STEM help / Data dialogs

Resource / Capacity and Lifetime

In this dialog, you enter details of the Resource Capacity, and its Physical Lifetime and Financial Lifetime.


Capacity Unit

The unit of capacity, e.g., Circuits, Connections, Lines. Either type a unit or choose from the drop-down list.

The selection has no mathematical effect on the model, but the text is used to label the y-axis on results graphs.

Default: None.


The amount of demand which is supported by one unit of a Resource.

It is vital that this capacity is consistent with the measure of demand specified by Service and Transformation Requirements.

Default: 1.0.

Maximum Utilisation

Limits the utilisation of a Resource and guarantees a complementary proportion of slack capacity. More units are installed than would be required to satisfy a certain level of demand, so that the actual utilisation does not exceed this limit.

Default: Constant {1.0}. Resource units can be utilised to their full capacity.

Minimum Slack Capacity

Brings forward the threshold for when a new Resource is installed and effectively limits the utilisation of the last unit installed by reserving the stated slack capacity. More units are installed than would be required to satisfy a certain level of demand, so that the slack capacity remains in excess of the required amount.

Note: if used in conjunction with Maximum Utilisation, then Minimum Slack Capacity will have no effect unless it is greater than the utilisation overhead already reserved for all units.

Default: Constant {0.0}. The next Resource unit is not installed until existing capacity is full (or exceeds a given Maximum Utilisation limit).


Physical Lifetime

The number of years a Resource lasts before it must be replaced. Its Physical Lifetime may exceed its Financial Lifetime, i.e., the Resource may be written off before the end of its Physical Lifetime. Effectively describes a shelf life for a consumable resource.

Default: 1.

Lifetime Months

For short-term resources for which a conventional lifetime in years may be too long if the model runs in months or quarters. The actual lifetime (in months) is calculated as Physical Lifetime × 12 + Lifetime Months. Allowed to be zero for a consumable resource and otherwise describes a shelf life for the resource.

Default: 0.

Depreciation Policy

Financial Lifetime

The number of years over which the capital value of a Resource is written off. This depreciation period must not exceed the Physical Lifetime. This input is only relevant for a Persistent resource.

Default: 0. A special case meaning the Financial Lifetime is equal to the Physical Lifetime.

Depreciation Rate

The write-off rate for reducing-balance depreciation as a proportion, e.g., 0.25 means 25% of the capital value is written off each year. All the remaining value is written off when a Resource is removed from the network. The depreciation rate may be set to zero or any positive annual rate less than 100%. The default is –1, which is a special value indicating that straight-line depreciation should be used. This input is only meaningful for a persistent resource.

Default: –1.0.

Capacity Options

Capacity Mode

A choice between different capacity dynamics:

Persistent: the full installed capacity of a resource may be used each period and this usually persists for its full physical lifetime.

Consumable: initial installed capacity is gradually used up according to the used capacity in successive periods until an installed unit is removed when it is fully used up.

Default: Persistent.

In time or per time

Time Factor

A choice as to whether an implicit time factor for the capacity should be inferred from the Capacity Period input:

No: no time factor is associated with the capacity.

Yes: a time factor is inferred so that in-time consumable capacity may be matched to instantaneous demand, or per-time persistent capacity may be matched to aggregate demand.

Default: No.

Capacity Period

A choice of time period which allows for a time-factor to be used to match in-time consumable capacity to instantaneous demand or, conversely, to match per-time persistent capacity to an aggregate demand. For this to work, you must first set the separate input Time Factor = Yes.

Default: Year.


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