Once the Antares study has been prepared for the Antares-Xpansion simulation, by the introduction of virtual nodes as described in Prepare the Antares study, the user must use the candidates.ini file to characterize the investment candidates.
Characterization of investment candidates in candidates.ini
Not all links in the Antares study are by default investment candidates. The candidates are defined in the candidates.ini file, which must be located inside the user/expansion/ directory of the Antares study folder: antares-study-folder/user/expansion/candidates.ini.
Overview of the candidates.ini file
Each investment candidate is characterized by the following properties:
- `name` (mandatory): name of the investment candidate (:warning: must not contain spaces and unique),
- `link` (mandatory): link on which there is a capacity investment,
- `annual-cost-per-mw` (mandatory): investment cost, per year and per MW,
- `unit-size`: size, in MW, of a single investment unit (e.g. one group of 300 MW),
- `max-units`: maximum number of units that can be built,
- `max-investment`: maximum capacity in MW that can be invested in the candidate,
- `already-installed-capacity`: capacity in MW that is already installed on the investment candidate's link,
- `direct-link-profile`: name of a file that links the invested capacity and the available capacity for the direct way,
- `indirect-link-profile`: name of a file that links the invested capacity and the available capacity for the indirect way,
- `already-installed-direct-link-profile`: name of a file that links the already installed capacity and the available capacity for the direct way,
- `already-installed-indirect-link-profile`: name of a file that links the already installed capacity and the available capacity for the indirect way.
The format is a standard .ini and should follow this template:
In Antares-Xpansion, the investment decisions only affect the capacity of the Antares' links. Investment in physical generation capacity is done with virtual nodes as described in Prepare the Antares study.
Details of the parameters
name
String, mandatory. Specifies the name of the investment candidates. Antares-Xpansion uses this name in the output and the logs.
:warning: This field must not contain spaces!
link
String, mandatory. Defines the link of the Antares study candidate for investment, whose capacities (direct and indirect) will be modified by Antares-Xpansion. The syntax of the link name includes the names of the two Antares nodes that are connected by the link, separated by "-", for example:
Node names that include spaces or dashes are not compatible with Antares-Xpansion. The origin area corresponds to the first in the spelling order. The same link may contain several investment candidates (see this section).
annual-cost-per-mw
Float, mandatory. The decimal separator is the point. It defines the fixed cost annuity of the investment candidate (in €/MW/year). Depending on the type of candidate, the fixed cost annuity can include:
- Fixed operation and maintenance costs,
- An investment cost annuity.
max-investment
Float. Represents the candidate's potential, i.e. the maximum capacity (in MW) that can be invested in this candidate. If this parameter is set, the invested capacity can take any value in the interval \( [0, \texttt{max-investment}]\).
unit-size
Float. Defines the nominal capacity (in MW) of the investment candidate's units.
max-units
Integer. Corresponds to the candidate's potential in terms of number of installable units. If the parameters max-units and unit-size are set, then the invested capacity is necessarily a multiple of unit-size from the set:
$$ \{0, \texttt{unit-size}, 2 \cdot \texttt{unit-size}, … , \texttt{max-units} \cdot \texttt{unit-size}\}. $$
!!! Warning The definition of an investment candidate must necessarily include either (i) a maximum potential in MW (max-investment) or (ii) a unit size in MW (unit-size) and a maximum potential in number of units (max-units).
already-installed-capacity
Float. Corresponds to a capacity that is already installed on the investment candidate's link. If Antares-Xpansion finds that the investment in this candidate is economically relevant, the new capacity will be added to the already installed capacity. The transmission capacities initially indicated in the Antares study are not considered in the already-installed-capacity parameter and are overwritten by Antares-Xpansion.
[in]direct-link-profile
String, specifying the name of a file. This file must be located in the user/expansion/capa/ directory of the Antares study. It must contain at least one column of 8760 numerical values (the decimal separator is the point), see Figure 5. Multiple columns are used in order to use different data depending on the Monte-Carlo year in process, see details here. When only one column is specified, the same profile is used by Antares-Xpansion for all Monte-Carlo years of the Antares study and all assessed capacities.
!!! Remark Both files direct-link-profile and indirect-link-profile must contain the same number of columns.
The [in]direct-link-profile makes the link between the invested capacity and the capacity that is actually available, in the [in]direct directions of the Antares link, for the 8760 hours of the year. More details are given in this section.
The [in]direct-link-profile can be used for example to represent the maintenance of a generation asset via a seasonalized power outage, or the average load factor of intermittent renewable generation, defined at hourly intervals.
File user/expansion/candidates.ini:
File user/expansion/capa/capa_pv.csv: 
Figure 5 – Example of a file containing a load factor profile in the Antares-Xpansion format.
already-installed-[in]direct-link-profile
String, specifying the name of a file. This file must be located in the user/expansion/capa/ directory of the Antares study and has the same format as a [in]direct-link-profile file, see Figure 5. The already-installed-[in]direct-link-profile makes the link between the already installed capacity and the available capacity, in the direct and indirect way of the Antares link, for the 8760 hours of the year. More details are given in this section.
!!! Note The same file can be used for [in]direct-link-profile and already-installed-[in]direct-link-profile of one or more candidates.
Link between invested capacity and capacity of the Antares study
!!! Note For simplicity, we often refer to [already-installed]-direct-link-profile and [already-installed]-indirect-link-profile link profiles as just [already-installed]-link-profile in the sequel.
The parameters link-profile, already-installed-capacity and already-installed-link-profile are used to define the link between the capacity installed by Antares-Xpansion, the already installed capacity and the truly available capacity in the Antares study, hour by hour and in both directions of the link, following the relationship presented in Figure 6.
Figure 6 – Link between the capacity invested by Antares-Xpansion, and the capacity available in the Antares study.
By default, the link-profile and already-installed-link-profile contain only 1's, thus assuming perfect availability of the invested capacity.
The parameters link-profile and already-installed-link-profile are conventionally used to:
- Take into account an NTC profile on an interconnection, possibly seasonalized and having a different impact on the direct and indirect directions of the link. It is possible to specify a different NTC profile for each Monte-Carlo year.
- Represent the maintenance of a thermal generation asset by considering a reduction of its power, possibly different according to the season (see Figure 7),
- Model renewable generation by multiplying the invested capacities by a load factor chronicle (e.g. an average chronicle or the chronicles of some Monte-Carlo years).
Figure 7 – Available hourly capacity of different types of power plants due to outages. Antares-Xpansion allows taking into account either an average hourly availability (purple line), which is still very different from the actual hourly availability over a year or a different profile for each Monte-Carlo year (green lines), more realistic.
If you use the average availability, to validate the results after running the Antares-Xpansion, it is preferable to re-simulate these outages according to a stochastic process by relaunching an Antares simulation with the capacities obtained by Antares-Xpansion in order to obtain the real production program with outages and RES intermittence varying according to the scenarios.
Using different profiles depending on the Monte-Carlo year
From Antares-Simulator 8.2, users can define different NTC chronicles for different Monte-Carlo years.
Briefly, users define any number of chronicles for each link. For each link, users can select (randomly or not) one of the said chronicles in a result we call scenario. Refer to Antares-Simulator documentation for more information.
In Antares-Xpansion, it is possible to use those scenarios to select a different link profile depending on the Monte-Carlo year. There are a few pre-requisites:
- For a given candidate, if specified,
direct-link-profile,indirect-link-profile,already-installed-direct-link-profileandalready-installed-indirect-link-profilemust have the same number of columns. - For a given link in the Antares-Simulator study, the number of columns for NTC chronicles must be the same as in the link profiles and already installed profiles for the candidates on this link.
- It is possible not to provide a link profile or already installed profile. A profile with a value of 1 is used whichever Monte-Carlo year is chosen.
Examples of candidates
Basic example
An example with two investments candidates, one in semi-base generation and one in network capacity, is given below.
The invested semi-base generation in area1 is shifted in the virtual node invest_semibase. During the optimization process, the capacity of the link between area1 and invest_semibase will be updated with the new invested capacity.
The candidates.ini file for this example is the following one:
Another example with solar generation in a virtual node:
where pv1.txt is a text file, located in the user/expansion/capa/ folder of the study, and which contains the load factor time series of the candidate, see Figure 5. When \(x\) MW of the candidate solar_power are invested, the actual time series of available power is equal to the product of \(x\) and the time series pv1.txt.
Several investment candidates on the same link
The same link in an Antares study can be the support of several investment candidates. The interest of such an approach can be :
- To define several potentials with different fixed cost annuities,
- To define several investment opportunities of different unit size.
The example in Figure 8 shows the case of an investment in photovoltaic production with three potentials of increasing cost.
Figure 8 – Three potentials of increasing investment cost that applies to the same link in the Antares study.
This only works with the Antares-Xpansion algorithm (Benders decomposition) if the costs are increasing and if the investment candidates with the same link have the same already-installed-capacity and already-installed-link-profile.
Decommissioning candidates
In this example, we show how to consider both an investment candidate and a decommissioning candidate on the same link. Candidates for decommissioning must be moved from their physical location to a virtual node as explained in Prepare the Antares study.
We strongly advise to explicitly specify candidates for decommissioning in the name field of the candidates.ini file (although this is not required by the tool), see Figure 9. This will ease the analysis of Antares-Xpansion output for the user.
By considering several investment candidates on the same link, it is possible to model both an investment and a decommissioning candidate.
- The candidate for decommissioning is defined by:
- A decommissionable capacity, that corresponds to a
max-investmentormax-units\( \times\)unit-size. - Fixed operation and maintenance costs (no investment cost) given in the field
annual-cost-per-mw.
- A decommissionable capacity, that corresponds to a
- The candidate for investment is defined as by:
- An expandable capacity, that corresponds to a
max-investmentormax-units\( \times\)unit-size. - A fixed-cost annuity that includes investment costs and fixed operation and maintenance costs given in the field
annual-cost-per-mw.
- An expandable capacity, that corresponds to a
An example of production process that can be decommissioned or expanded is given in Figure 9.
Figure 9 – Candidates for investment and decommissioning on the same link from an Antares study.
!!! warning The hourly availability time series of thermal generation CCG in Antares should be higher than the sum of currently installed and new potential buildable capacities (availability of CCG cluster in the virtual node \(fr_{ccg} > 330 \cdot 19 + 330 \cdot 50\) in this example).
!!! Remark If the user specifies an already-installed-capacity for the decommissioning candidate, this capacity will not be decommissioned by Antares-Xpansion.
From the modelling of decommissioning candidates, it follows that the final result should be read "in the opposite way" compared to investment candidates:
- If the result displayed in the console for
fr_ccg_decommissioningis 300 x 19 MW invested, this means that no unit is decommissioned. - If the result displayed in the console for
fr_ccg_decommissioningis 0 MW invested, this means that all units have been decommissioned.
