Our Roads, are Large Thermoelectric Power Generator!

Ian Weiss, Edison High School, Fountain Valley, CA, United States and Nicola Weiss, Edison High School, Huntington Beach, CA, United States
Asphalt pavement does not reflect the sunlight and hence heats up faster than a light surface that would reflect the sunlight. This means the asphalt absorbs the sunlight and gives off heat, which is wasted energy. By turning heat energy into electricity, cities can provide a source of clean, green energy and reduce their reliance on fossil fuels, which pollute the air.

The heat given off by asphalt increases the temperature of the air around the asphalt contributing to what is known as the urban heat island effect. This heating in turn contributes to the formation of smog and ozone depletion. With the population still growing this would mean an increase in city sizes, greater heat island effect and hence an increase in smog and ozone depletion, creating a significant health concern. By harvesting the heat energy in the pavement by installing pipes with water, cities can not only create green energy but also reduce the heat radiated from pavement and its harmful effects to our atmosphere.

A thermoelectric power generation system takes in heat from a source and outputs electricity.

It does this by using a thermoelectric module or plate, which needs a temperature difference from one side to the other to generate electricity: something that is technically challenging to implement in real-world applications. In a power generation system, the heat for the hot side of this temperature gradient must be supplied efficiently from a heat source such as the metal water basin with heated water. The cold side must be cooled by air, water, or another suitable medium. The plate acts as a heat exchanger. Inside the plate, conductive materials create an electric charge as electrons move away from the heat. A thermoelectric power generation system can be thought of as two heat exchangers, each of which have to move heat to (or from) the hot (or cold) side of the thermoelectric plate.

Maximizing the efficiency of a thermoelectric power generation system requires extensive engineering design. Trade-offs between total heat flow through the thermoelectric modules and maximizing the temperature gradient across them must be balanced. The design of heat exchanger technologies to accomplish this is one of the most important aspects of engineering of a thermoelectric generator. This results in electricity from otherwise wasted heat.