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'Thermally activated cooling system' puts waste heat to use


June 13, 2011

The prototype 'thermally activated cooling system' combines two technologies, for harnessi...

The prototype 'thermally activated cooling system' combines two technologies, for harnessing waste heat and using it run cooling systems (Photo: Oregon State University)

Automobiles, appliances, power plants, factories and electrical utilities all waste one thing: heat. More specifically, they produce heat as a by-product of their normal operations, but that heat is just dispersed into the air instead of being put to use. Researchers from Oregon State University, however, have created a prototype system that harnesses waste heat to (rather ironically) cool the device that's creating the heat in the first place. While it isn't the first system to do so, it is claimed to be unusually efficient ... and, it can generate electricity.

The "thermally activated cooling system" combines two systems that have previously been used for the harnessing and dispersion of waste heat - a vapor compression cycle and an organic Rankine cycle.

A vapor compression cycle is what's at work in a refrigerator. It incorporates a recirculating liquid refrigerant, that (in this case) travels through microchannel heat exchangers, absorbing and carrying heat away from hot surfaces, to be released elsewhere.

An organic Rankine cycle, on the other hand, utilizes an organic liquid with a lower liquid-vapor phase change point than that of water. This means that it doesn't take as high a temperature to get it to boil, and once it boils, it can generate electricity.

By combining the two cycles, heat is both drawn away, and put to work powering cooling systems. The prototype at OSU has already been shown to be capable of turning 80 percent of every kilowatt of waste heat into one kilowatt of cooling capability.

When it comes to pure electricity production, the thermally activated cooling system isn't quite as impressive, coming out at 15-20 percent efficiency. Not great, admit the researchers, but still considerably better than nothing.

They envision the system being used to cool electronics, factories, alternative energy systems, and perhaps even to use the heat from hybrid cars' combustion engines to charge their batteries.

The research was recently published in the journal Applied Thermal Engineering.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth

The system sounds interesting if it can be produced at cheaper cost. Just a thought that if this kind of system is used for cooling office and home buildings or even assisting those it can reduce significant amount of electricity grid load during peak hours...

14th June, 2011 @ 02:28 am PDT

The potential of such system, if effective as quoted, is unimaginable. From gigantic buildings to tiny electronics almost everything produces heat, which is energy wasted.

Chi Ken Sup
14th June, 2011 @ 04:00 am PDT

It's very simple to make it more powerful. I have made a portable devise that is so efficient that it runs off.... I'm not going to explain the details. I have made a much more efficient, smaller, portable, and cost effective generator. If you wish to converse, I will talk privately. All I will say is your going about it wrong and I have the answer.

Aj Jensen
14th June, 2011 @ 09:27 am PDT

Heat activated cooling is not new. Using it to generate electricity to run a typical vapor compression system is new. But this brief article is a little confusing. Is the Rankine cycle's electricity generation highly efficient leading to an overall thermal efficiency of nearly 80 percent? Why use the combined cycle for electricity to such a low efficiency, then, if electricity is the desired output, but inefficient?

And it would seem work is work. Meaning, 1kW as heat in which leads to almost 0.8kW of work out suggests a high intermediate efficiency regardless of energy form.

John Sullivan
14th June, 2011 @ 09:38 am PDT

I worked on this project and the motivation behind making cooling directly from heat is that you don't have the series losses of mechanical -> Electric and then Electric -> Mechanical conversion. With 90% efficiency motor/generator you get a 20% loss.

Not to poke fun of you John but you need to take a thermodynamics class to fully understand how Rankine and Vapor Compression cycles work. Heat is not work, it is heat. With a coefficient of performance of three a vapor compression cycle can move 3 kW of heat with 1 kW of mechanical work. The efficiency of the Rankine cycle is dominated by the temperature difference between the high and low side temperature and the efficiency of the components. In the realm of waste heat organic Rankine cycles usually have a thermal efficiency ranging between 8-25% depending on the heat source and components.

Kevin J Harada
14th June, 2011 @ 01:02 pm PDT

AJ, I'll invest in your product but I am currently working offshore on an oilrig and can't pick it up. If you send money via wire transfer to my Cayman Islands bank account to cover the discharge fees, I can send millions of dollars left to me by a Nigerian prince.


14th June, 2011 @ 08:52 pm PDT

I do not have money to give. Discharge fees?

Aj Jensen
15th June, 2011 @ 06:06 am PDT

Hearty congratulations. This would undoubtedly be a boon to power industry particularly in India to enhance efficiency of operation and save environment at the same time.

Asoor Shyam
21st June, 2011 @ 04:24 am PDT

kevin - your invention is very interesting I have been trying to get an email for you but so far - no luck contact me at please

24th June, 2011 @ 04:05 pm PDT
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