add soc_init_fraction

from PR#447

CHANGELOG.md

@@ -36,6 +36,7 @@ Classify the change according to the following categories:
   - ElectricUtility **annual_renewable_electricity_supplied_kwh**
   - Site **onsite_and_grid_renewable_electricity_fraction_of_elec_load**
   - Site **onsite_and_grid_renewable_energy_fraction_of_elec_and_thermal_load**
+- Added input option optimize_soc_init_fraction (defaults to false) to ElectricStorage, which makes the optimization choose the inital SOC (equal to final SOC) instead of using soc_init_fraction. The initial SOC is also constrained to equal the final SOC, which eliminates the "free energy" issue. We currently do not fix SOC when soc_init_fraction is used because this has caused infeasibility.
 ### Changed
 - Changed name of the following inputs: 
   - ElectricUtility input **cambium_metric_col** changed to **cambium_co2_metric**

src/constraints/storage_constraints.jl

@@ -38,10 +38,21 @@ end
 
 
 function add_general_storage_dispatch_constraints(m, p, b; _n="")
-    # Constraint (4a): initial state of charge
-	@constraint(m,
-        m[Symbol("dvStoredEnergy"*_n)][b, 0] == p.s.storage.attr[b].soc_init_fraction * m[Symbol("dvStorageEnergy"*_n)][b]
-    )
+    # Constraint (4a): initial and final state of charge
+    if hasproperty(p.s.storage.attr[b], :optimize_soc_init_fraction) && p.s.storage.attr[b].optimize_soc_init_fraction
+        print("\nOptimizing "*b*" inital SOC and constraining initial SOC = final SOC. soc_init_fraction will not apply.\n")
+        @constraint(m,
+            m[Symbol("dvStoredEnergy"*_n)][b, 0] == m[:dvStoredEnergy][b, maximum(p.time_steps)]
+        )
+    else
+        @constraint(m,
+            m[Symbol("dvStoredEnergy"*_n)][b, 0] == p.s.storage.attr[b].soc_init_fraction * m[Symbol("dvStorageEnergy"*_n)][b]
+        )
+        # TODO: constrain final soc to equal initial soc  
+        # @constraint(m,
+        #     m[Symbol("dvStoredEnergy"*_n)][b, maximum(p.time_steps)] == p.s.storage.attr[b].soc_init_fraction * m[Symbol("dvStorageEnergy"*_n)][b]
+        # )
+    end
 
     #Constraint (4n): State of charge upper bound is storage system size
     @constraint(m, [ts in p.time_steps],

src/core/absorption_chiller.jl

@@ -12,7 +12,7 @@
     min_ton::Float64 = 0.0, # Minimum thermal power size constraint for optimization
     max_ton::Float64 = BIG_NUMBER, # Maximum thermal power size constraint for optimization
     cop_thermal::Union{Float64, Nothing} = nothing, # Absorption chiller system coefficient of performance - conversion of hot thermal power input to usable cooling thermal energy output
-    cop_electric::Float64 = 14.1, # Absorption chiller electric consumption CoP from cooling tower heat rejection - conversion of electric power input to usable cooling thermal energy outpu
+    cop_electric::Float64 = 14.1, # Absorption chiller electric consumption CoP from cooling tower heat rejection - conversion of electric power input to usable cooling thermal energy output
     macrs_option_years::Float64 = 0, # MACRS schedule for financial analysis. Set to zero to disable
     macrs_bonus_fraction::Float64 = 0 # Percent of upfront project costs to depreciate under MACRS
     heating_load_input::Union{String, Nothing} = nothing # heating load that serves as input to absorption chiller

src/core/energy_storage/electric_storage.jl

@@ -185,6 +185,7 @@ end
     model_degradation::Bool = false
     degradation::Dict = Dict()
     minimum_avg_soc_fraction::Float64 = 0.0
+    optimize_soc_init_fraction::Bool = false # If true, soc_init_fraction will not apply. Model will optimize initial SOC and constrain initial SOC = final SOC. 
     min_duration_hours::Real = 0.0 # Minimum amount of time storage can discharge at its rated power capacity
     max_duration_hours::Real = 100000.0 # Maximum amount of time storage can discharge at its rated power capacity (ratio of ElectricStorage size_kwh to size_kw)
 ```
@@ -220,6 +221,7 @@ Base.@kwdef struct ElectricStorageDefaults
     model_degradation::Bool = false
     degradation::Dict = Dict()
     minimum_avg_soc_fraction::Float64 = 0.0
+    optimize_soc_init_fraction::Bool = false
     min_duration_hours::Real = 0.0
     max_duration_hours::Real = 100000.0
 end
@@ -263,6 +265,7 @@ struct ElectricStorage <: AbstractElectricStorage
     model_degradation::Bool
     degradation::Degradation
     minimum_avg_soc_fraction::Float64
+    optimize_soc_init_fraction::Bool
     min_duration_hours::Real
     max_duration_hours::Real
 
@@ -356,6 +359,7 @@ struct ElectricStorage <: AbstractElectricStorage
             s.model_degradation,
             degr,
             s.minimum_avg_soc_fraction,
+            s.optimize_soc_init_fraction,
             s.min_duration_hours,
             s.max_duration_hours
         )

src/results/electric_load.jl

@@ -1,7 +1,7 @@
 # REopt®, Copyright (c) Alliance for Sustainable Energy, LLC. See also https://github.com/NREL/REopt.jl/blob/master/LICENSE.
 """
 `ElectricLoad` results keys:
-- `load_series_kw` vector of site load in every time step
+- `load_series_kw` vector of site load in every time step. Does not (currently) include electric load for any new heating or cool techs.
 - `critical_load_series_kw` vector of site critical load in every time step
 - `annual_calculated_kwh` sum of the `load_series_kw`
 - `offgrid_load_met_series_kw` vector of electric load met by generation techs, for off-grid scenarios only

src/results/financial.jl

@@ -356,7 +356,7 @@ function get_depreciation_schedule(p::REoptInputs, tech::Union{AbstractTech,Abst
 
     federal_itc_fraction = 0.0
     try 
-        federal_itc_fraction = tech.federal_itc_fraction # TODO: also check for total_itc_fraction as storage does not use federal_itc_fraction?
+        federal_itc_fraction = tech.federal_itc_fraction
     catch
         @warn "Did not find $(tech).federal_itc_fraction so using 0.0 in calculation of depreciation_schedule."
     end