2,357 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 textElectricity in the Age of Enlightenment
No full textThe author gives a review of the historical development of electricity during the Age of Enlightenment (1600-1800), including work from William Gilbert to Benjamin Franklin
When cars went electric - part 1
No full textIn recent years, increasing attention to environmental pollution and concern about the depletion of oil reserves have boosted an interest in electric and hybrid cars as viable alternatives to gasoline-powered automobiles. R&D programs copiously supported in many countries are notably aimed at developing advanced management systems and high-efficiency motors and innovative batteries with high energy densities, both of the rechargeable and fuel-cell types. When we think of electric vehicles in this framework, they appear to us as future technologies in comparison with conventional internal combustion engines (ICEs). However, we may be surprised to learn that, a century ago, electric cars were far in advance of gasoline cars
A straightforward deduction of the electric circuit power
No full textAbstract: Purpose - The paper seeks to do the following. To provide an expression of the electromagnetic power flow that is alternative to the Poynting's theorem expression, overcomes its postulate feature, and is particularly suitable for electric circuit elements.
Design/methodology/approach - The paper proceeds from fundamental electromagnetic laws and, independently of Poynting's formulation, follows an approach that generalize established double formulations of the electrostatic and magnetostatic energies.
Findings - The paper proposes a compact and straightforward expression of the electromagnetic power flow based on the fundamental electromagnetic field sources, i.e. charge and current densities.
Practical implications - The achieved expression confirms Poynting's expression in the case of electric elements, overcoming its arbitrariness, generalizes previous partial results by other authors, deduced via the Poynting's power balance.
Originality/value - Is promising in the computation of power flow electromagnetic devices connected in electrical circuits, i.e. for coupled problems where the analysis of electromagnetic system interfaced to electric circuits is required. Due to its simple structure and straightforward deduction it has educational value to demonstrate the expressions of the electric power in circuit elements
Negative Feedback, Amplifiers, Governors, and More
No full textThe invention of the negative feedback amplifier by Harold S. Black (1898–1983) in 1928 is considered one of the great achievements in electronics and in fact it stands among the IEEE milestone, being credited to the Bell Labs. Black had been hired by Western Electric in 1921 and assigned to work on the Type C system, a newly introduced three-channel telephone network, whose push-pull vacuum-tube repeater amplifiers tended to produce a too large harmonic distortion when connected in tandem [1]. At that time, telephone network where in a great spread and the Bell Labs arose quickly as the major research company of the sector. The extension of lines over long distances required counteracting signal attenuation, which occurred, though at a reduced level, also in lines provided with Pupin’s loading coils to match the Heaviside condition for distortion-free transmission
"Blowin' in the Wind"
No full textThe title of this article may suggest that it constitutes a tribute to the recent Nobel Prize in Literature and a sweet remembrance of bour 20s for those of us who are now in our 60s. That could be the case. After all, scientists and technicians live in a diversified and interconnected world where culture, art, and civil actions are interdependent with technology. However, regardless of my esteem for Mr. Bob Dylan, this column deals with exploiting wind for energy, a longterm challenge to humanity, much longer than the time cannon balls flew
Looking back to electric cars
No full textVery early experimental electric cars appeared just after electromagnetism was discovered, in 1820. During the
nineteenth century they underwent improvements, staying in
advance of internal combustion engines. A breakthrough came
with the inventions of the rechargeable battery and of powerful and efficient electric motors, around 1870. Electrics peaked around the turn of the century, when they hold 38% of the automobile market in the US, compared with 40% of steam and 22% internal combustion. Their decline started in the second decade of the twentieth century when the internal combustion engine had a major boost, thanks to important advancements in the infrastructure, product and production technologies
Seventy Years of Getting Transistorized
No full textVacuum tubes appeared at the break of the twentieth century giving birth to electronics. By the 1930s, they had become established as a mature technology, spreading into areas such as radio communications, long distance radiotelegraphy, radio broadcasting, telephone communication and switching, sound recording and playing, television, radar, and air navigation. During World War II, vacuum tubes were used in the first electronic computers, which were built in the United Kingdom and the United States. Although vacuum tubes had been a successful technology, they were also bulky, fragile and expensive, had a short life, and consumed a lot of power to heat the thermo-emitters. These drawbacks promoted the search for completely new devices. Alternative solutions had long been considered, but without significant developments
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