NStar, one of the state’s biggest utilities, said Monday that it will again join the US Department of Energy in co-sponsoring the MIT Clean Energy Prize, a business-plan competition that seeks to showcase entrepreneurship in clean energy.

It is the sixth consecutive year that NStar and the Energy Department have sponsored the prize.

Ton May. Globe file photo by Bill Brett.

Administered by graduate students at the Massachusetts Institute of Technology under the leadership of the Martin Trust Center for MIT Entrepreneurship, the annual competition solicits business plans from teams aiming to develop clean energy solutions that diversify energy resources, increase energy efficiency, and reduce environmental impacts from energy use, said a press release from NStar, which merged last year with Northeast Utilities in a $17.5 billion deal.

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“So far, the MIT Clean Energy Prize has helped launch dozens of new companies that have raised more than $130 million in venture capital and government funding to bring innovative clean energy technologies and services to the marketplace,” Tom May, president and chief executive of Northeast Utilities, said in a statement.

At this point of the 2013 competition, there are 18 semifinalists. Among their proposals are ideas to enhance recycling processes; improve the design of energy storage systems; and reduce emissions from conventional fuels.

These teams will compete for more than $300,000 in prizes, which are scheduled to be awarded at a May 6 ceremony in Boston.