Sustainable & Attainable: The Physics of Efficiency
What do IRA's and 401k's have to do with R-134a you ask? Well, as I prepared to write this month's column, I found myself approaching sustainable design very much like I had approached investing a few years before. I found myself looking for something new and exciting, something cutting edge, something that would redefine HVAC as we know it. In essence, I was looking for our industry's equivalent to a hot stock tip.
But just as the new economy was just the old economy in a wild boom cycle, green engineering is simply good engineering with a more holistic perspective. So for this column, I chose to focus on what I consider the fundamentals, because they are more important now than ever.
Embrace EntropyParadigms are funny things, and to quote Kenny Rogers (albeit completely out of context), "you have to know when to hold 'em, and know when to fold 'em." Like it or not, as HVAC professionals we are defined and confined by the thermodynamic paradigm. And nothing makes the case for sustainable design like the immutable laws of thermodynamics.
If the Earth is our "system," then the limited amount of useable energy we have been granted (see the First Law) will eventually and irreversibly be converted into unusable energy (see the Second Law). Therefore, it is only logical to use less energy as a rule, and to move toward renewable, more efficient energy sources in general.
Entropy is the acknowledgment that the world is going to heck in a hand basket. Once you embrace that reality, you can either be part of the problem or part of the solution. You can do nothing and hasten the conclusion of the trip. Or, you can work to make the journey as long and as pleasant as possible.
Be Passive AggressiveOK, I admit it: I have an affinity for the affinity laws. As a designer, I had applied the square law for years to size pumps, fans, ductwork, and piping. But when I embarked on my first energy study, and I plugged dollar signs into the cube law, I was as amazed as when my Uncle Benny "got my nose" and I watched it wriggle under his index finger 20 years earlier.
In case you have been so focused on design and first cost lately that you haven't had an opportunity to think about energy, let me remind you that a 50% cut in flow reduces energy usage by 87.5%.
That's why we do variable flow systems. Which leads me to conclude that those conspiracy theories involving Area 54 and VFD manufacturers may not be entirely accurate.
And when you take low flow to the logical extreme - no flow - you see why getting aggressive with passive systems can make so much sense. The fact that heat flows from high temperature to low temperature (thanks again, Second Law) and warm air rises whether we want it to or not, should motivate all of us to come to terms with Mother Nature and allow physics to be our friend.
Psych Yourself UpYour psychrometric chart is a valuable road map that shows you where you are (the mixed air condition) and where you want to be (the space condition). The processes available, adding or removing moisture, raising or lowering temperature, dictate the paths you can take to get from here to there.
Similar to geometry, where we know the shortest distance between two points is a straight line, a straight line represents the most efficient HVAC process. Obviously a straight line is not always possible, but unfortunately, all too often a less cumbersome path isn't even considered.
When you understand the psychometrics, you may learn that an airside economizer is not always justified. You may find that evaporative cooling can be applied outside the desert. You may even understand the benefits of return air bypass and skip that humidifier after all.
Constantly CommunicateAs you may recall, what Cool Hand Luke and the Captain had in that classic film was a "failure to communicate." As engineers, we shouldn't emulate such dysfunction. Listen to your clients and don't choose style over substance. Work with the architect and other disciplines to create a truly integrated design team.
And finally, challenge anyone who tries to tell you that the rules have changed and the fundamentals don't apply anymore. ES