Overview

In this action, the user evaluates the emissions impact of each resilience solution. The emissions impact refers to measures that reduce a site’s carbon dioxide emissions. This emissions impact is considered alongside risk reduction potential and other decision criteria when prioritizing resilience solutions. This action uses a high-level approach that will help the user determine whether a solution will provide a notable change in the site’s energy-related CO₂ emissions, the metric for a solution’s emissions impact. The analysis focuses on emissions reductions (or increases) resulting from changes to the site’s energy systems (i.e., electricity and/or natural gas), with a specific focus on CO₂ emissions. The information generated from this action will serve as one of several inputs considered under this module that will help inform the overall solution benefit potential in Action 5: Prioritize Solutions.

In-Depth

This action uses a high-level approach to help the user assess the change in CO₂ emissions of each identified solution (or solution set). In the TRN, this is achieved via the following three-step process:

1. Identify present site emissions associated with energy usage.
2. Evaluate emissions reductions associated with enhancing energy efficiency.
3. Evaluate emissions reductions associated with shifts to lower emission sources of electricity.

The user will assess how well each solution (or solution set) reduces the site’s energy-related CO₂ emissions as a percentage of the site’s current CO₂ emissions associated with electricity and natural gas use. CO₂ emissions reduction is estimated relative to total current site CO₂ emissions associated with electricity and natural gas use (i.e., not relative to only critical energy loads as in the TRN’s risk assessment). The intent of this approach is to help estimate additional site-wide benefits associated with emissions reduction (i.e., a reduction in CO₂ emissions), which are considered alongside the risk reduction benefits captured through the risk analysis. This allows the solution analysis to take advantage of emissions reduction benefits beyond those impacting critical loads.

Emissions reductions during outage events associated with a change from higher-emission to lower-emission redundant systems (e.g., diesel generator to renewable microgrid) are not considered by this action. Given the typically limited annual runtime of redundant systems during outage events and for regular testing, their impact on overall site emissions is expected to be much smaller than changes provided by efficiency improvements or shifts to lower-emission sources of electricity for normal operations.

However, a key emissions reduction benefit resulting from changes to redundant systems is included in the action: any resulting emissions changes during normal operations. For example, a renewable microgrid would be unlikely to operate only during outages, but rather would be expected to serve some of the site’s electricity load during normal operations. Such a system may displace higher-emission electricity sources, and thus offer emissions reductions captured by the supply-shifting strategy mentioned above.

The following sections describe the Action 3 steps in greater detail.

Identify Present Site Emissions Associated with Energy Usage

In this step, provide inputs to help characterize the site’s present emissions and energy usage to calculate the potential impact of resilience solutions against present consumption and calculated emissions. The inputs are the following:

1. Average and marginal emissions factors of the site’s utility. These estimates are pre-populated using data from the Environmental Protection Agency’s (EPA’s) Emissions & Generation Resource Integrated Database (eGRID) Power Profiler. Users may vary this input to examine the sensitivity of their results to projected future grid changes.
2. Present annual site energy use which consists of the following:
   • Present annual site electricity use (MWh/year)
   • Present annual site natural gas use (MMBtu/year)

Evaluate Emissions Reductions Associated with Enhancing Energy Efficiency

Efficiency solutions can enhance resilience by reducing demand and allowing redundant systems to supply critical loads for longer. Efficiency solutions can also provide emissions reduction benefits by using less primary supply from carbon-intensive grids. This step allows the user to select the approximate energy use reduction or increase expected from each resilience solution from a drop-down menu. The displayed energy use values are calculated based on percentage ranges relative to the site’s present energy usage.

Evaluate Emissions Reductions Associated with Shifts to Lower Emission Sources of Electricity

Adding on-site electricity generation can enhance resilience by providing additional redundant supply, which in some cases can also be used to offset primary electricity demand. This step calculates the emissions reduction benefits associated with shifting some or all electricity consumption from the utility and/or existing electricity supply to new resources with different emissions factors. This step has two parts. First, the user will select from a drop-down box the approximate percentage of electricity that will be shifted to a resource with a different emissions factor for each resilience solution. Second, from a drop-down box, the user will enter an estimated CO₂ emissions factor for any new sources of electricity (e.g., solar PV microgrid). This factor could be as low as 0 lbs/MWh for a generation source that is fully renewable with no emissions. The appropriate value will depend on the expected emissions associated with the generation technology that would be implemented under the solution. Example emissions factors for a range of technologies can be found in the TRN Resource: Emissions Factors.

Output

Based on these inputs, the TRN determines the following:

• Present total annual site electricity and natural gas CO₂ emissions (lbs/year)
• Total annual avoided site electricity and natural gas CO₂ for each resilience solution (lbs/year)
• Percentage reduction in CO₂ emissions for each resilience solution

Based on user-defined major, significant, and marginal percent reduction categories, an emissions reduction category is automatically assigned to each solution.