From b7ab7ee9448373aab484713f0f80062fa4d39d13 Mon Sep 17 00:00:00 2001
From: lbonaldo <bonaldo.luca12@gmail.com>
Date: Fri, 27 Oct 2023 17:50:21 -0400
Subject: [PATCH] [Fix] eELOSSByZone expr: access before initialization

---
 CHANGELOG.md                               | 1 +
 src/model/generate_model.jl                | 4 +++-
 src/model/resources/storage/storage_all.jl | 7 +++----
 src/model/resources/vre_stor/vre_stor.jl   | 6 +-----
 4 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a36a453fe0..83710c9a69 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   Previously there was a typo in this in the multistage code that led to a silent bug, which affects outputs,
   for anyone running non-myopic multistage GenX with asymmetric storage.
 - Fix computation of cumulative minimum capacity retirements in multistage GenX (#514)
+- Fix access of eELOSSByZone expr before initialization (#541)
 
 ### Changed
 - Use add_to_expression! instead of the += and -= operators for memory performance improvements (#498).
diff --git a/src/model/generate_model.jl b/src/model/generate_model.jl
index 2577313df3..45c964c776 100644
--- a/src/model/generate_model.jl
+++ b/src/model/generate_model.jl
@@ -95,6 +95,9 @@ function generate_model(setup::Dict,inputs::Dict,OPTIMIZER::MOI.OptimizerWithAtt
 
 	create_empty_expression!(EP, :eGenerationByZone, (Z, T))
 	
+	# Energy losses related to technologies
+	create_empty_expression!(EP, :eELOSSByZone, Z)
+	
 	# Initialize Capacity Reserve Margin Expression
 	if setup["CapacityReserveMargin"] > 0
 		create_empty_expression!(EP, :eCapResMarBalance, (inputs["NCapacityReserveMargin"], T))
@@ -128,7 +131,6 @@ function generate_model(setup::Dict,inputs::Dict,OPTIMIZER::MOI.OptimizerWithAtt
 
 	co2!(EP, inputs) 
 
-
 	if setup["Reserves"] > 0
 		reserves!(EP, inputs, setup)
 	end
diff --git a/src/model/resources/storage/storage_all.jl b/src/model/resources/storage/storage_all.jl
index 4f5fd7424f..c9d69da1d1 100644
--- a/src/model/resources/storage/storage_all.jl
+++ b/src/model/resources/storage/storage_all.jl
@@ -128,10 +128,9 @@ function storage_all!(EP::Model, inputs::Dict, setup::Dict)
 		end
 	end
 
-	#From CO2 Policy module
-	@expression(EP, eELOSSByZone[z=1:Z],
-		sum(EP[:eELOSS][y] for y in intersect(STOR_ALL, dfGen[dfGen[!,:Zone].==z,:R_ID]))
-	)
+	# From CO2 Policy module
+	expr = @expression(EP, [z=1:Z], sum(EP[:eELOSS][y] for y in intersect(STOR_ALL, dfGen[dfGen[!,:Zone].==z,:R_ID])))
+	add_similar_to_expression!(EP[:eELOSSByZone], expr)
 
 	# Capacity Reserve Margin policy
 	if CapacityReserveMargin > 0
diff --git a/src/model/resources/vre_stor/vre_stor.jl b/src/model/resources/vre_stor/vre_stor.jl
index b3842571cf..6ddeca045b 100644
--- a/src/model/resources/vre_stor/vre_stor.jl
+++ b/src/model/resources/vre_stor/vre_stor.jl
@@ -1166,11 +1166,7 @@ function stor_vre_stor!(EP::Model, inputs::Dict, setup::Dict)
     # From CO2 Policy module
 	@expression(EP, eELOSSByZone_VRE_STOR[z=1:Z],
         sum(EP[:eELOSS_VRE_STOR][y] for y in intersect(dfVRE_STOR[(dfVRE_STOR[!,:Zone].==z),:R_ID],STOR)))
-    if !isempty(inputs["STOR_ALL"])
-        EP[:eELOSSByZone] += eELOSSByZone_VRE_STOR
-    else
-        @expression(EP, eELOSSByZone[z=1:Z], eELOSSByZone_VRE_STOR[z])
-    end
+    add_similar_to_expression!(EP[:eELOSSByZone], eELOSSByZone_VRE_STOR)
 
     ### CONSTRAINTS ###