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Using the Scenario Energy Cost and Energy Management tools in WaterGEMS and WaterCAD

Product(s): WaterGEMS, WaterCAD
Version(s): 08.11.04.xx and later, 10.xx.xx.xx
Area: Modeling

Overview

This article explains how to use the Scenario Energy Cost and Energy Management tools. The images in this article were taken from WaterGEMS, however the same general workflow applies to WaterCAD as well.

See this article for information on using the Scenario Energy Cost tool in SewerGEMS, SewerCAD and CivilStorm.

Table of Contents

Background

Scenario Energy Cost Analysis

Energy Pricing (Tariff Types)

  • Time of Day
  • Block Rate
  • Block Rate Based on Billing Demand
  • Constant

Viewing Results

Water Power, Wire Power, and Wire to Water Efficiency

Multiple Peak Charges in Energy Management

Turbine Energy Recovery Modeling

Energy Management

Power Meters

Carbon Emission Analysis

Background

There are two levels at which energy costs can be analyzed in the software. The tool called "Scenario Energy Cost" calculates energy use and cost for a single scenario. This tool is available in WaterGEMS, WaterCAD, SewerGEMS, SewerCAD and CivilStorm. "Energy Management" uses the results of multiple Energy Cost scenarios to determine energy costs at a higher level of aggregation to determine the energy cost for pump stations (not just pump-by-pump) for multiple scenarios that can occur over a billing period and determine economic costs such as net present worth of pumping energy. This tool is available in only WaterGEMS and WaterCAD.

The Scenario Energy Cost analysis determines the energy cost by pump for all pumps selected by the user. Pricing for energy cost is set up in the Pricing button in energy costing. Price functions are assigned to individual pumps in energy costing.


For users interested in a more complete energy analysis, running a single scenario may not be sufficient as block rate charges must be determined based on energy use over a complete billing cycle which may contain low, average and high water use periods which should be modeled as separate scenarios. In addition, the scenario corresponding to the setting of a peak demand charge is usually not an average day but some kind of peak condition that should be modeled in a separate scenario. In order to deal with the complexities of block rates, multiple scenarios, aggregation of pumps within a station, and performing present worth calculation, the user needs to use the Energy Management analysis. Such calculations are usually required because of complex tariffs for electric power.

 

 

Because there may be other energy uses at the pump station besides pumping, the user can specify non-pumping energy costs to account four uses such as lighting, HVAC, control systems, chemical feed equipment, etc. These costs are added in on a Power Meter basis. There may also be charges on the power bill that are not associated with individual pumping operations such as taxes, discounts, lump sum surcharges, etc. These can be added in to the overall cost and are referred to as "other costs".

The usual work flow for using the energy cost and energy management analyses may be followed as shown below:

  • Develop EPS scenarios to be used in energy cost.
  • Run scenarios.
  • Start scenario energy cost analysis.
  • Create price functions and optional carbon emission factors.
  • Assign price functions to pumps.
  • Run energy cost for each scenario of interest.

In WaterGEMS/WaterCAD, the user can also conduct a more thorough analysis using the following steps:

  • Close scenario energy cost analysis and start energy management.
  • Create new energy management study.
  • Identify which pump stations/pumps are associated with each power meter.
  • Specify the mix of scenarios to be analyzed.
  • Identify interest rate and number of periods if present worth calculations needed.
  • Compute study.
  • Review results and rerun or create new studies.

In the next section we will go through a detailed step by step guide of how to use the Energy Management and Scenario Energy Cost tools.

 

Scenario Energy Cost Analysis

To open the Scenario Energy Cost tool in WaterGEMS/WaterCAD Connect Edition, go to Analysis > Energy Cost > Scenario Energy Cost.

In WaterGEMS/WaterCAD V8i, the Scenario Energy Cost tool can be opened by going to Analysis > Scenario Energy Cost, or by selecting the Scenario Energy Cost icon in the toolbar.

This will open the Scenario Energy Cost manager as shown below.

 

On the left side of the manager, it will display the current scenario. If you wish to analyze a different scenario, you can choose it from the Scenario pulldown. Note: The Scenario must be an EPS run.

The right side of the manager is where you will set up the energy cost analysis. On the left side of the manager you will see some result fields and specific element options. You can specify which elements will be included in the analysis in the table located on the bottom left of the manager.

After selecting the scenario you will be analyzing, you will need to set up the energy pricing. To do this, click in a cell in the Energy Pricing column and click the ellipsis ("...") button. This will open the Energy Pricing manager.

There are four types of Energy Pricing.

  • Time of Day
  • Block Rate
  • Block Rate based on Billing Demand
  • Constant

Each of these types of Energy Pricing will act differently when you run an Energy Analysis. The Time of Day Energy Pricing will calculate energy cost comparing hours vs. $/kwh.

Note: You can change the units for the energy pricing by right-clicking on the current units and choose "Units and Formatting." This allows you to change the units and the precision that the data is displayed.

Time of Day

The Time of Day Energy Pricing will calculate energy cost comparing hours vs. $/kwh. Energy Supply Rate structure based on a Time of Day Pattern.

To create a new Time of Day Energy Pricing definition, click the New icon in the upper left. On the right side of the manager is where the data is entered. The energy pricing data itself is entered in the lower right of the dialog. First, change the Tariff Type to Time of Day. Then enter the “Starting Energy Price.” If the pricing changes over the course of the EPS run, you can enter that data in the table below "Starting Energy Price."

If the pricing will include Peak Demand Charge, you must place a checkmark in the box beside “Include Peak Demand Charges?” When this is done, the two fields used with this will become available. Enter the value for Peak Demand Charge and Billing Period. The Billing Period is used to convert the peak demand charge, which may be calculated for the month, year, or another period of time, into a daily cost which can be added to the energy cost to obtain the Daily Cost.

Block Rate

Block Rate Energy Pricing will calculate energy cost based on a Block Rate Cost Structure. A Block Rate is a certain price charged for the first definite number of units used and a successively lower or higher price for each additional block used.

„Block rate charges must be determined based on energy use over a complete billing cycle which may contain low, average and high water use periods which should be modeled as separate scenarios.
„
Note: Block Rate cannot work during Energy Scenario Cost Analysis because it must be determined based on Energy use for a complete billing cycle. Block Rate Energy Prices can only be calculated using the Energy Management tool.

Block Rate Energy Pricing will compare Energy Use (kWh) vs. Energy Price ($/kWh)

 

Block Rate based on Billing Demand

Block Rate Energy Pricing will calculate energy cost based on a Block Rate Cost Structure. A Block Rate is a certain price charged for the first definite number of units used and a successively lower or higher price for each additional block used.

Block Rate Energy Pricing will compare Energy Use per Billing Demand (kWh) vs. Energy Price ($/kWh)

Note: Block Rate Energy Prices can only be calculated using the Energy Management tool.

Constant

Constant Energy Pricing will use a constant Energy Price ($/kWh) for the entire model simulation.

If the pricing will include Peak Demand Charge, you must place a checkmark in the box beside “Include Peak Demand Charges?” When this is done, the two fields used with this will become available. Enter the value for Peak Demand Charge and Billing Period. The Billing Period is used to convert the peak demand charge, which may be calculated for the month, year, or another period of time, into a daily cost which can be added to the energy cost to obtain the Daily Cost.

Click "Close" to return to the Scenario Energy Costs manager. When you click a cell in the Energy Price column, the energy price definition that was created will be available for selection.

Viewing Results

Once the energy pricing and the elements to be used in the analysis are selected, the analysis can be run. Note: You must compute the scenario before you can calculate the energy cost.

Click the Compute icon in the upper left of the Energy Cost manager. Once completed, the pumps for which the calculation was run will appear in the window on the left side of the dialog. To view the results for an individual pump, select one of them from the window on the left. A Results table will appear on the right side of the manager.

You can also view the available results fields as a graph by selecting the Graph tab. To select which result field to view, click the pulldown and select the field.

Depending on the item you highlight different results are available. For instance, if you click on the top-most item in the tree, you will see a summary of results that include information on the energy used, the cost, the volume of flow, and the run duration. 

The Pump/Turbine Usage (or Pump Usage for SELECTSeries 6) folder includes this same information, but broken down by the pumps, VSPBs, or turbines that are in the model.

The Pump Time Details folder shows the combined results such as volume, flow, wire power, energy cost and energy usage for all pumps over time. There is also a graph tab that allows you to view these results in a graphical format. 

You will also be able to view these results, plus results for water power, motor efficiency, wire to water efficiency, and cost per unit volume. As with the Pump Time Details, this shows the results per time steps. The results can also be graphed.

Tank costs are accounted for in the Storage item. Peak Energy Demands shows when the peak occurs and any costs that are associated with that.

Water Power, Wire Power, and Wire to Water Efficiency

Many of the results that the Scenario Energy Cost manager generates are relatively straight forward. As an example, Volume Pumped (Incremental) is the volume pumped during that time step. For a few results, such as water power, wire power, and wire to water efficiency, some additional information may be needed. 

Water power is the amount of energy transferred to the water by the pump. This is related to the flow rate and the head added by the pump, in addition to the specific weight of the liquid (typically water). The equation used is: 

Wire power is the amount of energy delivered to the pump motor. Information below will show how this is derived in the program

Wire to water efficiency is the ratio of water power to wire power. This can found by taking the dividing the water power by the wire power. It can also be determined by multiplying the pump efficiency and the motor efficiency.

Note: results like Wire Power indicate the average during the given timestep, whereas the cumulative energy used refers to the beginning of the given timestep. So for example if you want to see how much wire power the pump was using at hour 3.0 (which is essentially 3.0 through 4.0 since the time step is set to 1.0 hour), you would look at the wire power for the hour 3.0 row whereas if you want to see the amount of energy used up until hour 3, you would look at the cumulative energy column for the hour 3.0 row.

If the cumulative energy were not done in this way, then the cumulative energy shown at the end of the simulation (last timestep) would not be quite right. Meaning, if the cumulative energy referred to the energy used at the end of the given timestep, then the 24.0 row (assuming a simulation duration of 24 hours) would actually show the energy used in 25 total hours. (because again, the 24.0 row indicates what happens between 24.0 hours and 1.0 hours later). On the other hand, with the way it currently works, the cumulative energy cost for the last row (24.0 hr) shows the energy used in 24 hours (because it accounts for the wire power from the previous, 23.0 hr timestep, which is the power used from 23 to 24 hours)

In addition to the items above, two other properties are important in the calculation of the energy used by the pump. This is the pump efficiency and the motor efficiency. Pump efficiency is derived based on the efficiency data you enter in the pump definition. 

You can choose to energy a Best Efficiency Point, Constant Efficiency, or Multiple Efficiency Points. Best Efficiency Power generates a curve based on the BEP Efficiency and the flow that the best efficiency occurs. Multiple Efficiency Points allows the user to enter the efficiency for different flow values. Constant Efficiency is a single efficiency value for all flows. Best Efficiency Point or Multiple Efficiency Points would likely yield the best results. 

Motor efficiency is also added in the pump definition under the Motor tab. It is a value set by the user.

Putting it all together

The energy results are determined using the wire power. In WaterGEMS and WaterCAD, the wire power is calculated by first finding the water power using the equation above. Once the water power is determined, this value is used to find the brake power using the equation:

where WP is the water power and ep is the pump efficiency at the given flow that the pump is pumping at. Once the brake power is calculated, this is used to find the wire power using the following equation:

where IP is the wire power and em is the motor efficiency.

With the wire power, the energy used by the pump can be calculated by multiplying the wire power and the time for the energy cost simulation.

Multiple Peak Charges in Energy Management

The software can also be used to manage tariffs with multiple peak charges.

After placing a checkmark in the box, the user can now edit the multiple peak changes. The Peak Charge Type can either be based on Clock Time or Simulation Time. The user will include the start and end times for the peak charge and enter the value for the peak demand change.

With this data entered, multiple peak charges can now be taken into account when running the Scenario Energy Cost simulation.

For information and assumptions on multiple peak charges, see the below Support Solution:

Using Multiple Peak Demand Charges

Turbine Energy Recovery Modeling

Starting with the CONNECT Edition release of WaterGEMS and WaterCAD, it is now possible to model turbines for energy and revenue generation using the Scenario Energy Cost module. Turbines are more often used in HAMMER's transient analysis because of potential transient impact of startup and shutdown, however they can also be modeled in WaterGEMS and WaterCAD as well.

The general setup for turbines will be the same as for pumps.

In the Scenario Energy Cost manager in WaterGEMS/WaterCAD CONNECT Edition, you will now see a Turbine tab. As with pumps and pump stations, you will select Energy Pricing and, if applicable, Unit Carbon Emissions. 

The pricing data you use may be the same as the pump pricing data, depending on the setup of your system. One key takeaway is that turbines are typically used for energy generation. For this reason, the energy data in the turbine energy results is the energy generated, and the cost information is the revenue from the turbine. 

Similarly, the Energy calculations for turbines are the same as pumps (see "water power" section further above), except it is an energy generated and it is multiplied by the efficiency:

Turbine Power (watts) = 1.33 ρ Q h eg et

Where ρ = 62.4 lb/cu ft, Q = turbine flow, cfs, h = head drop across the turbine, ft, 1.33 watts/ft-lb/s, eg = efficiency of generator, et = efficiency of turbine (efficiencies are entered as percent but are used a decimal in the equations.)

If you consider a case like the screenshot below, there is a pump and turbine in parallel. The setup of the model is such that the pump will be filling a downstream tank until the tank is full. The tank will then drain, passing through the turbine back to the reservoir upstream of the pump. The purpose of passing through the turbine is so that energy is generated as water flows into the reservoir. In running the scenario energy cost analysis for this system, you can see that some of the cost for running the pump is recouped by having the turbine in place. 

The energy cost data in the summary table above is a negative value because energy is being generated by the turbine. This allows you to see the net cost that includes the cost of running the pump and the revenue generated by the turbine. Note that turbines are not included in the Energy Management tool, which is discussed below, at this time.

Energy Management

The Scenario Energy Cost Manager is ideal for comparing different scenarios based on energy cost. However, if you would like to do more thorough analysis of Block Rates, Multiple Scenarios, or would like to consider all Energy Use you should open Energy Management tool.

The Energy Management tool will allow you to use Block Rates and compare Multiple Scenarios using a single tool. You will also be able to add other Energy Costs that are not associated with WaterGEMS/WaterCAD elements such as Lighting, HVAC, Taxes, etc.

Below is a list of the main differences between running the Scenario Energy Cost vs. Energy Management:

Scenario
  Energy Costs

Energy
  Management

Detailed Energy Use Results

Summary of Energy Costs

Single Scenario

One or More Scenarios

Cost by Individual Elements
and System Wide

Cost by Individual
Elements, Power Meter, Scenario and Systemwide

Pumps and VSPB’s and Tanks

Pump Stations, Pumps, and VSPB’s

Cost based on Unit Energy
cost or Time of Day and Peak Demand charge

Cost based on all types of Energy Tariffs including Block Rates and all those from Scenario Energy Cost

Considers Pump Energy and Demand

Considers All Energy Use

Considers only Energy Costs

Considers Pump, Non-Pump and
  Extraneous costs

To open an Energy Management Study in WaterGEMS/WaterCAD CONNECT Edition, go to Analysis > Energy Cost > Energy Management

In WaterGEMS/WaterCAD V8i,  click on the Energy Management icon or go to Analysis > Energy Management.

Once you open the Energy Management dialog you will see the following window appear. Click the New button in the top Left Corner to create a New Energy Management study.

Once you create a New Energy Management Study you will see multiple Tabs to enter data. The first Data Tab is the Options tab. Here you are able to set the Billing Period, Calculate Net Present Value, and Scenario Data.

The most useful part of using the Energy Management tool is the ability to compare scenarios in the same study. As shown below you can add and compare Scenarios based on Percentage of Billing Period. The model uses the Billing Period value entered to calculate the Total cost of the study.

Billing Period - Enter the total Billing Period for the Energy Study. EX. (730 days - 2 years)

Calculate Net Present Value - Check to calculate the Net Present Value using the Interest Rate and Number of Years variables.

Scenarios Table - Add all of the scenarios you would like to compare in a single Energy Management Study. In this example, Average Day and Peak Day scenarios are included.

Include in Cost Calculation - Check Box to include or exclude the Scenario from the Management Study.

Percent of Billing Period - Percentage of Billing Period entered above to use the specified scenario for the Energy Management Calculation.

Compute Scenario and Energy - Dropdown menu where you can select whether to recompute the Hydraulic model Data as well as recompute the Scenario Energy Cost. (Note: Leaving this as "None" will save Calculation Time.)

Use for Peak - Check Box to use the specified Scenario for Peak Demand Charge.

 

 

Power Meters

An important concept in energy management analysis is that of a "Power meter". A Power Meter is the basic unit that is billed by an electric utility which is used as the basis for the calculation of power bills. A Power Meter usually corresponds to a pump station. However, in WaterGEMS/WaterCAD, a pump station is a collection of pumps serving a single pressure zone. Therefore, if a pump station building has a single electric service but has a set of Low, Medium and High service pumps, for WaterGEMS and WaterCAD hydraulic calculations, it is three Pump Station elements but for energy management, it corresponds to a single Power Meter. The figure below shows how a single power meter can include multiple pumps and pump stations in a single building.

Power meters are used during Energy Management which is associated with pumping energy use, and also non-pumping energy use such as HVAC systems, SCADA systems etc. To enter data for a Power meter click on the Power meter Icon on the main toolbar inside the Energy Management dialog box.

  

The Power Meter Dialog box looks like the following. There are Tabs to enter Pump Data, Non-Pumping Energy, and Notes. To create a New Power Meter click on the New button in the top left corner of the Power Meter window.

Pumps Tab - Enter the Pumps corresponding to the specified Power Meter.

Non-Pumping Energy - Enter other cost data associated with the Power Meter such as HVAC, Lighting, Control Panels, Security Systems, Temperature Control Systems, or any other Extraneous data.

Notes - Enter any Notes or Instructions associated with this specified Power Meter.

Once all the Power Meter data is complete you can exit the Power Meter Dialog. In the Power Meter tab, enter the applicable Energy Pricing for the Various Power Meters. Once all of the data for the Energy Management tabs has been entered you are ready to calculate the Energy Management. Click on the Calculate button on the Taskbar.

  

 Once the Calculation process is complete you will get numerous detailed results. The Results Summary section will give you detailed results about the Energy Management study.  In the Results Summary you can compare results based on the entire billing period.  An example is shown below:

 

  

Carbon Emission Analysis

Carbon Emissions can also be considered when running a Energy Cost analysis. You can choose the pumps to be included in the analysis at the same time as you select which pumps to include with the energy cost analysis.

In order for the carbon emission analysis, you need to enter a Carbon Dioxide Emission Factor to complete the analysis. To do this, click in a cell under the column header Unit Carbon Emission. This will open the Unit Carbon Emission dialog. Create a new definition by select the New icon, then enter your value for the carbon dioxide emission factor. Click “Close” to return to the Energy Cost dialog and choose the new unit carbon emission definition from the pulldown menu.

When you select the Compute icon in the upper right, it will now calculate the carbon emissions from the pump.

To view the results, select “Pump Usage” directly under the scenario name in the window on the left. In the table, scroll all the way to the left. The Carbon Emission results field will be the last column.

See Also

Using the Scenario Energy Cost tool in SewerGEMS, SewerCAD and CivilStorm

Product TechNotes and FAQs

OpenFlows Product Tech Notes And FAQs

User Notification "The Billing Period must be greater than zero"

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