The Addition of a Hydro Pump to the Mathematical Model of OWASA's Reservoir System
Public Deposited- Last Modified
- February 28, 2019
- Creator
-
Baldridge, Janeen M.
- Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering
- Abstract
- The Orange Water and Sewer Authority (OWASA) currently operates a systenn of three reservoirs to supply water to the residents of Chapel Hill and Carrboro. Demand is currently met by electric pumping from University Lake and Cane Creek to the water treatment plant. Stone Quarry is used for backup storage and can be filled by transferring water from Cane Creek via electric pumps. Presently, Cane Creek Reservoir has excess storage capacity. Due to the higher marginal and fixed energy costs associated with pumping from Cane Creek, demand is presently being met by supplying water from University Lake first and then from Cane Creek as needed. If more water could be pumped from Cane Creek at a reduced total electric pumping cost, then more of the excess storage capacity at Cane Creek could be utilized. This can be accomplished by installing a hydropump at Cane Creek to pump water directly from Cane Creek to the water treatment plant free of charge. A hydropump would not incur any electrical charges since it would operate by the force of the water in the reservoir on the turbine of the hydropump. Several million gallons of water would be wasted to drive the turbine; however, the excess water in storage in Cane Creek will be sufficient to meet this requirement. A linear programming model previously developed by researchers at the University of North Carolina at Chapel Hill was revised to include hydropumping capability from Cane Creek to the water treatment plant. A monthly wastage rate for the hydropump was estimated based on typical drawdown patterns of Cane Creek reflected in the calculation of friction losses in the transmission main, static head to pump against, and static head available to drive the turbine. Median inflows were used to predict the savings in total electric pumping costs by the installation of a hydropump for a typical inflow year and twenty years of geometrically increasing demands. Sensitivity analyses were performed on the hydro wastage rate and inflows to determine their effect on savings in electrical pumping costs. The present value (PV) of the savings over the 20-year planning period from 1997 through 2016 was calculated for various discount rates to determine the potential range of savings. The PV of the savings ranged from $256,000 for 20 years of dry inflows to $639,000 for 20 years of wet inflows with a 10 mgd hydropump with median wastage rates. Assuming that the purchase and installation of a hydropump would be less than the lower bound of potential savings, the addition of a hydropump to the OWASA reservoir system would be considered a worthwhile investment.
- Date of publication
- January 1997
- DOI
- Resource type
- Rights statement
- In Copyright
- Advisor
- Lauria, Donald T.
- Aitken, Michael
- Crawford-Brown, Douglas J.
- Degree
- Master of Science in Environmental Engineering
- Academic concentration
- Water Resources Engineering
- Degree granting institution
- University of North Carolina at Chapel Hill
- Graduation year
- 1997
- Language
- Deposit record
- 56f7e058-1c97-4774-9946-7afdcd8e0e36
Relations
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