November 29, 2019 by Luke James
Hong Kong engineers have found a way to efficiently convert heat into electricity. This creates a huge potential to reduce CO2 emissions by converting low-grade waste to usable electricity.
A new ‘Direct Thermal Charging Cell’ (DTCC) developed by engineers from the University of Hong Kong’s Department of Mechanical Engineering has been shown to effectively convert heat to electricity. This creates a massive potential to reduce greenhouse effects by capturing and converting low-grade waste, for example, exhaust heat, and turning it into electricity.
There is an abundance of low-grade heat available through a myriad of sources such as automobiles, solar-thermal, geothermal energy, and industrial processes.
Dr. Tony Shien-Ping Feng of the University of Hong Kong. Image Credit: University of Hong Kong.
The new DTCC is an electrochemical unit that is bendable, stackable, low cost and has a small profile of 1.5cm2. It has been designed to reduce greenhouse gas emissions by converting low-grade heat into usable electricity.
In a demonstration of the DTCC’s capabilities, ten of them were used in tandem to take waste heat from a heated pipe and convert it into electricity. This electricity was then used to activate an OLED light and change the color of some window glass.
Speaking to journalists about the DTCC, Dr Feng said, "Efficient low-grade heat recovery can help to reduce greenhouse gas emission but current technologies to convert this heat to electricity is still far from optimum. DTCC yields a conversion efficiency of over 3.5%, surpassing all existing thermo-electrochemical and thermo-electric systems, which is either too costly or complicated or too low in efficiency for everyday applications. DTCC is a revolutionary design with great potentials in smart and sustainable energy devices."
The University of Hong Kong’s Technology Transfer Office has filed for the DTCC’s provisional patent in the United States and its Patent Cooperation Treaty patent.
To make use of low-grade waste, the DTCC uses asymmetric electrodes: a graphene oxide/platinum (GO/Pt) cathode and a polyaniline (PANI) anode in Fe2+/Fe3+ redox electrolyte via isothermal heating operation without building thermal gradient or thermal cycle.
When heated, the DTCC generates voltage using via a thermo-pseudocapacitive effect and then discharges continuously by oxidizing the PANI anode and reducing Fe3+ to Fe2+ under isothermal heating on the cathode side.
DTCC can be used across a broad range of applications to make use of low-grade heat waste. Examples of potential applications include HVAC by recycling heat from the compressor and conductor, medicals, and, potentially, wearables by harnessing body heat.
