Fuel Class

Description:	fuel for a thermal generating unit
Detail:

See also Fuel Property Reference for a detailed list of properties for this class of object.

Unit and Energy Density

Fuel data can be input either:

• In the default units, which is controlled by the Units of Data screen accessible from the Settings menu on the ribbon; or
• In custom units defined by the Unit property optionally combined with the Energy Density property.

See the Commodity Unit topic for details on how Unit and Energy Density work together.

Generation and Start Fuels

The Fuel class is used to represent all types of fuel used for generation or generating unit start up:

• Fuels are associated with generation using the Generator Fuels collection and for start up via the Generator Start Fuels collection.
• Fuels can produce Emissions.
• Fuels can be arbitraged in Markets.

Note that the collections Generator Fuels and Generator Start Fuels are one-to-one by default. To model multiple fuels for either generation or start-up you should change the collection to one-to-many using Configuration in the user interface.

Availability

The property Fuel Units is used to switch a Fuel in/out of a running Model.

The property Generator Is Available switches a Fuel in/out of use by a Generator.

Cost

The cost of the Fuel is set by either:

• defining the Fuel Price property with or without any Tax; or
• by associating the Fuel with one or more Fuel Contract objects.

You can define a different dispatch price for the fuel by using the Shadow Price property. In this case the Price inputs are used for accounting only.

Emissions

Broadly speaking, there are two sources of emissions associated with Fuel use:

Combustion emissions

Emissions produced when the Fuel is burned in a Generator.

Fugitive emissions

All other emissions e.g. those resulting from mining, transportation or leaking of the Fuel into the atmosphere.

There are many emission types that are commonly modelled, including but not limited to Carbon dioxide (CO₂), Sulfur dioxide (SO₂), Nitrogen oxide (NO_x), and Mercury (Hg). These are all modelled using the Emission class. Depending on the source and type of emission it might be more appropriate to equate emission production directly with Fuel Offtake or with Generator Generation or a combination. For example, fugitive emissions are usually modelled as a simple function of the Offtake whereas the best approach to modelling combustion emissions depends on the emission type, with CO₂ being a function of Offtake but mercury being more closely related to Generation.

You associate a Fuel with an Emission by adding the Fuel to the Emission Fuels collection, and then defining Emission Fuels Production Rate. For Generation related emissions define Emission Generators Production Rate.

Constraints

Simple limits can be defined on fuels using the properties Max Offtake and Min Offtake and their hour/day/week/month/year variants. Fuel Contract objects have similar constraints representing maximum offtake as take-or-pay commitments.

Other Constraints can be defined on Fuel Offtake or Emissions Production associated with the Fuel.

Gas-Electric Model

The Fuel class works with the integrated gas-electric function. Fuel objects provide the pricing information for gas. Fuel objects link to the gas network with the Fuel Gas Nodes membership. This membership indicates which gas nodes the Fuel can be purchased at. A Generator connects to the gas network with the Generator Gas Node membership but should also define a Generator Fuels membership.

See Gas Modelling for more details.

Stockpiles

A Fuel stockpile (inventory) can be modelled, so that any Offtake causes a Withdrawal from inventory. The stockpile is modelled by the simulator whenever you define Opening Inventory or Max Inventory with Delivery. Inventory is tracked through time during the simulation in much the same way as a Storage. Various limits can be placed e.g. Max Withdrawal and charges modelled including Delivery Charge, Withdrawal Charge, Inventory Charge and Reservation Charge. These inventory costs can be accumulated by a Company via the Fuel Companies membership.

Reporting

Fuel reports total usage as Offtake as well as the Total Cost and volume-weighted Price. The simple Time-weighted Price can also be reported. Costs are based on the Total Price if defined, otherwise on the Shadow Price.

Fuel-related costs are passed through to Generator objects and reported in Generator Fuel Cost and/or Start Fuel Cost. Generator SRMC is based on the Fuel Shadow Price.

Fuel stockpile levels are reported as Opening Inventory and Closing Inventory.

Fuel objects are reported by Company automatically based on the combination of Generator Fuels and/or Start Fuels and Generator Companies. This does not include inventory costs however, but these can passed to Company reporting if you define Companies membership in input.