Hydroelectric at the Mill

The Stockport Mill Inn is located on the west end of the dam at Lock 6 on the Muskingum River - an ideal location for a hydroelectric power plant. When the present mill was constructed in 1906, it was equipped with generators to power its equipment. Those generators  would later provide electricity to the Village of Stockport.

Long before the milling operation ceased in 1997, the generating equipment had fallen into disrepair. It was not until 2006, after more than two years of persistence and hard work, when the Muskingum again powered the Mill.

The original turbines were too corroded to be restored; however one is on display at the Mill. The current turbines are rebuilt Leffel Sampson turbines, like the ones originally used in the mill's grain operations. These turbines are the 'improved' 1913 design and weigh about 6200 pounds each. They are identical to the ones on display, except they have new stainless steel parts (the original turbines used regular carbon steel which easily rusted, hence the corrosion).

The two turbines in use and the one on display were rebuilt from the parts of four old rusting turbines - one came from the Mill, one from Michigan, and two from Wisconsin. The original turbines used wooden bearings made of Lignum Vitae wood, the world's hardest and densest wood. The rebuilt turbines use a thrust bearing in the speed increaser instead, and a guide bearing on the turbine, which is made of Thordon, a special elastomer bearing material.

The turbines can produce a maximum of 134 horsepower each, at the maximum water head at Stockport (the difference in elevation between the upper and lower pool of the dam). The Stockport Dam has a maximum head of about 12.6 feet. Water enters through the trashrack and into the forebay. The trashrack keeps floating logs from the river out of the turbines. The water then moves from the forebay into the turbine pit through a tunnel in the foundation wall which is 8' x 8'. The water then enters the turbines from the side when the 12 gates are opened. The water hits the ‘runner’, which turns and makes the power.

The water is then discharged through the bottom of the turbines, which is called the 'draft tube', into the cavity under the turbine pit. The water then exits through the tailrace (large opening in the South side wall of the Mill) and back into the lower pool of the river. The only way the water can get from the turbine pit to the lower pool of the river is through the turbines and into the tailrace.

The turbines run at about 140 revolutions per minute (rpm). The turbine shaft is connected to the Speed Increaser built by Byrne Gear of Mansfield, OH. The Speed Increaser is a two stage planetary gear box that increases the shaft speed by a factor of 13 times, to 1820 rpm, which is the speed of the generators.

The Generators sit on top of the Speed Increasers and are up this high to be above the 100-year flood level (meaning that flood water has been this high in the past 100 years). The control box is also at this height for the same reason.

The Generators are 'induction' generators that have a  rating of 100 kilowatts, and were built by Marathon Electric of Wausau, Wisconsin. The two generators will produce about 800,000 kilowatt-hours per year. The power output varies according to the water levels in the upper and lower pools, and the difference between the two (the head). The system can produce all the power the Mill needs and the surplus is sold to the local utility (American Electric Power).

This system was the second Distributive Generation system connected by AEP under the new deregulation plan. The turbines each use about 1000 gallons of water per second or 2000 gallons per second for both. That works out to over 17 million gallons of water each day. Even so, this is on average only about 4% of the flow in the Muskingum River.

A computer called a Programmable Logic Controller (PLC) runs the entire system. If the system detects any problems with the generators or the electric grid that it is connected to, the system will switch to an emergency battery power supply, which automatically shuts the gates and stops the turbines.

In 2003, both turbines were severely damaged and fell silent. The damage was caused from debris inside the forebay. The Mill was sold in July 2004. The new owner found the turbines silent and badly bruised.  After several months of evaluating the business situation, she contacted the original engineer on the Hydro Project, who then directed her son-in-law through the rebuild of the antique turbines. Making many parts himself and after months of tedious labor, both turbines were restored to pristine condition.

In November 2006, the turbines, once again, began the mighty job of powering the hotel restaurant at Stockport Mill Inn Hotel and Restaurant.