As many as 25 countries including France, Australia, Guyana , Bangladesh and Sri Lanka are scheduled to participate in the summit.
ISA is the brainchild of Prime Minister Narendra Modi, initiated in January 2016. It is a treaty-based international body for promotion of solar energy in alliance with 121 countries, which are fully or partially between the Tropics of Cancer and Capricorn.
The primary objective of the alliance is to work for efficient exploitation of solar energy to reduce dependence on fossil fuels.
Dignitaries from across the world have made their way to the national capital to attend the summit.
On Friday, the President of Guyana, Brigadier David Arthur Granger and the Vice President of Suriname, Michael Ashwin Satyandre Adhin arrived in Delhi. On Saturday, many leaders from Africa arrived here to participate in the one-day summit.
Bangladesh President Abdul Hamid and Sri Lankan President Maithripala Sirisena have also arrived.
The summit will focus on various aspects of promoting solar energy in 121 countries associated with the ISA like credit mechanism, crowd funding and sharing of technology breakthroughs.
India has set an ambitious target of having 100 GW of solar energy capacities by 2022. It is close to achieving 20 GW in the current fiscal itself and plans to auction 30 GW solar projects each in 2018-19 and 2019-20.
(With inputs from agencies)