Those involved in industrial process are familiar with waste heat recovery. The chase to capture and reuse excess BTUs in a process, whether from the exhaust stack, a byproduct of exothermic processes or condensing or consolidating from multiple thermal processes, continues to drive technological developments.

Researchers at Penn State University are exploring methods for harvesting low grade waste heat as electricity using reversible ammonia batteries. As the researchers note, low grade waste heat is a byproduct of many energy-generating processes such as power plants. Without an effective means to utilize it cost effectively, it is exhausted from the process via the stack or a cooling tower.

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

Although the idea of recapturing waste heat is not new, many of the methods for low grade energy recovery are too inefficient to be practical. In their research, Logan and his team employed a thermally regenerated ammonia-based battery. It is designed with copper electrodes, and ammonia is added to the anolyte (the electrolyte surrounding the anode). The subsequent chemical reaction charges the battery; in other words, electrical current is produced from the formation of copper ammonia complex. “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 research team member Fang Zhang, a postdoctoral fellow in environmental engineering. “Then the reaction stops.”

According to a paper on the research, the researchers distill ammonia from the effluent left in the battery anolyte using low grade waste heat from an outside source. Then, they recharge it into the original cathode chamber of the battery, thereby creating a regenerative process capable of serving as a constant source of electricity.

With the current design, the researchers produced a power density of about 60 W/m2 over multiple cycles, and they expect to improve that with further optimization.


Process Heating Welcomes New Sales Manager

Process Heating has a new National Sales Manager. Frank Prokos joins the team from within BNP Media, where he served other brands developing and opening new business as well as managing advertising accounts. Frank also has experience with a leading manufacturer and distributor of thermoplastic fluid flow solutions, including valves, actuators and piping systems to industrial, chemical, wastewater treatment and high purity markets. He looks forward to working with the thermal-processing market.