Three Maine early-stage companies have been named semifinalists in a nationwide accelerator and competition for startups in the clean-energy space.

The three Maine companies selected for the Cleantech Open Northeast region are Delta Dewatering, an environmental services company in South Portland that provides innovative technology solutions for the purpose of cleaning water; F.E. Wood Natural Energy, a Portland company with plans to build a wood-pellet fuel company; and Surge Hydro, a Belfast-based company that wants to use innovative technologies to leverage the country’s underutilized hydroelectric infrastructure.

Surge Hydro recently was the only Maine startup accepted into MassChallenge, a high-profile, Boston-based accelerator.

“It’s not surprising that more Maine companies are gaining regional and national traction for energy and environmental leadership,” said Jeff Marks, director of the Environmental & Energy Technology Council of Maine, otherwise known as E2Tech.

Maine ranked 18th in the country in the 2016 U.S. Clean Tech Leadership Index – a data-based comparison of all 50 states among 70 technology, capital, and policy indicators, according to Marks. In 2014, the state’s ranking was 29th, he said.

The Cleantech Open is the world’s largest accelerator for startups working in the areas of environmental science and clean energy. The six-month program provides startups with extensive mentoring, training, business clinics, and access to investors and capital. Since 2005, more than 1,000 startups have participated in its annual accelerator and mentorship program in the United States. These businesses have raised a total of more than $1.2 billion.

The chosen semifinalists will later compete in a national competition and the chance to win $250,000 in funding.

Eight Maine companies participated in the Cleantech Open Northeast in the previous four years, including two — Pika Energy and Rapport — that moved onto the national finals after besting entrepreneurs in New England, New Jersey, New York, and Pennsylvania.