标题: Long-Distance Electricity Transmission [打印本页] 作者: choi 时间: 2-5-2025 13:33 标题: Long-Distance Electricity Transmission (1) Trading electricity | Power to the Foreigners; To make electricity cheaper and greener, connect the world's grids. Economist, Jan 25, 2025, at page 9 (in the section Leaders)
("Connecting up grids bring a host of benefits. Countries need fewer largely redundant power plants that are used only when demand peaks or when other generation goes offline")
(2) International trade | Power-Sharing; Why don't more countries import their electricity> Same, at page 47
("Yet in 2023, only 2.8% of the world's electricity was traded internationally. Outside Europe, exchanges remain minimal * * * The hold-up used to be technical: lots of power was lost in transmission, making long-distance exports uneconomic. Nowadays, however, high-voltage direct current cables are extremely efficient., Projects in Brazil and China have shown their viability over distances of thousands of kilometres. Instead, the problem is geopolitics. Governments worry that neighbours might pull the plug on their power supply")
There is no need to read the rest.
Note: I have learned physics about a handful times, including once in my own by reading a textbook used by freshmen at Massachusetts Institute of Technology. I never could wrap my head around alternating current. I learn it today, via intitution.
(a) high-voltage direct current https://en.wikipedia.org/wiki/High-voltage_direct_current
(section 2 Comparison with AC: "Depending on voltage level and construction details, HVDC transmission losses are quoted at 3.5% per 1,000 km (620 mi), about 50% less than AC (6.7%) lines at the same voltage.[19] This is because direct current transfers only active power and thus causes lower losses than alternating current, which transfers both active and reactive power")
(i) Once you read Note (b)(i) below, you realize that reactive power is when electronics going backwards, which itself (just like electronics moving forwards) also causes energy loss (via heating) due to resistance.
(ii) If you take a look of this Wiki page, you learn that the HVDC concept is not new. I do not know why it was not implemented.
(b)
(i) Doug Lowe, What Is Alternating Current? Dummies, Mar 16, 2016 (under the topic of 'Electronics Basics;) https://www.dummies.com/article/ ... ing-current-179847/
(ii) Current and resistance. Khan Academy, undated https://www.khanacademy.org/test ... ct-current-circuits
(A) This essay is found in Khan Academy's MCAT, Unit 9, Lesson 11, where MCAT stands "Medical College Admission Test" -- the test an applicant to a medical school in North America (and Australia) must take.
(B) However, the last part (about nervous system) is all wrong. Yes, transmission of nerve pulse along an axon, say, of a nerve cell is extremely, unbearably, slow if the nature relies on transmission of electronics (or charged particles) -- not to mention that this essay implies that this is how nerve impulse transmits ACROSS a gap between two nerve cells, which actually use small-molecule transmitters and their receptors). But nature is very clever, deploying "Node of Ranvier" instead (Ranvier is the surname of a French biologist who observed it under microscope (without knowing its function).
(c)
(i) Basics of Electricity Transportation. Energy Basics (in collaboration with Yale Energy History), undated https://www.energybasics.org/electricity-transmission
("Due to certain physical principles beyond the scope of this module, alternating current is easier to generate * * * Because electrical energy dissipates over distances, it is much more efficient to transmit at high voltages. This is because higher voltage means the wires can transport electricity at a lower current through the wire, and therefore they will exhibit less energy loss")
(ii) Then we return to Note (a), whose section 1 High voltage transmission includes two formulas: P=V•I, and another.
(A) The former can be found in
power https://en.wikipedia.org/wiki/Power
(may refer to "Power (physics), meaning 'rate of doing work' ")
power (physics) 功率 https://en.wikipedia.org/wiki/Power_(physics)
(section 1 Definition: Power is the rate with respect to time at which work 功 is done; section 5 Electrical power: P=I•V)
(B) The second formula described in Note (c)(ii) is Joule's (first) law.
• James Prescott Joule https://en.wikipedia.org/wiki/James_Prescott_Joule
("he found the relationship between the current through a resistor and the heat dissipated, which is also called Joule's first law")
• Clicking the hyperlink leads to
Joule heating https://en.wikipedia.org/wiki/Joule_heating
(section 2 Microscopic description: the flowing electrons "collide with the quasi-particles in the conductor"/ section 4 Formulas, section 4.1 Direct current: P=I•R. Thanks to Ohm's law (V=I•R), P=I squared times R. And P is a rate of doing work, so W (heating here)=I squared times R times Time. (The last makes sense, because the longer electronics travels in the wire, the more heat this generates.)
• quasiparticle https://en.wikipedia.org/wiki/Quasiparticle
("For example, as an electron travels through a semiconductor, its motion is disturbed in a complex way by its interactions with other electrons and with atomic nuclei. The electron behaves as though it has a different effective mass [than or from: either is grammatically correct in English] travelling unperturbed in vacuum. Such an electron is called an electron quasiparticle")