Reliable and affordable electricity systems based on variable energy sources, such as wind and solar may depend on the ability to store large quantities of low-cost energy over long timescales. Here, we use 39 years of hourly U.S. weather data, and a macro-scale energy model to evaluate capacities and dispatch in least cost, 100% reliable electricity systems with wind and solar generation supported by long-duration storage (LDS; 10 h or greater) and battery storage. We find that the introduction of LDS lowers total system costs relative to wind-solar-battery systems, and that system costs are twice as sensitive to reductions in LDS costs as to reductions in battery costs. In least-cost systems, batteries are used primarily for intra-day storage and LDS is used primarily for inter-season and multi-year storage. Moreover, dependence on LDS increases when the system is optimized over more years. LDS technologies could improve the affordability of renewable electricity.

基于可变能源（例如风能和太阳能）的可靠且负担得起的电力系统可能取决于长期存储大量低成本能源的能力。在这里，我们使用39年的每小时美国天气数据和一个宏观能源模型来评估容量，并以最少的成本分配具有长期存储（LDS; 10 h或10h更大）和电池存储空间。我们发现，引入LDS相对于风光电池系统降低了总体系统成本，并且系统成本对LDS成本降低的敏感性是电池成本降低的两倍。在成本最低的系统中，电池主要用于日间存储，而LDS主要用于季节间和多年存储。此外，当系统经过多年优化后，对LDS的依赖性就会增加。LDS技术可以提高可再生电力的承受能力。