Sunday, March 31, 2013

The Introduction to Closing The Loop

The first question everyone asks is “what does it stand for?”  “CTL” stands for Closing The Loop and the “E” stands for Energy.  And it’s the philosophy we operate by.  Energy is no stranger to the built environment or its designers and has been a huge focus for sustainable/green buildings.  Rightly so, it is a critical component to building and strongly linked to overall building performance and occupant satisfaction.

In this blog, I hope to share my work, my experiences, and my overall understanding of what I do.  I tend to look at things a little differently than most engineers.  For example, when most engineers think of energy, they quickly attach the word efficiency or conservation.  Closing the loop isn’t reached by efficiency or conservation alone; it is achieved by meeting a preferred performance through a sustainable, robust, closed loop system.  Sometimes to accomplish this you have to sacrifice efficiency in some parts of the system for the good of the greater system.  And this can only be accomplished by understanding the systems, the processes, the components, and most importantly how they best work together to meet the desired performance levels in a sustainable manner. 

To answer the next question, “Where did closing the loop come from?”  It comes from my fascination with systems theory and more specifically ecological systems and energetics (the study of energy transformation in systems).  General systems theory basically assumes that complex systems are made up of a combination of fundamental interactions or processes within the systems they occur.  Systems theory has been applied to many different disciplines including ecology, biology, engineering, psychology, economics, etc.

Generally speaking, closing the loop entails completing the path, taking the output and somehow returning it to the input where it started.  Industrial ecology is a good example of how this works.  It is the study of industrial processes as linear (open loop) systems, in which resource and capital investments move through the system to become waste, to a closed loop system where wastes become inputs for new processes. (

When I first started reaching outside of the black box energy model world to create my own models, I found myself struggling to visualize the interactions between these dynamic systems.  I found myself lost and circling in the depths of massive excel spreadsheets.  Then one day I came across the energy systems language.

The Energy Systems Language (A.K.A. Energese) was developed by ecologist Howard T. Odum and colleagues in the 1950s who were studying ecological systems and the energy flows through these systems.  This language has various symbols/graphics that represent fundamental system characteristics specifically applied to energy in systems.  Similar language and systems characteristics are used throughout other systems theory applications and tend to be universally applicable across systems.   (

And the next day after I discovered the energy systems language (not literally), I came across something else called visual programing and suddenly my world got a little brighter.  When I say visual programming, I am referring to software like Simulink, Grasshopper, Dynamo and many others.  I checked on the web and counted nearly a hundred visual programming products (

In addition to stumbling across these products I found myself suddenly in a world that allowed me to very easily start running highly dynamic, highly complex models that were flexible enough to let me figure out the answers I was looking for.  It provided opportunities to do my work faster, smarter, with fewer mistakes and more clarity in understanding the results and interactions between.  Finally, it led me into the world of optimization and by this I mean true optimization… not just running a few iterations and picking the best, now actually running hundreds or thousands of iterations with multiple independent and dependent variables.

I have successfully used this for completing analysis and optimization for complex facades, optimizing individual air handling unit system controls, and optimizing the operation and control of large central plants.  At the same time I have been able to quickly and easily predict energy savings, calculate emissions, and calculate cost savings based on even the most complex Time of Use (TOU) rates.  I can literally set the analysis to minimize cost and it tells you how to operate the plant based on a multitude of changing input parameters (dependent variables) and derived equipment performance and operating characteristics (based on analysis of building automation system trend data or temporary data monitoring).  With the help of visual programming I can also create some of these very complex and very accurate models in a matter of days.  To do the same using the traditional energy model approach could take weeks to run the same number of iterations and the accuracy of the models would generally be very questionable.

In my building systems class at SCI-Arc, the students use Rhino and Grasshopper to develop parametric models for complex façades, the Galapagos evolutionary optimization plugin and various plugins and energy modeling software to identify an optimal design based on typical façade performance factors such as daylight factor, daylight autonomy, solar radiation, etc.  This helps the students perform many multiple tests/iterations at the touch of the button, to see how a range of parameters impact the various performance factors of the system.

Projects like this are what closing the loop is all about.  I look forward to sharing my work and other experiences with you on this blog and I hope to get your feedback along the way.  Don’t worry, wikipedia isn’t my sole source for information, but it is definitely a good one!


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