No, but it is important to have startup and shutdown data in the model in order for it to be robust. This allows the PEMS to provide accurate predictions for these normal operations. The PEMS will process the data like any other load condition and generate the appropriate prediction.
There are some methods we use in building the model that account for process hysteresis and other time related emission profiling that is typically associated with startup and shutdown. As an example, let us assume a gas turbine typically operates at 40 to 100 MW load and the megawatt output is used as a critical input in the model.
During startup, the unit is ramped up at 10 MW, then after 15 minutes the load is applied and brought up rapidly to 40 MW. If the database only contains data from 40 MW to 100 MW and the envelop reflects this, we would be unable to generate valid predictions when the load was 0 MW. If we include startup data (with 0 MW) in the database, the envelope would be extended such that 0 to 100 MW is covered.
If this turbine runs at 20 MW, the model will not show an envelope excursion, but will also not generate valid data at that point (the PEMS status will be invalid). Again, our solution is to add the 20 MW data to the database. It is always better to add data in correcting a model deficiency, as this allows the model to get progressively better over time with a wider envelope and more robust database underlying the predictions.
The same is true for dual fuels or multiple fuels. Each different fuel combination uses the corresponding data in the database. We do not need to treat the dual fuel condition differently than the single fuel or startup data. We just need to ensure we have the data in the database to handle all the different normal fuel firing conditions.