Ever since Democrats took over Congress at the start of the year, greening efforts have been at the forefront of talks on how best to manage the Capitol complex.

Much of that talk has centered around the Capitol Power Plant, the century-old institution that provides heating and cooling to the Capitol and more than 20 surrounding buildings — and also accounts for about 30 percent of Congress’ carbon dioxide emissions.

But, quietly, the plant has moved toward a greener complexion with the completion of an expansion project designed to regulate temperatures in the complex more efficiently.

Expansion spaces went online in the late spring in the West Refrigeration Plant, built in the 1970s to help chill new Congressional office buildings. The expansion is expected to better provide the chilled water that is used to cool the Capitol complex, said Eva Malecki, a spokeswoman for the Office of the Architect of the Capitol, which oversees the plant.

Among the highlights of the expansion, slated to cost $85 million, are new chillers. Those chillers are more energy efficient than previous equipment that had been serving the campus, some of which was a half-century old, Malecki said.

House Administration Chairman Robert Brady (D-Pa.), whose committee has jurisdiction over the power plant, is pleased that the expansion space is online, a spokesman said Tuesday.

“Its development and operation are consistent with efforts to introduce more energy- efficient equipment and processes to the Capitol and reduce our overall carbon footprint,” Brady spokesman Kyle Anderson said.

With the expansion, space at the facility increased by about 16,500 square feet. The project, which began in spring 2003, was designed to increase the chilled water production of the plant by about 23 percent and also enable central operation of the chillers.

As of now, the plant heats and cools about 16 million square feet of space, but it also will need to serve the 580,000-square-foot Capitol Visitor Center when that facility opens next year.

With the installation of the new chillers, the plant is expected to be able to maintain current cooling operations until at least 2025.

Energy reduction efforts have brought carbon dioxide emissions from the power plant down over the past several years. Between fiscal 2003 and fiscal 2006, the facility cut its electricity consumption by 6 percent and fuel energy consumption by 12.3 percent, according to the AOC.

Still, concerns linger about the sustainability of the plant, which greening experts have singled out as a top priority for bringing Congressional carbon emissions down. In fiscal 2006, the plant produced 102,659 metric tons of emissions, the Government Accountability Office found.

The expansion project predated a report made in conjunction with Speaker Nancy Pelosi’s (D-Calif.) Green the Capitol initiative. The study offered recommendations to make the House carbon-neutral by the end of the 110th Congress and also improve the environmental sustainability of chamber operations.

Thus, the power plant expansion did not factor into the initial evaluation or the plan, said Jeff Ventura, a spokesman for House Chief Administrative Officer Dan Beard, who oversaw the study.

But the report, released in June, did offer a slew of suggestions for improving overall plant operations.

Topping the list was a recommendation to have the plant burn only natural gas, a move that is expected to reduce the plant’s carbon emissions by 30 percent from 2006 levels. While the House has approved $2.75 million to help initiate the switch, the money remains tied up until the Senate passes the legislative branch appropriations bill.

In the greening report, the CAO’s office noted that making the plant as energy efficient as possible will take years to plan, finance and implement. It called for Congress to take an active role, with committees that oversee Congressional activities stepping up and reviewing how to best run the facility.

But in the meantime there are other steps the plant can take to reduce its carbon impact, the report noted.

For example, reducing boiler steam pressure output and monitoring energy-efficiency performance can improve steam production efficiency at the plant. Steam and chilled water distribution systems can be improved by upping maintenance on steam traps, adjusting steam delivery pressures to follow heat load requirements in Capitol buildings and determining the need for new insulation of distribution lines, which would reduce heating and cooling losses.