Henry Cavendish discovered hydrogen gas in 1766 and showed its lightness and combustibility. Antoine Lavoisier in 1783 burned hydrogen in oxygen gas and demonstrated that water consisted of a 2:1 hydrogen-oxygen ratio. Chemists developed several methods of producing hydrogen and found uses for the gas. Chemistry textbooks published in the 1950s-60s make little or no mention of hydrogen as a fuel, and when mention occurs, authors dismiss hydrogen as too expensive compared to other available gaseous fuels. Only in the early 2000s has hydrogen emerged as a clean energy source and raised the question of whether we should promote production of green hydrogen obtained from electrolyzing water or blue hydrogen obtained from the steam-methane reaction and whose other product is CO2.

Throughout history, hydropower was used, in rudimentary forms, to grind flour, irrigate fields, or provide drinking water. The watermill and windmill were the main sources of motive power for many centuries. Starting in the 1880s, hydropower became an important source of electricity. Most recently, hydropower is regarded globally as a renewable energy resource, being one of the essential components of the future energy mix that can ensure energy sustainability. This paper analyzes past and expected future of hydropower plants in different regions of the world, in close connection with environmental aspects and energy sustainability issues. It details a case study on Danube River hydroelectric plants.

AFASE, the first global network of solar energy technology researchers, was founded in 1955 in the United States, but in 1970 it took another name and moved from the northern hemisphere to the southern hemisphere with solar research pioneers met at the first International Solar Energy Society (ISES) Conference in Melbourne Australia.
Through the archives we approach a prosopography of these solar energy pioneers, complementing previous works with partial reports about the links generated between researchers at an intercontinental and cross-border level.
Information about local activities, shared at the world congress in Melbourne, illuminates the geopolitical controversies of the Cold War, the hemispheric blocs, and the distances between East and West in matters of renewable energy at a time of increasing concern about global warming problems.
Our findings are connections between engineers, designers, and managers of the research and development processes that were carried out around the world. Among others, John Duffie (USA), Ichimatsu Tanishita (Japan), and Julio Hirschmann Recht (Chile) met in Melbourne, as well as a series of researchers from Europe, who were participating in a collaboration network that allowed them to share advances in their discoveries and inventions. , at a time of increased interest in solar energy, even though a few years later the process would end up dismantling and losing the support that had been managed during the 1960s.
With this article, we contribute to the discussions about knowledge production around the problem of energy and civilization that is linked to explorations around techno-environmental history.