So how do you eat an elephant? One bite at a time! In our lesson today, we will take three bites to eliminate your highest cost: peak demand.
To build on our learnings from the first half of this blog post, let’s look at the figure below. Here you can see a peak shift of 30% in energy consumption from the red plot line down to the green one, which comes simply from leveraging your building’s thermal properties. At CoEng, we can help do this for you by using the thermal properties of your infrastructure coupled with model predictive control (MPC) as a first step. (You can even read more about MPC in further detail in a previous blog post of mine from March 8, 2017). Our approach comes from seeing the whole elephant – not just the trunk or the leg! In other words, it’s about the BIG picture. By understanding all the parts, you can proactively cut down your waste at the lowest capital cost.
First of all, you must always approach your energy challenge with the idea of leveraging assets you already have. You must first think of how to best use your existing infrastructure and do more with what you have there already! Capital expenditures should be a last resort (except where forces such as regulations, obsolescence, or the like are at play). The reason for this is that, if you take advantage of your existing infrastructure to do more with less, then you will have reduced the amount of future capital expenditures on your next retrofits, which reduces those capital costs exponentially.
Our second move is to determine the next lowest cost option to continue reducing your peak demand. As we examine this profile for example, we can see that about 30% of the cooling needs have been dealt with by applying passive thermal energy storage in the beginning. In the figure below, we’ve now added in a black plot line to show the electricity draw coming from everything in the building that is not HVAC. So now we must figure out how to reduce the remaining 35% of our peak energy load that is consumed by our HVAC for temperature control. Employing active thermal energy storage is your next lowest cost option to do just that!
There are many types of active thermal energy storage you could use for the third move. However, today’s lesson will discuss a particular method that relies on phase change materials (PCMs) to significantly reduce your HVAC energy requirements. So, what are phase change materials? They are those, which freeze or heat up at certain degrees, changing between being a solid, liquid, or a gas. For instance, you could use a PCM that will freeze when the ambient air reaches a warm 25°C/77°F; or conversely, one that heats up when the ambient air cools to 21°C/70°F. This technology can be used in new construction or can be retrofitted into existing buildings. In new construction, the material can be designed to fit behind walls. In a retrofit situation, it can be installed in the plenum. (For a more descriptive run-down about PCMs, we recommend checking out the Introduction section of this article from ClimateTechWiki). There are many ways to use such material and for specific applications, you can reach out to me, Sensei Bruce, for more information on how I can help you reduce your total energy profile by an additional 35%.
Next from the Energy Waste Sensei: We continue to explore peak shift strategies to eliminate our peak energy requirement!