Ah, Bloom Energy. Is there another company that can get such glowing press without actually saying much?

The secretive company, which has raised $350 million, is creeping out of stealth mode selectively. Last year, it appeared in New York Times articles. A few weeks ago, something appeared in the Atlantic. This week, BusinessWeek gets its turn.

The company doesn't say much, but what it does say is interesting in that the performance it touts seems roughly in line with products already on the market. And these products likely didn't burn through hundreds of millions and eight years in development. From BusinessWeek:

"Stu Aaron, Bloom Energy's vice-president for marketing and product management, confirms press reports about a University of Tennessee trial in which a Bloom box capable of powering a 5,000-square-foot home proved twice as efficient as a traditional gas-burning system and produced 60% fewer emissions."

That matches, to some degree, descriptions Panasonic and ClearFuel Technologies give for their natural gas fuel cells. Their fuel cells are about 35 percent to 40 percent efficient if you just count the electricity they produce, but about 80 plus percent efficient when the electricity and heat can be harvested and exploited. Traditional combined cycle turbines are in the 50 percent range for efficiency.

There are differences. Bloom, allegedly, will sell 25-kilowatt fuel cells, according to sources, although the one Aaron speaks of seems to put out about 5 kilowatts. Panasonic's is a 1 kilowatt system and ClearFuel puts out 5 kilowatts, but wants to move up to 10 kilowatts. Close enough? You make the call.

The raw ingredients are similar too. Bloom takes in natural gas and oxygen and produces energy through a solid oxide process. Again, BusinessWeek:

"For starters, Bloom's system relies primarily on oxygen rather than hydrogen. And instead of requiring expensive precious metals, the fuel cell is built from a cheap ceramic material, sand. That should allow it to be more easily mass-produced, helping cut costs and widen its potential market.

"The ceramic core acts as an electrode. At high temperatures, a hydrocarbon fuel—ethanol, biodiesel, methane, or natural gas—on one side of the cell attracts oxygen ions from the other. As the ions are pulled through the solid core, the resulting electrochemical reaction creates electricity. Though the technology consumes hydrocarbons, Sridhar says, it doesn't involve carbon-releasing combustion, so it emits only about half the greenhouse gases of conventional energy sources."

Panasonic and ClearEdge take oxygen and natural gas and produce the same thing. The underlying technology may be different--it probably is to some degree, and that could affect how well the product develops over time – but the results look at this point to be somewhat similar.

When the company fully comes out of its hidey hole, it should be fun to compare.