The Bloom Box—an as yet unbuilt in-home "power plant" designed to be about the size of a mini-fridge—could provide cheap, environmentally friendly electricity to U.S. households within ten years, according to Bloom Energy. Or not.

After days of speculation and hype, the fuel cell company unveiled their plans for Bloom Box mass production—but no prototype—at a press conference today with California governor Arnold Schwarzenegger and former U.S. secretary of state and Bloom Energy board member Colin Powell, among others.

But fuel cell experts say that, based on the information the company made public today, the Bloom Box technology is not revolutionary, nor is it the cheapest or most efficient fuel cell system available.

"It's a big hype. I'm actually pretty pissed off about it, to be quite honest," said Nigel Sammes, a ceramic engineer and fuel cell expert at the Colorado School of Mines.

"It really is nothing new. Go to any [solid oxide fuel cell] Web site and you'll see the same stuff."

Mike Brown, a vice president at fuel cell maker UTC Power—a competitor to Bloom Energy—also wasn't surprised.

"I think we had anticipated just about everything that's on their Web site," Brown said. "But it's nice to at least finally see something" after ten years, which is about how long the Bloom Box has been in development.

In an interview with CBS TV's 60 Minutes Sunday night—which did much to fuel anticipation for today's announcement—K.R. Sridhar, CEO of Bloom Energy, said that, for one thing, the Bloom Box fuel cell system is a much better, or at least more reliable, alternative to solar power as a green energy source.

Video: Bloom Box Segment From 60 Minutes

"The sun doesn't shine on your rooftop 24 hours a day," Sridhar said. "Our box produces electricity continually and reliably."

Fuel cells are devices that combine a fuel, such as natural gas, and an oxidant, such as oxygen, and turn their chemical energy directly into electrical energy.

Big Bloom Box Already in Use

For months now, Bloom Energy has been testing refrigerator-size Bloom Boxes at campuses of major corporations—including Google, FedEx, Wal-Mart, and eBay.

One of these jumbo Bloom Boxes, called Bloom Box Servers, could power a hundred homes, and four of them could power a 35,000-square-foot (3,250-square-meter) office building, Sridhar said on CBS.

Sridhar, a former NASA engineer, said he hopes to begin selling the mini-fridge-size Bloom Boxes within five to ten years. Each of the small Bloom Boxes should be able to power a household, he said.

How Bloom Box Should Work, Basically

At the heart of the Bloom Box will be solid oxide fuel cells—in this case, flat, coaster-size ceramic plates with a secret coating—widely considered by experts to be one of the most efficient types of fuel cells.

Bloom Box plates—already in use in the industrial models—can each power one light bulb, but a stack of 64 of the cells could be "big enough to power a Starbucks," Sridhar said.

Oxygen and natural gas would be fed into the Bloom Box and undergo a high-temperature chemical reaction in the fuel cells to produce electricity, heat, carbon dioxide, and water.

The fuel could be piped in from municipal natural gas systems—much as it is for gas stoves and ovens—or created from biogas or, as in the case of eBay, harvested from natural gas-rich landfills.

No Reason to Doubt Bloom Box Tech?

Friedrich "Fritz" Prinz, a fuel cell expert at Stanford University, said there's no reason to doubt that the Bloom Box works as Bloom Energy's Sridhar claims.

"The solid oxide fuel cell technology they're pursuing is one of the most attractive fuel cell technologies there is," said Prinz, who was not involved in the Bloom Box's development.

Based on the 60 Minutes segment, Prinz said, the design of the Bloom Box appears to be fairly standard and that there was nothing obviously revolutionary about it.

"They didn't reveal any new physics or any new principles, but I don't think they need to do that," Prinz added.

"They just need to take understood and recognized principles in material science and thermodynamics and implement them, and it looks like they've done that successfully.

"Whether they've done it economically, I don't know."

Bloom Box for the Budget Conscious?

The industrial-strength Bloom Boxes now in use cost eBay and other companies between U.S. $700,000 and $800,000. At eBay, Bloom Energy is maintaining the machines under a ten-year maintenance contract.

eBay CEO John Donahoe told 60 Minutes that the five Bloom Boxes installed seven months ago at the company's campus in San Jose, California, now provide almost 15 percent of eBay's electricity needs. Estimated energy savings for the seven months: $100,000.

At that rate, the Bloom Boxes should pay for themselves within three years, Donahoe told the business-news site Fast Company.

A residential Bloom Box should cost around U.S. $3,000, Bloom Energy's Sridhar said—much cheaper than most currently available consumer fuel cell systems.

"Manufacturing these things cheaply is not easy," said Michael Kanellos, editor-in-chief of Greentech Media, a business-news site specializing in green technology coverage and analysis. "ClearEdge initially sold theirs for $50,000, and they had to raise it to $56,000."

Those high prices are due in part to the fact that home fuel cell systems have been built by hand and because low demand hasn't allowed manufacturers to achieve economies of scale—for example to negotiate cheaper prices for raw materials in the way that large production runs allow—said Brown of UTC Power.

Previous systems have also used the precious metal platinum, though Bloom Energy says they've found a way around this—though the details are under wraps—according to Prinz, of Stanford University.

Bloom Box Safe and Solid?

It's also unclear how safe and durable the Bloom Box will be, said UTC Power's Brown. Solid oxide fuel cells must operate at extremely high temperatures, and as a result, they often crack or leak.

For the Bloom Box to become widely adopted by homeowners—who would presumably be nervous about replacing old reliable technology with a new, relatively untested one—the system will need an operational lifetime of about 85,000 hours, or about ten years, Brown said.

There are commercial fuel cells, such as ones made by UTC Power, that can operate continuously for that long, Brown said. Bloom Energy has not disclosed the operational lifetime of its Bloom Box.

It's also unclear as of yet how energy efficient the Bloom Boxes are, Brown said. Fuel cell systems in which both the generated electricity and heat are used can be 90 percent or more energy efficient.

Bloom Energy has not released specific details about the Bloom Box's energy efficiency or specified whether the heat produced by its units can be utilized.

"We didn't see any evidence of thermal recovery, so we assume it's an electricity-only device," Brown said. "If that's the case, it is somewhere between 45 and 55 percent electrically efficient."

That would make the Bloom Box only about 5 to 10 percent more efficient than conventional combined cycle gas turbine (CCGT) power plants, Brown said. Such plants create electricity in two phases: first via gas turbines, then via steam turbines, which take advantage of excess heat generated in the first phase.

Whitney Colella, a fuel cell researcher at Sandia National Laboratories, said the Bloom Box appears to be very similar to fuel cell systems developed by United Technologies Corp. (of which UTC Power is a unit) and FuelCell Energy, Colella said.

"All of them can run on natural gas, and all of them can run on biogas," she said. "The main difference is that the electrical efficiency [of the Bloom Box] is slightly higher" than the other two, at least according to figures posted online by Bloom Energy today.

Bloom Energy's Killer App?

While most experts seem to agree that the current Bloom Box appears to be a fairly standard solid oxide fuel cell system, Bloom Energy has filed patents in recent years that hint at a possible killer feature that could set its future devices apart from the competition, Greentech Media's Kanellos said.

The patents describe a process for taking the runoff of the main electricity generation—carbon dioxide and water—and using it to produce oxygen and a "methane-like fuel," he said.

This would essentially reverse the chemical reaction in the Bloom Box—a possibility Sridhar hinted at on 60 Minutes.

That new fuel and oxidant could be automatically run through the Bloom Box to generate even more electricity—and less waste.

The big Bloom Energy Servers already in use don't currently do this, but if such a reverse-reaction is possible—and it's not clear that it is—then "it would be huge," Kanellos said.