Energy Saving in Buildings; How Much and How Fast?
Published on Saturday, 28 June 2014 09:44:01 Written by Marc
A friend of mine sent mean article this week about a company, which claim that in every building they go into, they save over 40 percent of the total energy consumption. Since he sent that to a few people at the same time, I had a chance to see some comments of other friends, some of them in the same business field as the company claiming the large savings for their clients. One person indicated that it is impossible to find more than 40% savings in any building.
I indicated to the group that according to the article, they say that they saved over 40% on the buildings, which they do a project, so they probably select which buildings they target. Which would make sense, after all, if you have a brand new building, fully commissioned (and well commissioned, I must add), which is operating lower than its peers in the industry, chances are it’s simply not possible to find 40% energy savings. You might be lucky to find 5% and that may require substantial capital investment. However, is it possible to find 40% of savings on an older building? Yes, it is possible, depending on the condition of building, its location, its energy usage, and finally, depending on what kind of investment you are willing to make in the building. If you only replace the lighting system, chances are you can forget about 40% savings or anything near that number, although the lighting replacement can still be a great energy saving measure on its own. However, taken alone, it will not be enough to attain the numbers we are talking about here (40 percent overall energy saving for a building). But if take an office building that was built 50 years ago and which never had much investment in it, you do a complete building retrofit, improve the insulation, replace the windows, the heating cooling and ventilation system and a few other measures and yes, you could see a dramatic decrease in energy usage. In sending the article to the group of people, my friend asked, “Is this possible (referring to the claim about saving more than 40%)?” Therefore, to his question, yes, it is possible. However, since every single building on earth is probably different from the other, how can people get a better feeling for what is possible for their building? How can we know how much and how fast can we generate energy savings. Well, there are two main areas of energy saving. The first area, behavior, deals with how operations people manage the building using the tools they presently have. For example, in some office buildings, its common behavior to leave all lights on at night. We often see this in the core financial centers. While many may claim that it is for the security and cleaning people, there are ways to secure and clean these buildings by adapting a behavior that closes most of the lights when not required. This is a way to save energy by adopting a specific behavior. Depending on what is the present behavior and what you decide to change in terms of behavior, you can expect to save anywhere between three and 10 percent of the total building energy consumption, with the average sitting at about five percent. That is a five percent saving in energy without the need for capital investment. As for the how fast part of the question in the previous paragraph, the answer is, “probably” as fast as you can implement the behavior change. The second, and often most influential area of energy saving is related to retrofits; that is the physical replacement of equipment by more energy efficient one. I include the building automation systems in this area because a Building Automation System (BAS) actually replaces manual building systems or equipment. Knowing this, how much energy saving can retrofitting equipment provide for a building? The easiest way to calculate this is probably to start by comparing the building with similar ones, to see if their building seems to be doing better or worse than others are. Comparing with industry standards will help give a good idea of where the building stands. Unfortunately, it will not help much to determine how much capital investment needs to be put in the building, nor what kind of payback could the building owner expect. For this, a more detailed analysis will be required. However, one thing a building owner can do is to have a look at his or her building and look at what has been done so far over the years. There are some rules of thumbs that can help determine what kind of payback a building owner could experience by doing some specific retrofits. For example, lighting retrofits often carry a two years or less payback. While that may sound vague, it can at least give the user a quick idea of what kind of return on investment he or she might expect if they know that the lights in their building have never been replaced in the past 10 or 15 years. The numerous rules of thumb that exist can provide you with some guidance and give you only a hint of where you should look into your building. These provide some rough information on how much you could save by doing energy saving measures, which require capital expenditures. However, because of the uniqueness of every building, use these rules of thumbs only as a general guidance. For example, we know that large equipment retrofits (chillers, rooftops, boilers… etc.) often carry a payback of between five to well over 10 years, so if you have an old 300 ton chillers, by knowing the cost of replacing it, you can get some kind of idea of the potential payback. However, some building owners may have a 4-year payback and others may have a 14-year payback, depending on the condition of the old chiller and what it is being replaced. We can see that there is a huge range between four and 14 years, which is why detailed audits and calculations are so important to get information that is more precise. It would be nice to have some kind of universal way to calculate how much savings in percentage could be achieved depending on the age, location, and condition of a building without having to do a detailed building audit, but that would probably require a large algorithm to solve the question. Over the years, I adopted a rule of thumb that is more personal than scientific, but that most of the time proved me right. Take the age of the building, and for each year of age (up to a maximum of about 40), add one percent of potential energy saving to the potential five percent behavior potential saving. So for example, a building of 10 years of age, which has never had an energy retrofit and is not optimized from an operational behavior point of view, could normally expect to save five percent (from improving the behavior of operations), and another 10% because of its age (by doing some project retrofit of course), for a total of 15 percent. From this, you can subtract some points each time the building did receive a capital investment for an energy saving project or measure. So for example, if the building had a lighting retrofit done which reduced the overall energy consumption by four percent, remove those four percent from the initial 15 percent and you end up with a remaining 11 percent of potential energy saving, providing you are willing to improve both the operational behavior and do some capital investment for energy saving projects. These calculations are only personal and are open for debate. They also provide only a quick estimate of the potential for energy savings, but they have often helped me when we purchased buildings and when I needed to provide rough “guesstimates” on how much energy we could save for each building.
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