Kelvin Quinnine has shivered through more San Francisco nights than he can count, fog biting through whatever worn-out sleeping bag he pitched onto the sidewalk.

He stood last week on Ellis Street with his latest bag wrapped around him. When a young woman wearing a bizarrely baggy coat walked up to him, he cocked his gray-bearded head sideways.

"It's a coat for the homeless that turns into a sleeping bag at night," 22-year-old Veronika Scott said brightly. She held an edge out to him. Quinnine pinched it.

"Goes down to 17 degrees," Scott said.

"Is that right?" the 43-year-old Quinnine said, face lighting up with appreciation. "That'd be a good thing."

That's just what Scott is hoping other homeless people will think when they see her invention over the coming year.

A design student at the College for Creative Studies in Detroit, Scott conceived her coat-bag for a class project in 2010 - and now she's planning to go national with it.

The Detroit native has watched the homeless population of her economically savaged city explode to more than 30,000 in recent years, and she wants to help.

"What I found, in working at shelters and getting to know homeless people, is that pride is one of their biggest needs," Scott said. "Whether or not they can get into a shelter, they want to be able to take care of themselves."

Part of that pride, Scott learned, meant being able to sleep outside without freezing to death. In Detroit in the winter, a homeless person can die of exposure even in the daytime.

To Scott, the logical thing was to devise a warm coat for the daytime that could also be used as a life-saving blanket at night.

Effective in snow

Scott takes synthetic quilting used in industrial clothing and stitches it to an outer shell of Tyvek, a paper-thin, crinkly material used in mail envelopes and building insulation. Tyvek is so water resistant and heat-trapping that Scott and her friends have been able to sleep in 17-degree weather, in the snow, and stay warm, she said.

The coat-bag weighs only 1 pound and looks like an extra-large coat with a big hood. It costs $7 to $10 to produce.

"I didn't mean this coat to make it seem like it's OK to sleep outside, but our shelters are just so full," Scott said. "And this is something that can help people in the meantime. It's really a basic survival thing."

She presented one of her early prototypes Friday at the Social Capital Markets Conference at Fort Mason, an annual gathering of national entrepreneurs and innovators with an environmental and do-gooding mindset. Amid the admiring oohs and ahs, workshop co-organizer Sarah Brooks said Scott's idea could catch fire even on the less-frigid West Coast.

"I am so impressed with her," said Brooks, director of social innovation for the Hot Studio design firm in San Francisco. "She could totally take this thing to scale. I mean, it's even stylish - I'd wear it."

Over the past year, Scott has handed out 25 coat-bags to homeless people in the Motor City and gathered rave reviews from NPR and newspapers in Michigan. With companies from Dupont to Acme Mills interested in helping her, she said, she's ready to graduate in December and start producing her coat-bags - called Element S (for survival) - in big numbers.

Two versions

She'll start with three employees and intends to hire homeless women. The goal is to sell one type of the coat to non-homeless people for a profit, and to use the proceeds to produce others to give free to folks on the street.

In between appearances at Fort Mason, Scott showed her coat around the Tenderloin to Quinnine and others waiting for the Glide Memorial United Methodist Church soup kitchen to open. The coat was an early prototype, and not as sleek or stylish as her latest version, she said by way of apology - but it went over big anyway.

"Looks good. It gets really cold around here, so this would really help," said Vincent Henry, 51, with a much heavier and less efficient sleeping bag under his arm. "It'd be OK as long as it doesn't get ripped off."