In any industrial process, a vast amount of heat is produced that just goes to waste. Over the past decade, many researchers tried to use this energy somehow, but all their attempts were futile. Most of these studies were based on solid state materials and thermoelectric devices. These can be used for generating electricity if a temperature gradient is achieved, but the efficiency is very low because there are not enough materials available.
A new research conducted in collaboration with Stanford University and MIT might be able to make good use of this wasted heat. The results of this study are applicable if the temperature difference is not greater than 100 degrees Celsius.
The proposed technique uses the concept of thermogalvanic effects. Rechargeable batteries have a voltage that is dependent on temperature. A discharge voltage greater than the charged voltage can be achieved if the charging-discharging cycle is combined with heating and cooling. This system is characterized by high efficiency and will work even if the temperature difference is less than 50 degrees.
As the process is initiated, waste heat heats the charged battery. This increases the temperature and the battery charges itself. Once it is fully charged, it is cooled down again. Now when the temperature is higher, the charging voltage is less. As such, when the battery has cooled down, it can produce more energy than the one which it consumed for charging. This extra energy is actually the waste heat.
The concept is focused on utilizing heat which has a temperature of less than 100 degrees Celsius. Most of the power plants and industrial facilities generate waste heat within this range. If the temperature is maintained at 60 degrees Celsius, the system operates at an efficiency of 5.7%.
The researcher told the press that it was in the 1950s that this concept was proposed, but at that time, successful results were not produced because the material and engineering principles available were not so advanced. Moreover, this work was based on much higher temperatures of wasted heat.
The new system may prove to be beneficial for utilizing waste heat, but before it can be implemented on a practical scale, a number of challenges will have to be dealt with. These include the speed of the charging-discharging cycle, power density and reliability.