Handling Intermittency

The old complaint about solar and wind is intermittency: the sun sets, the wind drops. Storage is the answer, and three approaches now share the load:

• Lithium-ion batteries — costs have fallen sharply since the 1990s; huge grid sites like Moss Landing in California hold thousands of megawatt-hours
• Iron-air batteries — Form Energy's design stores power for 100 hours at a fraction of lithium's cost, built for multi-day calm spells
• Pumped hydro — the oldest, biggest method: pump water uphill with spare power, then let it fall through turbines on demand