THERMALLY REGENERATIVE AMMONIA-BASED BATTERY (TRAB)
Considering the depletion of fossil fuels and global climate change, the need for clean and sustainable energy sources is quite evident. A significant potential to obtain clean energy exists from harvesting low-grade thermal energy as electrical power. Low-grade heat (<100 ͦC) use has drawn increasing attention due to its potential for electricity production without the need for additional fuels. A vast amount of low-grade heat is generated from industrial processes and can be collected from solar geothermal sources (Fig. 1). There have been many different methods examined to transform thermal energy into electricity, including solid state devices based on semiconductor materials, organic Rankine cycles, thermoelectrochemical systems (TES), and systems based on salinity gradient energy (SGE).
Figure 1. Various sources of industrial waste heat
Recently, an efficient, inexpensive, and scalable approach was developed at Penn State to generate electrical power from waste heat sources by combining different aspects of the TES and SGE techniques, called a thermally regenerative ammonia-based battery (TRAB). A maximum power density of 115 W m–2 (normalized by the electrode projected area) was produced in a single (first) cycle, with 60 W m–2 produced over multiple successive cycles with electrolyte regeneration (Zhang et al. 2015).
Figure 2. Schematic of the TRAB to convert waste heat into electricity