Pumped-storage hydroelectricity
Pumped‑storage hydroelectricity is examined as a large‑scale energy storage method that can smooth intermittent solar and wind power, offering long lifespans and very low storage costs per kWh compared to lithium‑ion batteries, but only where suitable geography and political will exist. Commenters highlight major projects in Australia, New Zealand, Europe, and South Africa, noting cost blowouts, cancellations, and environmental concerns alongside examples where existing dams and reservoirs are being adapted for grid balancing. The exchange also contrasts pumped hydro with emerging battery technologies and other gravity‑based storage concepts, arguing that while batteries are rapidly getting cheaper for short‑duration storage, pumped hydro remains uniquely effective for multi‑hour to multi‑day energy buffering.
Large projects and politics
- Big pumped hydro projects are highly politicized. Examples include Snowy 2.0 in Australia and the Lake Onslow scheme in New Zealand.
- Criticisms: huge cost overruns, long timelines, construction/environmental risks, and claims that funds would be better used on solar, wind, batteries, and transmission.
- Defenders argue governments canceled or stalled projects with vague rationales, ignoring that such infrastructure is inherently expensive and slow but provides massive, long‑duration storage.
- Market structure matters: existing pumped hydro tied to coal plants has been used to maximize profits rather than to lower prices, requiring regulatory separation.
Costs vs batteries and other options
- One commenter’s initial cost/kWh calculation for Onslow was off by three orders of magnitude; corrected math shows pumped hydro is vastly cheaper per kWh of storage than current lithium batteries.
- However, others note that lithium battery prices are falling fast, pumped hydro costs are more static and site‑specific, and batteries are easier to deploy anywhere.
- Debate over whether future battery learning curves and alternative chemistries (sodium, iron) will erode pumped hydro’s economic niche.
Role in renewable‑heavy grids
- Pumped hydro is used for peak shaving, “black start” capability, and to firm intermittent renewables, especially multi‑day wind lulls; batteries are seen as better for sub‑10‑hour storage.
- Existing conventional hydro already acts as storage by varying output when solar/wind are abundant.
- Several countries (e.g., in Europe, South Africa, Australia, US) already rely on pumped storage as a non‑trivial grid component.
Physics, scale, and siting
- Core physics (m·g·h) implies very low energy density for gravity storage: 1 m³ of water raised 1 m stores roughly an AA battery’s energy, making small or low‑head systems mostly uneconomic.
- Effective sites need large reservoirs and significant elevation differences (hundreds of meters).
- Engineering challenges include high pressures, tunnel boring difficulty, and lining shafts to withstand stress.
Small‑scale and alternative gravity concepts
- Proposals for distributed pumped hydro using household tanks or snowmaking reservoirs are generally seen as physically and economically weak, though a few hybrid ski‑resort concepts exist.
- Non‑water gravity concepts (stacked concrete blocks, etc.) are discussed but viewed skeptically: physics and mechanical complexity make them expensive relative to pumped hydro and batteries.
Environmental and risk aspects
- Some argue pumped storage is low‑carbon and synergistic with natural water cycles; others stress dam projects can have major ecological impacts and hydro failures have killed far more people than nuclear incidents.