The head height of a pumped hydro storage (PHS) project significantly affects its overall cost structure in several ways related to both the size of the components required and civil engineering requirements:
- Impact on Reservoir Size and Volume: A higher head (greater vertical distance between the upper and lower reservoirs) allows the same amount of energy to be stored with a smaller reservoir volume. This reduction in reservoir size can reduce excavation and construction costs for the reservoirs themselves.
- Electromechanical Equipment Sizing and Cost: Higher head means the water pressure and energy per unit volume increase, which allows the electromechanical components such as pumps and turbines to be smaller for the same power output. This results in lower costs for pumps and motors, typically quoted at $550 to $650/kW depending on head, with higher heads reducing required capacity and cost.
- Civil and Infrastructure Costs (C&I): With smaller electromechanical components and reservoir size, the civil infrastructure costs related to the powerhouse and tunnels can be reduced. For example, project analyses show that higher heads can lead to reduced tunnel excavation and lower powerhouse costs, partially because the pump/turbine centerline depth below the lower reservoir decreases as head increases.
- Overall Project Cost Trends: Parametric sensitivity analysis using detailed bottom-up cost models indicates that total project costs are strongly sensitive to head and storage duration. While the cost for civil works and electromechanical equipment may decline with higher head, there is still an overall capital cost premium for pumped storage projects compared to other storage technologies due to site-specific geological and construction factors.
- Trade-off Summary: Higher head usually means higher water potential energy per unit volume, enabling a smaller reservoir and smaller, less expensive equipment, thus potentially lowering costs per unit of installed capacity. However, very high heads might introduce engineering challenges or increased costs in other areas, so an optimal head must be matched with site conditions.
In summary, increasing the head height in pumped hydro storage projects generally leads to a reduction in the size and cost of reservoirs and electromechanical equipment, translating into lower overall capital costs per unit of capacity, provided geological and engineering constraints are manageable.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-head-height-of-a-pumped-hydro-storage-project-affect-its-overall-cost/
