Allow BESS to Export

CHANGELOG.md

@@ -25,6 +25,13 @@ Classify the change according to the following categories:
     ### Deprecated
     ### Removed
 
+## bess-export
+### Added 
+- Allow **ElectricStorage** to export to the grid with input options for grid export: `can_net_meter`, `can_wholesale`, `can_export_beyond_nem_limit`and associated decision variable **dvStorageToGrid**
+- Add result **ElectricStorage** `storage_to_grid_series_kw` 
+### Fixed
+- Bug in max benefit constraint for WHL export; bug allowing for both WHL and NEM to be used 
+
 ## v0.59.3
 ### Changed
 - Updated Julia environment variable names from "NREL_DEVELOPER_API_KEY" and "NREL_DEVELOPER_EMAIL" to "NLR_DEVELOPER_API_KEY" and "NLR_DEVELOPER_EMAIL"

docs/src/developer/inputs.md

@@ -40,7 +40,7 @@ end
 The set maps are best explained with an example. The `techs_by_exportbin` map uses each technology'sattributes (eg. `PV`) to map each technology to which export bins that technology can access. The export bins include:
 1. `:NEM` (Net Energy Metering)
 2. `:WHL` (Wholesale)
-3. `:EXC` (Excess, beyond NEM))
+3. `:EXC` (Excess, beyond NEM)
 The bins that a technology can access are determined by the technologies attributes `can_net_meter`, `can_wholesale`, and `can_export_beyond_nem_limit`. So if `PV.can_net_meter = true`, `Wind.can_net_meter = true` and all the other attributes are `false` then the `techs_by_exportbin` will only have one non-empty key:
 ```julia
 techs_by_exportbin = Dict(

src/constraints/emissions_constraints.jl

@@ -120,24 +120,35 @@ function calc_yr1_emissions_offset_from_elec_exports(m, p)
 		return 0.0, 0.0, 0.0, 0.0
 	end
 	yr1_emissions_offset_from_elec_exports_lbs_CO2 = @expression(m, p.hours_per_time_step *
-		sum(m[:dvProductionToGrid][t,u,ts] * (p.s.electric_utility.emissions_factor_series_lb_CO2_per_kwh[ts])
-		for t in p.techs.elec, ts in p.time_steps, u in p.export_bins_by_tech[t])
+		sum( p.s.electric_utility.emissions_factor_series_lb_CO2_per_kwh[ts] * (
+			sum(m[:dvProductionToGrid][t,u,ts] for t in p.techs.elec, u in p.export_bins_by_tech[t])
+			+ sum(m[:dvStorageToGrid][b, u, ts] for b in p.s.storage.types.elec, u in p.export_bins_by_storage[b])
+			) for ts in p.time_steps
+		)
 	)
-		# if battery ends up being able to discharge to grid, need to incorporate here- might require complex tracking of what's charging battery
 
 	yr1_emissions_offset_from_elec_exports_lbs_NOx = @expression(m, p.hours_per_time_step *
-		sum(m[:dvProductionToGrid][t,u,ts] * (p.s.electric_utility.emissions_factor_series_lb_NOx_per_kwh[ts])
-		for t in p.techs.elec, ts in p.time_steps, u in p.export_bins_by_tech[t])
+		sum( p.s.electric_utility.emissions_factor_series_lb_NOx_per_kwh[ts] * (
+			sum(m[:dvProductionToGrid][t,u,ts] for t in p.techs.elec, u in p.export_bins_by_tech[t])
+			+ sum(m[:dvStorageToGrid][b, u, ts] for b in p.s.storage.types.elec, u in p.export_bins_by_storage[b])
+			) for ts in p.time_steps
+		)
 	)
 
 	yr1_emissions_offset_from_elec_exports_lbs_SO2 = @expression(m, p.hours_per_time_step *
-		sum(m[:dvProductionToGrid][t,u,ts] * (p.s.electric_utility.emissions_factor_series_lb_SO2_per_kwh[ts])
-		for t in p.techs.elec, ts in p.time_steps, u in p.export_bins_by_tech[t])
+		sum( p.s.electric_utility.emissions_factor_series_lb_SO2_per_kwh[ts] * (
+			sum(m[:dvProductionToGrid][t,u,ts] for t in p.techs.elec, u in p.export_bins_by_tech[t])
+			+ sum(m[:dvStorageToGrid][b, u, ts] for b in p.s.storage.types.elec, u in p.export_bins_by_storage[b])
+			) for ts in p.time_steps
+		)
 	)
 
 	yr1_emissions_offset_from_elec_exports_lbs_PM25 = @expression(m, p.hours_per_time_step *
-		sum(m[:dvProductionToGrid][t,u,ts] * (p.s.electric_utility.emissions_factor_series_lb_PM25_per_kwh[ts])
-		for t in p.techs.elec, ts in p.time_steps, u in p.export_bins_by_tech[t])
+		sum( p.s.electric_utility.emissions_factor_series_lb_PM25_per_kwh[ts] * (
+			sum(m[:dvProductionToGrid][t,u,ts] for t in p.techs.elec, u in p.export_bins_by_tech[t])
+			+ sum(m[:dvStorageToGrid][b, u, ts] for b in p.s.storage.types.elec, u in p.export_bins_by_storage[b])
+			) for ts in p.time_steps
+		)
 	)
 
 	return yr1_emissions_offset_from_elec_exports_lbs_CO2, 

src/constraints/load_balance.jl

@@ -27,6 +27,7 @@ function add_elec_load_balance_constraints(m, p; _n="")
             sum(sum(m[Symbol("dvProductionToStorage"*_n)][b, t, ts] for b in p.s.storage.types.elec) 
                 + sum(m[Symbol("dvProductionToGrid"*_n)][t, u, ts] for u in p.export_bins_by_tech[t]) 
                 + m[Symbol("dvCurtail"*_n)][t, ts] for t in p.techs.elec)
+            + sum(m[Symbol("dvStorageToGrid"*_n)][b, u, ts] for b in p.s.storage.types.elec, u in p.export_bins_by_storage[b])
             + sum(m[Symbol("dvGridToStorage"*_n)][b, ts] for b in p.s.storage.types.elec)
             + sum(m[Symbol("dvCoolingProduction"*_n)][t, ts] / p.cooling_cop[t][ts] for t in setdiff(p.techs.cooling,p.techs.ghp))
             + sum(m[Symbol("dvHeatingProduction"*_n)][t, q, ts] / p.heating_cop[t][ts] for q in p.heating_loads, t in p.techs.electric_heater)
@@ -96,7 +97,6 @@ function add_production_constraints(m, p; _n="")
         <= 
         p.production_factor[t, ts] * p.levelization_factor[t] * m[Symbol("dvRatedProduction"*_n)][t, ts]
 	)
-
 end
 
 

src/constraints/renewable_energy_constraints.jl

@@ -58,36 +58,43 @@ function add_re_elec_calcs(m,p)
 		@warn("The presence of a steam turbine may cause the renewable energy fraction to be inaccurate.")
 	end
 
-	# Note: when we add capability for battery to discharge to grid, need to make sure only RE that is being consumed 
-	# 		onsite is counted so battery doesn't become a back door for RE to grid.
 	m[:AnnualOnsiteREEleckWh] = @expression(m, p.hours_per_time_step * (
+			#total RE elec generation, excl steam turbine
 			sum(p.production_factor[t,ts] * p.levelization_factor[t] * m[:dvRatedProduction][t,ts] * 
 				p.tech_renewable_energy_fraction[t] for t in setdiff(p.techs.elec, p.techs.steam_turbine), ts in p.time_steps
-			) - #total RE elec generation, excl steam turbine
-			sum(m[:dvProductionToStorage][b,t,ts]*p.tech_renewable_energy_fraction[t]*(
+			)
+			#minus battery efficiency losses
+			- sum(m[:dvProductionToStorage][b,t,ts]*p.tech_renewable_energy_fraction[t]*(
 				1-p.s.storage.attr[b].charge_efficiency*p.s.storage.attr[b].discharge_efficiency) 
 				for t in setdiff(p.techs.elec, p.techs.steam_turbine), b in p.s.storage.types.elec, ts in p.time_steps
-			) - #minus battery efficiency losses
-			sum(m[:dvCurtail][t,ts] * p.tech_renewable_energy_fraction[t] 
+			)
+			# minus curtailment
+			- sum(m[:dvCurtail][t,ts] * p.tech_renewable_energy_fraction[t] 
 				for t in setdiff(p.techs.elec, p.techs.steam_turbine), ts in p.time_steps
-			) - # minus curtailment
-			(1 - p.s.site.include_exported_renewable_electricity_in_total) *
+			)
+			# minus exported RE, if RE accounting method = 0.
+			- (1 - p.s.site.include_exported_renewable_electricity_in_total) *
 			sum(m[:dvProductionToGrid][t,u,ts]*p.tech_renewable_energy_fraction[t] 
 				for t in setdiff(p.techs.elec, p.techs.steam_turbine), u in p.export_bins_by_tech[t], ts in p.time_steps
-			) # minus exported RE, if RE accounting method = 0.
+			)
+			# TODO: battery can now discharge to the grid, but this export is not yet accounted for in the RE calculation. 
+			# 	This is only relevant if include_exported_renewable_electricity_in_total = false. If false, the 
+			# 	battery could become a "back door" for export of RE to the grid since it's not subtracted here. Will require tracking of onsite vs grid RE in BESS. 
 		)
 		# + SteamTurbineAnnualREEleckWh  # SteamTurbine RE Elec, already adjusted for p.hours_per_time_step
 	)		
 
-	# Note: when we add capability for battery to discharge to grid, need to subtract out *grid RE* discharged from battery 
-	# 		back to grid so that loop doesn't become a back door for increasing RE. This will require some careful thought!
 	m[:AnnualGridREEleckWh] = @expression(m, p.hours_per_time_step * (
+			# renewable energy from grid 
 			sum(m[:dvGridPurchase][ts, tier] * p.s.electric_utility.renewable_energy_fraction_series[ts] 
-				for ts in p.time_steps, tier in 1:p.s.electric_tariff.n_energy_tiers) # renewable energy from grid 
+				for ts in p.time_steps, tier in 1:p.s.electric_tariff.n_energy_tiers) 
+			# minus battery efficiency losses from grid charging storage (assumes all that is charged is discharged)
 			- sum(m[:dvGridToStorage][b, ts] * p.s.electric_utility.renewable_energy_fraction_series[ts] *
 				(1 - p.s.storage.attr[b].charge_efficiency * p.s.storage.attr[b].discharge_efficiency)
 				for ts in p.time_steps, b in p.s.storage.types.elec
-			) # minus battery efficiency losses from grid charging storage (assumes all that is charged is discharged)
+			)
+			# TODO: battery can now discharge to the grid, but this export is not yet accounted for in the RE calculation.
+			# 	Need to subtract out *grid RE* discharged from battery back to grid so that loop doesn't become a back door for increasing RE. Will require tracking of onsite vs grid RE in BESS.
 		) 
 	)
 

src/constraints/storage_constraints.jl

@@ -33,7 +33,6 @@ function add_storage_size_constraints(m, p, b; _n="")
         )
     end    
 
-
 end
 
 
@@ -74,12 +73,21 @@ end
 
 function add_elec_storage_dispatch_constraints(m, p, b; _n="")
 
-	# Constraint (4g)-1: state-of-charge for electrical storage - with grid
+    # Constraint (4d): Storage export must be less than total storage dispatch
+    if !isempty(p.export_bins_by_storage[b])
+        @constraint(m, [ts in p.time_steps_with_grid],
+            sum(m[Symbol("dvStorageToGrid"*_n)][b, u, ts] for u in p.export_bins_by_storage[b])
+            <= 
+            m[Symbol("dvDischargeFromStorage"*_n)][b, ts]
+        )
+    end 
+
+    # Constraint (4g)-1: state-of-charge for electrical storage - with grid
 	@constraint(m, [ts in p.time_steps_with_grid],
         m[Symbol("dvStoredEnergy"*_n)][b, ts] == m[Symbol("dvStoredEnergy"*_n)][b, ts-1] + p.hours_per_time_step * (  
             sum(p.s.storage.attr[b].charge_efficiency * m[Symbol("dvProductionToStorage"*_n)][b, t, ts] for t in p.techs.elec) 
             + p.s.storage.attr[b].grid_charge_efficiency * m[Symbol("dvGridToStorage"*_n)][b, ts] 
-            - m[Symbol("dvDischargeFromStorage"*_n)][b,ts] / p.s.storage.attr[b].discharge_efficiency
+            - (m[Symbol("dvDischargeFromStorage"*_n)][b,ts] / p.s.storage.attr[b].discharge_efficiency)
         )
 	)
 	# Constraint (4g)-2: state-of-charge for electrical storage - no grid

src/core/bau_inputs.jl

@@ -42,6 +42,8 @@ function BAUInputs(p::REoptInputs)
     # export related inputs
     techs_by_exportbin = Dict{Symbol, AbstractArray}(k => [] for k in p.s.electric_tariff.export_bins)
     export_bins_by_tech = Dict{String, Array{Symbol, 1}}()
+    storage_by_exportbin = Dict{Symbol, AbstractArray}(k => [] for k in p.s.electric_tariff.export_bins) # Empty for BAU since cannot model "existing storage"
+    export_bins_by_storage = Dict{String, Array{Symbol, 1}}()
 
     # REoptInputs indexed on techs.segmented
     n_segs_by_tech = Dict{String, Int}()
@@ -197,6 +199,8 @@ function BAUInputs(p::REoptInputs)
         p.ratchets,
         techs_by_exportbin,
         export_bins_by_tech,
+        storage_by_exportbin,
+        export_bins_by_storage,
         n_segs_by_tech,
         seg_min_size,
         seg_max_size,

src/core/electric_utility.jl

@@ -138,10 +138,9 @@ struct ElectricUtility
     outage_time_steps::Union{Nothing, UnitRange} 
     scenarios::Union{Nothing, UnitRange} 
     net_metering_limit_kw::Real 
-    interconnection_limit_kw::Real 
+    interconnection_limit_kw::Real
     transmission_limit_kw::Real
 
-
     function ElectricUtility(;
 
         # Fields from other models
@@ -198,9 +197,9 @@ struct ElectricUtility
 
         ### Grid Clean Energy Fraction Inputs ###
         cambium_cef_metric::String = "cef_load", # Options = ["cef_load", "cef_gen"] # cef_load is the fraction of generation that is clean, for the generation that is allocated to a region’s end-use load; cef_gen is the fraction of generation that is clean within a region
-        renewable_energy_fraction_series::Union{Real,Array{<:Real,1}} = Float64[], # Fraction of energy supplied by the grid that is renewable. Can be scalar or timeseries (aligned with time_steps_per_hour)
-        )
-
+        renewable_energy_fraction_series::Union{Real,Array{<:Real,1}} = Float64[] # Fraction of energy supplied by the grid that is renewable. Can be scalar or timeseries (aligned with time_steps_per_hour)
+    )
+    
         is_MPC = isnothing(latitude) || isnothing(longitude)
         cambium_region = "NA - Cambium data not used" # will be overwritten if Cambium is used
 

src/core/energy_storage/electric_storage.jl

@@ -176,6 +176,9 @@ end
     soc_min_applies_during_outages::Bool = false
     soc_init_fraction::Float64 = off_grid_flag ? 1.0 : 0.5
     can_grid_charge::Bool = off_grid_flag ? false : true
+    can_net_meter::Bool = false
+    can_wholesale::Bool = false
+    can_export_beyond_nem_limit::Bool = false
     installed_cost_per_kw::Real = 968.0 # Cost of power components (e.g., inverter and BOS) 
     installed_cost_per_kwh::Real = 253.0 # Cost of energy components (e.g., battery pack)
     installed_cost_constant::Real = 222115.0 # "+c" constant cost that is added to total ElectricStorage installed costs if a battery is included. Accounts for costs not expected to scale with power or energy capacity.
@@ -219,6 +222,9 @@ Base.@kwdef struct ElectricStorageDefaults
     soc_min_applies_during_outages::Bool = false
     soc_init_fraction::Float64 = off_grid_flag ? 1.0 : 0.5
     can_grid_charge::Bool = off_grid_flag ? false : true
+    can_net_meter::Bool = false
+    can_wholesale::Bool = false
+    can_export_beyond_nem_limit::Bool = false
     installed_cost_per_kw::Real = 968.0
     installed_cost_per_kwh::Real = 253.0
     installed_cost_constant::Real = 222115.0
@@ -267,6 +273,9 @@ struct ElectricStorage <: AbstractElectricStorage
     soc_min_applies_during_outages::Bool
     soc_init_fraction::Float64
     can_grid_charge::Bool
+    can_net_meter::Bool
+    can_wholesale::Bool
+    can_export_beyond_nem_limit::Bool
     installed_cost_per_kw::Real
     installed_cost_per_kwh::Real
     installed_cost_constant::Real
@@ -311,6 +320,20 @@ struct ElectricStorage <: AbstractElectricStorage
             @warn "Battery replacement costs (per_kwh) will not be considered because battery_replacement_year is greater than or equal to analysis_years."
         end
 
+        if !s.include_exported_renewable_electricity_in_total && (stor.can_net_meter || stor.can_wholesale)
+            @warn "include_exported_renewable_electricity_in_total = false, but ElectricStorage can_net_meter or can_wholesale is true. REopt's calculation of onsite renewable electricity does not currently accurately account for exported renewable electricity via the battery and will thus overestimate onsite renewable electricity."
+        end
+
+        can_net_meter = stor.can_net_meter
+        can_wholesale = stor.can_wholesale
+        can_export_beyond_nem_limit = stor.can_export_beyond_nem_limit  
+        if stor.off_grid_flag && (can_net_meter || can_wholesale || can_export_beyond_nem_limit)
+            @warn "Setting ElectricStorage can_net_meter, can_wholesale, and can_export_beyond_nem_limit to False because `off_grid_flag` is true."
+            can_net_meter = false
+            can_wholesale = false
+            can_export_beyond_nem_limit = false
+        end
+
         if stor.min_duration_hours > stor.max_duration_hours
             throw(@error("ElectricStorage min_duration_hours must be less than max_duration_hours."))
         end
@@ -422,6 +445,9 @@ struct ElectricStorage <: AbstractElectricStorage
             stor.soc_min_applies_during_outages,
             soc_init_fraction,
             stor.can_grid_charge,
+            can_net_meter,
+            can_wholesale,
+            can_export_beyond_nem_limit,
             stor.installed_cost_per_kw,
             stor.installed_cost_per_kwh,
             stor.installed_cost_constant,

src/core/generator.jl

@@ -19,7 +19,7 @@
     sells_energy_back_to_grid::Bool = false,
     can_net_meter::Bool = false,
     can_wholesale::Bool = false,
-    can_export_beyond_nem_limit = false,
+    can_export_beyond_nem_limit::Bool = false,
     can_curtail::Bool = false,
     macrs_option_years::Int = 0,
     macrs_bonus_fraction::Real = 0.0,
@@ -116,7 +116,7 @@ struct Generator <: AbstractGenerator
         sells_energy_back_to_grid::Bool = false,
         can_net_meter::Bool = false,
         can_wholesale::Bool = false,
-        can_export_beyond_nem_limit = false,
+        can_export_beyond_nem_limit::Bool = false,
         can_curtail::Bool = false,
         macrs_option_years::Int = 0,
         macrs_bonus_fraction::Real = 0.0,

src/core/reopt.jl

@@ -199,6 +199,9 @@ function build_reopt!(m::JuMP.AbstractModel, p::REoptInputs)
         if !isempty(p.s.electric_tariff.export_bins)
             for t in p.techs.elec, u in p.export_bins_by_tech[t]
                 fix(m[:dvProductionToGrid][t, u, ts], 0.0, force=true)
+            end
+			for b in p.s.storage.types.elec, u in p.export_bins_by_storage[b]
+                fix(m[:dvStorageToGrid][b, u, ts], 0.0, force=true)
             end
         end
 	end
@@ -500,7 +503,7 @@ function build_reopt!(m::JuMP.AbstractModel, p::REoptInputs)
 	initial_capex_no_incentives(m, p)
 	if !isnothing(p.s.financial.min_initial_capital_costs_before_incentives) || !isnothing(p.s.financial.max_initial_capital_costs_before_incentives)
 		add_capex_constraints(m, p)
-	end
+	end 
 
 	#################################  Objective Function   ########################################
 	@expression(m, Costs,
@@ -682,6 +685,7 @@ function add_variables!(m::JuMP.AbstractModel, p::REoptInputs)
 
     if !isempty(p.s.electric_tariff.export_bins)
         @variable(m, dvProductionToGrid[p.techs.elec, p.s.electric_tariff.export_bins, p.time_steps] >= 0)
+		@variable(m, dvStorageToGrid[p.s.storage.types.elec, p.s.electric_tariff.export_bins, p.time_steps] >= 0)
     end
 
 	if !(p.s.electric_utility.allow_simultaneous_export_import) & !isempty(p.s.electric_tariff.export_bins)