Achieving Energy Efficiency
August 2009By Eric Lindquist
Renewable phase change material saves up to 30% in energy usage
Temperature can be a very difficult and costly property to control. It impacts every aspect of a person’s life—from the clothes put on in the morning, to the heat or air conditioning used in the car, to the comfort level in an office building, to the blankets used in bed each night—being too hot or too cold can ruin one’s day. What if there was a simple, cost-effective option to maintain temperature for virtually any application, including a person’s clothes, car, office building, and bed? New bio-based phase change materials (PCMs) are the answer.With environmentally friendly, bio-based (which simply means derived from all-natural resources) PCMs, the opportunities are endless, and that includes the building and construction industry. PCMs are increasingly being used in construction materials like insulation, flooring, ceiling tiles, and HVAC units with great success. In recent testing, using PCMs in conjunction with insulation contributed to a reduction of 30 percent energy usage in residential homes.
Bio-based PCMs provide a different, smarter way for builders and contractors to think about energy efficiency in both residential and commercial developments.
WHAT ARE PCMS?
Phase change materials do just what their name implies—change “phases” (for example, liquid to solid or solid to liquid) between set temperatures. During the process of liquefying and solidifying within a set temperature range, PCMs absorb, store, and release large amounts of energy. These natural properties of latent heat energy help maintain a product’s or structure’s temperature and buffer it from temperature swings. PCMs recharge as ambient (outdoor) temperatures fluctuate, making them ideal for many everyday applications.
AS SIMPLE AS A CUP OF JOE
Most coffee is brewed at 180°F. Optimal drinking temperature, though, is around 135°F. It takes several minutes to cool coffee to a temperature that won’t burn a person’s mouth, which can be frustrating. Consider, however, if PCMs were used in the walls of a coffee cup. The cup would now remove and store the heat from the coffee when it’s too hot for drinking, and cool it to a drinkable 135° to 140°F. Once the coffee temperature drops below 135°F, the cup will automatically begin to release the heat that it captured when the coffee was too hot, maintaining an optimal drinking temperature range for up to 60 minutes. No more burned tongues, and no more cold coffee.
In this particular case, the PCMs were created to melt and freeze at 135°F. When hot coffee at 180°F is added to the coffee cup, the heat from the coffee will cause the PCM to melt. This melting process causes a cooling effect. It is the same cooling effect that ice has when it melts at 32°F. When most pure materials melt and transform from a solid to a liquid, there is a cooling effect.
Conversely, when the coffee starts to cool down and drops below 135°F, the PCM, which was melted, will start to solidify. This solidifying process causes a heating effect. It is the same heating effect that hot liquid wax has when it solidifies (for instance, when dripped on a table). When most pure materials solidify and transform from a liquid to a solid, there is a heating effect.
The coffee analogy is but one example of how a PCM can be used to keep an object cooled down at a specific temperature or heated to a specific temperature. PCMs are a highly efficient way to sustain specific temperatures for prolonged periods of time.
EXPANDING CONSTRUCTION POSSIBILITIES
Available in a variety of forms, bio-based PCMs have myriad applications in the construction industry, with the most popular uses being an aid to insulation, and in flooring and ceiling tiles. It also can be used in bridges and sidewalks to prevent icy surfaces from forming.
PCMs are effective in residential and commercial new construction and remodels. The material works by absorbing and releasing energy (heat) based on the outside temperature to regulate the inside temperature of a structure. During the day it absorbs heat (cools), and at night it releases heat (heats). This makes a structure’s energy cycle more efficient—intelligently capturing and releasing otherwise wasted energy.
Some recognized applications for PCMs in the construction industry include:
- New home construction and renovation where micro-encapsulated PCM in flooring and wall materials capture and retain energy
- Micro-encapsulated PCM used in bridges or sidewalks to prevent dangerous icy surfaces
- Panel insulation used in telecom towers, replacing costly and inefficient diesel-powered cooling devices
- PCM embedded in ceiling and roofing tiles providing reduced energy consumption in retail, commercial, and industrial applications
- Thin PCM layers added to HVAC systems maintain specific temperatures enabling energy savings through repeated air circulation
GOING BEYOND INSULATION
It is important to note that PCMs will not replace insulation, but rather work with it. Insulation works by increasing the thermal resistance of a structure, slowing the heat flow through the walls of the building. Phase change materials work by increasing a structure’s thermal mass, and its resistance to temperature change.
PCMs have the natural tendency to absorb heat when they melt and to release heat when they solidify. Some of them, however, do this very well and at temperatures that are much more useful to us. When phase change materials that melt near room temperature are encapsulated in materials and distributed throughout the structure of a building, they can help cool buildings by absorbing excess heat when temperatures rise and also heat buildings when the thermometer drops. In addition, PCMs act as a buffer to temperature swings and shift energy usage to off-peak times.
DELIVERING COST SAVINGS
So how effective are phase change materials? Adding this technology to existing building design without any design changes will generally yield between 20 to 35 percent decrease in HVAC energy usage. For the future, research shows that with proper design, a blend of new construction techniques, and the use of PCMs will result in a dramatic reduction in new buildings’ energy usage, perhaps up to 90 percent. Certain modeling software is already incorporating the ability to model buildings, which use PCMs. The Department of Energy also has conducted extensive research confirming performance and opportunities to use PCMs for meaningful energy savings.
Phase Change Energy Solutions (www.phasechangeenergy.com), a company based in Asheboro, North Carolina, is currently using PureTempTM, the world’s first and only 100-percent renewable, biodegradable, and environmentally friendly material, to power its biopcmTM construction product. PureTemp is manufactured by Minneapolis-based Entropy Solutions. Biopcm can be installed in new construction, or be used to retrofit buildings and temporary structures. It was Phase Change Energy Solutions’ testing that proved PCMs can be used to consistently deliver a 30 percent reduction in energy use in residential structures. ■
About The Author:
Eric Lindquist is president of Entropy Solutions, a thermal technology company based in Minneapolis, Minnesota, which created PureTempTM Renewable Phase Change Material. For more information, visit www.entropysolutionsinc.com.
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