. To make a fair comparison, the flow factor is also optimized by simulating cycles with different charging/discharging currents. It is shown through the obtained results that the efficiency is increased by up to 1.2% points; in addition, discharge capacity is also increased by up to 1.0 kWh or 5.4%. Detailed loss analysis is carried out for the cycles with maximum and minimum charging/discharging currents. It is shown that the proposed method minimizes the sum of losses caused by concentration over-potential, pumping and diffusion. Furthermore, for the deployed Nafion 115 membrane, it is observed that diffusion losses increase with stack SoC. Therefore, to decrease stack SoC and lower diffusion losses, a higher flow rate during charging than during discharging is reasonable. •The study is carried out using practical stack dimensions.•A method for deriving an operation point-based efficiency is presented.•An optimization algorithm is deployed to minimize losses in all operation points.•Efficiency gain is up to 1.2% points; capacity gain is up to 5.4%.•Diffusion is also found to affect the optimal flow rate.