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11 points every architect, engineer, contractor and their clients should know about exergy - sample slides. For additional support visit our visitor services page.

Our integrated design program has over 2100 slides illustrating architectural, interior design and HVAC engineering principles which contribute to indoor environmental quality and energy allocation for conditioning the occupants and building.

The following course materials on exergy theory are samples from our E5 lecture and based on a Steven Covey principle of "Begin with the End in Mind". They are a very small but important sample of the Covey principle and are provided here to give you an idea of what kind of materials we'll be discussing during the program.

The course is also registered with AIA and participants can earn up to 21 Learning Units.

For more sample slides visit our list of training modules.

Figure 1: I call this the E5 for encompassing five words representing elements of energy sustainability. Most consumers have some basic understanding of energy and efficiency and perhaps the word entropy but exergy and efficacy are terms that escape the general public and many also within the world of architecture and engineering.(1)

Figure 2: In the world of exergy analysis it possible to have a community of homes having the zippiest 97% energy efficient appliances with sophisticated programmable thermostats but still be only 3% exergy efficient. Let me explain...within building science, the exergy efficiency of an energy system evaluates the destruction of potentially useful work contained in the energy. Most buildings in North America have very low exergy efficiency in that they only use a very small fraction of the work potential in the energy used for furnaces, boilers, water heaters and air conditioners - regardless of their Energy Star rating!

Figure 3: A exergy comparison from the past and present. I took these photo's of the Manitoba Hydro Building while there teaching an IAQ course for the Heating, Refrigeration and Air Conditioning Institute of Canada. Framed by the light hardware in the left image is the solar chimney used to pull a draft for naturally ventilating the entire building - see all the open windows? On the right is a picture of the same solar chimney from another angle; and next to it a chimney from the old power plant located just down the street. If you can - try to picture a time when that old brick chimney was working to pull a draft on a combustion system and then compare that image to the solar chimney on the Manitoba Hydro Building. In both case there is/was a flow of energy but in the modern chimney it is being done without combustion and the work being done is accomplished with low duty temperatures differentials within a very narrow band; and in the other with temperatures of an extremely wide band. The old process used heavy duty temperatures and destroyed a lifetime of opportunities to accomplish much greater work...it was exergy inefficient.

Figure 4: In heating, ventilation and air conditioning (HVAC), exergy asks, what is the most possible work we can do with the range of temperatures we are working with, starting with the temperature of the flame and the temperature we need to create comfortable conditions. Consider most natural gas power plants and consumer gas appliances generate approximately 2800°F (1500°C) flame temperature so that we can have approximately 90°F (32°C) media for creating space temperatures of 72°F (22°C). But what happens to the rest of the highly useful temperature? It becomes part of the entropy process which is why - when energy is converted (heat from gas), entropy occurs (jacket losses and vented exhaust) and exergy (work potential) is destroyed. In a preferred process, 2800°F (1500°C) flame temperature could be used to convert water to steam, steam to generate power and the condensate cooled in less industrial process such as space heating. The latter example is know to be, "exergy efficient" because we are doing as much work as we possibly can with the temperatures we have generated.

Figure 5: So now that you have considered that the flame at the power plant or in your basement is 3889% hotter than the conditions we are trying to maintain, can you see how incredibly wasteful it is using an industrial process such as combustion for such non-industrial purposes as HVAC.  When we burn hydrocarbons - a limited resource - we are in fact destroying for future generations an opportunity to create high temperatures which can and should be used for more "heavy duty" needs. We can say that the high temperatures generated are not proportional to the low temperatures needed - it is, "exergy inefficient". On the other hand if we can use non-combustion or non-compression systems such as solar (appx. 220°F (104°C)) or geothermal (appx 50°F(10°C)) we are significantly closer to the temperatures we need to condition our buildings.(2) These systems are said to be, "low exergy systems"; and when source temperatures are close to the demand temperature they are said to be, "exergy efficient".  

Figure 6: In our course we emphasize the message above and point out that radiant based HVAC systems are ideally suited for low exergy systems because the low temperatures needed for heating and high temperatures needed for cooling are closer to the source temperatures available from the earth and sun.

Figure 7: When we use high exergy fuels like hydrocarbons to heat our bodies - it is as I like to point out, equivalent to putting a blow torch to your skin. Using a limited resources to heat our bodies when better matched temperatures are available is likely the most selfish act one generation can do to another.

Figure 8: I love this Tony McConnell image from our friends at Science Photo Library; it illustrates the entropy flow from a cooling tower at a power plant.  The entire purpose of a cooling tower is to shed heat - heat that could be used elsewhere. This slide is for those who believe that all electricity is 100% efficient.

Figure 9: Take some time to study this slide - it really summarizes what exergy is all about...and by all means come to our classes to learn a little more about this very important topic.

Figure 10:  So there you have it, E5 ...when you connect it to the pure principles of "green" you end up with the study of energy and environmental sustainability.

Figure 11: At the end of the day no matter what program you subscribe to or promote it all comes down to earth stewardship and in my opinion that is what mankind ought to be focused upon.

So there you have it, a few sample slides from our E5 lecturer...just a hors d'oeu·vre from our library of over 2100 slides addressing a small but important element of integrated design and radiant based HVAC systems. In the program we will get into this and a whole lot more? How much more? Well just follow the links to the other parts of our website and you’ll get a feel for the scope of materials that we’ll be covering.

See you soon.

Robert Bean, R.E.T., P.L.(Eng.)
Registered Engineering Technologist - Building construction (ASET #8167)
Professional Licensee (Engineering) - HVAC (APEGA #105894)
Building Sciences / Industry Development
ASHRAE Committees: T.C.61. (CM), T.C.6.5 (VM), T.C. 7.04 (VM), SSPC 55 (VM)
ASHRAE SSPC 55 - User Manual Task Leader

Note: The author participates on several ASHRAE and other industry related committees but be advised the materials and comments presented do not necessarily represent the views of these societies, only the president of the society or nominated representative may speak on behalf of the organization.

  1. I don't recall where the quote came from so if anyone knows please let us know so we can provide the appropriate credit.

  2. Geothermal should not be confused with ground source heat pumps. Pure geothermal is done without compression, i.e. it relies strictly on the ground temperature without aid of an electromechanical device such as a compressor.



For further studies on this topic visit:

Master Yoda – the E5 Jedi
IEA Annex 37 Low Exergy Systems for Heating and Cooling
IEA Annex 49 Low Exergy Systems for High Performance Buildings and Communities
LowEx.net
International Journal of Exergy
A road map for emerging low-exergy HVAC systems
Exergy Analysis of Residential Heating Systems
Thermal Environment and Exergy Analysis of a Ceiling Radiant Cooling System
Exergy Analysis of A Low Temperature Radiant Heating System
Exergy Analysis of Conventional and Low Exergy Systems for Heating and Cooling of NZE Buildings
Heating and Cooling with Focus on Increased Energy Efficiency and Improved Comfort
An Approach to Exergy Analysis of Human Physiological Response to Indoor Conditions and Perceived Thermal Comfort
CosteXergy project
Thermodynamical analysis of human thermal comfort
Introduction to the Concept of Exergy
Energy and exergy performance of residential heating systems with separate mechanical ventilation
Exergy Assessment Guidebook for the Built Environment: Summary Report
Exergy Assessment Guidebook for the Built Environment: Guidebook


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