Overview

This Technote will describe in detail the process for running an Energy Cost Analysis in WaterCAD v8i and WaterGEMS v8i (SELECTSeries 4). It is meant to provide a more detailed description of running the Energy Cost Analyses than the Help Documentation.

Background

There are two levels at which energy costs can be analyzed in WaterGEMS. The tool called "Scenario Energy Cost" calculates energy use and cost for a single scenario while "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.

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.

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. A Power Meter usually corresponds to a pump station. However, in WaterGEMS, 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 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.

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.
• If more thorough analysis is desired, 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.

<h2>Energy Management</h2>

<h2>Energy Pricing</h2>

<h2>Power Meters</h2>

Scenario Energy Cost Analysis

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 Energy Cost manager.

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. When you change the scenario, you will also see the scenario change on the left window as well.

Note: the scenario used must be an EPS run.

The right side of the manager is where you will set up the energy cost analysis and view the results. At the top are some general results fields. Below that is a table with the elements that are included in the energy cost analysis. In the table, you can specify which elements will be included in the analysis and the energy pricing.

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.

The left side of this manager will include any energy pricing definitions. To create a new 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. Start by entering 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.

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.

Click "Close" to return to the 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.

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.

Note: to see general results for all pumps, you can select the item “Pump Usage” in the window on the left; a new table will appear on the right side of the dialog.

Energy Management

Power Meters

Carbon Emission Analysis

Carbon Emission calculation is included with Energy Cost analysis. You can choose the pumps to be included for 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

Product TechNotes and FAQs

Haestad Methods Product Tech Notes And FAQs

External Links

Water and Wastewater Forum

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

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