Assolar-energy fans gathered at the Solar Power 2007 conference in Long Beach, Calif., last week, one man was hitting them up for support for a more controversial technology.

He called it coal-based solar and claimed to represent CoalSol, a non-existent company with a "cutting edge technology" using coal furnaces to supplement solar panels.

The motto, "Sunshine & Coal Working Together" - along with a picture of a smiley-faced sun on a lump of coal - graced the cover of the brochure that Charlie Todd, founder of Improv Everywhere (motto: "We Cause Scenes") handed out in the exhibit hall.

"People say it's not green," Todd told Solar Power 2007 attendees as part of the prank, which was captured on video. "What could be more green than [shoveling coal,] getting back to the Earth?"

He added the technology is green because the pollution is "not going to get on you; it's going to go out in the air."

As the dirtiest of the fossil fuels, coal is definitely controversial. Even as coal-fired plants around the world continue to grow, utilities have seen a backlash against the cheap form of energy.

Energy company TXU Corp., for example, enraged environmentalists last year when it applied to build 11 new coal-fired plants. Private-equity firms Texas Pacific Group, Kohlberg Kravis Roberts & Co. and Goldman Sachs cut eight of the planned plants when it bought TXU for $45 billion in February.

Earlier this month, utility East Kentucky Power Cooperative agreed to pay a Clean Air Act fine related to its coal-fired plants and New York Attorney General Andrew Cuomo subpoenaed five energy companies to determine whether plans to build coal-fired plants would result in previously undisclosed financial risks (see Coal Under Fire).

In light of all this controversy, Todd - whom Sharp Solar hired to pull the prank on the exhibit-hall floor - said putting smokestacks on people's roofs was "the worst thing I could think of."

Why did Sharp do this?

"Definitely Sharp indicated there's not a lot of comedy in the industry; it's a little dry," Todd said. "It's important to poke some fun."

The video aired at Sharp's party Tuesday, and was met with laughter and applause.

"Hey, sign me up," one attendee told him with a smirk.

"It's a great growth industry. You should get involved," Todd said, handing him a flyer without missing a beat.

Todd said he gave out 50 to 100 brochures in one day. Sharp hasn't yet decided whether it will post the video on its web site.

But oddly enough, Todd said 90 to 95 percent of the people he talked to at the conference believed CoalSol was real.

"They thought it was a bad idea, but they didn't think it was a prank. And some thought it was an OK idea," he said, with a laugh. "Maybe they were being nice or thought they could sell me some solar panels."