Calculations

The system features a graphical Formula Editor that allow users to define a set of formulas using mathematical functions referring to user input variables (such as Fuel Usage) and Attributes of the Material(s) used (like the CO2 Emissions Factor). The formulas can be setup to calculate any Metric, such as Scope 1, 2 or 3 Emissions and Energy Usage.

A "Calculation" consists of:

Inputs which may need to be provided to calculate emissions
e.g. amount of Fuel used for a vehicle.
Formula(s) used to calculate the emissions.

Within the formulas, the system supports different types of variables, which will need to be referred to as follows:

Input.[name]: any Input which needs to be provided by a user
Source.[name]: used to retrieve an attribute from the Emission Source
Material.[name]: used to retrieve an attribute (like an Emissions Factor) of the Material associated with the Emissions Source
Constant.[name]: any defined Constant

To record Calculations & Formulas, navigate to ...Emissions Management Administration Calculations.

Definitions for Calculations

Field

Explanation

Name

Be clear with naming the individual calculations so it can be easily identified when linking them to the individual Emission Sources.

For example:

Emissions from Vehicle Usage
Emissions from Electricity Production
Emissions from burning fossil fuels

NOTE:
Calculation Name must be unique across the system.

A calculation can have multiple Formula Inputs that can be used in the formulas and these have to be defined individually

Identifier

Variable Name used in the formula with the prefix "input"

For example: If the variable name is "Fuel", it must be defined as "input.Fuel" in the formula

NOTE:
Cannot have Mathematical function names in the Identifier

Name (Optional)

Will be used as Input label in the Data Entry Screens where users are prompted to provide values. If left empty, the system will use the Identifier as the Label instead.

Emissions_Data_Input_Sample

NOTE:
Name is mandatory for Emission Data Imports

Description (Optional)

This will be used as a "tool-tip" during data input

Emissions_Data_Input_Sample_Tooltip

Target Unit

This is the unit of measure that the formula(s) expects the input value in. The system will allow users to enter in other units of the same type and convert the entered value into this Target Unit (using Unit of Measure Conversion) before passing the value into the formula.

e.g. if the Target Unit is defined as "gallons", the users will be able to enter data in "litres" from Data Entry Screens

note_awesome

NOTE:
If new Formula Inputs are created, please ensure to save the Calculation record before using the Formula Input in the Formulas

A Formula should be defined for each required Emission Metric

Date Active

Date the Formula comes into effect

Date Inactive (Optional)

Last date the Formula is valid

note_awesome

NOTE: Date Ranges
Whenever a user enters new input data for a given time period, the system will use the active date range to determine which formula to use to calculate emissions in that time period.

Formula Code

The formula builder allows users to create mathematical formulas using any of the following operators/functions:
+, -, *, /, SQRT, log, log10, exp, use of brackets ()

Formulas can use variables to retrieve information from other parts of the system, such as Material attributes, Emission Factors and User Inputs.

A range a variables can be referred to within a formula. To view the list of all currently available variables and help around the formula builder, click the "i" icon beneath the formula field.

An example formula referring to two variables:

formula_code_sample_formula_valid

The indicator beneath the input field depicts if the code entered

Has a mathematically valid syntax
Refers to valid variables

Testing the Formula
The "calculator" icon beneath the formula field can be used for testing the formula. Once a formula is built, the user can test it to check / verify if it behaves the intended way by providing dummy values for all inputs and variables.

formula_code_test

Formula Text

This is a read-only field depicting the formula in its pure text form

Output Metric

For each formula, an Output Metric must be selected - this is the type of Emission which is being calculated