Using the Sun for cooling

Researchers at the Rensselaer Polytechnic Institute (RPI) have worked during 4 years on a climate control system which includes solar panels and thermoelectric heat pumps. Now, they're working on a microscale version of the technology which would allow for various applications such as self-cooling soda bottles.

Researchers at the Rensselaer Polytechnic Institute (RPI) have worked during 4 years on a climate control system called the Active Building Envelope (ABE) system. The ABE includes solar panels, solid-state, thermoelectric heat pumps and a storage device to provide energy on rainy days. And with a grant from the National Science Foundation (NSF), the researchers are working on a microscale version of the technology. By using thin-films, they think it could be possible to "attach the system to various building surfaces" and to package self-cooling soda bottles. They currently didn't reach this goal, but they're already working on a nanoscale version of the ABE system which would operate at the scale of molecules.

Here is an introduction from the NSF news release.

On July 12, 2006, Rensselaer Polytechnic Institute (RPI) researcher Steven Van Dessel and his colleagues will announce their most recent progress--including a computer model to help them simulate the climate within their test structure atop the RPI Student Union -- at the Solar 2006 Conference in Denver, Colo.
For 4 years, the researchers have been working on their prototype Active Building Envelope (ABE) system. Comprised of solar panels, solid-state, thermoelectric heat pumps and a storage device to provide energy on rainy days (literally), the ABE system accomplishes the jobs of both cooling and heating, yet operates silently with no moving parts. NSF is supporting the team to determine if a microscale version of the technology will function effectively.

In fact, most of this information is available since December 6, 2005 when RPI issued a news release titled "Harnessing the Heating -- and Cooling -- Powers of the Sun."

And you could read that a self-heating and cooling prototype of the original ABE system is still on the roof of the Student Union at RPI. Below is an image of this prototype(Credit: Steven Van Dessel, RPI).

A prototype of the ABE system

And on this diagram, you can see the concept behind this system and its future evolution (Credit: Steven Van Dessel, RPI).

The ABE concept and its future

Here are some more details about this ABE system.

[It] uses a photovoltaic (PV) system to collect and convert sunlight into electricity. That power is then delivered to a series of thermoelectric (TE) heat-pumps that are integrated into a building envelope (the walls, windows, and roof). Depending on the direction of the electric current supplied to the TE heat-pump system, the sun's energy can actively be used to make the inside space warmer or cooler. An energy storage mechanism is also integrated to collect extra energy for use when little or no sunlight is available.

But what did they say about the future microscale version of the ABE?

The miniaturized system would function in a similar fashion to the original, but would use thin-film photovoltaic and thin-film thermoelectric materials instead of bulk components. The use of thin-film technologies could potentially result in extremely thin (less than 500 µm) ABE-surfaces. The very fine, transparent material would function as a thermal coating system that could be applied on to various surfaces, much like a glaze. This ease of application would make it possible to seamlessly apply the system to both new and existing building surfaces, rendering conventional air conditioning and heating equipment obsolete, according to Van Dessel.

And while the researchers have not yet reach this goal, they're already working on future versions, such as solar-powered spaceships, sunroofs, and soda bottles, and even smaller versions.

In conjunction with recent advances in the area of nanotechnology and biotechnology, this research may also open the theoretical path toward the development of future ABE materials that operate at the scale of molecules, according to Van Dessel.

If you want to learn more about the ABE prototype, please read this short technical paper, "Active Building Envelopes: A new solar driven heat transfer mechanism" (PDF format, 4 pages, 462 KB), which was presented at the 19th European Photovoltaic Solar Conference in Paris (June 7-11, 2004).

Sources: National Science Foundation news release, via EurekAlert!, July 11, 2006; and various web sites

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