566 research outputs found
A glance at hydroelectricity evolution
No full textThe ecological transition that many governments are implementing, notably the EU, will stand on the phase-out of fossil fuels and the consequent expansion of renewable sources, which will develop as a technological revolution.
However, hydropower is a major renewable source already at a mature stage and widely exploited. It early uses appeared quite soon in early isolated plants when mechanical generator became available, but in limited cases were flowing water was easily accessible. Plants and lines had limited extension at that time and thermal engines (both steam and internal combustion) allowed a more flexible adoption.
The advent of alternating current, which allowed the use of stepping-up and stepping-down transformer and thus power transmission at high voltage over long distances opened the way to the exploitation of large water resources in remote areas. An early hydroelectric power plant of this kind was put into service at Willamette Falls, Oregon, in 1889, to supply Portland through a 4-kV 125 Hz 22-km line. The soundness of the technology was proven in the 1890s. A major step ahead occurred in 1891, on occasion of the International Electrotechnical Exhibition at Frankfort, where the first three-phase power line, rated 240 kW at 15 kV and 40 Hz, extending over 175 km between the Lauffen waterfalls, were a hydrogenator was installed, and Frankfurt, was presented. Shortly after, some hydropower stations powering long lines were opened, e.g.:
1892: Aniene–Rome, Italy (1.2 MW, 5 kV, 42 Hz single-phase, 28-km)
1893: Lake Hellsjön–Grängesberg, Sweden (300 kW, 9.5 kV three-phase, 14 km)
1893: Mill Creek n.1 hydroelectric plant, California US (250 kW, 2.4 kV 50 Hz three-phase,12 km)
In 1895, the Niagara hydropower station was started, with three (increased to 10 by 1898) two-phase alternators each rated 3.7 MW 2.2 kV 25 Hz. Step-up transformers with Scott connection fed the three-phase 11 kV line powering Buffalo 35 km apart. Two similar systems appeared in the Alps, Europe, in 1898, namely the Paderno d’Adda three-phase hydropower station, rated 9 MW at 13.5 kV 42 Hz that fed Milan, 30 km apart; and the Rheinfelden three-phase hydroelectric power plant, rated 12.5 MW at 50 Hz (Germany-Switzerland). Following these achievements, countries and regions rich with water resources exploited them increasingly in the early decades of the 20th century, while extending their power lines and network which eventually were interconnected into national grids.
In the first decade of the century, also pumped hydro power station appeared, with early notable installations in Germany and Switzerland, in 1908. US followed starting in 1929 and major developments occurred in different countries after World War Two.
The growth of hydropower was massive in countries rich with water resources, notably Switzerland, Italy, Canada, Sweden, Norway, Soviet Union, and, more recently, Brazil and China, as long as more water resources were exploitable. By 1920, 40% of the electricity produced in the United States was hydroelectric and in the mid 20th century, 96% of the installed power in Canada, 94% in Switzerland, 90% in Italy, and 80% in Sweden 80%, came from hydroelectricity.
However, when the water resources were saturated, the growing demand was satisfied with thermoelectricity fed with fossil fuels. For the sake of example, hydroelectric energy share in Norway was 96.2% of the total production and 117.9% of the domestic demand in 2016; conversely, in Italy hydroelectric energy production remained substantially constant in the last 60 years, counting 44,257 GWh in 2016, but hydroelectric energy share had dropped to 15.3% of the total domestic electricity production, although flanked by 22% of other renewables. On the other hand, pumped hydro is today by far the largest-capacity form of grid electric energy storage worldwide, accounting for 181 GW of power capacity and 1.6 TWh of storage capacity, which correspond to 95% of the global figures for energy storage
Evolutive waves in electrochemical batteries
No full textWe are now entering an epoch-making evolution in energy supply, in the framework of decarbonization and ecological transition, which are strongly addressed in Europe and other countries and continents. The phase-out of fossil fuels and the expansion of renewable sources, notably photovoltaic and wind that are intermittent and unpredictable, on one side, and the advent of electric vehicles on the other side, will imply a growing need for electrochemical batteries in both stationary and mobile versions. Huge research programs are under development to provide better and cheaper cells able to meet the future demand.
However, when we look at the past of electrotechnology, we see that batteries have already played major roles in the evolution of electrotechnology, starting with the first cell, invented by Alessandro Volta in 1799, that allowed electricity to get rid of the narrow limitations of electrostatics. Over more than half a century, primary cells derived from Volta’s invention powered the early exploitations of electricity. When reliable electromechanical generators appeared, capable of delivering cheap and large power, secondary (rechargeable) cells were developed, which were instrumental in the first season of electric vehicles, at the turn of the century, both above ground and underwater.
Just after the mid of the 20th century the advent of the transistor and solid-state electronics allowed the downsizing of many appliances. However, devices like hearing aids and radio receivers called for compact and better performing cells to became portable and the answer consisted in a new generation of primary cells, in particular alkaline.
Shortly after, space exploration called for new generations of rechargeable batteries, mostly based on Nickel-based chemistries (Ni-Cd, Ni-H2, Ni-MH), which found application also in other fields.
Toward of the end of the century, new scientific horizons were opened by the lithium technologies, first in primary cells and then in secondary ones. The evolution of rechargeable lithium-ion battery was gradual, being implemented first in low-power portable electronics (mobile phones, laptops, organizers, media players, ... rated 5-60 Wh), then in middle-power electric vehicles (HEV, PHEV, BEV, with power and energy ranging as 5-600 kW and 1–100 kWh), and in both fields they quickly became dominating. Still afterward, large stationary Li-ion (up to 150 MW and 300 MWh) started to be installed in support of electric grids with power for discharge durations up to 4 hours
Some facts on History Activities with a Glance at Notable Women in Science and Technology
No full textGuarnieri (Romana) Don Giuseppe De Luca tra cronaca e storia
No full textDurand Jean-Dominique. Guarnieri (Romana) Don Giuseppe De Luca tra cronaca e storia. In: Archives de sciences sociales des religions, n°82, 1993. p. 327
Tra storia dell’eresia e storia della pietà: Delio Cantimori e don Giuseppe De Luca
No full textDelio Cantimori e Giuseppe De Luca furono in contatto per circa venti anni, dai primi anni ’40 alla morte di De Luca, avvenuta nel 1962, dopo essersi conosciuti grazie alla mediazione di un’allieva comune, Romana Guarnieri. Il saggio si basa sul carteggio, che i due intellettuali si sono scambiati durante questo periodo, e sulle testimonianze della stessa Guarnieri. Attraverso queste fonti sono ricostruiti i loro incontri e le collaborazioni editoriali di Cantimori con le Edizioni di Storia e Letteratura, fondate da De Luca nel 1941. Pur partendo da posizioni ideologiche diverse, Cantimori e De Luca convergono su una concezione della storia religiosa che privilegia i temi della sensibilità e della pietà
La “singolare amicizia” tra la beghina e il prete Inversione di ruoli tra Romana Guarnieri e Giuseppe De Luca
No full textLa recensione concentra il proprio focus sulla figura di Giuseppe De Luca, alla luce di due contributi. Il primo «Tra le stelle e il profondo». Carteggio tra Giuseppe De Luca e Romana Guarnieri 1938- 1945, a cura di V. Roghi (Morcelliana, 2010); il secondo, a cura di Luisa Mangoni, "In partibus infidelium". Don Giuseppe De Luca: il mondo cattolico e la cultura italiana del Novecento, (Einaudi, 1989). La pubblicazione di una parte del carteggio tra De Luca e la Guarnieri evidenzia i caratteri di una figura complessa e ricca di sfaccettature, emblema di un periodo storico e di una profonda e articolata sensibilità cristiana. Lo scambio tra loro, fatto di affondi teologici, esistenziali e psicologici e progetti comuni, produrrà molti frutti intellettuali, teologici e pratici, come la fondazione delle edizioni di «Storia e Letteratura», concepita non solo come una vera impresa spirituale e culturale
Aida
No full textDirector Antonio Guarnieri i director d'escena E. SalarichÒpera en quatre actes, poesía d'Antoni Chislanzoni i música de Giuseppe Verd
El Mercurio Peruano, Giuseppe Rossi Rubí y la difusión de los nuevos conocimientos científicos en el Virreinato del Perú
No full textLa influencia de la Ilustración en la América española, y en Perú en particular, se puede encontrar principalmente a finales del siglo XVIII en la Revista El Mercurio Peruano de Historia, Literatura y Noticias Públicas. El principal animador de la revista, expresión del ambiente cultural limeño, fue Giuseppe Rossi Rubì, un italiano, originario de Milán. Rossi Rubí escribió artículos sobre diferentes temas: educativos, psicológicos, sanitarios, de interés público en general. Una contribución importante de Rossi Rubí a través del Mercurio, es una serie de artículos sobre la minería. Estos escritos, así como otros, expresan una clara intención de conocer el Perú, para estimular el progreso, la difusión de la ciencias, especialmente la medicina y la historia natural, la economía. No era más que una forma de erudición, sino también la intención de llevar a cabo una actividad “útil” para mejorar la “felicidad” del país
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