SharePhase-change materials result in huge cost savings
Phase-change materials (PCMs) are being used in a new building for the molecular engineering department of the University of Washington, in Seattle. The 7150 m² building has PCMs encapsulated in its wall and ceiling panels, and the expectation is that cooling costs will be as much as 98% lower than those of a building without PCMs.
Phase-change materials (PCMs) are being used in a new building for the molecular engineering department of the University of Washington, in Seattle. The 7150 m² building has PCMs encapsulated in its wall and ceiling panels, and the expectation is that cooling costs will be as much as 98% lower than those of a building without PCMs.
The PCM used in the Seattle building is a gel derived from vegetable oils and the phase change occurs, not at the freezing point of water, but at room temperature. It remains a gel when the air in the building is cool, but gradually absorbs heat and liquefies as the building’s heat load increases during the day. The result is an indoor environment with small temperature fluctuations.
The PCMs are set during manufacture to maintain a temperature of about 23°C. As the building’s heat load increases, the PCMs melt, storing heat and cooling the building’s interior. Then, at night, as the heat load diminishes, the PCMs change back to gel.
In Seattle’s climate, the overnight cooling will be accomplished by having automatic windows open to flood the interior with cool night air.
Scientists have been experimenting with other PCMs. There is a system that uses tiny capsules of paraffin waxes embedded in drywall. There have been lab experiments trying to use the phase-change properties of beeswax to store solar energy. A British firm, Star Refrigeration, is experimenting with carbon dioxide, which changes phase (from gas to solid) at extremely low temperatures.
Buildings are energy hogs. In the USA, it’s estimated that buildings consume more than 70% of the electricity generated in the country. There has been a push to make buildings lighter, making them quicker and cheaper to build. The trade-off, though, is indoor temperatures that fluctuate to a greater extent, which means higher heating and cooling costs. PCMs seem to offer one way to deal with that trade-off.
The PCM used in the Seattle building is a gel derived from vegetable oils and the phase change occurs, not at the freezing point of water, but at room temperature. It remains a gel when the air in the building is cool, but gradually absorbs heat and liquefies as the building’s heat load increases during the day. The result is an indoor environment with small temperature fluctuations.
The PCMs are set during manufacture to maintain a temperature of about 23°C. As the building’s heat load increases, the PCMs melt, storing heat and cooling the building’s interior. Then, at night, as the heat load diminishes, the PCMs change back to gel.
In Seattle’s climate, the overnight cooling will be accomplished by having automatic windows open to flood the interior with cool night air.
Scientists have been experimenting with other PCMs. There is a system that uses tiny capsules of paraffin waxes embedded in drywall. There have been lab experiments trying to use the phase-change properties of beeswax to store solar energy. A British firm, Star Refrigeration, is experimenting with carbon dioxide, which changes phase (from gas to solid) at extremely low temperatures.
Buildings are energy hogs. In the USA, it’s estimated that buildings consume more than 70% of the electricity generated in the country. There has been a push to make buildings lighter, making them quicker and cheaper to build. The trade-off, though, is indoor temperatures that fluctuate to a greater extent, which means higher heating and cooling costs. PCMs seem to offer one way to deal with that trade-off.