What keeps you comfortable? But is not air conditioning. Nor insulation, as you know it. Phase Change Materials.
They sound like something from a science fiction movie like, Hyper Drive, Warp Speed or Temporal Agent. Even a simple explanation does nothing to dispel that notion.
Materials that store (and release) heat, all the while retaining a near constant temperature. They do it up to a dozen times more effectively than other ‘thermal mass’ mediums, such as water and masonry. And they keep doing this for decades, with no powered input, nor maintenance. Just the sort of thing you’d expect to find aboard the Millienium Falcon or the Enterprise. But increasingly Phase Change Materials (or PCMs for those who prefer TLAs) are being teleported into our buildings.
Water is the classic PCM. At room temperature it’s a liquid. Heat it enough and it turns to a gas — water vapour or steam. Cool it sufficiently and you have a solid — ice, snow, frost. Gas. Liquid. Solid. These are three primary states or ‘Phases’ that most of us are familiar with. (There is technically a fourth state, known as Plasma, when a material becomes responsive to electromagnetism, i.e. lightning.)
Heaps of energy is inherent in these changes of phase. Much of it expressed as heat. PCMs that can capture and store that heat have great potential in architectural design. They equip designers with the opportunity to eliminate, or at least reduce, the inclusion of electricity guzzling air conditioning systems.
In 2009, Charles Sturt University’s Thurgoona campus at Albury (pictured above) was apparently the first in the world to use phase change materials in their concrete flooring. PCMs were also integrated in the plasterboard ceilings. Such attributes helped the site score six green stars and ‘world leader’ status from the Green Building Council of Australia. Speaking of six star buildings, the first one in Victoria to rate such a thing for Office Interiors was the offices of architectural firm Umow Lai. They picked up a maximum of five innovation points for their use of phase change materials to control temperatures in a meeting room, without resorting to mechanical cooling and heating systems.
It was around 2004 when Phase Change Materials really started to make inroads into architecture. About this time the world’s largest chemical company, Germany’s BASF, introduced their Micronal product. They encased a paraffin wax storage medium inside a microscopically small acrylic plastic sphere. When temps rise, the wax in the spheres starts to turn to a liquid —changing its phase — and in the process absorbs heat. When the mercury drops the wax starts the process toward solidify again and releases all that stored heat.
Tate Access Floors also use PCMs in flooring, but with a couple of twists. Firstly their EcoCore panels (pictured above) are used for raised access floors, that allow for an office’s services, like cabling and air conditioning, to be hidden underneath. Secondly, they advocate a perimeter placement of the panels on sunward side of building. As heat enters the office, the phase change materials mixed with structural cement and contained within steel welded shells absorb this increased temperature. Tests performed by Tate suggest their system can reduce air conditioning demand by 17.7 per cent, when contrasted with a typical concrete slab floor.
Floors and walls aren’t the only building products utilising phase change materials. One of the more intriguing adoptions of PCMs is GlassX’s Crystal product (pictured below), which the Swiss firm believe “makes it possible to replace solid walls with glass elements.” Crystal is essentially a quadrupled glazed window. Positioned between two of the panes is a translucent salt-hydrate PCM. The 79mm thick glazing unit is credited with absorbing “about the same amount of energy as a 400 mm thickness of concrete.” But here is the extra kicker: with the PCM in its crystalline state, the panel transmits between up to 28 per cent of visible light, and up to 45 per cent in its liquid phase. Thus, a thermal mass external wall that allows the passage of diffused sunlight.