Engineers at Oregon State University develop technology they say dramatically reduces the loss of energy produced by vehicles, factories and power plants.
The system captures low- to medium-grade waste heat now going out the vehicle’s exhaust pipe and uses much of the heat either for cooling or generating electricity.
Oregon State system recycles waste heat.
Hailei Wang, a research associate at OSU’s School of Mechanical, Industrial and Manufacturing Engineering, says a just-completed prototype device demonstrates the effectiveness of the technology.
“This could become a very important new energy source and way to improve energy efficiency,” Wang says in a statement. “The prototype shows these systems work as well as we expected they would.”
He says a vehicle’s internal-combustion engine generally operates at about 25% to 40% conversion efficiency. The function of the radiator is to dissipate wasted heat, but there have been various attempts, some of them now in use, to capture at least some of that waste heat for cooling.
Wang says the system being developed at OSU may be more efficient and more portable than existing methods, and with an additional advantage: the ability to produce electricity.
Called a thermally activated cooling system, it gains much of its efficiency by using extraordinarily small microchannels that help to better meet performance, size and weight challenges.
Wang says it effectively combines a vapor-compression cycle with an organic Rankine cycle, an existing energy-conversion technology.
The OSU prototype is turning 80% of every kilowatt of waste heat into a kilowatt of cooling capability.
The engineers say the conversion efficiency wouldn't be nearly as high – 15% to 20% – if the goal is to produce electricity. But their system still outperforms the current approach, which wastes the energy potential of all the heat.
The system has possible use in hybrid-vehicle technology, by taking waste heat from the gasoline engine and using it not only for air conditioning but also to help recharge the battery that powers the vehicle, Wang says.
In a study published in the journal Applied Thermal Engineering, Rich Peterson, an OSU professor of mechanical engineering and an expert in thermal sciences and energy systems, says more research is needed to perfect the technology and adapt it to different uses.
The work takes advantage of OSU's advanced programs in microchannel technology, a key focus of the Microproducts Breakthrough Institute operated by OSU and the Pacific Northwest National Laboratory. Peterson also is an associate director of the institute.
Mass production of miniaturized components and devices will be a reality in this century, the institute predicts. In the same way the microchip resulted in portable electronic devices, microtechnology has the potential to revolutionize many products.
By miniaturizing pumps, channels, connectors, valves and materials, interaction distances of fluids and chemicals is reduced and performance is intensified. New applications may become possible as device size is reduced.
“There continues to be significant potential for reducing energy consumption and greenhouse-gas emissions by improving overall energy efficiency for various energy systems,” Wang says.
“One route toward satisfying both paths is to develop technology able to recover waste heat that would be otherwise rejected to the atmosphere without usage.”
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