Olafur Eliasson's Little Sun lights up Tate Modern

Saturday saw the start of Tate Blackouts, a showcase for artist Olafur Eliasson's Little Sun project in Tate Modern. During the Blackout evenings, visitors can explore the darkened Surrealism galleries after closing time using the lamp developed by Eliasson and the engineer Frederik Ottesen.

The Little Sun is a lightweight, solar-powered lamp that Eliasson hopes will change the lives of people in off-grid areas around the world. In the video above, he explains the thinking behind the project.

Tate Blackouts take place every Saturday night until 18 August, 10.15pm-midnight. Entry is free but visitors must purchase a Little Sun at £16.50. Visitors can also learn more about solar energy in a special exhibition on the third floor and practice 'light graffiti' using the lamp.

• Here's a round-up on Storify of some of the Twitter feedback to Saturday's first Tate Blackout.

Olafur Eliasson was talking to Eleanor Mills

• Royal Academy of Arts