# Hybrid Wind-Redox Flow Battery System for Decarbonizing Off-Grid Mining Operations
## 3 Methodology
### Sizing of the Energy System
#### 3.3.2 Sizing, Implementation, and Cost of the Storage System  
Despite the abundant wind energy potential at the Ragland site, an energy storage solution is essential to mitigate wind power's intermittency and ensure grid stability. \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Localization**} & **OPEX** & **OPEX** & **CAPEX** & **CAPEX** & **LCOE** \\  & **(CAD/kW-yr)** & **(CAD/MWh)** & **(CAD/kW)** & **(CAD/MWh)** & **(CAD/MWh)** \\ \hline Canada & 46.9 & 11.84 & 1833 & 23.15 & 35.0 \\ \hline Ragland & 117.6 & 30.76 & 4857 & 84.69 & 115.5 \\ \hline \end{tabular}
\end{table} 
Table 4: Wind CAPEX, OPEX, and LCOE in Canada and Ragland. This study assesses the feasibility of integrating redox flow batteries (RFBs) as the primary storage technology, given their proven advantages, pre-installation readiness, and technological maturity. To accurately size the storage system for the Raglan mining site, this study relies on agency reports, laboratory data, and direct manufacturer specifications. Given the region's extreme climatic conditions, a critical design consideration is protecting batteries from subzero temperatures. While redox flow battery systems are typically delivered in insulated containers, prolonged exposure to temperatures below \(-5~{}^{\circ}\)C can cause performance degradation. Specifically, low temperatures can impair electrolyte flow, reduce electrochemical efficiency, and shorten system lifespan. To mitigate these risks, the storage units are housed in a heated shed, ensuring protection against snow, wind, and frost while maintaining optimal operating conditions. Two key parameters determine the size of the shed:  
* The footprint of the redox battery system;
* The required storage capacity. This study directly consulted battery manufacturers since literature sources do not provide standard values for redox battery footprints. The responses varied between 30 m\({}^{2}\)/MWh and 80 m\({}^{2}\)/MWh, with an average value of 50 m\({}^{2}\)/MWh selected for this project. Given the large footprint of the mining site, the battery storage facility is strategically located near the main complex in Katinniq, ensuring efficient integration into the mine's energy circuit. As with the wind farm investment analysis, the cost estimation for redox batteries is a critical aspect of the feasibility assessment. Due to the harsh environmental conditions at Raglan, cost adaptations are necessary to account for additional infrastructure requirements. This study uses the Levelized Cost of Storage (LCOS) metric to quantify the financial viability of storage deployment. LCOS represents the cost per kWh of stored electricity over the system's lifetime, incorporating capital (CAPEX) and operational (OPEX) expenses. This metric provides a long-term perspective on the economic feasibility of storage solutions, where a lower LCOS indicates greater profitability [51]. Table 5 presents the estimated LCOS for the Raglan site based on different storage durations. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **10 MW, Raglan** & \\
**Parameters** & **4 h** & **6 h** & **8 h** \\ \hline \multicolumn{4}{c}{**Storage system**} \\ \hline Storage unit and electrolyte & 118.1 & 105.2 & 98.3 \\ \hline Storage balance & 23.6 & 21.0 & 19.8 \\ \hline \multicolumn{4}{c}{**Energy system**} \\ \hline Power supply equipment & 14.3 & 9.5 & 7.1 \\ \hline Control and communication & 0.9 & 0.6 & 0.4 \\ \hline System Integration & 21.9 & 19.3 & 18.0 \\ \hline \multicolumn{4}{c}{**System balance**} \\ \hline Engineering, transportation, and construction & 83.0 & 73.0 & 68.7 \\ \hline Project development & 41.8 & 37.2 & 34.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: LCOS of redox systems at Raglan (CAD/MWh). The estimated LCOS values of 347.8, 305.8, and 285.0 CAD/MWh correspond to 4 h, 6 h, and 8 h storage durations, respectively. These values align with literature estimates and manufacturer-provided data, confirming their validity as benchmarks for cost assessment.