Europe is investing in technologies to help create a more reliable renewable energy system and one of the latest developments demonstrates the interest in long-duration energy storage. Traditional lithium-ion batteries typically store energy for hours, but the iron-air battery will be designed to hold electricity for 24 to 100 hours. Long-duration storage could be an important part of addressing curtailment, while reducing reliance on fossil-fuel backup generation. Which sectors/areas will be the first to benefit from multi-day energy storage? I’d be interested to see what others think about the role of long-duration energy storage in Europe’s energy transition.