Energy Conservation in Buildings 1 – Overview

I’ve been thinking about thermodynamics way too much in recent posts, so let’s get back down to earth for a few posts.

I am not going to argue the merits of conserving energy (or entropy) here.  Rather, we will take it as axiomatic that conserving energy is a good thing.  And it is – financially, environmentally and morally.  But what I’d like to outline here is the way that some energy engineers think about saving energy in rough outline.  The details may or may not come later.

The way I see things, investigating/monitoring/improving how energy is used simply requires that we look at

  • Stuff
  • Systems
  • Documentation

I will discuss how we look at these things some other time, but first let’s deal with these three things.

Stuff are individual pieces of equipment.  A motor, a light bulb, a computer screen, a transformer, a (lacking) blanket of insulation, a pump.  Energy evaluations should always confirm that the most efficient, cost-effective (yeah, we’ll need to conjure up a meaning for cost-effective at some point soon) technologies are in place.  Stuff upgrades, e.g. inefficient lighting to efficient lighting systems upgrades, are what people just love to call low hanging fruit.  Any junior engineer – hell, any trained high school graduate – can be taught to identify low efficiency stuff and be taught to identify and calculate the energy savings associated with alternate high efficiency stuff.

As an aside, I have always found it curious that while energy conservation programs will often provide incentive money for high efficiency motors [for pumps] that save a percent or two in energy use, I have never seen an incentive for an updated pump selection that might deliver several percentage points in pump efficiency improvement.  Maybe it isn’t cost effective.  But I worked running a conservation program for a utility company for a little while, and I don’t think I ever saw the fan or pump selections scrutinized to see if the selections were optimal.

Note that if stuff is operating when it does not need to, we may want to embed it into a system so that the hours of operation can be controlled.

Systems are ensembles of stuff, unexpectedly, and evaluating such systems identifies whether the interactions, or synergies, of the various components making up the system are operating at peak efficiency.  This sounds a bit abstract, but an example or two can quickly demonstrate what I mean.

Perhaps the simplest example I can think of is the light switch.  Replacing a conventional light switch with an occupancy sensor creates a system, whereby the lights will be turned off after a predetermined delay whenever the room is not in use.  This can greatly diminish the energy use of our lighting system.  Evaluating this system would simply be confirming that the sensor works, and that the predetermined delay is not overly long.

A more complicated example would  be so-called air side economizing.  Large buildings often require air conditioned ventilation air even in the winter.  There are times in the year when it is possible to use cold outdoor air from the environment rather than mechanical cooling (i.e. air conditioning equipment.)  However, it is not at all uncommon for air side economizing to have not been implemented (only older buildings, economizers are now required by code), or to not be functioning properly due to bad sensors (that check the building and outdoor air conditions), bad actuators (that manipulate how much outdoor air is admitted) or bad control logic.  Air side economizing can save huge amounts of energy.  Evaluating this system would include physical inspections of things like dampers, actuators and temperature or enthalpy sensors, investigation of air flow to assure flow is not physically stratified in the air handling systems (which can cause freeze trips), and review of the control sequences.  This review would also investigate the opportunities to turn the entire system off, or to at least reduce the airflow, when the building is unoccupied or lightly occupied.

As you will have noted in the air side economizing example, evaluating systems is much more difficult than evaluating stuff, so the expertise you throw at it needs to be greater.

I would also point out that, while building systems are not overly complex from a technical engineering perspective, solutions that maximize energy performance in such systems can be remarkably cunning and unexpected.  Ideally, a junior engineer should not be doing systems evaluations, though in reality many consultants will throw their junior engineers into the fire, with diminished results.

I have heard PhD types disparage energy engineering as too simple to be interesting, but I do not personally find that to be the case.  One reason is that engineering conservation solutions is not theoretical.  It is real world.  And that means that you are acquiring and manipulating real data.  Or are at least trying to.  The imperfection of the data, the physical limitations to what you can see and measure, the inability to do much empirical experimentation, all lead to a need to interpret incomplete data.  Thus there are many apparently possible solutions that require consideration in a systems energy assessment.

Documentation.  In discussing documentation, what I mean is that implementing energy efficiency projects includes finding a way to record not only what projects were done, but also what they were supposed to accomplish and that the savings continue to accrue.

While this may sound like a pretty trivial piece of bookkeeping, it can actually be quite difficult to do.  There are few reasons why.

First of all, energy projects are often done piecemeal, by different people using different methodologies.  Therefore, information pertaining to conservation can come in all kinds of calculation methodologies and presentation formats.  Finding a way to consistently and concisely document multiple project can therefore get messy.

Secondly, actual performance requires field data, so this is more than an accounting exercise.  Data from building automation systems and/or data archiving systems must be periodically reviewed, and depending upon how that data is structured, may even require interpretation to establish what is actually going on.

Finally, it should be borne in mind that discussions of energy savings may need to be tailored to different audiences.  A chief financial officer might be interested in financial performance, a sustainability officer might care principally about carbon emissions, while a fellow engineer might care about real-world energy performance.  This can’t all be done with one monster spreadsheet.  Well, it can be, but it ain’t pretty.

In my opinion, trying to document projects and generate reports tailored to specific audiences is madness without using a database.  If you need to record and manipulate large volumes of stored data and have never learned how to use a simple database like Microsoft Access, you are creating an awful lot of unnecessary work for yourself.

I would like to say one more thing about documentation.  There is growing emphasis in large enterprises on energy use, carbon emissions, and sustainability in general.  I predict there will be a concomitant increased emphasis on documenting and reporting services for these sustainability initiatives, and that current industry practices are going to be exposed as inadequate.

So there’s the overview.  Stuff, systems and documentation.  The question is, when you walk into a building, what do you do?  I’ll offer one proposed approach in a future post.

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