Researchers unveil innovative solar cooling project

September 30, 2011
UC Merced professor Roland Winston (left) and a team of student researchers designed and developed a system of non-tracking solar thermal collectors.

Using solar thermal energy to power an air conditioning unit can be difficult and expensive. But a team of researchers at the University of California, Merced, have added a game-changing advance to the process that could make it much simpler, less costly and more effective.

UC Merced professor Roland Winston and his team of student researchers have designed and developed a system that gathers and concentrates sunlight onto specially made collector tubes. The heat generated can then be transformed using existing technology for cooling, heating and a number of other potential uses.

The key factor in their design is this: The collectors are entirely stationary. Typically, must move and track the to achieve optimal , necessitating additional equipment that can be costly to install and complex to maintain.

The UC Merced design — called an External Compound Parabolic Concentrator (XCPC) — generates solar thermal efficiency of 60 percent at temperatures up to 400 F, achieving thermal performance previously seen only in tracking systems. And in contrast to tracking systems that work only on clear, sunny days, the UC Merced design can work in hazy conditions because it "sees" most of the sky, allowing collection of both direct and indirect .

Winston said other scientists and industry leaders have been skeptical regarding claims of the technology's performance and efficiency. So to demonstrate it, Winston's team installed a mobile office trailer at their facility at Castle in Atwater and are cooling the trailer using air conditioning powered by an array of 160 XCPCs in two parallel rows. The used in the demonstration comes from a high-performance, double-effect absorption unit - a type that requires a significant heat source to generate cooling.

"We believe this is the first working system of its kind anywhere in the world," Winston said. "For any application that requires process heat, the XCPC system is potentially a very cost-effective way to reduce conventional fuel consumption and greenhouse gases. Its non-tracking design also enables it to be installed in any number of ways, including on rooftops and walls. You don't have this type of architectural flexibility with tracking thermal systems."

The students who were the backbone of this project have been led for the past two years by Heather Poiry, who is in the process of completing her master's degree in mechanical engineering at UC Merced while studying under Winston.

Poiry hopes the work she's put into the project can ultimately benefit businesses all over the world, but especially those in the San Joaquin Valley food processing industry, which could use solar thermal energy to offset the need to burn coal or oil for heat in their operations.

"Solar thermal technology can also have a very positive effect on air quality," Poiry said. "And I think being able to create this technology right here and know we can make an impact here in the Valley is very important to all of us."

The cooling project design and assembly were done by Winston, Poiry and a team that included more than 30 different students over the course of two years. Poiry said the students ranged from undergraduates to postdocs, and some were volunteers interested in learning about solar technology.

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not rated yet Sep 30, 2011
Now how can I get one. :)
1 / 5 (3) Sep 30, 2011
Good lord! The first solar heated absorption air conditioning system that I can recall was built in Queensland in Australia in the early 1950s. George Löf at Colorado State University in Ft Collins built another in the late 1970s. Now it's 2011 and they're trying it again? How silly!
1 / 5 (2) Sep 30, 2011
Good Lord! This was done in Queensland in Australia in the early 1950s and again by George Oscar Löf at Colorado State University in the late 1970s. The problem with small scale absorption air conditioning systems is that they require an evaporative cooling tower which uses a lot of water and pumps to recirculate it which typically draw more power than an efficient conventional air conditioning unit. The approach is a dead loss.
1 / 5 (1) Sep 30, 2011
Sorry for the double posting. The scripts are acting up. :-(
not rated yet Oct 01, 2011
Just looks like a corrugated reflector...
1 / 5 (2) Oct 01, 2011
My solar AC design was based upon the 12 foot C band TV attenna in my Tucson backyard.
Put a reflective coating on the dish, a Stirling engine at the focal point to drive an AC compressor using hydraulics.
Add a solar tracker and voila.
not rated yet Oct 02, 2011
From what the article said this is not an air conditioning unit they have reinvented. It's a solar heat collection unit. "The heat generated can then be transformed using existing technology for cooling, heating and a number of other potential uses." Emphasis on other uses.

It's not an air conditioner. Yes, solar heat abosorption has been tried, but they haven't acheived this level of efficiency previously.Besides, Absorption Chilling Technology is in the market place already.

"Because of the Santa Clara University Solar Decathlon Team's development of the integrated solar air-conditioning system, Yazaki has obtained UL approval ... for the 5-ton system...and Solarsa is taking it to market."

Admitedly this quote is from a marketing blog for the chilling technology. But if it works efficiently, when previous inventions didn't, I would call that a success. And if UC Merced has a more efficient solar heat collector, then pairing the two technologies is obvious.
1 / 5 (2) Oct 05, 2011
No tracking system to wear out means a 30 year service life so the economics compete with other energy sources.

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