Uptime/downtime limits

Description

Here we define various different constraints to represent the same intent: to stop a technology from operating too little or too much in a year. This can be used to represent technology downtime when e.g. undergoing maintenance. It can also be used to represent a simplistic inability to ramp technologies up/down too often, e.g. for nuclear power plants. The exact constraint you activate depends on how resolved your technologies are. For instance, the two annual capacity factor constraints can work to represent a fleet of nuclear power plants which tend to operate within an annual capacity factor range of e.g., 75-85%. The downtime_period constraint can be used if you know a specific period in time where your technology will need to be down for maintenance and can be defined by setting a value in those timesteps, leaving all other timesteps empty (i.e., NaN). The downtime_period_decision constraint will allow a technology with integer decision variables activated to decide on a certain number of timesteps in the year to not be operating, although it is not possible to enforce that these downtime periods are consecutive.

New technology-level parameters:

• capacity_factor_min
• capacity_factor_max
• downtime_periods (from CSV as a timeseries)
• uptime_limit

Helper functions used:

• sum (expression)

YAML definition

Download the YAML example

constraints:
  annual_capacity_factor_min:
    description: >
      Limit the lower bound of annual technology operation as a
      fraction of annual operation at maximum capacity.
    foreach: [nodes, techs, carriers]
    where: capacity_factor_min
    equations:
      - expression: >
          sum(flow_out * timestep_weights, over=timesteps) >=
          flow_cap * capacity_factor_min * $total_time
    sub_expressions:
      total_time: &total_time
        - expression: sum(timestep_resolution * timestep_weights, over=timesteps)

  annual_capacity_factor_max:
    description: >
      Limit the upper bound of annual technology operation as a
      fraction of annual operation at maximum capacity.
    foreach: [nodes, techs, carriers]
    where: capacity_factor_max
    equations:
      - expression: >
          sum(flow_out * timestep_weights, over=timesteps) <=
          flow_cap * capacity_factor_max * $total_time
    sub_expressions:
      total_time: *total_time

  downtime_period:
    description: >
      Force outflow to zero in pre-defined timesteps of technology downtime.
    foreach: [nodes, techs, timesteps]
    where: downtime_periods
    equations:
      - expression: sum(flow_out, over=carriers) == 0

  downtime_period_decision:
    description: >
      Force operation to zero in an integer number of timesteps,
      for technologies with integer decision variables activated.
    foreach: [nodes, techs]
    where: operating_units AND uptime_limit
    equations:
      - expression: >
          sum(operating_units * timestep_weights, over=timesteps) <= uptime_limit