Greenhouse Gas Management of Emissions from Purchased Energy

Carbon emissions associated with energy use are often a mix of on-site fossil fuel usage and off-site emissions from regional utilities. When evaluating a building’s or campus’s present-day carbon footprint tied to energy use, assessing the impact of carbon emissions associated with purchased energy can be complicated.

The blend of fuels used to support an electric grid can vary greatly by both region and time of day, but there are resources available to gain a better understanding of this data. To simplify the process, health care organizations can also use a simplified location-based methodology such as eGRID.  

How to measure:  

The measurement process begins with assembling electricity consumption. This can be directly from bills, or from a bill pay service, if used.  

Electric grids typically powered by a blend of renewable (solar, wind, nuclear, etc.) and fossil fuel-based (natural gas, coal, petroleum) energy sources. Each fossil fuel type results in a quantity of carbon emissions per kilowatt-hour (kWh) generated, often referred to as a CO2 emissions intensity, measured as total carbon dioxide per thousand British thermal units (tCO2/kBtu) or per kilowatt-hour (tCO2/kWh). Fossil fuels have a relatively stable CO2 emissions factor (for example, natural gas combustion generates 0.00005311 tCO2e per kBtu; #2 fuel oil combustion generates 0.00007421 tCO2e per kBtu.) Each local grid generates electricity using a blend of these fuels sources throughout the year, resulting in a resultant CO2 emissions intensity that directly ties to the fuel sources of that generation. The Energy Information Administration collects and shares energy data from each state to help estimate the carbon emissions per kBtuh or kWh used.1  

Carbon emissions associated with the electric grid also varies based on time of use. The Emissions & Generation Resource Integrated Database (eGRID)2 is a comprehensive source of data that can help support a detailed analysis of grid emissions. Utilities typically base-load the more efficient and “green” generation plants so they run the most hours of the year. As the electric load on the network increases (e.g., during the hottest days of summer), the worst-performing plants start to run, resulting in a higher level of carbon emissions. This level of precision can vary by specific grids and, in urban environments, can even be impacted per each neighborhood. The value of load shifting to off-hour electric usage can be challenging to quantify for emissions, but a target of “flattening” the energy usage throughout the day can support this effort. Cambium3 is another emissions dataset that may be useful to further understand the impact of hourly impacts on emissions.  

Predicting the trajectory for this fuel blend in the future adds another layer of complication to the equation. This may have an impact on decisions for capital infrastructure investments, but it can be hard to pin down a specific “carbon payback” of system selections. In many parts of the United States, there are significant indicators of a shift toward additional reliance on green energy sources. This improvement can be more closely anticipated for states where upgrade projects are planned, approved, funded or in progress. Even in states without a formal plan, societal pressure and rising costs of fossil fuels make investment in renewable energy sources more appealing. Shifting from on-site fossil fuel burning to systems that are dependent on the electric grid positions buildings to improve their carbon footprints passively as the central electric grid improves.  

How to manage:

Emissions associated with purchased energy can vary significantly from region to region and are typically beyond the control of the institution to directly impact. One way to have more selectivity on the electric source is by purchasing renewable energy certificates (RECs). RECs certify that a portion of the energy supplied to the building was generated from a renewable source and support the growth of the renewable energy market. RECs are a green-power procurement strategy that allows utility users to purchase specific renewable portions of the power generated. Although the renewable blend of power delivered to the site is still the same, this solution allows a health care organization to take ownership of the renewable electricity to support carbon tracking efforts.  

The Environmental Protection Agency4 provides resources on the how RECs can positively affect the end user’s carbon usage and support the continued growth of a green electric grid. RECs play an important role in the gridwide transition to green power and are a significant first step, but they are not a comprehensive solution. Regional policies may have differing strategies on how these play into carbon accounting, so the impacts of these credits vary.  

With limited ability to influence the grid directly, the most impactful adjustments that an institution can make to reduce its carbon impact remain with the buildings themselves through energy use reduction. Until the grid is fully powered by renewable energy, reduction in electric use is the most reliable way to mitigate carbon emissions from utilities. ASHE’s Energy to Care®5 program offers a range of tools and resources for tackling large and small projects to reduce energy usage. It provides tools for:  

  • Benchmarking to help health care organizations understand their current energy use and track improvements over time.
  • Educational tools for teams to learn more about best practices for energy use reduction.
  • Dashboards to help manage ENERGY STAR® data and energy and utility costs.  

Some of the improvements that can make the most impact involve simply ensuring that systems are operating as intended. A thorough retro commissioning analysis (see ASHE’s Health Facility Commissioning Handbook for more) can help identify operational shortfalls that result in significant increases in energy use. ASHRAE6 provides tools to guide facilities professionals through performing energy audits at different levels. This process includes evaluating existing conditions to develop a baseline, reviewing that operation for improvements in system operation and developing a strategy for enhanced capital improvement projects. Control modernization programs and similar strategies can also result in significant improvements without requiring major renovations and disruption to hospital operations. These updates can allow for more accurate operations of heating, ventilation and cooling (HVAC) systems and can take advantage of setbacks when there is an opportunity do so.  

More aggressive carbon emission goals typically require shifting fuel sources to electrified solutions, commonly referred to as electrification7. Current and projected technology indicates a limited improvement in carbon emissions associated with natural gas-based fuel sources over the coming decades, but electricity has many renewable technologies that continue to be implemented. Opting for the utility with the lowest carbon intensity (electricity) and moving away from direct fossil fuels (like utility-provided natural gas) ties the building’s energy use to a more renewable source.  

To take full advantage of these improvements as the grid becomes more renewable, health care organizations should consider shifting to electrified cooling and heating systems and decommissioning steam-driven chillers and on-site boiler plants that rely on purchased natural gas. With electrified chiller plants, hot water can be generated through condenser water heat recovery, providing electrified cooling and heating. When winter heating needs of the building are more significant than the cooling need, solutions like air-source heat pumps can be deployed to provide additional electrified heat. These can also support loads where low-temperature hot water is insufficient for heating but provides heat to water-source heat pumps generating domestic hot water or steam.  

Robust transitions such as these can have a significant impact on hospital operations and often require years of planning and strategy to achieve, so developing a framework to tailor these solutions to a given hospital can be beneficial even before the local grid has achieved significant improvements.  

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