Adelaide City councillor Robert Simms has been named as the replacement for retiring Greens Senator Penny Wright.

Mr Simms, 31, is a former adviser to senators Scott Ludlam and Sarah Hanson-Young.

He said the renewable energy sector would be critical to tackling the state's unemployment issues.

"I'll be working very hard for the best interests of our state and to stand up for progressive values," he said.

"Like so many Australians I have been horrified by the Abbott Government's attacks on public health and education, the attacks on the most vulnerable in our community and the attacks on the environment.

"The Green's positive agenda for the future of our country is more important than ever and I'm looking for in playing a part in promoting that in Canberra."

Greens Leader Richard Di Natale in a statement welcomed the party's newest member.

"Robert will be an exceptional asset for our party and the nation, bringing a proven track record in representing communities and a strong and positive vision for the future," Dr Di Natale said.

Senator Wright, who was elected in 2010, revealed plans to step down in July to deal with an illness in her family.

She said she was proud of what the party had achieved so far.

She said her proudest achievements included introducing "the concept of justice reinvestment" to South Australia to "reduce the disproportionate rate of Aboriginal people in our jails".

"I am also proud of advocating for the mental health needs of rural people throughout Australia," she said.

Mr Simms is expected to take his seat in the Senate in October.