So given these conditions, it will come as no surprise that researchers led by Peter McGrail out of the Pacific Northwest National Laboratory have been working a new porous nanomaterial that improves an existing process used for refrigeration and air conditioning called adsorption chilling.

Image courtesy colmaccoil.com

All refrigerators and air conditioners make the environment cooler by creating phase changes in a refrigerant so that the chemical absorbs heat.  Most familiar air conditioners use electrically driven compressors to mechanically compress the vaporized refrigerant, whereas adsorption chillers use heat to condense the refrigerant. Evaporated refrigerant “adheres to a surface of a solid, such as silica gel. The silica gel can hold a large amount of water in a small space—it essentially acts as a sponge for the water vapor. When the gel is heated, it releases the water molecules into a chamber. As the concentration of water vapor in the chamber increases, the pressure rises until the water condenses” (Bullis). When that happens, heat is absorbed out of the environment and the newly cooled people rejoice!

Image courtesy emissionless.com

Historically, bulky adsorption chillers have been more expensive and far less efficient to operate than chillers that use electrical compressors.  The flip side is that they are cheap to operate and, if you’re an industrial facility or power plant manager who has massive quantities of waste heat lying around, you can practically run them for free. That’s right people: absolutamente GRATIS.

The new material will make it easier to cool smaller buildings with solar water heaters or waste heat from generators by shrinking the hulking adsorption machines by 75% in size and cutting associated costs in half (Bullis).  Size and cost reductions could make adsorption chillers competitive with compressor driven chillers.

The researchers’ nanomaterial consists of “nanoscopic structures that self-assemble into complex three-dimensional shapes. It’s more porous than silica gel, with a larger surface area for water molecules to cling to. As a result, it can trap three to four times more water, by weight, than silica gel, which helps reduce the size of the chiller” (Bullis). The other interesting thing about the material is that it forms weak bonds with water molecules.  This is a good thing because it means less heat is required to free the molecules (or other refrigerants), making the process of adsorbing and desorbing water 50-100 times faster.

While the nanomaterial definitely makes adsorption chilling more attractive, it’s tricky to match the demand for cooling with the production of heat. For example, if you needed to run the chiller when the sun had set because you lived somewhere humid, you might need a heat storage system (and those can be expensive). Still, anytime things get more efficient a little fairy creature gets some wings!

WU XING:

Cited:

Bullis, Kevin. “Using Heat to Cool Buildings.” Technology Review Online. 03/30/11. Accessed 06/29/11. URL.

The material on which I intend to focus today is water in solid form, commonly known as ice.  You may have seen the substance lurking as chunks in your super-large coke, or possibly it has formed, dagger-like, on the eaves of your house in winter.  But did you know that ice can be used to save money on cooling costs all year long?

Image courtesy www.agrichill.com

During normal working hours (9-5) almost everyone uses his or her air conditioning system to cool buildings, which means the demand on the grid is the greatest.  Power companies charge the most money per kilowatt hour at this time of day because it strains the system to meet the demand, and because they can do what they want.

Thermal energy storage (TES) systems take advantage of changes in temperature over the diurnal cycle, storing energy in a thermal reservoir for later reuse.  The systems perform well in commercial and institutional buildings, whose peak energy demand occurs during daytime hours and drops off precipitously at night because everyone has gone home.  The thermal reservoir may be maintained at a temperature above (hotter) or below (colder) than that of the ambient environment, but today I’m writing about ice chiller TES.

Photo courtesy Greensource Magazine

The most widely used form of this technology is in large building or campus-wide air conditioning or chilled water systems. “In this application a relatively standard chiller is run at night to produce a pile of ice. Water is circulated through the pile during the day to produce chilled water that would normally be the daytime output of the chillers” (Source: Wikipedia).  Ice storage systems surprisingly inexpensive; full storage systems are often priced competitively with conventional air conditioning designs.

Baltimore Aircoil Company, out of (you guessed it: Baltimore, MD) is one of the nation’s leading manufacturers of TES systems.  They make ice-chillers “out of serpentine steel tubing that has been galvanized to protect against corrosion. The tubing rests in an R-18 insulated tank and can produce between 237 and 761 ton-hours of ice (one ton-hour equals 12,000 Btu), but much larger custom units are also available” (Greensource Magazine).  The ice chillers take the form of enormous metal-clad boxes (although I’ve seen some systems that get partially set into the ground).  But even though they’re not exactly attractive, if you’re using them they’re probably saving you money and that’s a beautiful thing.

*UPDATE – 07/29/10

I recently heard from another producer of Thermal Energy Storage Systems – CALMAC.  According to a representative, CALMAC’s technology can store renewable energy overnight to reduce next-day cooling costs by 40%.  The technology was recently employed at the Bank of America building at 1 Bryant Park, which acheived a LEED platinum rating.

WU XING:

Ice chillers use frozen water to chill the air, reducing energy consumption.  Therefore, I’ve filed them under Water and Fire.

Cited:

“Ice Chiller Thermal Energy Storage.” Greensource Magazine.  Accessed 07/19/10.  URL.