Using EPANET for Irrigation System Design

EPANET FOR PRESSURIZED PIPE SYSTEMS

WHAT IS IT? “EPANET is a Windows computer computer program that performs extended period simulation of hydraulic and water-quality water-quality behavior within pressurized pipe networks. A network can consist of pipes, nodes (pipe  junctions), pumps, pumps, valves and storage tanks or reservoirs.”

WHO DEVELOPED IT? Water Supply & Water Resources Section of the Environmental Protection Agency (Lewis Rossman)

WHERE CAN I GET IT? EPANET AND MANUAL CAN BE DOWNLOADED AT http://servicecenter.kcc.usda.gov/sfw_e_l.htm

ADVANTAGES OF USING EPANET: • SURVEY DATA CAN BE READ INTO PROGRAM (A LITTLE EDITING IN EXCEL) • ALL CALCULATIONS ARE DONE INTERNALLY AND QUICKLY • GRAPHICS, SUMMARY OUTPUT TABLES • EASY TO CHECK OTHER PERSONS WORK • CHANGES ARE QUICK AND EASY • UNLIMITED NETWORK SIZE AND COMPLEXITY (LOOPED SYSTEMS, ETC.) • ERROR CHECKING AND WARNINGS DISADVANTAGES OF USING EPANET: • HAVING TO LEARN THE PROGRAM (CAN TAKE SOME TIME).

IT HAS USDA CCE CERTIFICATION

Program components • Lets check out the various components with a simple example. •  A gravity pipe running from a diversion to a pond

EXAMPLE PUMPED SYSTEM PROBLEM We are installing a pump in a stream to pump water to an on-farm irrigation system. After analyzing the on farm system, we have determined that the peak crop water requirement is 350 gpm and the pressure requirement at the turnout is 60 psi. The location of the pump and pipeline have already been surveyed. PVC pipe will be used. Pump site elevation = 3500 ft

Determine the: 1. Pump selection to deliver the flow and pressure to the turnout 2. Pressure rating of the pipe 3. Daily electrical costs to run the pump

GPS Survey Pro Exported Text File

1 2 3 4 5 6 7 8 9 10 11  base

802.2700 815.1200 824.7000 1058.0700 1161.3700 1216.9900 1555.9200 1928.6900 2293.3500 2682.3300 2933.5500 5000.0000

1458.6700 1467.9300 1467.9400 1524.3300 1589.3400 1665.9100 1880.0600 2009.7200 2066.4500 2123.1800 2252.8400 5000.0000

100.0343 110.0037 110.2987 113.2476 115.3981 117.2178 119.3127 120.4318 125.2222 130.3264 150.5632 500.0000

stream pump intake pump discharge gs gs gs gs gs gs gs Smith TO base

EPANET NETWORK INPUT FILE (*.inp) [TITLE] EXAMPLE PUMPED SYSTEM EPANET-ENGINEERS MEETING 2005 [JUNCTIONS] 1 100.0343 2 110.0037 3 110.0037 4 113.2476 5 115.3981 6 117.2178 7 119.3127 8 120.4318 9 125.2222 10 130.3264 11 150.5632

[COORDINATES] 1 802.27 2 815.12 3 824.7 4 1058.07 5 1161.37 6 1216.99 7 1555.92 8 1928.69 9 2293.35 10 2682.33 11 2933.55

1458.67 1467.93 1467.94 1524.33 1589.34 1665.91 1880.06 2009.72 2066.45 2123.18 2252.84

Import file

WATER TO WIRE EFFICIENCY

Example: TDH= 200 ft Q = 400 gpm Pump Efficiency (from curve)= 75% Pump Motor Efficieny (assumed) = 85% NO VFD drive to pump (set motor rpm = 3600) WHP = (200 x 400)/ 3960 = 20.20 hp BHP = 20.2 / 75% = 26.94 hp EHP = 26.94/ 85% = 31.69 hp Water to wire Efficiency (pumping plant eff.) = 75% x 85 % = 64%  Assume you draw t hrough the meter 30 hp (22.38 Kw ) for 1 day.  Assume the cost of electricity = $0.05 /Kw-hr  DESIGN PARAMETERS TDH = 200 ft Q = 400 gpm

To run the pump for 24 hours: 22.38 Kw x 24 hours x $0.05/Kw-hr = $26.86

  m   s  t  e   S  y    i  o  n   a  t   g     i   r   I  r    T  o

BHP

Meter 

  H  P    W

EHP

VFD

PUMP MOTOR

 .    f    f   e    %    8    9      5    9

 .    f    f   e    %    0    9      0    8

   P    M    U    P  .    f    f   e    %    0    8      0    6

From Berkeley Pump Selection Software, Q = 350 gpm, TDH = 215 f t Power, hydraulic (water) : 18.97 hp Power, brake : 26.90 hp Minimum recommended driver rating set @ : 30.00 hp / 22.37 kW

Electronic Variable Frequency Drives (VFD’s) “control the speed and torque of an AC electric motor by varying the frequency and voltage of the electricity supplied to the motor. They replace inefficient, energy robbing controls such as control valves, pressure reducing valves, etc.”

Why Use VFD’s? From Pump Affinity Laws (constant impeller diameter): P1/P2= (N1/N2) 3 P = Power N= Speed (rpm) Initially we have a 10 hp pump running at 3600 rpm to meet demand and pressure requirements in our piping system. Demand declines and the VFD lowers the pump speed to 3200 rpm. What are the power savings?

P1 = 10 hp N1 = 3600 rpm N2 = 3200 rpm P2 = 7 hp An 11.1% speed decrease results in a 30% decrease in power Consumption! Small speed decreases result in large energy savings.

The Real Cost of Electricity-Whats On Your Bill!

Example Bill

**Demand Charge is based on the highest average 15 minute power usage for the billing period. Demand charge kicks in at > 15 kw usage. (pacific power)

Pump Example

Summary of Pipeline/Irrigation Projects Using GIS Survey--EPANET 1) Conduct the GPS survey of water levels, pumps, pipelines, sprinkler locations, etc. 2) Export the data from Survey Pro to a text format. 3) Read the exported text file into Excel and manipulate it into The EPANET input format. 4) Import the nodes into EPANET 5) Draw the pipe network and begin the simulation

Sprinkler Simulation EPANET

Emitter-Sprinkler Orifice Equation

q = C py q = emitter flow rate C = discharge coefficient p = pressure y = pressure exponent y =

0.5 for sprinklers/nozzles

Calculate the Emitter Coeficients for the Varying Nozzles For the rainbird 30H (SBN-3) with plug @ 50 psi: 9/64” nozzle, C = q/p 0.5 = 4.1 gpm/ 500.5 = 0.580 5/32” nozzle, C = 0.707 11/64” nozzle, C = 0.863 3/16” nozzle, C = 1.018

Change the emitter coefficient in EPANET to change the Sprinkler/nozzle.

Questions ?