At the heart of most Power-to-X (PtX) concepts is the utilization of renewable electricity to produce hydrogen through the electrolysis of water. This hydrogen can be used directly as a final energy carrier or it can be converted into, for example, methane, synthesis gas, liquid fuels, electricity, or chemicals. Technical demonstration and systems integration are of major importance for integrating PtX into energy systems. As of June 2020, a total of 220 PtX research and demonstration projects in Europe have either been realized, completed, or are currently being planned. The central aim of this review is to identify and assess relevant projects in terms of their year of commissioning, location, electricity and carbon dioxide sources, applied technologies for electrolysis, capacity, type of hydrogen post-processing, and the targeted field of application. The latter aspect has changed over the years. At first, the targeted field of application was fuel production, for example for hydrogen buses, combined heat and power generation, and subsequent injection into the natural gas grid. Today, alongside fuel production, industrial applications are also important. Synthetic gaseous fuels are the focus of fuel production, while liquid fuel production is severely under-represented. Solid oxide electrolyzer cells (SOECs) represent a very small proportion of projects compared to polymer electrolyte membranes (PEMs) and alkaline electrolyzers. This is also reflected by the difference in installed capacities. While alkaline electrolyzers are installed with capacities between 50 and 5000 kW (2019/20) and PEM electrolyzers between 100 and 6000 kW, SOECs have a capacity of 150 kW. France and Germany are undertaking the biggest efforts to develop PtX technologies compared to other European countries. On the whole, however, activities have progressed at a considerably faster rate than had been predicted just a couple of years ago.

大多数Power-to-X（PtX）概念的核心是利用可再生电力通过水的电解生产氢。该氢可以直接用作最终的能量载体，也可以转化成例如甲烷，合成气，液体燃料，电力或化学物质。技术演示和系统集成对于将PtX集成到能源系统中至关重要。截至2020年6月，欧洲已经实现，完成或正在计划进行220个PtX研究和示范项目。审查的主要目的是根据相关项目的调试年份，位置，电力和二氧化碳来源，电解应用技术，容量，氢气后处理类型，以及目标应用领域。多年来，后一个方面已经发生了变化。首先，应用的目标领域是燃料生产，例如用于氢总线，热电联产以及随后注入天然气网的燃料。今天，除了燃料生产外，工业应用也很重要。合成气态燃料是燃料生产的重点，而液态燃料的生产严重不足。与聚合物电解质膜（PEM）和碱性电解槽相比，固体氧化物电解槽（SOEC）仅占很小的比例。装机容量的差异也反映了这一点。虽然安装了容量为50至5000 kW（2019/20）的碱性电解槽和容量为100至6000 kW的PEM电解槽，SOEC的容量为150 kW。与其他欧洲国家相比，法国和德国正在最大程度地开发PtX技术。但是，总的来说，活动的发展速度比几年前的预期要快得多。