It started with a drawing on a napkin. Now, AirLoom Energy is raising $12.7 million in fresh funding, TechCrunch has learned.

The funding came from 21 investors, according to a regulatory filing that does not list the names of the backers. The company did not immediately respond to a request for comment.

The Wyoming-based startup has a novel approach to wind power. Rather than placing massive turbines atop 100-plus meter tall towers, it attaches vertical blades to cables that run along an oval-shaped track just 25 meters (82 feet) above the ground. The company is hoping to produce electricity at $13 per megawatt hour, which would be more than 50% cheaper than traditional onshore wind.

The idea for the racetrack configuration was inspired by kiteboarding, founder Robert Lumley’s hobby. He first sketched the concept on a napkin during a wind energy conference in Berlin.

Much of the projected cost savings comes from AirLoom’s lower profile. Today’s wind turbines get more efficient as they get larger, but the massive towers and blades are challenging to transport, sometimes requiring up to a year of advance planning. AirLoom’s parts are smaller, making them easier to manufacture, move and assemble once on site.

AirLoom last raised a $4 million seed round in November from Bill Gates-founded Breakthrough Energy Ventures, Lowercarbon Capital and MCJ Collective. At the same time, it also appointed a new CEO, Neal Rickner, who had previously served as COO of Makani Energy, the Alphabet company that sought to use kits to harvest wind energy.

In November, Rickner told TechCrunch that the company’s next step is to refine the technology to the point where it can build a 1-megawatt pilot, which he had targeted for 2026. The new funding is likely to help finance that project.