Co-generation, of course, means that the fuel consumed is used for more than one purpose. Usually it means the steam left over from generating electricity, say by burning coal, is used to heat nearby buildings. Consolidated Edison in New York delivers co-generation steam to 100,000 buildings in New York; MIT is heated by a co-generation facility.
Feldman is applying co-generation principles to his power plant located inside 60 Hudson St., where Western Union's telegraph lines used to reach out to the rest of the world and where one of the largest concentrations of Internet connections are now based. With natural gas plentiful and cheap, he is installing two Caterpillar Solar Mercury gas turbines to generate electricity. Instead of generating steam, however, the hot exhaust gases from the turbines will be used to drive absorption chillers used as cooling equipment for the data center.
Some of the waste heat will be used to heat the building in winter; during the summer, some will be dumped as well.
It sounds counter intuitive, but 900-degree turbine exhaust gases can be used to run a cooling system. The gases boil a refrigerant can be used to cool nearby premises when those gases condense into liquid again. Condensation is a cooling process and takes heat out of the environment in which it occurs. It's the opposite, in a sense, of your refrigerator's condenser starting to run to compress a refrigerant, dumping heat out the back of the refrigerator. The refrigerant then circulates the compressed gas through a heat exchange coil in the refrigerator, where the gas expands, taking away heat. No compressor or other moving parts needed in DataGryd's absorption chiller system; the turbine exhaust gases do all the work.
The absorption chillers reduce the amount of air conditioning needed to keep the data center cool. At many facilities, cooling represents 25% of the total power consumed, second largest energy consumer after running computer equipment itself, so DataGryd is assured of lowering its electricity needs by at least 20% through reduced cooling need and other energy saving maneuvers.
Heavy Amperium cables at 60 Hudson will carry the electricity from the turbines to the racks of servers for another savings. Amperium is a product of AMSC, formerly American Superconducting Corp., which is known for its brass-laminated steel cables that transport 100 times more power with less resistance than copper lines.
[ Power isn't the only thing to think about when putting together a data center. Read How To Choose Best SSD For Midsize Data Centers. ]
DataGryd has designed into the building a distribution grid that operates at high voltage from generators close to the server racks. Power is transmitted over Amperium cables at 13,200 volts, then 480 volts, finally stepped down to 220 or 120, because less electricity is lost when it's transmitted at high voltage. Ten percent or more electricity is typically lost to resistance between the standard power generating plant and the computer that's going to use it. That reflects what happens to power on transmission lines hundreds of miles long from Canada or Ohio to New York. Feldman's longest distance from generator to server rack is about 400 feet, he noted in an interview.
Feldman won't know exactly how well the design is working until he has more experience in operation. The first turbine representing phase one of the project goes on line around Thanksgiving. The second will be in operation by Thanksgiving 2013. Total energy consumption may be reduced as much as 30% compared to simply drawing power off the city's electrical grid.
The power not used in his new data center will mean "seven million pounds of carbon emissions" that were not sent into the air each year, compared to the standard data center, Feldman said. That total will be nudged a little higher as Feldman sells his surplus power into the Consolidated Edison grid in New York. He's not trying to convert his power generation into a profit center but he expects to regularly export about 15% of what's generated, leaving his data center with a comfortable margin. That's power that Con Ed doesn't have to generate itself.
Like other data centers, Feldman must install an uninterruptible power supply that provides a few minutes of battery power as backup diesel generators start up during any kind of outage and takeover the load. And like other data centers, he must test the ability of the generators to start up on cue each month. He's figured out if he times his diesel test at the same time that Con Ed experiences peak demand, he can export three megawatts of power to the city's grid at a time when it most needs it. But such a maneuver must be coordinated with the giant utility.
Feldman says his cost per unit of electricity produced will be "substantially less" than the going Consolidated Edison going rate, thanks in part to assured supplies and low prices on natural gas. Plus, his customers will not be faced with Con Ed's add-on, delivery charges. But just how much less, he won't know until he has operational experience.
"We are in construction now. We've gone through the process of getting a long list of approvals from the Department of Buildings, the Landmark Commission, the Environmental Protection Agency, the Fire Department, the Office of Sustainability, the Department of Transportation," recalled Feldman.
Putting together his data center's odd combination of elements has been a lot like TV's Iron Chef candidates being given an odd list of ingredients and told "to make a gourmet meal out of them," he said.