Pumped-storage hydroelectricity

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.