EnergyModelsX · JulStraus · Apr 16, 2026 · Apr 14, 2026 · Apr 16, 2026 · Apr 16, 2026
diff --git a/NEWS.md b/NEWS.md
@@ -1,5 +1,14 @@
 # Release notes
 
+## Unversioned
+
+### Enhancements
+
+* Improved `MinUpDownTimeNode`:
+  * Rewrote the function `constraints_capacity` based on core functionality.
+  * Updated the test set to identify all potential problems with the node.
+
+
 ## Version 0.2.11 (2026-02-16)
 
 ### Enhancements
@@ -18,7 +27,6 @@
 * Removed `ext/EMGUIExt/descriptive_names.yml` as this will now be provided directly in `EnergyModelsGUI`.
 * Removed `docs/src/example/flexible_demand.md` as the markdown versions of the example files are now generated automatically (and these are thus added to the `.gitignore`-file).
 
-
 ## Version 0.2.9 (2025-07-08)
 
 * Adjusted to [`EnergyModelsBase` v0.9.0](https://github.com/EnergyModelsX/EnergyModelsBase.jl/releases/tag/v0.9.0):

diff --git a/docs/src/links/capacitycostlink.md b/docs/src/links/capacitycostlink.md
@@ -87,7 +87,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id links-CapacityCostLink-math-var)
 

diff --git a/docs/src/nodes/network/activationcostnode.md b/docs/src/nodes/network/activationcostnode.md
@@ -25,7 +25,7 @@ The standard fields are given as:
   If the node should contain investments through the application of [`EnergyModelsInvestments`](https://energymodelsx.github.io/EnergyModelsInvestments.jl/), it is important to note that you can only use `FixedProfile` or `StrategicProfile` for the capacity, but not `RepresentativeProfile` or `OperationalProfile`.
   In addition, all values have to be non-negative.
 - **`opex_var::TimeProfile`**:\
-  The variable operational expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
+  The variable operating expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
   Hence, it is directly related to the specified `input` and `output` ratios.
   The variable operating expenses can be provided as `OperationalProfile` as well.
 - **`opex_fixed::TimeProfile`**:\

diff --git a/docs/src/nodes/network/combustion.md b/docs/src/nodes/network/combustion.md
@@ -22,7 +22,7 @@ The standard fields are given as:
   If the node should contain investments through the application of [`EnergyModelsInvestments`](https://energymodelsx.github.io/EnergyModelsInvestments.jl/), it is important to note that you can only use `FixedProfile` or `StrategicProfile` for the capacity, but not `RepresentativeProfile` or `OperationalProfile`.
   In addition, all values have to be non-negative.
 - **`opex_var::TimeProfile`**:\
-  The variable operational expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
+  The variable operating expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
   Hence, it is directly related to the specified `input` and `output` ratios.
   The variable operating expenses can be provided as `OperationalProfile` as well.
 - **`opex_fixed::TimeProfile`**:\

diff --git a/docs/src/nodes/network/flexibleoutput.md b/docs/src/nodes/network/flexibleoutput.md
@@ -21,7 +21,7 @@ The standard fields of a [`FlexibleOutput`](@ref) node are given as:
   If the node should contain investments through the application of [`EnergyModelsInvestments`](https://energymodelsx.github.io/EnergyModelsInvestments.jl/), it is important to note that you can only use `FixedProfile` or `StrategicProfile` for the capacity, but not `RepresentativeProfile` or `OperationalProfile`.
   In addition, all values have to be non-negative.
 - **`opex_var::TimeProfile`**:\
-  The variable operational expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
+  The variable operating expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
   Hence, it is directly related to the specified `input` and `output` ratios.
   The variable operating expenses can be provided as `OperationalProfile` as well.
 - **`opex_fixed::TimeProfile`**:\
@@ -66,7 +66,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-FlexibleOutput-math-var)
 

diff --git a/docs/src/nodes/network/limitedflexibleinput.md b/docs/src/nodes/network/limitedflexibleinput.md
@@ -18,7 +18,7 @@ The standard fields are given as:
   If the node should contain investments through the application of [`EnergyModelsInvestments`](https://energymodelsx.github.io/EnergyModelsInvestments.jl/), it is important to note that you can only use `FixedProfile` or `StrategicProfile` for the capacity, but not `RepresentativeProfile` or `OperationalProfile`.
   In addition, all values have to be non-negative.
 - **`opex_var::TimeProfile`**:\
-  The variable operational expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
+  The variable operating expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
   Hence, it is directly related to the specified `input` and `output` ratios.
   The variable operating expenses can be provided as `OperationalProfile` as well.
 - **`opex_fixed::TimeProfile`**:\

diff --git a/docs/src/nodes/network/minupdowntimenode.md b/docs/src/nodes/network/minupdowntimenode.md
@@ -21,7 +21,7 @@ The standard fields are given as:
   If the node should contain investments through the application of [`EnergyModelsInvestments`](https://energymodelsx.github.io/EnergyModelsInvestments.jl/), it is important to note that you can only use `FixedProfile` or `StrategicProfile` for the capacity, but not `RepresentativeProfile` or `OperationalProfile`.
   In addition, all values have to be non-negative.
 - **`opex_var::TimeProfile`**:\
-  The variable operational expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
+  The variable operating expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
   Hence, it is directly related to the specified `input` and `output` ratios.
   The variable operating expenses can be provided as `OperationalProfile` as well.
 - **`opex_fixed::TimeProfile`**:\
@@ -55,18 +55,18 @@ The standard fields are given as:
 
 [`MinUpDownTimeNode`](@ref) nodes add four additional fields compared to a [`NetworkNode`](@extref EnergyModelsBase nodes-network_node):
 
-- **`minUpTime::Real`**:\
+- **`min_time_up::Real`**:\
   Minimum number of operational periods the unit must remain on after being started.
-- **`minDownTime::Real`**:\
+- **`min_time_down::Real`**:\
   Minimum number of operational periods the unit must remain off after being stopped.
-- **`minCapacity::Real`**:\
+- **`load_min::Real`**:\
   Minimum power output when the unit is on. The value must be larger than zero.
-- **`maxCapacity::Real`**:\
+- **`load_max::Real`**:\
   Maximum power output when the unit is on (usually aligned with `cap`).
-  The value must not be less than `minCapacity`.
+  The value must not be less than `load_min`.
 
 !!! tip
-    The fields `minUpTime` and `minDownTime` are defined in terms of operational period durations and should be consistent with the time granularity of the model.
+    The fields `min_time_up` and `min_time_down` are defined in terms of operational period durations and should be consistent with the time granularity of the model.
 
 ## [Mathematical description](@id nodes-minupdowntimenode-math)
 
@@ -194,11 +194,11 @@ The function `constraints_capacity` receives a new method to handle the minimum
 - **Capacity conditional on on/off status:**
 
   ```math
-  \texttt{cap\_use}[n, t] \leq \texttt{on\_off}[n, t] \times n.maxCapacity
+  \texttt{cap\_use}[n, t] \leq \texttt{on\_off}[n, t] \times n.load_max
   ```
 
   ```math
-  \texttt{cap\_use}[n, t] \geq \texttt{on\_off}[n, t] \times n.minCapacity
+  \texttt{cap\_use}[n, t] \geq \texttt{on\_off}[n, t] \times n.load_min
   ```
 
 - **Upper bound by installed capacity:**

diff --git a/docs/src/nodes/sink/loadshiftingnode.md b/docs/src/nodes/sink/loadshiftingnode.md
@@ -58,7 +58,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-loadshiftingnode-math-var)
 

diff --git a/docs/src/nodes/sink/multipleinputsink.md b/docs/src/nodes/sink/multipleinputsink.md
@@ -42,7 +42,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-mul_in_sink-math-var)
 

diff --git a/docs/src/nodes/sink/multipleinputsinkstrat.md b/docs/src/nodes/sink/multipleinputsinkstrat.md
@@ -67,7 +67,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-mul_in_sink_strat-math-var)
 

diff --git a/docs/src/nodes/sink/perioddemand.md b/docs/src/nodes/sink/perioddemand.md
@@ -84,7 +84,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-perioddemandsink-math-var)
 

diff --git a/docs/src/nodes/source/inflexiblesource.md b/docs/src/nodes/source/inflexiblesource.md
@@ -22,7 +22,7 @@ The [`InflexibleSource`](@ref) has the same standard fields as the [`RefSource`]
   If the node should contain investments through the application of [`EnergyModelsInvestments`](https://energymodelsx.github.io/EnergyModelsInvestments.jl/stable/), it is important to note that you can only use `FixedProfile` or `StrategicProfile` for the capacity, but not `RepresentativeProfile` or `OperationalProfile`.
   In addition, all values have to be non-negative.
 - **`opex_var::TimeProfile`**:\
-  The variable operational expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
+  The variable operating expenses are based on the capacity utilization through the variable [`:cap_use`](@extref EnergyModelsBase man-opt_var-cap).
   Hence, it is directly related to the specified `output` ratios.
   The variable operating expenses can be provided as `OperationalProfile` as well.
 - **`opex_fixed::TimeProfile`**:\
@@ -59,7 +59,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-inflexiblesource-math-var)
 

diff --git a/docs/src/nodes/source/payasproducedppa.md b/docs/src/nodes/source/payasproducedppa.md
@@ -24,7 +24,7 @@ The fields of a [`PayAsProducedPPA`](@ref) are:
   In addition, all values should be in the range ``[0, 1]``.
 
 - **`opex_var::TimeProfile`**:\
-  The variable operational expenses are based on the capacity utilization through the variable `:cap_use`.
+  The variable operating expenses are based on the capacity utilization through the variable `:cap_use`.
   Hence, they are directly related to the specified `output` ratios.
   The variable operating expenses can be provided as `OperationalProfile` as well.
 
@@ -55,7 +55,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-payasproducedppa-math-var)
 
@@ -100,8 +100,8 @@ These standard constraints are:
   profile(n, t) \times \texttt{cap\_inst}[n, t]
   ```
 
-
 - `constraints_capacity_installed`:
+
   ```math
   \texttt{cap\_inst}[n, t] = capacity(n, t)
   ```
@@ -111,13 +111,15 @@ These standard constraints are:
       Nodes with investments are then no longer constrained by the parameter capacity.
 
 - `constraints_flow_out`:
+
   ```math
   \texttt{flow\_out}[n, t, p] =
   outputs(n, p) \times \texttt{cap\_use}[n, t]
   \qquad \forall p ∈ outputs(n) \setminus \{\text{CO}_2\}
   ```
 
 - `constraints_opex_fixed`:
+
   ```math
   \texttt{opex\_fixed}[n, t_{inv}] = opex\_fixed(n, t_{inv}) \times \texttt{cap\_inst}[n, first(t_{inv})]
   ```

diff --git a/docs/src/nodes/storage/storageefficiency.md b/docs/src/nodes/storage/storageefficiency.md
@@ -47,7 +47,7 @@ with square brackets, while functions are represented as
 
 ``func\_example(index_1, index_2)``
 
-with paranthesis.
+with parantheses.
 
 ### [Variables](@id nodes-stor_eff-math-var)
 

diff --git a/examples/flexible_demand.jl b/examples/flexible_demand.jl
@@ -65,11 +65,10 @@ line = MinUpDownTimeNode(
     FixedProfile(0),
     Dict(Power => 1),
     Dict(Product => 1),
-    min_up_time, # minUpTime
-    min_down_time, # minDownTime
-    50, # minCapacity
-    300, # maxCapacity
-    [],
+    min_up_time, # min_time_up
+    min_down_time, # min_time_down
+    50, # load_min
+    300, # load_max
 )
 
 # Define the simple energy system

diff --git a/src/link/datastructures.jl b/src/link/datastructures.jl
@@ -124,7 +124,7 @@ EMB.capacity(l::CapacityCostLink, t) = l.cap[t]
 """
     EMB.has_opex(l::CapacityCostLink)
 
-A `CapacityCostLink` `l` has operational expenses.
+A `CapacityCostLink` `l` has operating expenses.
 """
 EMB.has_opex(l::CapacityCostLink) = true
 

diff --git a/src/network/checks.jl b/src/network/checks.jl
@@ -1,28 +1,39 @@
 """
     EMB.check_node(n::MinUpDownTimeNode, 𝒯, modeltype::EnergyModel, check_timeprofiles::Bool)
 
-This method checks that a `MinUpDownTimeNode` node is valid.
+This method checks that a [`MinUpDownTimeNode`](@ref) node is valid.
+
+It reuses the standard checks of a `NetworkNode` node through calling the function
+[`EMB.check_node_default`](@extref EnergyModelsBase.check_node_default), but adds an
+additional check on the data.
 
 ## Checks
- - The minimum capacity must be greater than zero.
- - The minimum capacity must not be larger than maximum capacity.
+- The field `cap` is required to be non-negative.
+- The value of the field `fixed_opex` is required to be non-negative and
+  accessible through a `StrategicPeriod` as outlined in the function
+  [`EMB.check_fixed_opex()`](@extref EnergyModelsBase.check_fixed_opex).
+- The values of the dictionary `input` are required to be non-negative.
+- The values of the dictionary `output` are required to be non-negative.
+
+ - The field `load_min` is required to be greater than zero.
+ - The field `load_min` is required to be not larger than the field `load_max`.
 """
 function EMB.check_node(
     n::MinUpDownTimeNode,
     𝒯,
     modeltype::EnergyModel,
     check_timeprofiles::Bool,
 )
-    # EMB.check_node_default(n, 𝒯, modeltype, check_timeprofiles)
+    EMB.check_node_default(n, 𝒯, modeltype, check_timeprofiles)
 
     # We need the minimum capacity to be greater than zero.
     @assert_or_log(
-        n.minCapacity > 0,
+        n.load_min > 0,
         "The minimum capacity must be greater than zero."
     )
 
     @assert_or_log(
-        n.minCapacity <= n.maxCapacity,
+        n.load_min ≤ n.load_max,
         "The minimum capacity must not be larger than maximum capacity."
     )
 end

diff --git a/src/network/constraint_functions.jl b/src/network/constraint_functions.jl
@@ -24,42 +24,41 @@ function EMB.constraints_capacity(
     𝒯::TimeStructure,
     modeltype::EnergyModel,
 )
+    # Extract the strategic time structure
     𝒯ᴵⁿᵛ = strategic_periods(𝒯)
-    sps = collect(𝒯ᴵⁿᵛ)
 
-    for sp ∈ sps
-        ops = collect(sp) #array of al operational periodes
+    for t_inv ∈ 𝒯ᴵⁿᵛ
+        ops = collect(t_inv) #array of al operational periodes
 
-        N_h = n.minDownTime #min down time in the tinme unit used in the case
-        M_h = n.minUpTime
-        durations = [duration(t) for t ∈ ops]
+        N_h = n.min_time_down #min down time in the tinme unit used in the case
+        M_h = n.min_time_up
+        durations = [duration(t) for t ∈ t_inv]
 
-        N_arr = zeros(length(ops))
-        M_arr = zeros(length(ops))
+        N_arr = zeros(length(t_inv))
+        M_arr = zeros(length(t_inv))
 
-        for j ∈ 1:length(ops)
-            sum_duration_N = durations[j]
+        for (j, t) ∈ enumerate(t_inv)
+            sum_duration_N = duration(t)
             count = 1
             while sum_duration_N < N_h
                 sum_duration_N += circshift(durations, -count)[j]
                 count += 1
             end
             N_arr[j] = count
             count = 1
-            sum_duration_M = durations[j]
+            sum_duration_M = duration(t)
             while sum_duration_M < M_h
                 sum_duration_M += circshift(durations, -count)[j]
                 count += 1
             end
             M_arr[j] = count
         end
 
-        min_cap = n.minCapacity
-        max_cap = n.maxCapacity
-        for i ∈ 1:length(ops) # i from 1 to number of operational periodes
+        min_cap = n.load_min
+        max_cap = n.load_max
+        for (i, t) ∈ enumerate(t_inv) # i from 1 to number of operational periodes
             M = Int(M_arr[i])
             N = Int(N_arr[i])
-            t = ops[i]
 
             @constraint(
                 m,