Sets and Parameters - iea-etsap

Based on the storage characterization given by prc_stgips, prc_stgtss or prc_nstts for a
process p, internally a prc_map(r,’STG’,p) entry is generated to put the process in the group
of the storage processes. A further prc_map entry is created to specify the type of storage
(‘STK’ for inter-operiod storage, ‘STS’ for time-slice storage and ‘NST’ for a night-storage
device).
2.2.1.2 Commodities
As mentioned before the set of commodities ( c ) is a subset of the commodity group set (cg).
A commodity in TIMES is characterised by its type, which may be an energy carrier (‘NRG’),
a material (‘MAT’), an emission --or environmental impact (‘ENV’), a demand commodity
(‘DEM’) or a financial resource (‘FIN’). The commodity type is indicated by membership in
the commodity type mapping set (com_tmap(r,com_type,c)). The commodity type affects
the default sense of the commodity balance equation. For NRG, ENV and DEM the
commodity production is normally greater than or equal to consumption, while for MAT and
FIN the default commodity balance constraint is generated as an equality. The type of the
commodity balance can be modified by the user for individual commodities by means of the
commodity limit set (com_lim(r,c,lim)). The unit in which a commodity is measured is
indicated by the commodity unit set (com_unit(r,c,units_com)). The user should note that
within the GAMS code of TIMES no unit conversion, e.g., of import prices, takes place when
the commodity unit is changed from one unit to another one. Therefore, the proper handling
of the units is entirely the responsibility of the user (or the user interface).
2.2.2 Definition of the time structure
2.2.2.1 Time horizon
The time horizon for which the energy system is analysed may range from one year to many
decades. The time horizon is usually split into several periods which are represented by socalled
milestone years (t(allyear) or milestonyr(allyear), see Figure 5). Each milestone year
represents a point in time where decisions may be taken by the model, e.g. installation of new
capacity or changes in the energy flows. The activity and flow variables used in TIMES may
therefore be considered as average values over a period. The shortest possible duration of a
period is one year. However, in order to keep the number of variables and equations at a size
that can be processed by the current solution and reporting software as well as computer
hardware a period usually comprises several years. The durations of the periods do not have
to be equal, so that it is possible that the first period, which usually represents the past and is
used to calibrate the model to historic data, has a length of one year, while the following
periods may have longer durations. Thus in TIMES both the number of periods and the
duration of each period are fully under user control. The beginning year of a period
B(allyear), its ending year E(allyear), its middle year M(allyear) and its duration D(allyear)
have to be specified as input parameters by the user (see Table 12 in subsection 3.1.3), except
for past years where B=E=milestonyr.
To describe capacity installations that took place before the beginning of the model
horizon, and still exist during the modeling horizon, TIMES uses additional years, the socalled
past years (pastyear(allyear)), which identify the construction completion year of the
already existing technologies. The amount of capacity that has been installed in a pastyear is
specified by the parameter NCAP_PASTI(r,allyear,p), also called past investment. For a
process, an arbitrary number of past investments may be specified to reflect the age structure
in the existing capacity stock. The union of the sets milestonyr and pastyear is called
modelyear (or v). The years for which input data is provided by the user are called datayears
(datayear(allyear)). The datayears do not have to coincide with modelyears, since the
preprocessor will interpolate or extrapolate the data internally to the modelyears. All
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