For those of you who don't know, EnergyPlus version 8 was recently released and available for download at http://apps1.eere.energy.gov/buildings/energyplus/. I thought this would be a great opportunity to share a few experiences I have had with this amazing energy simulation engine.
EnergyPlus has been around for a while now. I just did some quick research and found out it actually started being developed in 1996 and had its first released in 2001. Needless to say it has been around for more than a decade, longer than my professional career...
Most people who aren't familiar with the software, don't realize that it is actually a calculation engine and not in the same categories as eQuest, EnergyPro or others which are really only graphical user interfaces. EnergyPlus is the replacement or next generation of the DOE-2 and BLAST calculation engines. Most are familiar with DOE-2 which has various versions and is used by a significant number of graphical user interfaces including eQuest, EnergyPro, Vasari (Autodesk) and many others.
Graphical user interfaces (GUIs) that use EnergyPlus as their calculation engine include DesignBuilder, AECOsim (Bentley Systems), Hevacomp (Bentley Systems), and a few others. OpenStudio (NREL) and Simergy (LBNL) are the two GUIs developed by the DOE and free.
I have been actively using the EnergyPlus for about 4 years now (I can't remember if I started with verison 4 or 5... ) and am continually impressed with the capabilities of the software engine, the forward thinking development of the overall product and most importantly the interoperability and development capabilities.
The documentation is also outstanding... and sometimes a little overwhelming. There are thousands of pages of documentation and I have probably made it through 60% of them. Not in one sitting... or in any particular order. I have learned a great deal about energy modelling and system performance in general, just by reading the documentation pages. If you are a serious modeler, or aspiring modeler... check it out.
To wrap up, I just wanted to add a little bit about some of the more common GUIs, add-ons and other tools I have used related to EnergyPlus:
EnergyPlus Weather Files - One of the most used sources of weather data for energy modelling... but have you ever tried to open and read an .epw file? It is not easy to immediately decipher what data is there, but I created an excel file that reads and graphs the data (a much lower grade version of Climate Consultant software). If anyone wants it email me and I will send you a copy.
EnergyPlus Benchmark Files - These are great for quick benchmarking and tweaking of variables to determine relative changes in energy performance. They are also referenced to ASHRAE 90.1 so you have a dependable/defendable benchmark model.
EnergyPlus Example File Generator - Great starting point for really quick and simplified models. Easily accessible on the web.
Sample EnergyPlus Files - There is an enormous list of example files (more than 400) that come with the software install. They are compiled in a spreadsheet that you can keyword search. I usually use this to find a special system type, like say a fan powered VAV box and can strip out, copy and paste the code into whatever file I am working in.
Ecotect - I can't express enough how great of a tool this is. I hope Autodesk keeps it around. It is such an amazing conduit for software interoperability. I have used Ecotect for generating EnergyPlus .idf files. It isn't my "go-to" tool for geometry creation, but it allows you to do so many quick solar and energy analysis studies. I think I am going to do a whole separate post on how amazing Ecotect is...
OpenStudio - This is probably my "go-to" tool for geometry creation, importing and initial results viewing. It has a Sketchup plug-in which is great for quick, simple geometry modifications. There have also been some significant developments in the overall software that I have yet to explore including a SDK. I plan on exploring this further very soon!
DesignBuilder - Probably the most well known EnergyPlus GUI with its first official release in 2005. This software was originally developed in the UK and has been used as a compliance model there and other places. I tried using Design Builder a few times on a trial basis and found it very useful for model generation and results viewing for simple models (compliance type) which is what I think it was originally intended for. Then, for the detailed or more complex systems, I would take the idf generated by Design Builder and start modifying it to suit my specific needs. I think it is a great "gateway" software for EnergyPlus users. It lets you understand what the typical model inputs are and how those are used to generate an IDF. It also has some decent results reviewing components. But it does have a cost, and as a new business owner, sometimes that cost is not something that is easy to swallow.
Simergy - Similar to opening the EP Launch window and IDF editor of EnergyPlus for the first time and a lot of the new commercial software (IES-VE, AECOsim, etc.), the Simergy interface for me is a little scary. Unfortunately I haven't had the time to really use this tool, but I have heard some positive feedback from some of my peers. Another one I look forward to exploring more!
Title 24 Compliance - One last note. I have heard rumors that EnergyPlus will be the simulation engine required for the 2013 California Energy Code Compliance. The CEC and others are working on a strategy/framework for making it happen. I hope to hear more soon!
I look forward to hearing feedback and recommendations from others!
Wednesday, May 1, 2013
Sunday, March 31, 2013
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. (http://en.wikipedia.org/wiki/Systems_ecology)
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. (http://en.wikipedia.org/wiki/Energy_Systems_Language)
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 (http://en.wikipedia.org/wiki/Visual_programming_language)
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!