Global Sources
EE Times-Asia
Stay in touch with EE Times Asia
?
EE Times-Asia > Power/Alternative Energy
?
?
Power/Alternative Energy??

Reversible ammonia cells harness waste heat as electricity

Posted: 08 Dec 2014 ?? ?Print Version ?Bookmark and Share

Keywords:Pennsylvania State University? waste heat? ammonia batteries? anolyte?

Engineers at Pennsylvania State University have claimed to have discovered what they say is an efficient method to harvest low-grade waste heat as electricity by using reversible ammonia batteries. Using low-grade waste heat from an outside source, the researchers were able to distill ammonia from the effluent left in the battery anolyte and then recharge it into the original cathode chamber of the battery.

"The use of waste heat for power production would allow additional electricity generation without any added consumption of fossil fuels," said Bruce E. Logan, Evan Pugh professor and Kappe professor of environmental engineering, Penn State. "Thermally regenerative batteries are a carbon-neutral way to store and convert waste heat into electricity with potentially lower cost than solid-state devices."

Low-grade waste heat is an artifact of many energy-generating methods. The researchers want to take waste heat and capture it to produce more power. Other researchers have tried a variety of methods, but most produce too little power to be workable, or they cannot provide a continuous resource. Logan and his team are using a thermally regenerated ammonia-based battery that consists of copper electrodes with ammonia added only to the anolyte, the electrolyte surrounding the anode.

Reversible ammonia batteries

"The battery will run until the reaction uses up the ammonia needed for complex formation in the electrolyte near the anode or depletes the copper ions in the electrolyte near the cathode," said Fang Zhang, postdoctoral fellow in environmental engineering. "Then the reaction stops."

This type of battery would be useless as a constant source of electricity if the reaction were not regenerative.

The chamber with the ammonia now becomes the anode chamber and copper is re-deposited on the electrode in the other chamber, now the cathode, but formerly the anode. The researchers switch ammonia back and forth between the two chambers, maintaining the amount of copper on the electrodes.

"Here we present a highly efficient, inexpensive and scalable ammonia-based thermally regenerative battery where electrical current is produced from the formation of copper ammonia complex," the researchers reported in the latest issue of Energy and Environmental Science. The ammonia liquid stream can convert the thermal energy to electrical energy in the battery. "When needed, the battery can be discharged so that the stored chemical energy is effectively converted to electrical power."

One of the problems with previous methods was that the amount of energy produced in, for example, a system using salty and less salty water to generate electricity, was too small relative to the amount of water used. The thermally regenerative ammonia battery system can convert about 29 per cent of the chemical energy in the battery to electricity and can be greatly improved with future optimisation.

The researchers produced a power density of about 60W per square meter over multiple cycles, which is six to 10 times higher than the power density produced by other liquid-based thermal-electric energy conversion systems. The researchers noted that the current thermally regenerative ammonia battery is not optimised, so that tinkering with the battery could both produce more power and reduce the cost of operating the batteries.

The researchers were able to increase power density by increasing the number of batteries, so that this method is scalable to something that might be commercially attractive.

- Paul Buckley
??EE Times Europe





Article Comments - Reversible ammonia cells harness was...
Comments:??
*? You can enter [0] more charecters.
*Verify code:
?
?
Webinars

Seminars

Visit Asia Webinars to learn about the latest in technology and get practical design tips.

?
?
Back to Top