Merge pull request #401 from NREL/fix-net-metering-and-demand-charges

bug fixes for max net metering benefit, multi-period and multi-tier demand charges
NREL · Jun 11, 2024 · ea92b7c · ea92b7c
2 parents 8ac9ea8 + ccfcb51
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -23,6 +23,14 @@ Classify the change according to the following categories:
     ### Deprecated
     ### Removed
 
+## Develop - 2024-06-05
+### Fixed
+- Increased the big-M bound on maximum net metering benefit to prevent artificially low export benefits
+- Fixed a bug in which tier limits did not load correctly when the number of tiers vary by period in the inputs
+- Set a limit for demand and energy tier maxes to avoid errors returned by HiGHS due to numerical limits
+- Index utility rate demand and energy tier limits on month and/or ratchet in addition to tier.  This allows for the inclusion of multi-tiered energy and demand rates in which the rates may vary by month or ratchet, whereas previously only the maximum tier limit was used.
+
+
 ## v0.47.1
 ### Fixed
 - Type issue with `CoolingLoad` monthly energy input
@@ -40,17 +48,13 @@ Classify the change according to the following categories:
 - Refactored various functions to ensure **ProcessHeatLoad** is processed correctly in line with other heating loads.
 - When the URDB response `energyratestructure` has a "unit" value that is not "kWh", throw an error instead of averaging rates in each energy tier.
 - Refactored heating flow constraints to be in ./src/constraints/thermal_tech_constraints.jl instead of its previous separate locations in the storage and turbine constraints.
+- Changed default Financial **owner_tax_rate_fraction** and **offtaker_tax_rate_fraction** from 0.257 to 0.26 to align with API and user manual defaults. 
 ### Fixed
 - Updated the PV result **lifecycle_om_cost_after_tax** to account for the third-party factor for third-party ownership analyses.
 - Convert `max_electric_load_kw` to _Float64_ before passing to function `get_chp_defaults_prime_mover_size_class`
 - Fixed a bug in which excess heat from one heating technology resulted in waste heat from another technology.
 - Modified thermal waste heat constraints for heating technologies to avoid errors in waste heat results tracking.
 
-## v0.46.2
-### Changed
-- When the URDB response `energyratestructure` has a "unit" value that is not "kWh", throw an error instead of averaging rates in each energy tier.
-- Changed default Financial **owner_tax_rate_fraction** and **offtaker_tax_rate_fraction** from 0.257 to 0.26 to align with API and user manual defaults. 
-
 ## v0.46.1
 ### Changed
 - Updated the GHP testset .json `./test/scenarios/ghp_inputs.json` to include a nominal HotThermalStorage and ColdThermalStorage system.
@@ -182,7 +186,7 @@ Classify the change according to the following categories:
 ## v0.37.5
 ### Fixed
 - Fixed AVERT emissions profiles for NOx. Were previously the same as the SO2 profiles. AVERT emissions profiles are currently generated from AVERT v3.2 https://www.epa.gov/avert/download-avert. See REopt User Manual for more information.
-- Fix setting of equal demand tiers in scrub_urdb_demand_tiers!, which was previously causing an error. 
+- Fix setting of equal demand tiers in `scrub_urdb_demand_tiers`, now renamed `scrub_urdb_tiers`. 
 - When calling REopt.jl from a python environment using PyJulia and PyCall, some urdb_response fields get converted from a list-of-lists to a matrix type, when REopt.jl expects an array type. This fix adds checks on the type for two urdb_response fields and converts them to an array if needed.
 - Update the outages dispatch results to align with CHP availability during outages
 

diff --git a/src/constraints/electric_utility_constraints.jl b/src/constraints/electric_utility_constraints.jl
@@ -52,7 +52,7 @@ function add_export_constraints(m, p; _n="")
             @warn "Adding binary variable for net metering choice. Some solvers are slow with binaries."
 
             # Good to bound the benefit - we use max_bene as a lower bound because the benefit is treated as a negative cost
-            max_bene = sum([ld*rate for (ld,rate) in zip(p.s.electric_load.loads_kw, p.s.electric_tariff.export_rates[:NEM])])*10
+            max_bene = sum([ld*rate for (ld,rate) in zip(p.s.electric_load.loads_kw, p.s.electric_tariff.export_rates[:NEM])])*p.pwf_e*p.hours_per_time_step*10
             NEM_benefit = @variable(m, lower_bound = max_bene)
 
 
@@ -135,7 +135,7 @@ function add_export_constraints(m, p; _n="")
         else
             binWHL = @variable(m, binary = true)
             @warn "Adding binary variable for wholesale export choice. Some solvers are slow with binaries."
-            max_bene = sum([ld*rate for (ld,rate) in zip(p.s.electric_load.loads_kw, p.s.electric_tariff.export_rates[:WHL])])*10
+            max_bene = sum([ld*rate for (ld,rate) in zip(p.s.electric_load.loads_kw, p.s.electric_tariff.export_rates[:WHL])])*p.pwf_e*p.hours_per_time_step*100
             WHL_benefit = @variable(m, lower_bound = max_bene)
 
             @constraint(m, binNEM + binWHL == 1)  # can either NEM or WHL export, not both
@@ -200,7 +200,7 @@ function add_monthly_peak_constraint(m, p; _n="")
         b = m[Symbol(dv)]
         # Upper bound on peak electrical power demand by month, tier; if tier is selected (0 o.w.)
         @constraint(m, [mth in p.months, tier in 1:ntiers],
-            m[Symbol("dvPeakDemandMonth"*_n)][mth, tier] <= p.s.electric_tariff.monthly_demand_tier_limits[tier] * 
+            m[Symbol("dvPeakDemandMonth"*_n)][mth, tier] <= p.s.electric_tariff.monthly_demand_tier_limits[mth, tier] * 
                 b[mth, tier]
         )
 
@@ -209,7 +209,7 @@ function add_monthly_peak_constraint(m, p; _n="")
 
         # One monthly peak electrical power demand tier must be full before next one is active
         @constraint(m, [mth in p.months, tier in 2:ntiers],
-        b[mth, tier] * p.s.electric_tariff.monthly_demand_tier_limits[tier-1] <= 
+        b[mth, tier] * p.s.electric_tariff.monthly_demand_tier_limits[mth, tier-1] <= 
             m[Symbol("dvPeakDemandMonth"*_n)][mth, tier-1]
         )
         # TODO implement NewMaxDemandMonthsInTier, which adds mth index to monthly_demand_tier_limits
@@ -233,7 +233,7 @@ function add_tou_peak_constraint(m, p; _n="")
 
         # Upper bound on peak electrical power demand by tier, by ratchet, if tier is selected (0 o.w.)
         @constraint(m, [r in p.ratchets, tier in 1:ntiers],
-            m[Symbol("dvPeakDemandTOU"*_n)][r, tier] <= p.s.electric_tariff.tou_demand_tier_limits[tier] * b[r, tier]
+            m[Symbol("dvPeakDemandTOU"*_n)][r, tier] <= p.s.electric_tariff.tou_demand_tier_limits[r, tier] * b[r, tier]
         )
 
         # Ratchet peak electrical power ratchet tier ordering
@@ -243,7 +243,7 @@ function add_tou_peak_constraint(m, p; _n="")
 
         # One ratchet peak electrical power demand tier must be full before next one is active
         @constraint(m, [r in p.ratchets, tier in 2:ntiers],
-            b[r, tier] * p.s.electric_tariff.tou_demand_tier_limits[tier-1] 
+            b[r, tier] * p.s.electric_tariff.tou_demand_tier_limits[r, tier-1] 
             <= m[Symbol("dvPeakDemandTOU"*_n)][r, tier-1]
         )
     end
@@ -299,15 +299,15 @@ function add_energy_tier_constraints(m, p; _n="")
     ##Constraint (10a): Usage limits by pricing tier, by month
     @constraint(m, [mth in p.months, tier in 1:p.s.electric_tariff.n_energy_tiers],
         p.hours_per_time_step * sum( m[Symbol("dvGridPurchase"*_n)][ts, tier] for ts in p.s.electric_tariff.time_steps_monthly[mth] ) 
-        <= b[mth, tier] * p.s.electric_tariff.energy_tier_limits[tier]
+        <= b[mth, tier] * p.s.electric_tariff.energy_tier_limits[mth, tier]
     )
     ##Constraint (10b): Ordering of pricing tiers
     @constraint(m, [mth in p.months, tier in 2:p.s.electric_tariff.n_energy_tiers],
         b[mth, tier] - b[mth, tier-1] <= 0
     )
     ## Constraint (10c): One tier must be full before any usage in next tier
     @constraint(m, [mth in p.months, tier in 2:p.s.electric_tariff.n_energy_tiers],
-        b[mth, tier] * p.s.electric_tariff.energy_tier_limits[tier-1] - 
+        b[mth, tier] * p.s.electric_tariff.energy_tier_limits[mth, tier-1] - 
         sum( m[Symbol("dvGridPurchase"*_n)][ts, tier-1] for ts in p.s.electric_tariff.time_steps_monthly[mth]) 
         <= 0
     )

diff --git a/src/core/electric_tariff.jl b/src/core/electric_tariff.jl
@@ -8,17 +8,17 @@
 """
 struct ElectricTariff
     energy_rates::AbstractArray{Float64, 2} # gets a second dim with tiers
-    energy_tier_limits::AbstractArray{Float64,1}
+    energy_tier_limits::AbstractArray{Float64,2} # month X tier
     n_energy_tiers::Int
 
     monthly_demand_rates::AbstractArray{Float64, 2} # gets a second dim with tiers
     time_steps_monthly::AbstractArray{AbstractArray{Int64,1},1}  # length = 0 or 12
-    monthly_demand_tier_limits::AbstractArray{Float64,1}
+    monthly_demand_tier_limits::AbstractArray{Float64,2} # month X tier
     n_monthly_demand_tiers::Int
 
     tou_demand_rates::AbstractArray{Float64, 2} # gets a second dim with tiers
     tou_demand_ratchet_time_steps::AbstractArray{AbstractArray{Int64,1},1}  # length = n_tou_demand_ratchets
-    tou_demand_tier_limits::AbstractArray{Float64,1}
+    tou_demand_tier_limits::AbstractArray{Float64,2} # ratchet X tier
     n_tou_demand_tiers::Int
 
     demand_lookback_months::AbstractArray{Int,1}
@@ -42,7 +42,7 @@ end
 `ElectricTariff` is a required REopt input for on-grid scenarios only (it cannot be supplied when `Settings.off_grid_flag` is true) with the following keys and default values:
 ```julia
     urdb_label::String="",
-    urdb_response::Dict=Dict(),
+    urdb_response::Dict=Dict(), # Response JSON for URDB rates. Note: if creating your own urdb_response, ensure periods are zero-indexed.
     urdb_utility_name::String="",
     urdb_rate_name::String="",
     wholesale_rate::T1=nothing, # Price of electricity sold back to the grid in absence of net metering. Can be a scalar value, which applies for all-time, or an array with time-sensitive values. If an array is input then it must have a length of 8760, 17520, or 35040. The inputed array values are up/down-sampled using mean values to match the Settings.time_steps_per_hour.
@@ -120,11 +120,11 @@ function ElectricTariff(;
     # TODO remove_tiers for multinode models
     nem_rate = Float64[]
 
-    energy_tier_limits = Float64[]
+    energy_tier_limits = Array{Float64,2}(undef, 0, 0)
     n_energy_tiers = 1
-    monthly_demand_tier_limits = Float64[]
+    monthly_demand_tier_limits = Array{Float64,2}(undef, 0, 0)
     n_monthly_demand_tiers = 1
-    tou_demand_tier_limits = Float64[]
+    tou_demand_tier_limits = Array{Float64,2}(undef, 0, 0)
     n_tou_demand_tiers = 1
     time_steps_monthly = get_monthly_time_steps(year, time_steps_per_hour=time_steps_per_hour)
 
@@ -241,7 +241,7 @@ function ElectricTariff(;
         if remove_tiers
             energy_rates, monthly_demand_rates, tou_demand_rates = remove_tiers_from_urdb_rate(u)
             energy_tier_limits, monthly_demand_tier_limits, tou_demand_tier_limits = 
-                Float64[], Float64[], Float64[]
+                Array{Float64,2}(undef, 0, 0), Array{Float64,2}(undef, 0, 0), Array{Float64,2}(undef, 0, 0)
             n_energy_tiers, n_monthly_demand_tiers, n_tou_demand_tiers = 1, 1, 1
         end