Updates variable costs

[trevorb1]

Description

In this PR I have:

• Refactored the variable costs module to make custom updates a little easier
• Corrected international variable costs data

The logic for international variable costs data is:

• All international variable costs (mining techs the operate on mode 2) are assigned a standard international cost factor
• If a country level fuel resource limit exists, this cost factor remains
• If a country level fuel resource limit does not exist, the country can NOT contribute to international markets (via a very high variable cost to operate on mode 2)

Issue Ticket Number

Closes #14

Documentation

na

[trevorb1]

@maartenbrinkerink; I believe this is ready for a review now! This includes the changes we discussed with @abhishek0208 the other day. Including:

• MIN techs no longer operate on mode 2
• International costs are the (CMO x TradeMultiplier) unless specified by the user in fuel_prices.csv
• Domestic costs are the CMO unless specified by the user in fuel_prices.csv
• Domestic mining activity limits are zero, unless specified by the user in fuel_limits.csv (see note below on this)

Please find below a schematic showing these changes.

A couple notes:

• The fuel_limits.csv has year as a value, and im not sure why? This file is supposed to specify available reserves? If we have annual changing limits, we should put in capex/opex costs for mining as well? Right now, the limit is taken as the last year value.
• I am assuming the fuel_limits.csv is in PJ?
• I have the variable costs and fuel limits as their own rules, as they relied on very little data from the powerplant script (basically just set definitions). Im happy to push it back into the main script though if you think thats easier.
• I did a couple tests on this with providing a user INT values and whatnot, and it seemed to work fine. But a double check would be great!

[maartenbrinkerink]

@trevorb1 The workflow runs fine on my end. Regarding the multi-year fuel limits I think we should confirm this with @abhishek0208 today. If constant values are the way to go, and not by year, than I think we need to change this in fuel_limits.csv as it gives the wrong impression to users that fuel limits can be changed by year (yet filtered out within the workflow).

Single rules for var costs/fuel limits is grand as long as they stay within the powerplant folder (which they are).

[trevorb1]

@maartenbrinkerink okay, great! I believe this has been updated to reflect our discussion earlier today. Specifically:

• The model period limit constraint has been removed
• A yearly activity limit on each of the domestic mining technologies has been applied, following the values from the fuel_limits.csv file. The same restriction applies though; if no user limits are applied, the max activity is set to zero and the country must import from the international market

[maartenbrinkerink]

Good stuff @trevorb1. I'll merge this into the target updates PR and solve any potential conflicts before merging it into master.