Clean-energy startups are booming as oil companies are giving them more attention and cash in a bid to speed up their own green transitions. Investors want oil producers to accelerate a move away from fossil fuels by selling cleaner energy and developing technology to eliminate climate-warming gases. Entrepreneurs proposing to harness energy from offshore wind and waves, generate hydrogen from waste gas and build fuel storage networks from old wells are attracting attention from Big Oil. Oil companies are often partnering with and investing in new enterprises that have started at clean-energy incubators. Some oil firms have set up their own incubators and venture teams to find and fund greentech. U.S. oilfield services firm Halliburton works with eight clean-tech fledglings and is recruiting more for an in-house startup accelerator that provides each $100,000 in seed money. Baker Hughes is collaborating with incubator Greentown Labs to get a window into emerging technologies and provide advice to startups. Oil majors Eni SpA and Repsol SA have approached U.S. clean-tech ventures through investment arms. There are roughly 20 clean-tech U.S. incubators tracked by the Electric Power Research Institute. But that number likely undercounts the total because of their rapid growth, said Julia Travaglini, vice president of marketing for Greentown Labs. "We're seeing across-the-board an uptick in clean energy" incubators, added Lindsay Schuenke, director of content at the International Business Innovation Association, which works with business development groups.