原题
There are four locations █ in the passage that indicate where the following sentence could be added.
Thermoelectricity
Thermoelectric materials offer a promising solution for converting waste heat into usable electrical energy, making them a valuable option for sustainable energy generation. Thermoelectric devices consist of thermoelectric materials arranged so that one side is heated while the other is cooled; the ensuing temperature difference generates an electric current (the Seebeck effect). Waste heat sources include industrial exhaust or even body heat. In the automotive industry, thermoelectric generators have been integrated into hybrid and electric vehicles to recover heat from exhaust systems and convert it into electricity. That electricity can then be used to power onboard electronics or charge the battery, improving the car's efficiency.
█ Many of the most effective thermoelectric material types, however, rely on rare or environmentally harmful elements, such as lead and tellurium, which limits their practicality for large-scale use. █ Additionally, the amount of electricity that can be produced from heat is still relatively low compared to other energy technologies. █ Researchers are working to overcome these issues by developing safer, more abundant materials—such as modified forms of silicon that can be engineered to exhibit thermoelectric properties—and by optimizing device architecture to improve energy conversion efficiency and scalability. █
Thermoelectric devices typically achieve conversion efficiencies of 5-8%, whereas solar panels reach 15-22%, and natural gas power plants can attain efficiencies of 45-50%, or even more.
解题思路
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