Monthly Archives: March 2008

Plant Dispatch

Is it really March already?

I must be having way to much fun, because time really seems to be flying these days.

One item which keeps coming up, is plant dispatch.  What is the best way to dispatch a plant?  I would vote for efficiency based dispatch, of course.  Which means you need to know what your current efficiency (heat rate) is, and how that will change when you go to a new load – or need to operate under different conditions.

To that end, I’m working with a number of clients on putting together dispatch tools – all spreadsheet based.  In some cases, these are day-ahead spreadsheets, where the user enters the weather forecast for tomorrow, and the spreadsheet will spit back the expected capacities and heat rates for various “units” of the plant (base load, steam augmentation, duct burners, chillers, etc.).  In other cases, the user provides a long-range forecast, with expectations for different months or seasons, to see how the plant will do over the next 1, 5, 10 or 20 years.  When you add in expected gas and electricity prices, a picture of the overall plant economics comes into play. 

While some might call these “just spreadsheets” (which is what they are), they also lean on the power of VBA (visual basic for applications, or macros).  By putting the expected plant performance curves into VBA functions, you gain a lot of flexibility in how you can use the information.  You can determine when the plant will beat the spark spread and be in the money – when you can expect to be dispatched – when the best time to plan a major outage would be (when you expect not to be dispatched) – the list could go on…

I mentioned using these spread-sheets for day-ahead expectations, but they can also be used for hour-ahead expectations, or even current hour expectations.  Where are you versus where you expected to be?  How much can you offer the dispatcher if they call on you to “max out” your available capacity? 

Maybe you know of another application for these spreadsheet models – is there anything you need that you haven’t been able to find out  there in industry?

Or, do you use something besides a spreadsheet tool for these kinds of questions?

I’d be interested to hear from you.  I’m always looking for a better, more efficient, way to do things!

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