The following information identifies some of the basic requirements for the site work. The intent is to develop the existing site to integrate the Powerhouse with the existing and planned park uses.
2. Barrier Free Access to Main Level
3. Parking, Sidewalk & Landscape
4. Spillway Access Barrier
5. Donor Recognition
FLUME & SPILLWAY REQUIREMENTS
The southeast section of Moore Lake relies on the Powerhouse flume to maintain a flow of water through the lake. Without this flow the section of lake would become stagnant and fill with algae.
Whether the Powerhouse is utilized for power generation or not, the existing intake structure, piping and valves should be maintained to accommodate this flow of water.
With the continuing development and paving of natural areas, the amount of surface water runoff into Pettibone Creek is much greater and increases the potential for flooding. Having the existing flume and equipment in good operating condition would provide the ability to control the excess water during flood conditions and relieve the pressure on the other dams and structures on Pettibone Creek.
In the Pettibone Creek Dam #1, National Dam Safety Program Inspection Report, prepared by Wade Trim Associates for the Village of Milford, Dated August 1998, one alternative that was mentioned was to utilize the existing flume during high water conditions to divert water around the dam.
Based on the design drawings, the flume is constructed of ½” thick welded steel pipe installed in 40 foot sections. It is supported by concrete saddles every 12 feet and 12” diameter, 20 feet long, concrete piles in the marsh area south of Moore Lake and across the upper mill pond. There are six concrete anchors and five expansion joints to allow for thermal expansion. There is a 36” vertical vent pipe connected to the flume at the midway point which is now located in the parking lot of Rite Aid. There is also an 8” pipe connection and valve pit just north of Commerce Street for a mill water supply to the manufacturing building.
The Village of Milford has inspected the flume by video camera and found it to be in good condition. The only problem identified was the accumulation of sediment at the lower end of the flume.
The following is a summary of the recommended work associated with the flume and spillway:
1. Intake Trash Rack Replacement
2. Concrete Repair at Intake, Spillway and Powerhouse
3. Handrail Repairs
4. Intake Valve Repair and Maintenance
5. Flume Sediment Removal
6. Gate Valves and Flange Installation
7. Piping and Tank Prep and Insulation
POWER GENERATION REQUIREMENTS
Since the goal of the Powerhouse Restoration Committee is to preserve the building, and the flow of water through the flume should continue to maintain the quality of Moore Lake, it makes sense to explore the feasibility of utilizing the infrastructure and water flow to generate electricity.
The process in which to activate a power generating facility is a complicated one and requires the approval of several governing bodies; including the Federal Energy Regulatory Commission (FERC). This report will present the general requirements of this process along with specific items of work.
Originally, the station contained two vertical, Francis type turbines, one 75 KW and one 62.5 KW capacity, manufactured by the James Leffel Company. A Francis turbine is typically defined a having a runner with fixed vanes, to which the water enters the turbine in a radial direction, with respect to the shaft, and is discharged in an axial direction. Principal components consist of the runner, a water supply case to convey the water to the runner, wicket gates to control the quantity of water and distribute it equally to the runner, and a draft tube to convey the water away from the turbine.
Both of the original turbine runners, shaft and wicket gates have been removed. However, the water supply case, and draft tube are still intact. The mechanical energy derived from the turbines was converted to electrical energy through two generators located on the main level, which have also been removed, therefore requiring replacement. For the purposes of this investigation, only one of the turbines would be replaced with original type equipment and the generator would be installed on the lower level to allow for other uses of the main floor.
Estimation of Potential Power Generation
As previously mentioned, the amount of power that can be generated by a hydroelectric plant is determined by the total head pressure or elevation of the water and the available water flow. Since the head pressure remains relatively constant, the determining factor is the flow of water.
In order to accurately estimate the power generation capacity of the existing hydroelectric station, an analysis must be performed involving the hydrological and mechanical features of the site, along with the expected operation mode.
Originally, the hydroelectric station was operated as a “reservoir plant”. In this situation the upstream reservoir capacity is used to augment the flow to the turbines, during periods of low stream flow. This type of operation is typified by a reservoir whose water surface elevation is extremely variable, being lowered as additional flow is required, and raised during periods of excess stream flow. While this type of system was acceptable at the time of construction, to operate the station as a reservoir plant today would be unacceptable due to the environmental considerations and numerous upstream residents who rely on a fairly constant stream level.
An alternative to the “reservoir plant” is the “run-
Since the flow of Pettibone Creek is essentially split for 3400 feet between the Powerhouse flume and the creek supplying the mill ponds, it will be assumed that half of the total flow would be available in each branch.
If the smaller of the original two generating units were operating at full load, the required water flow can be determined by the following formula:
Electrical Power (KW) = Q x H x Ep
Where: Q = Flow of water (cfs)
H = Available head (feet) 50 for the Pettibone Station
Ep = Plant efficiency assumed to be 86%*
11.8 = Conversion constant
* Based upon recommended values from “Feasibility Studies for Small Scale Hydropower Additions” – a guide manual, U. S. Army Corps of Engineers.
62.5 KW = Q x 50 x .86
Flow Required for Rated Output, Q = 17.15 cfs
Vertical Francis type turbines can only be operated within a certain percent of their
design flow. At flows below this level, the turbines are unable to provide the required
rotational speed, and at flows greater than this level, the turbine will begin to
operate in a “run-
Therefore, the minimum flow required to operated the turbine would be:
Q (minimum) = Q (rated) x .5 = 8.6 cfs
From the State of Michigan, Department of Natural Resources, Fisheries Division, Special Report, titled Huron River Assessment, April 1995, Table 14, Pettibone Creek is identified as having a Median daily discharge of 22 cfs (cubic feet per second). If half of this median daily discharge were allowed to flow through the turbine, then the median electric power output would be:
Median Electrical Power Generated (KW) = Q x H x Ep
= (22 x ½) x 50 x .86
= 40.08 KW
If the power generated was used to supplement the power consumed at the Village well house and iron removal plant, located in Central Park, then the daily median cost savings could be calculated as:
Median Daily Cost Savings = 40 KW x 24 hours/Day x .0853 $/KWH *
= $81.88 / Day
*Current energy charge for Municipal Water Pumping at 195 N. Main St.
It should be noted that this is only an estimate of the average cost savings and the actual amount would depend on the seasonal rainfall and resulting flow of water in Pettibone Creek, as well as the length of time the turbine/generator was on line.
If the turbine and generator were operating at rated capacity for one day, the cost savings would be:
Maximum Daily Cost Savings = 62.5 KW x 24 hours/Day x .0853 $/KWH
= $134.09 / Day
Powerhouse Restoration Proposal Continued