Tutorial 11: Global Warming Potential Refrigerant Comparison

Motivation

Global Warming Potential (GWP) values represent how much a substance contributes to climate change compared to CO2. For example, consider HFC-134a with a GWP of 1,430 kgCO2e / kg versus R-600a which has only 3. This means that each kilogram of HFC-134a has the same climate impact as 477 kilograms of R-600a.

Previous tutorials included investigation of modeling these values but this section takes a closer look at specifying tCO2e for substances, modeling both with and without different policies. More specifically, we'll look at a refrigerant substitution policy that gradually replaces HFC-134a with R-600a in domestic refrigeration. This simulation can track this transition as it dramatically reduces overall climate impact (measured in tCO2e) even when total refrigerant consumption remains similar.

Setting Up the Business-as-Usual Scenario

First, let's create our baseline scenario with both HFC-134a and R-600a refrigerants in domestic refrigeration. We'll start with HFC-134a as the dominant refrigerant and minimal R-600a consumption.

Note: In these feature specific tutorials, we will start from scratch each time. Click Save File to save your current work and then click New File to start a simulation.

Step 1: Create the Domestic Refrigeration application

• Click Add Application
• Name it "Domestic Refrigeration"
• Click Finish

Step 2: Add HFC-134a substance

• In your Domestic Refrigeration application, click Add Consumption
• On the General tab:
  • Name the substance "HFC-134a" without quotes.
  • Use Domestic Refrigeration as the Application.
  • Set GHG equivalency to 1430 kgCO2e/kg.
  • Leave Annual energy consumption alone for now.
  • Enable domestic manufacture.
• On the Equipment tab:
  • We will leave Equipment type alone for now.
  • Set initial charge to 0.15 kg/unit for domestic.
  • Set annual retirement rate to 5% each year.
• On the Servicing tab:
  • Set recharge to 10% with 0.15 kg/unit in all years
• On the Set tab:
  • Set prior equipment to 1,000,000.0 units in year 2025.
  • Set domestic manufacture to 20 mt in year 2025.
• Click Finish

Step 3: Add R-600a substance

• Again in the Domestic Refrigeration application, Add Consumption for R-600a with similar equipment properties except different GWP.
• On the General tab:
  • Name the substance "R-600a" without quotes.
  • Use Domestic Refrigeration as the Application.
  • Set GHG equivalency to 3 kgCO2e/kg.
  • Leave Annual energy consumption alone for now.
  • Enable domestic manufacture.
• On the Equipment tab:
  • We will leave Equipment type alone for now.
  • Set initial charge to 0.15 kg/unit for domestic.
  • Set annual retirement rate to 5% each year.
• On the Servicing tab:
  • Set recharge to 10% with 0.15 kg/unit in all years.
• On the Set tab:
  • Set prior equipment to 50,000.0 units in year 2025.
  • Set domestic manufacture to 1 mt in year 2025.
• Click Finish

Step 4: Create baseline simulation

• Click Add Simulation.
• Name it "BAU" without quotes.
• Set duration from years 2025 to 2035.
• Click Finish

You should now see your baseline simulation running.

Step 5: review business as usual

• Select Population.
• Ensure total and million units are selected.
• Select Equipment.
• Ensure All is selected.

This view shows HFC-134a as the dominant refrigerant.

Adding the GWP Reduction Policy

Now let's create a policy that gradually replaces HFC-134a consumption with R-600a. This will demonstrate how a substance substitution policy can reduce overall climate impact.

Step 1: Create the substitution policy

• Click Add Policy.
• Name it "Replacement" without quotes.
• Select Domestic Refrigeration as the application.
• Select HFC-134a as the substance.

Step 2: Configure the replacement mechanism

• Go to the Replace tab.
• Add Replacement of 10% of sales.
• Indicate that it should be replaced with R-600a.
• Set timing to 2028 to onwards.
• Click Finish to finish the policy.

This policy will progressively reduce HFC-134a consumption by 10% each year starting in 2028, with that demand being met by R-600a instead. Over time, this creates a significant shift in the refrigerant mix while maintaining overall service levels.

Creating the Simulation

Now let's create a simulation to compare the policy scenario with our business-as-usual baseline.

• Click Add Simulation.
• Name it "Replacement" without quotes.
• Check the Replacement policy checkbox.
• Set duration from years 2025 to 2035.
• Click Finish.

You should now see both your BAU and Replacement scenarios displayed side by side in the results panel.

Results

Let's examine how the substitution policy affects both substance consumption and climate emissions:

Emissions Changes

• Compare simulations by selecting Simulations and then selecting All in the simulations panel.
• Select the Emissions radio button
.
• Click configure custom and combine recharge and end of life.

The dramatic emissions reduction demonstrates the power of GWP-focused policies. Each kilogram of HFC-134a replaced with R-600a eliminates approximately 1,427 kg of CO2-equivalent emissions. This shows how substance choice can be impactful for climate. However, before concluding, let's also confirm that, despite this drop in GWP, the overall amount of sbustance consumed is the same.

Consumption Changes

• Ensure you are comparing simulations by selecting Simulations and then selecting All in the simulations panel.
• Select the Consumption radio button.
• Select domestic (both substances are domestic only).
• Ensure mt/ year is selected.

Indeed, despite the reduction in GWP, the overall consumption remains unchanged.

Conclusion

You've successfully modeled a Global Warming Potential-focused refrigerant substitution policy! This tutorial demonstrated:

• GWP significance: How refrigerant choice dramatically affects climate impact independent of consumption volumes.
• Substitution policies: Using "replace X% of sales with substance" to model market transitions.
• Climate effectiveness: How targeting high-GWP substances can achieve large emissions reductions.
• Comparative analysis: Evaluating policy impacts against business-as-usual baselines.

The GWP reduction policy shows how focusing on substance characteristics rather than just consumption volumes can maximize co-benefits.

Download the completed tutorial: tutorial_11.qta - this contains the complete GWP comparison model with substitution policy

Next Steps

Tutorial 12 will explore energy efficiency comparisons between different equipment models. You'll learn how energy consumption trade-offs interact with refrigerant choice to provide a more comprehensive environmental impact assessment.

Previous: Tutorial 10 | Next: Tutorial 12