Life Cycle Data Management

Managing data for a fuel cycle analysis requires the handling several hundred data. This requirement is often applied to dozens of fuel pathways and scenarios. Managing the data and calculating life cycle inventory data becomes a challenging task.

GREET 1.8b is Argonne National Laboratory’s latest version of its fuel cycle model. The recent release includes both functional changes to the model as well as revised data inputs. While the overall structure of the GREET model remains the same, version 1.8b includes minor calculation fixes and new data inputs.

The most conceptually simple approach is to populate GREET 1.8 with all of the CA specific data and move the control panel to GREET 1.8. A key disadvantage is that this approach is time-consuming, especially if the model is to be updated at some point in the future. Life Cycle Associates has developed an alternative tool to populate the GREET model with parameters for different regions and scenarios.

Peek/Poke Life Cycle Associates’

Peek/Poke technique populates the GREET model with new inputs using a simple Visual Basic macro. The macro plugs in the new data and extracts the model results. The Peek/Poke tool includes an organized user interface for both process specific specific and average process fuel pathways.

The tool first “pokes” the data into GREET via the macro for each model scenario. The data are then “peeked” from the GREET model. The Peek/Poke tool can be organized to cycle through a set of fuel pathways automatically. This approach has several advantages. First, it allows for easy synchronization with future versions of GREET. Life Cycle Associates has applied Peek/Poke to both GREET1.7 and GREET 1.8 with limited modifications. In practice, only a small number of “target” cells in GREET are likely to change between model releases, and only those items need to be updated. Secondly, input assumptions can be organized to present a clearer overview to the user, and to facilitate documentation of changed assumptions. Finally, the Peek/Poke tool also includes macros that will automate the GREET runs. A sample user interface for corn ethanol inputs is shown here.

The poke/peek approach has several advantages:

Transparency:Customizations are consolidated in one place, complete with documentation.

Reproducibility:Applying the changes to an unmodified copy of GREET always produces the same results. The best approach is to make the GREET Excel spreadsheet “read-only” to prevent inadvertently saving modifications.

Manageability: GREET is big: version 1.8a weighs in at nearly 10 MB. Rather than proliferating copies of GREET to correspond to different parameterizations, you need only keep copies of the much smaller (~250 KB) “Poker” files.

Easy Updating: When a new version of GREET is released, it is easy to quickly scan the list of customizations to ensure that the locations of the target cells haven’t changed. Generally, only small fraction of cells move in any release. Only those cells that moved require updates.

Peek/Poke Tool allows for the efficient calculation and retrieval of life cycle inventory data from models such as GREET