The energetic transition will be a major challenge in the next years. Today, we must imagine future needs and uses of alternative energy such as hydrogen. For this, we need to define and design innovative services which will satisfy future expectations of future users. But how can we evaluate and design products and services when they do not yet exist? In this case, it is hard to animate focus groups of users, impossible to analyze the usages, complicate to understand user's opinions… To deal with these questions, it is necessary to introduce prospective and creativity in the ergonomics approaches, so-called prospective ergonomics. Our project and the first results obtained show how different " actors of hydrogen " imagine the future uses of this energy from different points of view. We chose to organize three staff of professionals (production, transport and energy distribution) and we made a lexical analysis of their conversations. We present in this communication the process of lexical analysis and main results obtained. We explain, how we created 4 fictitious users called " Personas ". The main role of these personas is to facilitate ideation in order to allow the hydrogen professionals to design new products and innovative services.