Man, I've forgotten more that I knew about alternative energy years ago, Phase Change Materials being one of them. Something triggered that memory today so I thought I'd post it here.
Quoting:
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.
http://en.wikipedia.org/wiki/Phase_change_material
[quote] Phase Change Materials
When the temperature becomes warmer, PCMs liquefy and absorb and store heat, thus cooling the house.
Phase change materials (PCMs), currently under research and development, can smooth daily fluctuations in room temperature by lowering the peak temperatures resulting from extreme external daily temperature changes. PCMs reduce home heating or cooling loads, thereby producing energy savings for the consumer, and ultimately reducing the need for new utility power plants.
PCMs are solid at room temperature. When the temperature becomes warmer, PCMs liquefy and absorb and store heat, thus cooling the house. Conversely, when the temperature drops, the material will solidify and give off heat, warming the house. By incorporating PCMs in the building envelope, they absorb the higher exterior temperature during the day, and dissipate the heat to the interior at night when it is cooler.
Properties of PCM that are desirable for residential use include: (1) A melting temperature above 25°C (77°F), (2) material is low cost, (3) not toxic, corrosive, or hydroscopic, and (4) commercially available in sufficient quantities for producers to incorporate into ordinary building materials.
Researchers have identified a number of materials that meet most of the specifications. For example, paraffin compounds (linear crystalline alkyl hydrocarbons) are commercially available from petroleum refining or polymerization. Some manufacturers have demonstrated processes that successfully incorporate paraffin beads into wallboard. However, more research is needed before the technology can be marketed.
A private company, with the help of the U.S. Department of Energy's (DOE) Oak Ridge National Laboratory, also developed another building envelope application. It tested an attic insulation that absorbs daytime heat, releasing it at night. The insulation consists of perlite embedded with hydrated calcium chloride. Perlite is a naturally occurring siliceous rock, that when heated to a suitable point in its softening range, it expands from four to twenty times its original volume. The resulting PCM, changes phases from solid to liquid at 82°F (28°C), at that point absorbing heat from a hot attic during the day, before it can penetrate into the home. When attic temperatures cool at night, the phase change material solidifies and releases heat back into the attic, moderating outdoor temperatures.
http://www.toolbase.org/Technology-Inventory/HVAC/phase-change-materials
I was wondering today today when I realized I have many cases of empty aquafina bottles with caps which I had hoped to fill with spring water instead of buying more at $4.99/24 bottles. Now I'm wondering if I cannot fill them with water or a phase change salt and incorporate them horizontally in a matrix for a greenhouse wall. They are 16 oz, and about 10" tall. Put in a heat-absorbing matrix might keep them from freezing in winter, and even if they do freeze, even water gives off heat as it changes phases (like ice to water, then to steam.
Whatcha think?