A Great Article Contrasting Chilled Water Cooling Technologies, their Efficiencies, and their Emissions and Some Thoughts on Climate Change

Michael Ivanovich recently did a blog post that published the results of CSE’s January on-line poll on climate change.  In it, CSE asked visitors to the site how serious they thought climate change was and included a list of reading materials for both the skeptic and, I guess you could say, the “believers”.

Personally, I’m probably more of a believer than not, but I think its a really complex issue (on all of the fronts) and likely does not lend itself to a “black and white” answer. I also think there are a couple of related issues which, for me, are much clearer and are generally related to sustainability and resource conservation.

In the broader holistic sense, I personally believe that as engineers, we have a moral and ethical obligation to make sure we use resources as efficiently as possible and mitigate any adverse impact our processes might have on the environment to the extent possible within the financial and technical constraints we are challenged with. I say that because our actions and ideas typically result in the consumption of resources and the generation of waste.  Most of the resources are, in practical terms, finite at some point. That point in time, of course is subject to great debate as is the definition of what an adverse environmental impact might be.

For me, this started out as childhood curiosity that turned to technical interested fueled to some extent by the “passion of youth” and an environmentalist outlook on things. But, as I have aged, my interest has evolved to a broader somewhat spiritual awareness of the need (for me) to be mindful of how I interact with others and my surroundings based on a growing sense that everything is ultimately connected. All of that stuff, of course, is just my personal belief and I say it just to frame the context of the rest of this and hope it does not offend.

“Mushy” stuff aside, in practical terms, it seems like a sort of “win-win”  perspective;

  • Efficiency and cost effectiveness have always been fundamental engineering goals.
  • If resources are in fact finite, making the most efficient use of them will ultimately be beneficial in terms of preserving the for future generations.
  • Process that are efficient in terms of how they use energy and other resources tend to have less impact on the environment.
  • If climate change turns out to be related to the activities of humans, then having minimized our impact on the environment will probably turn out to be a good thing.

That brings me to the article I wanted to point you at. For those of you who are interested in different approaches to generating chilled water for cooling and the efficiency and emissions associated with different approaches, Jerry Williams has a really great article in this months issue of Heating Piping, and Air Conditioning. There is also a pretty cool cover shot of Discovery sitting on the pad at the Cape.


Too bad about the need for address labels.

Anyway, in the article, Jerry looks at the energy input and emmissions output associated with producing 1 ton-hour of cooling for the following approaches:

  1. High efficiency electric centrifugal chiller
  2. Standard efficiency electric centrifugal chiller
  3. Single stage steam fired absorption chiller
  4. Two-stage steam fired absorption chiller
  5. Gas fired two stage absorption chiller
  6. Natural gas engine/generator powered electric chiller without heat recovery
  7. Natural gas engine/generator powered electric chiller with heat recovery
  8. Electric centrifugal heat recovery chiller

Each option is discussed and depicted in a little flow chart like this.


The article includes a table of all the pertinent parameters used in the analysis, a description of the calculations that were used, and a really good sidebar about how carbon dioxide is produced in the combustion of coal and natural gas and how those combustion processes come into play with regard to the production of electricity when it is fueled by those sources of energy.

Conclusions, costs and emissions are discussed in the context of the  St. Louis environment but the ideas could easily be extrapolated to any location.  In fact, that’s one of the points;  “emissions comparisons are highly related to the site locations and the source of electrical generation”.

The article concludes with a few rules of thumb that might help you make an initial assessment of a particular location’s suitability for a heat recovery chiller or a congeneration option for making chilled water and includes links to pertinent resources like the Campus Carbon Calculator that is available from Clean Air Cool Planet.

So, if you have a chance, take the opportunity to read Jerry’s article, bookmark the resources, and download it to your technical archives for reference (you all have those, right?). No matter what you believe about the bigger picture stuff, I think you’ll find that its full of sound engineering advice and a great example of how we all should go about making technical decisions for our clients.

David Sellers
Senior Engineer – Facility Dynamics Engineering

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