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Hand-drawn curve representing the energy stored as a function of temperature of a substance as it transitions from solid to liquid (phase-change). For example, it takes 80 calories to melt one gram of ice. In reverse, one gram (1 cc) of water gives off 80 calories as it turns to ice; this is called the heat of fusion. This heat of fusion principle is often used to save orchard blossoms from freezing if the temperature drops below freezing in the Spring by sprinkling them with water. As the water freezes, it gives off this heat of fusion and saves the blossoms. Thermal storage using water is not nearly so efficient, as water only stores one calory per gram per degree centigrade.

Thermal storage for passive heating and cooling applications by utilizing the energy required for a material to change phase between solid and liquid.

About

Wikipedia - A Phase Change Material (PCM) is a substance with a high heat of fusion which, melting and solidifying at certain temperatures, is capable of storing or releasing large amounts of energy. Unlike conventional storage materials, when PCMs reach the temperature at which they change phase (their melting point) they absorb large amounts of heat without getting hotter. When the ambient temperature in the space around the PCM material drops, the PCM solidifies, releasing its stored latent heat.

PCMs therefore absorb and emit heat while maintaining a nearly constant temperature. Within the human comfort range of 20° to 30°C, latent thermal storage materials are very effective. They store 5 to 14 times more heat per unit volume than sensible storage materials such as water, masonry, or rock.

Eutectic Salt

The David Allan home, which has no central furnace, yet is situated at 6,000 feet in Utah, utilizes a phase change principle (Glauber's salt) as one of seven solar gain principles for its climate control.

One of the best phase change materials to use is sodium sulfate deca-hydrate (NaSO4 • H2O -- Glauber's salt). Glauber's salt has the convenient property that it melts at 90^o F (32.4^oC)and has about 83 calories per gram. It does not take a lot of salt to heat several rooms. The salt can be stored in black tubes, and rows of these tubes can be arranged to collect the sun's energy during the day. As the salt pulls in the daytime sun energy, the salt melts. At night as the salt freezes, it gives off most of its energy at the phase change temperature of 90^o F. This can be circulated passively through a home through the floor joists. The air is heated as it passes by the tubes, like a radiator, causing the air to rise. This small mass of air rising then displaces the air through the floor joists. The air is cooled in other parts of the home, causing the cooled air to return to the bottom of the eutectic chamber.

Companies

• PCM Energy P. - Phase Change Materials (PCMs) are "latent" energy storage materials. They use chemical bonds to store and release heat. The thermal energy transfer occurs when a material changes from a solid to a liquid, or from a liquid to a solid. This is called a change in state, or "phase." Ice changes phase when heated at 0 deg C and is converted to water.

• Climator - Phase change material products for body, room, equipment and shipping applications. Use Climsel CoolPac C-18 instead of dry ice. Protect your notebook when travelling! Use our LapTopCooler pad. Cooldeck system keeps the low temperatures in the night and releases the coolness into the room during the day.

Buildings

• BASF - Micronal® PCM gypsum wall boards offer architects, house builders and tradesmen a building material for lightweight construction that actively ensures pleasant room temperatures thanks to the use of phase change materials. See also SmartBoard™ - the Micronal® PCM plasterboard and BASF’s Micronal® PCM phase-change materials now also in aerated cement blocks

• Thermal Storage Research Group - Microencapsulated phase change materials have been incorporated into vinyl sheets to produce a thermal energy storage wall-lining, which can be applied to walls or ceilings to reduce overheating, minimise temperature fluctuations and improve thermal comfort for occupants of the room.

• T3Energy - The thermal storage contains high efficiency phase change material capable of storing up to 20 kWh of energy for use when the sun is not available to heat the system directly.

Shipping and Packaging

• Packexpo - The TCP (Thermal Control Panel) is a new approach to thermal product protection. The panels are blow-molded bottles with tabs that allow them to be interconnected in a variety of ways. Inside the TCP's, special formulations of chemicals are used whose phase change temperatures are at the optimum storage temperature of the temperature-sensitive product.

Electronics Cooling

• ThermaFlo - Phase change thermal interface material or films offers exceptionally low thermal impedance for today's high performance electronic devices. Heat dissipating components across the electronics spectrum from digital devices to RF, as well as power semiconductors and IGBTs benefit from the improved heat transfer of phase change materials.

Electronic Memory

• Philips Research - Innovative phase-change memory promises to match the speed, density, low voltage and low power consumption requirements of future deep sub-micron silicon chips. Unlike existing non-volatile memory technologies such as Flash memory, the performance of this new memory improves in virtually every respect the smaller you make it.

Cooling Vests

• Cool Vest - RCPM™ (Renewable Phase Change Material) - a thermal energy storage material that is designed to absorb heat generated by the wearer. It maintains a comfortable 59 degrees F.
• Texas Cool Vest™ - Wear a Safety Body Cooling System. Phase change cooling packs maintain a comfortable 65° F temperature, and help stabilize your body's core temperature!
• ClimaTech Safety by SummitStone - HeatShield II will not make you look bloated. It Lasts....3, 6, 8, hours.. replaceable inserts make this possible. A unique design using a two-phase shift system.
• Klimeo - Microcapsules containing a natural temperature-regulating ingredient applied to a fabric undergo a phase change depending on the outer temperature: it is solid in a cold environment and liquid when warm. This enables Klimeo® to compensate for swings in temperature, guaranteeing comfort and well-being for the wearer, while remaining invisible to the naked eye and without changing the fabric’s properties.

In the News

• All Cell Plug-in Escape Hybrid - All Cell Technologies is testing a converted Ford Escape Hybrid designed to double the fuel efficiency without altering the original controller. They added a li-ion battery pack that utilizes a passive thermal management system using phase change material (PCM), solving lithium's problem of heat release. (Green Car Congress; Mar. 14, 2007)
  

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See also

• Directory: Air Conditioning
• Directory:Ice-chiller_Cooling

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