24-05-2012, 02:39 PM
I have a question that I believe there may not be an established answer for but I'm hoping to get some ideas of how to implement.
In our model, we would like to assign "upstream" emissions to downstream processes in order to put a constraint on them. Specifically, policies like the Low Carbon Fuel Standard (LCFS) in California assigns life-cycle emissions to the fuels and then sets an intensity target for these fuels to reach over time (gCO2e/MJ). Similarly, California also has a hydrogen emissions mandate requiring that H2 produced needs to have a 30% reduction in life-cycle GHG emissions relative to gasoline (adjusted for differential vehicle efficiency). Obviously we can use static emissions factors from many LCA studies but these don't take into account the dynamics of the choices made in TIMES (like the mix of power plants used to generate electricity, or the resources used chosen to make biofuels). Also the life-cycle emissions can be calculated in excel after the model run is over, but this prevents these calculations from affecting the model run (as in the case of the above mentioned policies).
It seems to me any energy commodity that must be produced but can be used in multiple sectors (electricity, hydrogen, even biomass depending on how the emissions are assigned to its harvest and transport) will have a problem of assigning emissions to end use sectors.
So my questions to start this off are:
1) Is there a good way to endogenously assign a portion of emissions from an endogenous electricity supply to transportation? That is, if transportation uses 5% of total electricity demand, then using a simple average approach, we would assign 5% of electricity related emissions to transportation. Another example would be emissions associated with harvesting and transporting biomass. To the extent that we know that all biomass eventually is used in transportation then it could easily be assigned to transportation, but if some is used for electricity generation, then again we would need to split biomass related emissions up and allocate the correct fractions to each downstream process.
2) I am assuming that once we can assign emissions we can make a user constraint to cap emissions (even it it is an intensity target). In the example of an LCFS, we would sum up all endogenous transportation emissions (from gasoline, diesel, CNG, the assigned emissions from electricity, etc) and
divide by the energy of all transportation fuels (also endogenous) and this must be less than or equal to some specified intensity value for a given year.
This could get really complex really quickly as many levels of allocation might have to be made (ie. some biomass goes into making electricity and some electricity goes into a refinery to make transportation fuels. But I'm looking for a way to just make the large allocations (i.e. electricity for use in EVs).
thanks in advance for your help. I look forward to hearing any suggestions or options you might be aware of or can think of.
Chris
In our model, we would like to assign "upstream" emissions to downstream processes in order to put a constraint on them. Specifically, policies like the Low Carbon Fuel Standard (LCFS) in California assigns life-cycle emissions to the fuels and then sets an intensity target for these fuels to reach over time (gCO2e/MJ). Similarly, California also has a hydrogen emissions mandate requiring that H2 produced needs to have a 30% reduction in life-cycle GHG emissions relative to gasoline (adjusted for differential vehicle efficiency). Obviously we can use static emissions factors from many LCA studies but these don't take into account the dynamics of the choices made in TIMES (like the mix of power plants used to generate electricity, or the resources used chosen to make biofuels). Also the life-cycle emissions can be calculated in excel after the model run is over, but this prevents these calculations from affecting the model run (as in the case of the above mentioned policies).
It seems to me any energy commodity that must be produced but can be used in multiple sectors (electricity, hydrogen, even biomass depending on how the emissions are assigned to its harvest and transport) will have a problem of assigning emissions to end use sectors.
So my questions to start this off are:
1) Is there a good way to endogenously assign a portion of emissions from an endogenous electricity supply to transportation? That is, if transportation uses 5% of total electricity demand, then using a simple average approach, we would assign 5% of electricity related emissions to transportation. Another example would be emissions associated with harvesting and transporting biomass. To the extent that we know that all biomass eventually is used in transportation then it could easily be assigned to transportation, but if some is used for electricity generation, then again we would need to split biomass related emissions up and allocate the correct fractions to each downstream process.
2) I am assuming that once we can assign emissions we can make a user constraint to cap emissions (even it it is an intensity target). In the example of an LCFS, we would sum up all endogenous transportation emissions (from gasoline, diesel, CNG, the assigned emissions from electricity, etc) and
divide by the energy of all transportation fuels (also endogenous) and this must be less than or equal to some specified intensity value for a given year.
This could get really complex really quickly as many levels of allocation might have to be made (ie. some biomass goes into making electricity and some electricity goes into a refinery to make transportation fuels. But I'm looking for a way to just make the large allocations (i.e. electricity for use in EVs).
thanks in advance for your help. I look forward to hearing any suggestions or options you might be aware of or can think of.
Chris