By Julie Shapiro
LOWER MANHATTAN — City Hall is going off the grid.
After nixing plans to build rooftop solar panels, officials are in the final stages of designing a massive fuel cell that will generate more than enough electricity to power to historic building, a city architect said this week.
"It's a means of providing more affordable energy to the building, using a chemical reaction that does not involve any harmful emissions to the environment," Lawrence Gutterman, an architect with Beyer Blinder Belle, said during a presentation to Community Board 1 Thursday night.
The fuel cell, housed in a large, green-painted box on the north side of City Hall, will produce 100 kilowatts of electricity by using natural gas to heat two chemicals inside of it, Gutterman said.
An earlier plan to put solar panels on the building's roof was deemed too expensive and would have powered only half of one floor of City Hall.
The fuel cell, on the other hand, will quickly begin saving the city money on electricity costs, Gutterman said.
It is part of a major renovation of City Hall that has gone far over budget, after unexpected problems added extra work to the job.
The metal box containing the fuel cell will be 45 feet long, 9 feet wide and 8 feet high and will be located on the northeast side of the building, along a pathway that is not accessible to the public, Gutterman said.
The fuel cell will emit a constant hum of about 70 decibels, which Gutterman likened to the volume of several people having a conversation. It will also give off carbon dioxide, which is why it can't be buried underground.
CB1's Landmarks Committee had objected to the city's plans for highly visible solar panels on the landmarked City Hall building, and members were glad to hear the panels were off the table.
"It's better than a whole bunch of solar panels," said Roger Byrom, chairman of the Landmarks Committee. "[But] it's regrettable [the fuel cell] is such a large size."
Gutterman said the city also investigated tapping into geothermal energy, but the massive infrastructure would have required ripping up most of City Hall Park and destroying many of the trees — which would have been expensive as well as unpopular.
CB1's Landmarks Committee gave an advisory vote of 7 to 1 in support of the plan for the fuel cell.
The Landmarks Preservation Commission, which has the final say, will review the design at a public hearing June 21.