Calculation engine for etmodel PRO, etmodel LIGHT and Energymixer.
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Energy Transition Engine (ETE)

This is the source code for the Calculation Engine that is used by the Energy Transition Model and its various interfaces (clients).

It is an online web app that lets you create a future energy scenario for various countries. This software is open source, so you can fork it and alter at your will.

ETEngine does not contain an easy-to-use frontend for creating and editing these energy scenarios; that role is instead fulfilled by separate applications such as ETModel, ETFlex, and the EnergyMixer, which each use ETEngine's REST API for manipulating and calculating scenarios.



The ETE is released under the MIT License.


Installing ETEngine on a local machine can be a bit involved, owing to the number of dependencies. Assuming you can run a 'normal' rails application on your local machine, you have to follow these steps to run ET-Engine.

  1. Install the "Graphviz" library

    • Mac users with Homebrew: brew install graphviz
    • Ubuntu: sudo apt-get install graphviz libgraphviz-dev
  2. Install "MySQL" server

    • Mac: Install latest version using the Native Package (choose the 64-bit DMG version)
    • Ubuntu: sudo apt-get install mysql-server-5.5 libmysqlclient-dev
  3. Clone this repository with git clone

  4. Run bundle install to install the dependencies required by ETEngine.

  5. Create your personal configuration files from the samples with

    cp -vn config/database.sample.yml config/database.yml
    cp -vn config/config.sample.yml config/config.yml

    Then make any changes -- particularly to the database configuration -- as you see fit.

    • Probably set "standalone" to true in "config/config.yml"
  6. Clone a copy of ETSource –– which contains the data for each region:

    1. cd ..; git clone
    2. cd etsource; bundle install
    3. rake decrypt –– to decrypt the energy balance data files
    4. Edit "config/config.yml" and enter the ETSource directory into the "etsource_export" and "etsource_working_copy" options –– or leave at default if possible.
  7. Create the database you specified in your "database.yml" file, and

    1. run bundle exec rake db:setup db:seed to create the tables and add an administrator account –– whose name and password will be output at the end –– OR
    2. run bundle exec rake db:create to create your database and bundle exec cap staging db2local to fill your database with records from staging server
  8. You're now ready-to-go! Fire up the Rails process with rails s or use Pow.

  9. If you run into an dataset error, check out this explanation on CSV files

Technical Design


The ETEngine uses heavily caching of calculated values by using the fetch function that stores and retrieves calculated values. This has some drawbacks, but is necessary to keep performance up.


When the user starts a new scenario, the user has to choose the end_year and the area for which this scenario applies. This can/should not be altered later.

Present and future

The ETEngine uses two graphs that store all the data: one for the present year and one for the future year. In this sense, the ETengine is a 'two state' model: everything is calculated twice: once for the start year, and once for the end year. It is important to note that ETengine therefor does not calculate intermediate years. An exception to this is Merit, a module for ETengine (that can also be used independently which contains time series at a one hour resolution for one year.


A user can alter the start scenario with the use of inputs. Every input has a key and a value can be sent to ETEngine. For example a user can tell ETengine:

number_of_energy_power_nuclear_gen3_uranium_oxide = 2

This means that the user wants to 'set' the number of nuclear power plants to 2 in his/her current scenario.

The current set of inputs can be found on ETSource.

Every times the user requests some output, all the inputs that have been touched by that user for that scenario are applied again. The order in which they are applied can be controlled if necessary.

The priority of every input defaults to 0, and can be set a manual value (e.g. 100) on inputs which need to be executed first. For example, an input with priority=100 gets executed before an input with priority=99, etc...

This is someting to keep in mind when designing your input statements.

Competing inputs

For example, when you have two inputs:

  • input A: update attribute X to have value 1
  • input B: update attribute X to have value 2

The outcome of this X will be 1 or 2 depending on the priority of these inputs (if they both have no priority or the same priority), this will be randomly determined.

Complementary inputs

For example, when you have two inputs:

  • input A: update attribute X to increase with 1%
  • input B: update attribute X to increase with 2%

Then the outcome of the X will be 1.01 * 1.02.


The user can request output from his/her scenario with the use of gqueries. A gquery always returns the present and the future output value, although there are exceptions to this.

E.g. when the user sends the dashboard_co2_emissions query to ETEngine, it will receive the following feedback:

  • present: 123
  • future: 456
  • unit: MJ

A gquery is nothing more then a stored statement. These statements are written in our own language called the Graph Query Language (GQL) and a recent list can be found on ETSource.

Auto-reloading your changes to etsource

Sometimes you want to play around or tweak some gqueries. Then, you don't want to create commits every time and import them. Because when you are satisfied, you'll probably have 10 commits, that needs to be cleaned up, squashed.

You can add the option etsource_live_reload: true in your config.yml file.

Change queries, inputs, datasets, gqueries, inputs or topology directory in your et_source_export folder, and Etengine reloads your changes automatically!

B.t.w. By default your etsource_export directory is not under version control. In order to gain the advantages of Git, just point etsource_export to the etsource directory, either by using a symbolic link or using the same directory in your config.yml file. But be carefull NOT to use the interface's 'import' action on /etsource: that will delete/overwrite your etsource_export directory!


GQL Functions

Converter methods


Password for all the screencasts below is quintel.

GQL Console

GQL Docs

How to use this documentation.

GQL Console and ETsource

How to work with different etsource directories, make changes and load them in the gql console.

ETsource: Create a new basic etmodel

We build a new etmodel with 3 converters from scratch. This helps you understand how the etsource works.

The result you can find in: etsource/models/sample