PEAKING STORAGE TANKS FOR WATER SUPPLY SYSTEMS¹

Abstract

Construction of a "peaking storage tank" may reduce the operational cost of municipal water in the availability of a time-of-use energy rate. A peaking storage tank is used for storing water that is pumped from wells or other sources of supply during off-peak periods when energy costs are less for use during periods of on-peak water demand. The optimal size of a peaking storage tank is that which results in the minimum total cost, which includes both the storage construction cost and the cost of operation of the pumps. The operational cost for a given time-of-use rate is determined by help of a pipe network simulation model solved by the Newton-Raphson technique and a dynamic programming optimization model. A more simplified method is also introduced. Analyses show that low off-peak energy costs make the construction of peaking storage tanks economically attractive and reduce on-peak energy use, which results in electrical load leveling.(KEY WORDS: pipe network, peaking storage tank, water supply, time-of-use, dynamic programming, Newton-Raphson.)

Zeta potential distributions in particle treatment processes

“…For town water supply systems and off-peak pumping, the typical value of regulating capacity needed is a fraction of 0.25 -0.50 of tbe maximum daily demand (Fuertes et al 1996;Mays 2000)-A review of the methods used to determine the storage capacity in town water supply systems is reported by Lauria (1983) and Sabet & Helweg (1989).…”

“…This allows pumping stations to operate near optimum energy efficiency (Mays 2000;Pulido-Calvo et al 2002). Likewise if time-of-day energy tariff is available, the reservoir can be used for storing water that is pumped during off-peak hours to be used during peak hours (Sabet & Helweg 1989;doi: 10.2166/aqua.2006 Operating pumping facilities include the following: 1) Flow adjustment to roughly match demand and minimize use of storage; 2) Constant rate operation to simplify management and reduce demand charges; 3) Off-peak pumping to take advantage of timc-of-day energy pricing. Alternative 1 has a high operation cost and a low storage construction cost.…”

“…The preferred combination is that which results in tbe minimum total cost, which includes both pump costs and the amortized reservoir construction costs. The addition of a regulating reservoir is not economically feasible if it results in an increased total cost (Sabet & Helweg 1989). ln this paper, a model is proposed to determine a regulating reservoir's capacity and establish tbe scheduling of a pump system to give the minimum total cost for any particular demand.…”

“…Sabet & Helweg (1989) proposed the addition of a 'peaking storage tank' to reduce the operational cost of municipal water wbere time-of-use energy tariffs are used. The peaking storage tank stores water pumped from the source of supply during off-peak periods when energy costs are less than tariffs charged during periods of peak water demand.…”

Optimal operation of water pumping stations

“…Therefore, in a water distribution system, the control of a reservoir or tank's operation reduces the overall operational cost as well as improves its reliability. Tanks are used for storing water that is pumped from resources during off-peak period (i.e., low-energy tariff) and used for supplying water to consumers during peak electrical demand (i.e., high-energy tariff) [5].…”