Ancient Romans in western England bathed in naturally warm spring water of the spa town of Aquae Sulis, now named Bath. Nearly 2,000 years later, the city’s 16th century abbey is now preparing to draw warmth from the still functioning Great Roman Drain to replace the former monastery’s dilapidated Victorian-era heating system.

As part of a $24-million refurbishment, new heating will include water filled pipes buried in the Abbey’s 800-sq-meter floor, which is being rebuilt. “Hundreds of burials over the years have created voids under the floor,” says the Abbey’s project director Alix Gilmer. Stablizing the floor provided “an opportunity to rethink the heating system,” she adds.

The Abbey’s project design firm, BuroHappold Consulting, explored options for tapping energy from warm water flowing along the roughly 250-m-long Roman Great Drain at about 36° C into the River Avon.

Running alongside the Abbey and about 7 m below ground, the drain carries most of 1,200 cu m a day of warm water that rises from springs and boreholes into the Roman bath area, according to Neil Francis, a BuroHappold associate director.

Because of the water’s corrosive nature, the designers ruled out flowing it directly through the heating pipes, says Edward Levien, commercial director of Isoenergy Ltd. The privately owned renewable energy designer/contractor provided early advice to BuroHappold and last May won a roughly $350,000 subcontract to supply and install the system.

“We introduced them to the energy blade idea…(and) helped them do some modeling. They worked out the final solution,” says Levien. The energy blade is basically a thin, stainless steel hollow panel filled with a water/glycol mix. When immersed, the glycol warms to the surrounding water temperature and is then stepped up by heat pumps. For the Abbey, 10 pairs of 3-m-long, 35-cm-deep energy blades will be fitted along an accessible 40 m stretch of the Roman drain. When in operation, they will provide enough water at 55° C to supply Abbey’s under floor heating, according to Francis. Conventional supplementary heating will boost temperatures when needed.

Isoenergy is now preparing technical proposals for installing the blades through a small roadway access hatch. “We worked out what length could be fitted and [BuroHappold] made up a wooden replica,” say Levien. Installation will take two to three weeks this fall with “rolling team” working 20-minute shifts in the hot, cramped drain, he adds.