Evaporation impacts the overall efficiency of pumped hydroelectric energy storage (PHES) by causing water loss from reservoirs, which reduces the volume of water available for energy generation and thus leads to energy and economic losses.
How Evaporation Affects Pumped Hydroelectric Storage Efficiency
- Water Loss and Reduced Storage Capacity: Evaporation decreases the amount of stored water in the upper reservoir of a PHES system. Since the energy output depends on the volume of water and the hydraulic head (height difference), evaporation reduces the potential energy that can be converted to electricity.
- Operational and Economic Impact: Loss of water increases the need to replenish reservoirs, which may not always be feasible, especially in regions with limited rainfall. This water loss translates into lower energy production and negatively affects the economic viability of PHES projects. The reduction in stored water due to evaporation also impacts the efficiency of energy storage and retrieval cycles.
- Significance in Certain Climates: Evaporation has a more pronounced effect in arid or semi-arid regions where high temperatures and low humidity increase evaporation rates. In such regions, careful water management and design considerations are necessary to mitigate these losses.
Quantification and Technical Considerations
- Studies have observed that considerable amounts of water evaporate during operation, which might significantly impact long-term system management and efficiency, especially in hybrid renewable energy systems that combine PHES with solar or wind power.
- Some designs address water loss by employing seasonal pumped-storage plants with large reservoir level variations, which can result in a relatively lower evaporation-to-storage ratio, thus improving operational viability where evaporation impacts water management.
Mitigation Strategies
- Variable Speed Pump-Turbines: Enable greater flexibility in managing reservoir levels and operational heads, potentially limiting evaporation losses by optimizing water use across different storage cycles.
- Dual Pump-Turbine Arrangements: Operating multiple pump-turbines in series or parallel to optimize head variation can also help enhance operational efficiency, indirectly reducing evaporation losses by adapting more effectively to reservoir conditions.
- Site Selection and Design: Choosing locations with minimal evaporation potential or designing reservoirs that minimize surface area exposed to evaporation can reduce water loss.
Summary Table
| Aspect | Impact of Evaporation on PHES |
|---|---|
| Water Volume | Reduction due to evaporation limits water available for generation |
| Energy Efficiency | Decreased as less potential energy can be converted |
| Economic Viability | Lower due to reduced generation and possible water replenishment costs |
| Regional Sensitivity | More severe in dry, hot climates |
| Mitigation Measures | Variable speed turbines, reservoir management, optimized design |
In conclusion, evaporation is a crucial environmental factor that reduces pumped hydroelectric energy storage efficiency by diminishing stored water volumes, thereby lowering energy output and increasing operational costs. Addressing evaporation through design innovations and site selection is key to improving PHES performance and viability.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-evaporation-impact-the-overall-efficiency-of-pumped-hydroelectric-energy-storage/
