Park Hills, MO., taps into underground energy

Abandoned, water-filled lead mines, dating back to the Civil War are getting a second chance to be useful to communities in Missouri. One such mine, which is located under the town of Park Hills, is being used to heat and cool a new city hall building.

Technology engineered by Union Electric, St. Louis, uses wastewater from the mine to heat and cool the building while trimming operating costs substantially. For example, heating costs thus far have been about half of the previous costs when gas was used. The electric company also predicts a 37 percent reduction in future cooling costs.

Used until the 1960s, the mines in southern Missouri originally provided lead during the Industrial Revolution and Reconstruction Era. Once the mining operations were abandoned, the mines filled with about 70 billion gallons of water, which remain at a constant 57 degrees to 58 degrees.

The electric company designed a water-loop heating and cooling system that allows the mine water to be pumped to a plate-and-frame heat exchanger, a device located o the first floor of the city hall building that removes heat from or adds heat to a water loop.

Lead contamination from the old mine is not a problem, as the water loop is totally enclosed. In addition, the supply and return wells are sealed with Bentonite.

The system’s pumps provide the flexibility to create temperature zones and control comfort for building employees. Nine separate water-loop heat pumps, each of which services a different zone and is stored within its own room, are used.

Each pump has a shut-off valve so it can be repaired without requiring that the entire building be shut down.

The heat pumps work in concert to meet temperature needs throughout the building heating or cooling a zone depending on its thermostat setting. The thermostat setting. directs the water-loop pumps to extract or reject heat from the mine water to heat or cool the zone.

Once the process is complete, the water is returned to the mine via a specially designed return well.

The energy-efficient water-loop system not only saves utility customers money, it protects the environment as well. Such systems exceed federal guidelines for seasonal energy-efficiency rates performance of air conditioning equipment. The systems also conserve energy by heating or cooling zones only when necessary.

In addition, the greenhouse gases and global warming effects of this type of system are very low.