Consultation about cost index

[zasddsgg]

Hello, may I ask you some questions about the cost index. Thanks for your help.

a) How does the price of stream, such as CSL, DAP (https://github.com/BioSTEAMDevelopmentGroup/Bioindustrial-Park/blob/master/biorefineries/cellulosic/streams.py#L78-L79), which is in year 2009, translate into price in year 2007? By calling the cost of the stream, it seems that the cost of the stream is still calculated using 2009 prices.

b) For equipment, such as ContinuousPresaccharification in https://github.com/BioSTEAMDevelopmentGroup/Bioindustrial-Park/blob/master/biorefineries/cellulosic/units.py#L340, it gave the 2009 cost index, but does not give 2007 cost index, so could I consult you how the cost is translated into 2007?

c) If the process is simulated now, is it more appropriate to convert all cost to 2024 (Assume duration=(1994, 2024))? If so, for example, if the price of 2021 can be checked now, is the formula cost(2021)*cost_index(2024)/cost_index(2021) used to translate equipment cost and chemical cost in 2021 to 2024?

[yoelcortes]

@zasddsgg, costs of material streams are not altered in any way. The equipment cost (including purchase costs) is automatically adjusted to the new CEPCI through biosteam.settings.CEPCI: https://biosteam.readthedocs.io/en/latest/tutorial/Getting_started.html#Process-settings

The costs of material streams should not be adjusted by the CEPCI. Instead, there are other cost indexes that can be used (e.g., the producer price index). You will find that the price index can be very dependent on the specific commodity chemical (so you might not want to use it for all streams) and it can oscillate from year to year. I am open to including the option of using producer price indexes, but it would take a while to introduce this feature.

[zasddsgg]

So when defining the price of material stream, the price of the reference year should be directly adopted, such as in the cellulosic_ethanol model, cost of the material stream in 2007 (not in 2009) should be adopted when defining the price of material stream, is it right?

Besides, if the process is simulated now, is it more appropriate to convert all cost to 2024 (Assume duration=(1994, 2024))? If so, for example, if the price of 2021 can be checked now, is the formula cost(2021)*cost_index(2024)/cost_index(2021) used to translate equipment cost and chemical cost in 2021 to 2024?

[yoelcortes]

I don't understand your questions too well. But it is pretty simple:

• BioSTEAM assumes stream prices are constant (no cost index).
• Capital costs are rescaled to the present cost index as explained here (https://biosteam.readthedocs.io/en/latest/tutorial/Inheriting_from_Unit.html#Cost-decorator).

[zasddsgg]

What I want to express is the following meaning.

In NREL's corn stover model, both equipment cost and material cost are cost in 2007. If material cost is cost in other years, index will be used to convert the cost in 2007. BioSTEAM assumes material cost as constant, so when defining material stream cost (such as in https://github.com/BioSTEAMDevelopmentGroup/Bioindustrial-Park/blob/master/biorefineries/cellulosic/streams.py#L68-L71), the input price should be the price of the material in 2007, not the price in other years, is that right?

Besides, if the process is simulated in year 2024, is it more appropriate to convert all cost to 2024 (Assume duration=(1994, 2024))? If so, for example, if the equipment cost in 2021can be found, is the formula cost(2021)*cost_index(2024)/cost_index(2021) used to translate equipment cost in 2021 to 2024?

[yoelcortes]

The prices in cellulosic/streams.py are for NREL's 2011 report (yes).

If you would like to update capital costs to 2024, just set the CEPCI to it's value in 2024 just like in the documentation: https://biosteam.readthedocs.io/en/latest/tutorial/Getting_started.html#Process-settings

Thanks