Nantenna: Technique of Energy Harvesting for Industry 4.0
One of the biggest threat that our civilization is facing today is energy crisis.
The conventional energy resources are yet to be replaced by the renewable energy sources due to limited stock and high emission of pollutants. When the world goes for green, solar energy takes the attention of the researcher. But the state of the art Photovoltaic technology has failed to get the success in cost, efficiency and size point of view. As the wavelength of the sunlight is getting smaller so scaling of the device is necessary to capture the energy from that wave coming. In that case, when size and efficiency both are considered in Nano-scale, nantenna comes in front of the scientists. In this discussion, we mainly focussed on the how solar radiation can be transformed to the usable electrical energy using nantenna. Also we have discussed several nantenna prototypes available in the market. The nantenna is better than conventional PV technology, not only that it produces more than 70% electrical energy but also there are many advantages. This short theoretical perspective completely emphasizes on green energy for the better world and concludes about how the efficiency of the nantenna can be increased.
To eliminate this problem of energy crisis non-conventional energy sources need to be considered. Solar energy is the only source of renewable energy and can be the best possible solution to address the problem of energy crisis. Different types of solar cells are present there to collect the solar energy coming from the sun but the problem is with the conventional solar cells that do not have good efficiency, so it cannot absorb radiations having lower wavelength. Nantenna is a device used to collect solar energy most efficiently in place of conventional photovoltaic cells. A nantenna (Nano-antenna) is a rectifying antenna and an electromagnetic collector in Nano-scale. When the wavelength is proportional to the size of the device, then nantenna can absorb it. The idea was first proposed by Robert L. Bailey in 1972 and received a patent in 1973 for an electromagnetic wave converter. The conventional solar cells cannot absorb all the rays coming from the sun but the nantenna can do that as the size of it is very small.
CONVENTIONAL SOLAR CELLS:
Conventional solar cells are made up of different materials. Basic work of the solar cell is to absorb the solar radiation from the sun and convert that energy to the electrical energy. On the basis of material and the efficiency of the solar cells it has been classified as first generation, second generation, third generation and fourth generation solar cells. The efficiency of the conventional solar cell varies up-to 40% or little bit more.
- First generation solar cell:
First generation solar cells are made up of Silicon and Germanium p-n junctions. The doping elements used in those solar cells are boron, phosphorus and few others. This first generation solar cell is quite efficient because of its high mobility of the carrier and broad absorption of the solar spectrum. These kinds of solar cells are the market leader. Almost 85% of the solar cells available in the market are the first generation solar cells. But the drawback of this first generation solar cells is the manufacturing cost.
- Second generation solar cells:
Second generation solar cells are made to reduce the manufacturing cost of solar cells. Hydrogen is introduced to the amorphous silicon for the purpose of doping with boron and phosphorus. The mass is reduced to some extent in these types of solar cells.
- Third generation solar cells:
Third generation solar cells are not made up of conventional p-n junctions or either thin films. It includes nanocrystal solar cells. It contains multi layered solar cells which consist of gallium arsenide, amorphous silicon. Despite being a great advantage over the first and second generation solar cells it has some disadvantages that the efficiency is a bit lower than the silicon solar cells and the band-gap is much higher in these solar cells.
- Fourth generation solar cells:
Fourth generation solar cells are the solar cells in which thin multi spectrum solar cells are stacked. Efficiency is much higher than the previous generation solar cells. It is basically based on the multi junction technology
Advantages over PV cells:
This comparative study has shown that efficiency of the nantenna can be more than 95% and this efficiency depends on fabrication technology of PV cells as well as the material of the nantenna. If we change the materials the quantum properties will change according to the material junction potential and the Schrodinger equation will vary. Due to the transition of electrons in different sub-bands the required current density is achieved, which will increase the quantum efficiency of nantenna.
Prof. Surajit Sur,
Department of Electronics & Communication Engineering,
University of Engineering & Management (UEM), Jaipur