Silicon Valley’s fuel cell maker Bloom Energy continues to add customers looking to power part of their data center operations with distributed, cleaner power in California. On Thursday, the U.S. division of Japanese telecom giant NTT, NTT America, said it will install five Bloom fuel cells at one of its data center facilities in San Jose, Calif.

Nine-year-old Bloom Energy sells an industrial-sized fuel cell (which looks like a large refrigerator) that uses a chemical reaction to produce electricity. The Bloom Boxes suck up oxygen on one side and fuel (usually natural gas or biogas) on the other side, and produce power on-site for companies in a more efficient and less carbon-intensive manner than using the grid (depending on what fuel the company uses).

NTT America says it will use biogas (gas generated by decomposing organic material) produced at a California dairy farm as fuel for the Bloom fuel cells. That means NTT’s fuel cells won’t emit as much carbon as many of the Bloom fuel cells that are being powered by natural gas. Updated: NTT America has corrected the source of the biogas to two landfills in Pennsylvania.

Five Bloom fuel cells have a capacity of 500 kilowatts, which is the equivalent power for about 500 houses or five large office buildings. Each Bloom fuel cell costs around $700,000 to $800,000 before subsidies, so NTT is spending a couple million dollars on the installation.

Data center operators are looking for ways to make their facilities more energy-efficient and greener as a way to cut growing energy bills and also to highlight company sustainability. While fuel cells are still not commonly used to power data centers, Bloom has been slowly growing its customer list of telcos and Internet companies that want to use the Bloom boxes for part of their data center operations.

Earlier this month, AT&T said it plans to install a whopping 7.5 MW worth of Bloom fuel cells (that’s 75 fuel cells) at 11 AT&T offices in California. AT&T said it would use the fuel cell power for data centers as well as administration offices and facilities that house network equipment.

Fuel cells likely won’t be used as a main, or stand alone, power source for a data center. As we pointed out on GigaOM Pro (subscription required) last year, data centers need a power source that is so-called “five nines” (99.999 percent). Google has said the Bloom Box it was using on its campus had an availability rating of 98 percent, which translates into around seven days of downtime a year: no good for a stand alone power source for a data center running web sites that can’t go down.

Bloom has also found success with data center operators in California because state subsidies make the Bloom boxes a lot more economical in California. Customers in the state include Google, eBay and Adobe .

Top image is NTT’s installation, and the bottom is the installation at Adobe.

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