“地质氢能电池”：氢气储存于煤炭将有助于推动清洁能源和经济发展

  据世界能源网站7月3日报道，开发氢能作为清洁能源以减少对化石燃料依赖的追求，可能会引领我们走向一个意想不到的地方——煤炭（煤矿）。宾夕法尼亚州立大学的科学家团队发现，煤炭可能是一种潜在储存氢气的方式，就像电池储存能量供未来使用一样，这解决了开发清洁能源供应链的一个重要障碍。

“我们发现煤炭（煤矿）可以成为这种‘地质氢能电池’，”宾夕法尼亚州立大学能源与矿业工程副教授Shimin Liu说道，“我们可以将氢注入煤炭（煤矿）和储存，并在需要时取用。”

“氢气是一种清洁燃料，在我们经济中最耗能的领域——交通、电力和制造业中有着潜力。但是，要建立氢能基础设施并使其成为一种经济实惠和可靠的能源来源，还有很多工作要做。”科学家们表示。

这些工作中包括开发储存氢气的方法，但目前的方法成本高昂且效率低下。科学家们表示，“好好利用煤炭（煤矿）的地质构造是一个有趣的选择，因为它们可以储存大量氢气，以满足每天或季节性变化的能源需求峰谷起伏”。

“煤炭经过了深入研究，我们已经商业化生产煤气将近半个世纪了，”Liu说，“我们对它有所了解，并且在煤炭开发所在的煤矿已建成基础设施。我认为煤炭（煤矿）将是进行氢能地质储存的合理选择。”

为了测试这一理论，科学家们分析了来自美国各地的8种煤炭，以更好地了解它们的吸附和扩散潜力，也就是它们能够储存多少氢气。

科学家们在《应用能源》杂志上报告称，所有8种煤炭都表现出了可观的吸附特性，来自弗吉尼亚东部的低挥发分无烟煤和来自宾夕法尼亚东部的无烟煤在测试中表现最好。

“从科学角度来看，我认为煤炭（煤矿）极有可能是氢能地质储存的首选，”Liu说，“我们发现煤炭（煤矿）优于其他地质构造，因为它可以储存更多氢气，它具有现有的基础设施，并且在全国范围内和人口密集地区广泛可得。

“已耗尽的煤层气储库可能是最佳的候选地。这些煤层包含类似甲烷的非常规天然气，几十年来已成为重要的化石燃料能源来源。甲烷会附着在煤炭表面，这个过程称为吸附。

“同样地，将氢气注入煤炭会使氢气被吸附或附着在煤炭上。这些构造通常在顶部有一层页岩或泥岩，起到密封作用，使甲烷（或在这种情况下的氢气）密封存储，直到需要时再抽取出来。”

“很多人把煤炭定义为一种岩石，但实际上它是一种聚合物，”Liu说，“它具有高碳含量和许多小孔，可以储存更多的气体。因此，煤炭就像一个海绵，相比其他非碳材料，它可以容纳更多的氢分子。”

科学家们设计了特殊设备来进行实验。与其他吸附气体如甲烷和二氧化碳相比，煤炭与氢气的亲和力较弱，因此传统的压力设备无法确定吸附特性。

“我们设计了一种非常新颖且具有挑战性的实验设备，”Liu说，“花了好几年时间才找到正确的方法。我们必须根据我们以前对煤炭和页岩的经验，进行试验和错误的设计实验系统。”

根据Liu及其科学团队的研究结果，科学家们确定无烟煤和半无烟煤是将氢气储存在已耗尽煤层的良好备选材料，而低挥发份无烟煤则更适合将氢气储存于含气煤层。

在煤炭采矿社区开发氢气储存技术可以为这些地区带来新的经济机遇，同时利用当地已有煤炭开采设施，也有助于更加便捷地建设国家氢气基础设施。

“在能源转型中，煤炭社区在经济上受到了最大的影响，”Liu说，“这无疑是重塑采煤地区经济发展形态的机会，煤炭开发地区拥有专业知识和能源工程技能人才和经验。如果能够建立基础设施并给予他们经济发展机会，这将是我们应该考虑的问题。”

未来的研究工作将集中在煤炭的动态扩散性和动态渗透性上，这些特性决定了氢气注入和抽取的速度，科学家们表示。

“我认为宾夕法尼亚州立大学是进行这项研究的合适地点——我们拥有开发煤炭储量和煤层气的经验，多年来还在高等学府中持续进行工程和经济方面的专业知识传授与创新，”Liu说，“这是进行这项研究的合乎逻辑的原因。”

 John, Willie Leone and Ang Liu作为宾夕法尼亚州立大学的能源和矿业工程系教授参与了这项研究工作。

吴奇之 译自 世界能源网

原文如下：

Hydrogen Battery: Storing Hydrogen in Coal May Help Power Clean Energy Economy

The quest to develop hydrogen as a clean energy source that could curb our dependence on fossil fuels may lead to an unexpected place — coal. A team of Penn State scientists found that coal may represent a potential way to store hydrogen gas, much like batteries store energy for future use, addressing a major hurdle in developing a clean energy supply chain.

“We found that coal can be this geological hydrogen battery,” said Shimin Liu, associate professor of energy and mineral engineering at Penn State. “You could inject and store the hydrogen energy and have it there when you need to use it.”

Hydrogen is a clean burning fuel and shows promise for use in the most energy intensive sectors of our economy — transportation, electricity generation and manufacturing. But much work remains to build a hydrogen infrastructure and make it an affordable and reliable energy source, the scientists said.

This includes developing a way to store hydrogen, which is currently expensive and inefficient. Geologic formations are an intriguing option, the scientists said, because they can store large amounts of hydrogen to meet the peaks and valleys as energy demand changes daily or seasonally.

“Coal is well-studied, and we have been commercially producing gas from coal for almost a half century,” Liu said. “We understand it. We have the infrastructure. I think coal would be the logical place to do geological hydrogen storage.”

To put this to the test, the scientists analyzed eight types of coals from coalfields across the United States to better understand their sorption and diffusion potential, or how much hydrogen they can hold.

All eight coals showed considerable sorption properties, with low-volatile bituminous coal from eastern Virgina and anthracite coal from eastern Pennsylvania performing the best in tests, the scientists reported in the journal Applied Energy.

“I think it’s highly possible that coal could be the very top selection for geological storage from a scientific perspective,” said Liu. “We find that coal outperforms other formations because it can hold more, it has existing infrastructure and is widely available across the country and near populated areas.”

Depleted coalbed methane reservoirs may be the best candidates. These seams contain unconventional natural gas like methane and have become an important source of fossil fuel energy over the last several decades. The methane sticks to the surface of the coal, in a process called adsorption.

Similarly, injecting hydrogen into coal would cause that gas to absorb or stick to the coal. These formations often have a layer of shale or mudstone on top that act as a seal keeping methane, or in this case hydrogen, sealed until it is needed and pumped back out, the scientists said.

“A lot of people define coal as a rock, but it’s really a polymer,” Liu said. “It has high carbon content with a lot of small pores that can store much more gas. So coal is like a sponge that can hold many more hydrogen molecules compared to other non-carbon materials.”

The scientists designed special equipment to conduct the experiments. Coal has a weaker affinity with hydrogen compared to other sorbing gases like methane and carbon dioxide, so traditional pressurized equipment for determining sorption would not have worked.

“We did a very novel and very challenging design,” Liu said. “It took years to figure out how to do this properly. We had to properly design an experiment system, trial and error based on our previous experience with coals and shales.”

based on their results, the scientists determined anthracite and semi-anthracite coals are good candidates for hydrogen storage in depleted coal seams, and low-volatile bituminous coal are better candidates for gassy coal seams.

Developing hydrogen storage in coal mining communities could bring new economic opportunities to these regions while also helping create the nation’s hydrogen infrastructure.

“In the energy transition, it’s really coal communities that have been the most impacted economically,” Liu said. “This is certainly an opportunity to repurpose the coal region. They already have the expertise — the energy engineer and skills. If we can build an infrastructure and change their economic opportunities — I think that’s something we should consider.”

Future work will focus on the dynamic diffusivity and dynamic permeability of coal, features which determine how quickly hydrogen can be injected and pumped back out, the scientists said.

“I think Penn State is the right place to do all this research — we have the coal reserves, we have natural gas, we have both the engineering and economic expertise at the University,” Liu said. “This is the logical place to do this.”

Also contributing from Penn State was Ang Liu, instructor, John and Willie Leone Family Department of Energy and Mineral Engineering.