Direct Energy Conversion Angrist.pdf
The cost associated with solar energy is much higher than that of fossil fuel due to the fact that the cost of extracting and transmitting solar energy is much higher than that of fossil fuel. The cost of electricity from solar energy systems is approximately equal to that of fossil fuel, but the systems are only dependable during the day and can break down during the night.
Direct Energy Conversion Angrist.pdf
The tenet of the book is that there are no free lunches. The energy we extract is not free but is obtained from burning fossil fuels, which can lead to a potentially serious environmental problem. However, a Green House Gas emission standard can be used to bring down the amount of fossil fuel burned to produce the same amount of energy. The cost of fossil fuel is what dictates the level of efficiency that can be obtained.
Solar cells or panels convert the energy from the suns rays into electrical energy. The process includes converting the energy from light into chemical bonds, which are known as electrons. These electrons can then be drawn out of the chemical bonds and collected into a device, which is used to create electricity.
To apply thermoelectric energy conversion, the temperature difference for heat source has to be generated by energy conversion or by thermal energy flow. The thermal transport in a solid occurs at lattice (phonon) frequency through bulk and boundary scattering, and the slowest process of the transport is interfacial phonon-boundary scattering caused by boundary roughness. The phonon scattering in thermoelectric materials causes the heat transfer rate to decrease as a function of the frequency. At low temperature, phonon-boundary scattering increases and becomes the dominating mechanism. At a certain temperature, most of the thermal energy is transferred by the boundary scattering. To overcome the low level of the phonon-boundary scattering at a low temperature, the energy transport can occur by resonant mechanisms, wherein two phonon modes with similar polarization properties and a phonon mode with different polarization properties are combined to form a hot-cold phonon pair. The second phonon mode with different polarization properties is called the phonon assistance mode or the trapped mode, which generates heat by a stepwise thermal transport. Consequently, the phonon assistance mode is considered to be an important mechanism to control thermal transport in the thermoelectric system. To enhance the performance of a thermoelectric materials, the phonon assistance modes and the associated thermal transport properties need to be considered by analyses and experiments.