CAS-Climate: Bubble generation and ripening in underground hydrogen storage

国际能源机构将氢确定为本世纪中叶全球能源部门脱碳的关键支柱之一。这是因为大多数可再生能源（如风能和太阳能）都是间歇性的，需要在高产量时期储存，以确保在低产量时期可用。氢气是一种极好的储存介质，但需要非常大的容量。地表设施和地下盐洞提供了一些容量，但不足以满足需要。由多孔岩石组成的深层地质地层是一种很有前途的解决方案，因为它们提供了大容量，并且在储存其他流体（例如二氧化碳）方面取得了成功。目前尚不清楚的是，夏季注入的氢气有多少可以在冬季回收，以及氢的纯度如何受到共同注入的流体（称为缓冲气体）的影响。季节性的注入-退出周期可能会在岩石中产生并捕获许多氢气和缓冲气体气泡，这些气泡随后通过称为奥斯特瓦尔德成熟的过程相互交换质量。两者都能导致氢的损失和纯度下降。该奖项旨在了解控制与氢储存相关的多组分气泡的捕获和成熟的基本机制。这种理解将有助于选择合适的地质储存地点和相容的缓冲气体。氢被广泛认为是全球能源系统脱碳的关键支柱。为了大规模地缓解风能和太阳能的间歇性负担，必须季节性地储存大量的氢。现有的解决方案（例如，储罐和盐穴）不能提供所需的足够容量。深层地层的地质储氢可以满足需求，但人们对氢气如何与预先存在的和共注入的流体（称为缓冲气体）相互作用知之甚少。该奖项的目标是了解循环注入的多组分气体如何被捕获在多孔微观结构中，以及它们如何通过弥漫性质量交换或奥斯特瓦尔德成熟演变。提出了一种综合实验和建模方案，以获得以下基本见解：(1)循环注入和提取过程中控制捕获气泡空间分布的因素；(2)气泡的大小、形状和成分如何随着成熟而演变；(3)集体气泡平衡对多孔介质宏观储存量和流动阻力的影响。该教育计划将培训一名博士生，并通过面对面/虚拟博物馆展览吸引服务不足的K-12学生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The international energy agency identifies hydrogen as one of the key pillars for decarbonizing the global energy sector by mid-century. This is because most renewable energy sources such as wind and solar are intermittent, requiring storage during times of high production to ensure availability during times of low production. Hydrogen is an excellent medium for storage, but very large volumes will be required. Surface facilities and underground salt caverns provide some capacity, but not enough for what is needed. Deep geologic formations comprised of porous rocks are a promising solution because they offer large capacity with demonstrated success in storing other fluids (e.g., carbon dioxide). What is not well understood is how much of the hydrogen injected during summertime can be recovered during winter and how hydrogen purity is impacted by the presence of a co-injected fluid, called cushion gas. The seasonal injection-withdrawal cycles will likely generate and trap many hydrogen and cushion-gas bubbles in the rock that subsequently exchange mass with each other through a process known as Ostwald ripening. Both can contribute to the loss and purity degradation of hydrogen. This award aims to understand the basic mechanisms controlling entrapment and ripening of multicomponent bubbles relevant to hydrogen storage. This understanding will help select suitable geologic storage sites and compatible cushion-gasses.Hydrogen is widely regarded as a key pillar for decarbonizing the global energy system. To buffer the intermittency burden of wind and solar at scale, vast quantities of hydrogen must be stored seasonally. Existing solutions (e.g., tanks and salt caverns) do not provide nearly enough capacity for what is needed. Geologic hydrogen storage in deep formations meets the demand, but very little is understood about how hydrogen interacts with pre-existing and co-injected fluids, called cushion gas. The goal of this award is to understand how cyclically injected multicomponent gases become trapped within a porous microstructure and how they evolve through diffusive mass exchange, or Ostwald ripening. An integrated experimental and modeling plan is proposed to gain fundamental insights into: (1) the factors that control the spatial distribution of trapped bubbles during cyclic injections and withdrawals; (2) how bubble sizes, shapes, and compositions evolve due to ripening; and (3) how collective bubble equilibration impacts the macroscopic storage capacity and flow resistance of the porous medium. The educational plan will train one PhD student and engage underserved K-12 students through in-person/virtual museum exhibits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.