How to Evaluate Environmental Preservation Benefits of an Energy Option

An earlier article in this series – How to Evaluate Benefits Delivered by an Energy Option – showed that a second step in a decision-making process for adopting a renewable energy option might look decision-makers evaluating benefits of energy options available for adoption.  In this article, I’m going to show how anyone can evaluate the environmental preservation benefits of any energy option.

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An energy option might be said to deliver environmental preservation benefits to the extent that adoption of the energy option reduces emissions of greenhouse gases into the atmosphere.

Decision-makers might evaluate environmental preservation benefits of an energy option by modeling and/or measuring reduced greenhouse gas emissions in grams of carbon dioxide-equivalent (gCO₂-e) per unit of electric power service (kWh), per unit of heating & cooling service (kWh or GJ), or per unit of transportation service (person∙km or kg_FRT∙km), supplied or saved by the energy option.

Environmental preservation benefits of an energy option might look like (1) the difference between (a) the sum of the greenhouse gas emissions (in gCO₂-e) incurred to adopt and operate the option over its expected service life (“Incurred Emissions”), and (b) the sum of the greenhouse gas emissions (in gCO₂-e) of already-adopted energy options that are avoided through adoption of the energy option (“Avoided Emissions”), and (2) dividing that difference (in gCO₂-e) by the sum of the energy service (electric power, heating & cooling, transportation) supplied or savedby the energy option over its expected service life, as shown in Figure 1:

Environmental preservation benefits of an energy option for electric power uses might look like this:

Decision-makers evaluating environmental preservation benefits of an energy option for electric power uses might look like this:

Hawaii Story: Decision-makers in Hawaii have entered into and approved a 25-year power purchase agreement (PPA) under which the electric utility serving the island of Kauai is purchasing 36,161 MWh per year of dispatchable renewable energy from a facility that combines 19.3 MW of PV generation with a 70 MWh lithium-ion battery energy storage system (BESS).

Using an incurred emissions figure of 50 kg of CO₂-equivalent (CO₂-e) for each MWh of electric power delivered by the facility, the incurred emissions attributable to the PV component of the facility might be calculated as 45,201,250 kg of CO₂-e over the 25-year term of the PPA. Using an incurred emissions figure of 175,000 kg of CO₂-e for each MWh of energy storage capacity provided by the lithium-ion BESS, the incurred emissions attributable to the BESS component might be calculated as 24,500,000 kg of CO₂-e if the lithium-ion BESS is replaced once during the 25-year term of the PPA. Dividing the facility’s total incurred emissions of 69,701,250 kg of CO₂-e by the 904,025 MWh of electric power delivered by the facility over the 25-year term of the PPA yields an incurred emissions figure of 77g of CO₂-e per kWh of electric power delivered by the facility.

The electric utility has calculated that the PV generation plus BESS facility will avoid consumption of 2,800,000 gallons of diesel fuel per year by the utility. Using a figure of about 10.16 kg of avoided CO₂-e emissions for each gallon of diesel fuel avoided being consumed by the utility, total avoided emissions attributable to the facility might be calculated as about 711,200,000 kg of CO₂-e over the 25-year term of the PPA. Dividing the facility’s total incurred emissions of about 711,200,000 kg of
CO₂-e by the 904,025 MWh of electric power delivered by the facility over the 25-year term of the PPA yields an avoided emissions figure of about 787g of CO₂-e per kWh of electric power delivered by the facility. The difference of about -710g of CO₂-e per kWh between incurred emissions and avoided emissions might be said to be environmental preservation benefits of a 19.3 MW PV plus 70 MWh BESS renewable energy option in Hawaii:

Environmental preservation benefits of an energy option for heating & cooling uses might look like this:

Decision-makers evaluating environmental preservation benefits of an energy option for heating & cooling uses might look like this:

Hawaii Story: A typical solar water heater that serves a tropical household in a place like Hawaii, that has total incurred emissions of about 2643kg of CO₂-e over a 15-year service life, and that saves about 1371 kWh per year of electric power, might be said to have incurred emissions of about 129g of CO₂-e per kWh. A typical solar water heater in Hawaii has been estimated to deliver avoided emissions of about 693g of CO₂-e per kWh. The difference of about -564g of CO₂-e per kWh between incurred emissions and avoided emissions might be said to be environmental preservation benefits of a solar water heater option in Hawaii:

Environmental preservation benefits of an energy option for mobile uses that moves a person might look like this:

Environmental preservation benefits of an energy option for mobile uses that moves a kilogram of freight (kg_FRT) might look like this:

Decision-makers evaluating environmental preservation benefits of an energy option for mobile uses that moves a person might look like this:

Hawaii Story: In urban Honolulu, the percentage of workers who commute to work by bicycle is about 2.0%, more than triple the Unites States national average of about .6%. A bicycle that serves an individual commuter has been estimated to have incurred emissions of about 21g of CO₂-e per person∙kilometer. To the extent that a commuter using a bicycle avoids using a passenger sedan to travel the same commuting distance, the avoided emissions of using a bicycle instead of a passenger sedan have been estimated to be about 237g of CO₂-e per person∙kilometer. The difference of about -216g of CO₂-e per person∙km between incurred emissions and avoided emissions might be said to be environmental preservation benefits of a bicycle option for commuting in Hawaii:

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To evaluate environmental preservation benefits of an energy option, decision-makers might use a computer model – called a “greenhouse gas emissions model.” The greenhouse gas emissions model simulates the greenhouse gas emissions (grams of CO₂-e) attributable to flows of an energy service (electric power, heating & cooling, transportation) in an energy service system (an electric power grid, a heating and/or cooling system, a transportation system) serving a locality or region, as the energy service system presently exists.

Decision-makers might use such a greenhouse gas emissions model to determine what energy services supplied or saved in what amounts by what available energy options serve user demand for those energy services at the lowest total greenhouse gas emissions (called “Total GHG Emissions”).

Decision-makers might evaluate the environmental preservation benefits of an energy option by using an evaluation method that looks like this:

(1)       Create and validate a “base case” for a greenhouse gas emissions model of an energy service system that assumes that greenhouse gas emissions of energy service flows in an energy service system remain as they presently exist (adjusted for known future changes in such greenhouse gas emissions)

(2)       Identify an energy option available for adoption and specify its incurred emissions (in grams of CO₂-e) over its service life

(3)       Assume that the energy option being evaluated is adopted with the energy service system as it presently exists

(4)       Input data – into the greenhouse gas emissions model – about incurred emissions (in grams of CO₂-e) attributable to the energy option over its service life

(5)       Input data – into the greenhouse gas emissions model – about avoided emissions (in grams of CO₂-e) attributable to the energy option over its service life.  For example, avoided emissions attributable to the energy option might look like emissions attributable to existing non-renewable generation that would be avoided under the production cost model used to evaluate economic benefits of the energy option.

(6)       Use the greenhouse gas emissions model to calculate the Total GHG Emissions (in grams of CO₂-e) of the energy service system.

• with the energy option, and
• without the energy option.

(7)       Subtract the Total GHG Emissions without the energy option from the Total GHG Emissions with the energy option, and divide that difference (in grams of CO₂-e) by the amount of energy service (kWh, GJ, person∙km, kg_FRT∙km) supplied or saved by the energy option over its service life, to obtain a figure expressed in dollars per unit of energy service (grams of CO₂-e per kWh, grams of CO₂-e per GJ, grams of CO₂-e per person∙km, grams of CO₂-e per kg_FRT∙km).

Here’s a summary of such a method for evaluating environmental preservation benefits of an energy option for electric power uses:

An energy option might be said to deliver environmental preservation benefits to the extent that the figure expressed in grams of CO₂-e per unit of energy service is negative (reflecting reduced greenhouse gas emissions from avoided emissions in excess of incurred emissions) because Total GHG Emissions with the energy option is less than Total GHG Emissions without the energy option. An energy option that delivers environmental preservation benefits might be said to deliver a “carbon drawdown” because its avoided emissions exceed its incurred emissions.

An energy option might be said to deliver environmental preservation detriments to the extent that the figure expressed in grams of CO₂-e per unit of energy service is positive (reflecting incurred emissions in excess of avoided emissions) because Total GHG Emissions with the energy option is more than Total GHG Emissions without the energy option. Such an energy option might be said to be adopted at a net increase in the greenhouse gas emissions borne by users of the energy service.

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An energy option delivers an environmental preservation benefit to the extent that avoided greenhouse gas emissions attributable to the option are greater than its incurred greenhouse gas emissions (color-coded green in Figure 10 below). Such an option reduces greenhouse gas emissions – and reverses global warming — because the avoided emissions from adopting and using the option exceed the emissions of acquiring and using the option.

An energy option delivers an environmental preservation detriment to the extent that its incurred greenhouse gas emissions are greater than avoided greenhouse gas emissions attributable to the option (color-coded red in Figure 10 below).  Decision-makers might be expected to resist adopting options that deliver an environmental detriment if other options are available that deliver performance benefits, economic benefits and environmental preservation benefits.

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If decision-makers are in consensus on a method for evaluating environmental preservation benefits of available energy options, they next might ask themselves, “What might evaluating supply security benefits of an energy option look like?”

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In the next article in this Reversing Global Warming series, you’ll learn how to evaluate the supply security benefits of any energy option.

Thank you for reading this article.  I’m grateful for your comments.