# Overview¶

ficus consists of several model entities. These are exterrnal imported/exported commodities, processes and storages. Demand and intermittent commodity supply are modelled through time series datasets.

The objective of the model is to supply the given demand with minimal costs. The main restriction is the power balance of every commodity for every timestep. Commodities are goods that can be imported/exported, generated, stored and consumed. They are represented by their power flow (in kW) per timestep.

The timebase of the model can be configured depending on the timebase of the given data (demand). For all commodities and entities then the same timebase is used.

## External imported/exported commodities¶

External imported/exported commodities are goods that can be imported or exported from/to “external sources”, e.g. the elctric grid. The prices for buying/selling for every timestep are given by a timeseries.

Additional a demand rate with an extra time interval can be given, to consider peak demand charges. A Demand-Rate-Factor Timeseries allows to raise, reduce or turn off the demand rate for specific timesteps to consider special tariff systems.

Exterrnal imported/exported commodities are defined over the commodity itself (commodity), for example (elec) or (heat).

## Process¶

Processes describe conversion technologies from one commodity to another. They can be visualised like a black box with multiple inputs (commodities) and multiple outputs (commodities). Conversion efficiencies between inputs and outputs for full load (and optional partload) are the main technical parameter. Fixed costs for investment and maintenance (per capacity) and variable costs for operation (per output) are the economic parameters.

Processes can be assigned to a Process Class, which allows to consider addtitional fees/subsidies for inputs or outputs of this class (e.g. subsidies for pv generation).

Processes are defined over the tuple (process , number, commodity, direction) that specifies the inputs and outputs for that process. The number variable is needed, if more than one identical process is given For example, (chp, 1, gas, In), (chp, 1, electricity, Out) and (chp, 1, heat, Out) describes that the process named chp (combined heat and power) has a single input gas and two outputs electricity and heat.

## Storage¶

Storage describes the possibility to deposit a deliberate amount of energy in form of one commodity at one time step, and later retrieving it. Efficiencies for charging/discharging and self discharge depict losses during input/output. Storage is characterised by capcities both for energy content (in kWh) and charge/discharge power (in kW). Both capacities have independent sets of investment, fixed and variable cost parameters to allow for a very flexible parametrization of various storage technologies from batteries to hot water tanks.

Storage is defined over the tuple (storage, number, stored commodity). For example, (Li-Ion Battery, 1, electricity) represents a Li-Ion Battery that can store and retrieve energy in form of electricity.

## Timeseries¶

### Demand¶

Each commodity (demand commidty) may have one timeseries, describing the (average) power demand (kW) per timestep. They are a crucial input parameter, as the whole optimisation aims to satisfy these demands with minimal costs from the given technologies (process, storage, external import/export).

### Intermittent Supply¶

A timeseries normalised to a maximum value of 1 relative to the installed capacity of a process using this commodity as input. For eample, a wind power timeseries should reach value 1, when the wind speed exceeds the modelled wind turbine’s design wind speed is exceeded. This implies that any non-linear behaviour of intermittent processes can already be incorporated while preparing this timeseries.