I had some questions concerning running optimization scenarios in LEAP.

1- Why does the results differ when running the same scenario but choosing a different optimizing framework ( NEMO vs. OSeMOSYS) ?

2- Does the number of iterations set in the calculations tab affect the results of the optimizing framework?

3- What is the difference between maximum capacity and maximum capacity addition relating to optimization? If I put a process unlimited in Maximum capacity and set it to zero in maximum capacity addition, how will it be interpreted by LEAP?

4- If I have entered that a process will retire by 2035 for example and then left the maximum capacity and maximum capacity addition unlimited, will the optimizing framework assign a value to it after 2035?

5- After running the optimizing framework, and then checking the optimized new capacity tab in Analysis, I find that almost all processes are "0 calculated by NEMO" and only 2 or 3 processes have values . On which basis the optimizing framework chooses the processes to calculate(as they change from optimizing framework to another)? Is there a way to choose more (or all ) processes to optimize?

6-If I want to put a cap on a process in optimization, Is it entered in maximum capacity? and in that case what to enter in maximum capacity addition?

7- When running NEMO optimizing framework and using the MOSEK solver, an error message appears that the MOSEK license can't be found?

Thank you so much for your help.

>>1- Why does the results differ when running the same scenario but choosing a different optimizing framework ( NEMO vs. OSeMOSYS) ?

You should get very similar results in most circumstances. However, different solvers can identify different optimal solutions. Note also that NEMO does support some capabilities that OSeMOSYS does not and in particular has superior handling of times slices. If you are getting very different results, please feel free to send us your LEAP data set and we will investigate if there are any issues with LEAP and/or NEMO or OSeMOSYS.

>>2- Does the number of iterations set in the calculations tab affect the results of the optimizing framework?

It might. If a system needs to be solved iteratively (most do not) then the module being optimized may see different overall requirements for the fuels it produces.

>>3- What is the difference between maximum capacity and maximum capacity addition relating to optimization?

The first is the overall maximum across all years in the scenario. The second is a maximum addition for any particular year.

>>3a If I put a process unlimited in Maximum capacity and set it to zero in maximum capacity addition, how will it be interpreted by LEAP?

It won't add any of that process because you have told it the max addition is zero in any year.

>>4- If I have entered that a process will retire by 2035 for example and then left the maximum capacity and maximum capacity addition unlimited, will the optimizing framework assign a value to it after 2035?

You can manually retire plants that existed in Current Accounts using the "Exogenous Capacity" variable. The optimization calculations then occur on whatever demand cannot be met the exogenously specified plants. If the optimization thinks the plant type is cheap enough it may add back capacity for it.

>>5- After running the optimizing framework, and then checking the optimized new capacity tab in Analysis, I find that almost all processes are "0 calculated by NEMO" and only 2 or 3 processes have values . On which basis the optimizing framework chooses the processes to calculate(as they change from optimizing framework to another)? Is there a way to choose more (or all ) processes to optimize?

If the values are zero this means LEAP/NEMO thinks those plants would not figure in the least cost system. You can force plants back into the system using a number of different "constraint" variables, such as the "Minimum Capacity", "Minimum Capacity Addition" or the "Renewable Target" variables. Bear in mind that the more you force plant types to be built and operated, the further you will diverge from the least cost energy system. Note that other variables such as emission constraints may also cause different mixes of plants may be built and operated.

>>6-If I want to put a cap on a process in optimization, Is it entered in maximum capacity? and in that case what to enter in maximum capacity addition?

The Maximum Capacity and Maximum Capacity Addition variables will cap the amount built of a process (MW). The Maximum Availability variable can be used to cap how much the process is dispatched. Note that this variable can be set for a whole year or it can be used to specify how availability varies by season, by day-type or even by hour of the day.

>>7- When running NEMO optimizing framework and using the MOSEK solver, an error message appears that the MOSEK license can't be found?

That probably indicates you have not yet purchased (and installed) a license for MOSEK. Details on how to do that here.

In general, I would recommend to start by testing out the free CBC solver. You can't argue with the price and it seems to calculate almost as quickly as the more expensive commercial solvers (CPLEX, GUROBI, MOSEK, etc.). It is also built in to NEMO.

>>If I have some processes in my optimization scenario which will not be available by a certain year in the future, some other processes I want to cap the amount built of them (MW) , and the rest "unlimited". What shall I enter in the Maximum capacity and maximum capacity addition for each case of the three (1- Retired process by 2030. 2- Process I want LEAP to stick to the exogenous capacity of it. 3- Process which LEAP can add unlimited capacity)?

Suggest using Maximum Capacity variable to retire (1). Use Maximum Capacity Addition of 0 for (2) No capacity constraints for (3).

>>Secondly, If I enter the same expression of the exogenous capacity in the maximum capacity for a process, and the maximum capacity addition is "unlimited" , how will LEAP interpret this ? Will LEAP ,while optimizing, exceed the capacity of this process specified in the exogenous capacity?

(If the maximum capacity addition is zero in the previous case instead of "unlimited", LEAP optimizing framework will not include this process capacity while optimizing , right? )

You should not normally enter the same expressions for exogenous capacity and maximum capacity. The former is intended to describe pre-existing processes. The latter is intended to constrain how much capacity of a process is built.