PILTON, BRITAIN •Even as music will recharge fans once again at this year's Glastonbury Festival, it is also a time to plug into "Pee-ple" Power.
Urine from the folks attending the revered festival will be converted into electricity, thanks to technology developed by the University of the West of England.
A second Pee Power site on the Worthy Farm grounds will charge lighting and mobile phones.
There are also 10 information signs powered by urine, thanks to a new 40-person urinal near the main Pyramid Stage.
The gates to the festival swung open on Wednesday for five days of the world's biggest greenfield music festival, headlined this year by Radiohead, Foo Fighters and Ed Sheeran.
About 175,000 people were expected to turn up at the site outside Glastonbury in south-west England, amid sizzling temperatures and reinforced security measures after a string of terror attacks in Britain.
"Hooray! Welcome to Glastonbury!" said founder Michael Eavis, greeting those queueing outside as the green metal gates opened.
Shows on the seven biggest stages start today, but rucksack-lugging revellers like to get there early to secure a decent spot to pitch their tents.
"There were some checks, but there are so many people and it is so hot. The queues were better than I thought they would be," said Ms Anna Harris, 25, from London, who was among the first to get in.
Tickets cost £238 (S$419) and all 135,000 have sold out, with a further 40,000 people expected to attend.
"It's like going to another country, a thrilling (trip) that appears every year or so," the festival said.
"You enter a huge tented city, a mini-state under canvas. British law still applies, but the rules of society are a bit different, a little bit freer.
"Everyone is here to have a wild time in their own way."
Glastonbury started off as a loss-maker in 1970, with 1,500 people paying £1 to watch glam rocker Marc Bolan top the bill, with free milk from the farm to tempt musicloving hippies.
It is now one of the world's landmark music festivals, with dozens of stages, fields and areas. The site has a perimeter of about 13.5km.
Radiohead top the bill today on the main Pyramid Stage, backed by The xx, Royal Blood and Kris Kristofferson.
Tomorrow, the Foo Fighters are headlining after sets by The National, Katy Perry, Run The Jewels and Craig David.
Sheeran closes the festival on Sunday, supported by Biffy Clyro, Chic and Barry Gibb.
Opposition Labour Party leader Jeremy Corbyn is due to give a talk and introduce US rap duo Run The Jewels.
On the secondary Other Stage, Major Lazer, alt-J and Boy Better Know are the headliners, with sets from Liam Gallagher, Kaiser Chiefs, Emeli Sande and The Courteneers.
Status Quo, Goldfrapp, The Pretenders, The Jacksons, Dizzee Rascal, Alison Moyet and Kiefer Sutherland are also on the bill.
Movie star Johnny Depp will present the 2004 film he starred in, The Libertine, in a new film zone at the festival.
Organisers and police have urged attendees to pack light and expect searches.
"The policing style may look and feel slightly different this year," police officer Caroline Peters said.
"Like the rest of Britain, festivalgoers should be alert but not alarmed," she added, following four terror attacks in recent months in London and at a Manchester pop concert held by Ariana Grande.
Mobile phone network EE, which is providing free Wi-Fi on site, is expecting Glastonbury to be the most shared live event of the year, with 40 terabytes of data predicted to be used.
There will be no festival next year, with the dairy farm needing a fallow year every five years to recover.