No wind turbine can capture more than 59.3% of the wind's energy

science & techWikipedia1919

No wind turbine can capture more than 59.3% of the wind's energy

the gist

Betz's law sets a hard ceiling on how much energy any wind turbine can extract from moving air. Albert Betz, a German physicist, published the result in 1919. Using conservation of mass and momentum, he modelled the turbine as an idealised disk that slows the air passing through it. If the air is slowed too little, little energy is taken; if it is slowed too much, it can't flow through the disk fast enough. The best balance captures 16/27, about 59.3 percent, of the wind's kinetic energy. This limit applies regardless of blade design. Real utility-scale turbines reach around 75 to 80 percent of this theoretical maximum.

how it works

The turbine is modelled as a disk that removes energy by slowing the air passing through it. Slowing the air more captures more energy but also blocks the flow, so the air piles up and bypasses the disk. Balancing these two effects gives the maximum fraction of the wind's energy that can be taken, which works out to 16/27.

so what

Betz's limit tells engineers and investors what is physically possible, so designs are judged against a fixed ceiling rather than endless improvement. It explains why wind power is efficient but never captures all the energy available in the wind.

Hampi was once one of the world's largest cities, until its Vijayanagara capital was destroyed in 1565

the gist

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.

how it works

The city was built around a fortified core with temples, markets and water structures along the river, supplied by an extensive network of roads and waterworks. When the empire fell, the city was not rebuilt, so its stone monuments were left standing.

so what

Hampi shows how quickly a great city can vanish after a military defeat, and how a ruined capital can remain sacred. Its ruins give historians a view of medieval South Asia that few other sites can match.

fun fact

The name Hampi comes from Pampa, an old name for the Tungabhadra River.

From Wikipedia, the free encyclopedia · text CC BY-SA 4.0

Image: Wikimedia Commons

source: Wikipedia ↗

2 min

politicsshortCNA2:01

False allegations about Singapore’s hand in Indonesia’s markets and a made-up meeting

from CNA

CNA Verify has found close to 400 posts pushing falsehoods tying Singapore to Indonesia’s stock market rout and to a secret meeting that never took place. Together, they drew nearly 12 million views, and some were circulated by accounts that appeared to be working in concert, across multiple social media platforms.

Here’s how the disinformation campaign targeting Singapore was uncovered.

on YouTube: CNA ↗