# Carriers ESDL allows you to describe a list of carriers with parameters that are used inside your model There are two types of carriers: * Commodities * Energy carriers They serve different purposes but can be combined in the same model if required. Choices depend on the scope of the model. The `Carriers` class is a collection of the abstract class `Carrier`. The `Carrier` class can have the following parameters: * an `id` paramater that is used for referring to carriers. * a `name` parameter to describe the name of the carrier. * a `cost` paramater of type GenericProfile (allows both a fixed value as a profile that changes over time). * a `dataSource` parameter to document the origin of the information you're using The `Commodity` and `EnergyCarrier` classes are subclasses of `Carrier`. ## Commodity The `Commodity` class is an abstract class, with the following subclasses: * ElectricityCommodity: can be used for electricity. If required a distinction between different voltage levels can be made (LV, MV, HV, ...). A `voltage` parameter can be specified. * GasCommodity: can be used for natural gas, biogas, carbon dioxide (CO2), hydrogen (H2), and so on. Distinction is done based on the `name` parameter. * HeatCommodity: can be used for heat. If required a distinction between different temperature levels can be made (LT, MT, HT, ...). A `temperature` parameter can be specified. * EnergyCommodity: can be used for describing energy balances (expressed in Joules, independent of the specific commodity). ## EnergyCarrier The `EnergyCarrier` class has the following parameters: * an `energyContent` parameter: allows the specification of the energy content of the energy carrier * an `energyContentUnit` parameter: the unit of the `energyContent` paramater * an `emission` parameter: allows the specification of emission values per energy content * an `emissionUnit` parameter: the unit of the `emission` parameter * an `energyCarrierType` parameter: an enumeration with options `UNDEFINED`, `RENEWABLE`, `FOSSIL` * a `stateOfMatter` parameter: an enumeration with options `UNDEFINED`, `SOLID`, `LIQUID`, `GASEOUS` This class is based on the [list of energy carriers](https://www.rvo.nl/sites/default/files/2018/03/Nederlandse%20energiedragerlijst%202018.pdf) as published by RVO: ![](https://2468807995-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LEUR-fboF2eOWi4I9zf%2F-LXs3jyn4gHrEZe5jV6F%2F-LXs3khrgfHXS2k_bodJ%2FRVO-emission-energycarriers.PNG?generation=1549276484295790\&alt=media) An example ESDL file with this information looks like: ```markup ```