Friday, April 12, 2013

Transient Modelling: Wikipedia

12 April 2013: I was very glad to learn of the concept of Transient Modelling (as against Steady State modelling).  Duncan Faulkes of Sustain Ltd was a speaker at CIBSE before me, and used this expression when he described his work with optimising the size of a heat store as part of a biomass boiler system. This is what I have been doing for the thermal model for my boreholes, but didn't call it that. I also checked Google and Wikipedia and found that it is referred to in many documents, but was astonished to find that nobody has created a Wikipedia entry for it. I have taken the liberty of creating a Wikipedia entry for it, and hope that it will be accepted by the editors. Even if it is not, here it is anyway. I have avoided mentioning my Sunboxes, boreholes or anything specific to the Peveril Solar project, but have linked it to skyscrapers, another of my special interests. The temporary entry reference is but I have found in the past that the Wikipedia editorial team are very analytical, so who know if it will still be there in a week's time? I have already been asked to do some edits - put in more links and improve the formatting.

Transient modelling is a way of looking at a process with the primary criterion of time, observing the pattern of changes in the subject being studied over time. The obverse of it is Steady state, where you might know only the starting and ending figures but do not understand the process by which they were derived. Transient models will reveal the pattern of a process, which might be sinusoidal or another shape that will help to design a better system to manage that process. Transient models can be done on a spreadsheet with an ability to generate charts, or by any software that can handle data of inputs and outputs and generate some sort of a display. Transient modelling does not need a computer.  It is a methodology that has worked for centuries, by observers noting patterns of change against time, analysing the result and proposing improved design solutions. 
    A simple example is a garden water butt. This is being topped up by rainfall from the roof, but when the butt is full, the remaining water goes to the drain. When the gardener draws water off, the level falls. If the garden is large and the summer is hot, a steady state will occur in summer where the butt is nearly always empty in summer. If the season is wet, the garden is getting water from the sky, and the butt is not being emptied sufficiently, so in steady state it it will be observed to be always full.
    If the gardener has a way of observing the level of water in the butt, and a record of daily rainfall and temperatures, and is precisely metering the amount of water being drawn off every day, the numbers and the dates can be recorded in spreadsheet at daily intervals. After enough samples are taken, a chart can be developed to model the rise and fall pattern over a year, or over 2 years. With a better understanding of the process, it might emerge that a 200litre water butt would run out 20-25 days a year, but a 400 litre water butt would never run out, and a 300 litre butt would run out only 1-2 day a year and therefore that would be an acceptable risk and it would be be the most economical solution. 
      One of the best examples of transient modelling is [transient climate simulation]. The analysis of [ice cores] in glaciers to understand [climate change]. Ice cores have thousands of layers, each of which represents a winter season of snowfall, and trapped in these are bubbles of air, particle of space dust and pollen which reveal climatic data of the time. By mapping these to a time scale, scientists can analyse the fluctuations over time and make predictions for the future.
     Transient modelling is the basis of weather forecasting, of managing ecosystems, rail timetabling, managing the National Grid, setting the national Budget, floating currencies, understanding traffic flows on a motorway, solar gains on glass fronted buildings, or even of checking the day-to-day transactions of one's monthly bank statement.
     With the transient modelling approach, you understand the whole process better when the inputs and outputs are graphed against time.

References or examples:

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