Tory Clark 3/23/2011

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We recently received a good question about how LEAP does multiple scenario inheritance. Though documentation already exists for the manage scenarios screen and scenario inheritance, a bit more explanation may be helpful for those looking to do detailed multiple scenario inheritance. Links to user guide documentation are below.

Manage Scenarios: http://tinyurl.com/6fdou6u

Scenarios: http://tinyurl.com/4opbvq3

I have posted a simple example of highlighting how more complex scenario structures work in LEAP named 'Scenario Inheritance Example." You can get it from the Area: Install: Install from Internet menu. I will now walk through that example.

The example has 10 scenarios with values for final energy intensity only. They scenarios are:

(1) Current Accounts
(1) Baseline
(5) Options (representing individual mitigation options)
(2) Packages (representing packages of mitigation options)
(1) Total package (representing packages of packages)

If you look in the manage scenarios screen, I have set it up with only 3 levels. All of the packages are at the same level as the scenarios they inherit from. Also, All scenarios are “Based on” the baseline scenario. This is a best practice for setting up complex scenario structures, but is not required.

In order to think about how LEAP does scenario inheritance you have to know that LEAP just looks for blue equations, or equations that are new in a particular scenario. LEAP finds the “first” blue expression and uses that in the scenario. This is easy to understand in the “baseline” or “option 1” scenario, but is key as we add detail. The order that we look for equations is important, because it defines which blue expression is “first.” I’ve only put in data for the final energy intensity variable to keep things simple.

1) First we look in the immediate scenario for any given expression. If there is a blue expression, we use it and stop the search. If not,
2) We look in the scenarios we immediately inherit from (in order of inheritance), If no blue expressions,
3) We look in secondary inheritance scenarios, and if still no blue expressions
4) We go back up the tree to previous inheritances (i.e. baseline and current accounts)
5) This repeats for all expressions.

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Easy example – Option 1 scenario:

- First we look at the immediate scenario and inherit the value for electricity and MSW.
- This scenario doesn’t inherit from any other scenarios, so we walk up the tree to the scenario that it is based on (Baseline), and inherit the natural gas value.
- Then we go to Current accounts to inherit the blue expression for coal and diesel.

Hard example – Total Package scenario:

- First we inherit the diesel value b/c it is blue in the total package scenario. At this point we stop looking at any of the diesel values and it is set.
- Next we look in the PAC1, sees no blue expressions and goes to PAC 2 and takes the MSW number.
- Next we look at the scenarios PAC1 inherits from (OPT1, 2 and 3) and take electricity from OPT1 and coal from OPT3, then we look at the scenarios PAC 2 inherits from (OPT 4 and 5) and take natural gas number from OPT5.
- Now we have expressions for all branches, so no need to look further (for final energy intensity at least).