`invest_method` to be used for a storage group when there is a lower limit but infinite upper limit.

[hbshrestha]

I have defined 10 battery nodes for 10 regions in node_c sheet as shown:

I also specify the invest costs, lifetime and interst rate in node_c sheet.

Then, I define connection objects in connection_c sheet where I specify invest_cost as zero as stated here.

I have a Battery_Storage_Group group which is created in group_connection_node sheet as shown:

I want to allow a minimum investment of 1357 MW in battery storage group in a year. But there should not be any upper limit to it.
I am using the invest_no_limit method. Is it the correct invest_method to be used in this case?

[ArttuTupala]

If you want the invest_min_total to be active, use invest_total as the method. The maximum limit is used only if it is defined in the 'invest_max_total' for that entity

The methods are the following:

• invest_no_limit: no limits
• invest_total: uses the invest_max_total and invest_min_total limits, if they exist
• invest_period: uses the invest_max_period and invest_min_period limits, if they exist
• invest_period_total: uses invest_max_total, invest_min_total, invest_max_period and invest_min_period, if they exist

The same applies if one wants to retire. For example:

• retire_total uses the retire_max_total and retire_min_total limits, if they exist

Also, the combination of the two exists:

• invest_retire_total uses invest_max_total and invest_min_total, retire_max_total and retire_min_total, if they exist

Finally, if one wants to have all the limits:

• invest_retire_period_total

[hbshrestha]

Thanks Arttu!

Does that mean I need to have two rows in this case for the same alternative to set a fixed lower limit and infinite upper limit?
Row1: invest_total: 1357 MW (invest_min_total)
Row2: invest_no_limit: kept blank

Or would you suggest to specify invest_total with 1357 MW as lower limit and a very high number (say 999999) as upper limit?

[jkiviluo]

The 2nd option (very high upper limit - don't make too high though, helps the solver) at least works. The first option I would need to check.

[hbshrestha]

This is an interesting case as I want to have minimum investment limit and infinite upper limit. Moreover, I want to invest in a group of storage nodes.

What failed for me:
I understand the default invest_method is not_allowed.
When I specified invest_total limits of 1357 MW minimum and 99999 maximum to Battery_Storage_Group, the model was infeasible.
This is because it is not possible to define this minimum limit across different nodes in node_c sheet, and the limits/no limits in node_c sheer or connection_c sheet contradicts with specific limits in group_c sheet.

When was the model feasible:
When I did not include the Battery_Storage_Group in group_c sheet, plus
i.) I specified invest_no_limit method in node_c and connection_c sheets respectively, the model is feasible.

ii.) I specified invest_total of 99999 in node_c sheet and invest_no_limit in group_c sheet, the model was feasible. In this case, I got about 480 MW of battery investment across two nodes.

[jkiviluo]

So, there was a group limit saying that there should be at least 1357 MWh of Battery storage capacity, but all of your battery storage nodes were using the default invest_method 'not_allowed'. Consequently, there could not be any battery capacity. And that is of course infeasible. We should have a warning about that.