We humans have got success in inventing new technologies for harnessing alternate sources of energy. The pursuit for alternative energy sources is taken for meeting the increasing demand of energy. This could be achieved by focusing on those sources of energy which are abundant in nature and renewable unlike fossil fuels. Solar energy has huge potential to be the major energy sources if harnessed efficiently. Scientists by now have gained huge success in solar energy conversion. There are various methods which have been employed by the researchers and still looking for more to increase the efficiency of solar panel. Currently we can only use about 21.5 percent of the solar energy into electricity commercially. Researches are in progress add more conversion rate to it. In this article we would discuss the new researches which have gained popularity in news and inspired many others too. There are three researches summed up below. I your ‘engineer buddy’ hope that it would be helpful to you and assist you in your engineering projects, science fair, seminar, in thesis or report making.
1-New organic semiconductor material: Organic tin in polymers increases their light absorption
For the first time, Researchers of Germany successfully integrated organic tin into semiconducting polymers or plastics. These semi conducting polymers can be used for the increasing absorption capability of sunlight by the solar cells. By fusing the organic tin into the polymer, sunlight can be absorbed over a wide range of spectrum.
Unlike electric conductors such as metals, semiconductors conduct current under certain conditions. Due to this property semiconducting plastics also called as semiconducting polymers. These are extremely promising materials for the latest generation of solar cells in organic solar modules. The traditional inorganic versions are heavy and costly in terms of fabrication. The advantage of new organic variant besides cheap and light weight is that it can be used in transport sector too. However organic semiconductors are not as much efficient as the silicon based solar panels and still needs more research in this arena.
The working of solar cell is very simple. The light excites the electron which leaves its place reaching to higher energy level and leaving behind a cavity or the hole in the process. The hole or cavity acts as the positive charge. The charge is then percolated into different poles and a current can be observed. The closer the energy levels, more the solar energy utilization.
The polymer needs close energy levels as polymer with small energy gap has the red and even rare purple color. Therefore the researchers were focused towards developing such strongly light absorbing, deeply coloured plastics which was difficult to achieve. Finally they got new material in their labs which are visible with the bare eyes. The polymer is deep purple in solution and black when processed into a thin film or wafer.
The scientists used a new concept to achieve the small energy gap. They introduced organic tin in the form of cyclic molecules called as ‘stannoles’ into the carbon –polymer backbone. Tin belong the same chemical group of carbon and somewhat similar to required properties. The electronic properties between stannoles and corresponding carbon congeners are very different. It is not just an overweight carbon atom but also it can lower the energy levels in its organic compounds drastically. Before now, nobody was able to use these special properties of tin in polymeric materials. This was quite a difficult experiment for the researchers but they succeed. The team used palladium as catalyst during forming the desired plastic. This material can be processed easily into thin films and application on solar cell can be tested. The full potential can be assessed in the near future.
2- Solar power device would use heat to enhance efficiency
Apart from the above finding, another research is done. The new approach of harnessing the solar energy is developed by researchers of MIT. It involves of heating a high temperature material mass, which then radiate the infra-red radiations. Those radiations thus collected by conventional photovoltaic cells. This technique also enables to store energy for later use.
Adding additional steps would certainly improve the performance, as those wavelengths of sunlight go waste mostly. The conventional silicon based solar module does not take advantage of all the photons contained in sunlight. The main reason for such inability is that the band gap or energy level of photovoltaic material must match with the energy associating the photons. The silicon energy levels respond to many wavelengths of light but not all of them.
To remove that limitation, the team inserted a two – layered absorber –emitter device which is made of noble materials, involving carbon nanotubes (or CNT which are close to perfection one-dimensional structures, with diameters of only 1–3 nm and lengths upto few centimeters.) and photonic crystals (the periodic optical nanostructures that affect the motion of light photons just like ionic lattice affects electrons in solids).
In between the sunlight and PV cells. The intermediate material gathers the energy from the broad spectrum of sunlight and heats up during the process. While heated up, it turns into red hot and emits the radiations of corresponding wavelengths. That wavelength is then harnessed by the tuned PV cell mounted nearby, thus improving the overall efficiency of the Photovoltaic. The researchers said that an efficiency of upto 80 percent can be achieved.
How it solar Power Device works –
The outer layer which faces towards the sun is an array of multiwall nanotubes. This absorbs the heat very efficiently and converts that into heat. This layer is bonded strongly with the layer of a photonic crystal, concisely designed and engineered that when the adjacent layer heats up of nanotube, it glows having the peak intensity above the band gap of the PV. The initial tests are carried out on 1cm chip and follow up test would be done on 10 cm chip. With the increase in dimension of the solar cell panel, the loses of heat as compared to the size increases though.
3-Solar Photovoltaic thermal system
Two Researchers from Queen University have given a great contribution in solar cell technology. The research has led to a new solar photovoltaic thermal system, generating both thermal energy and electrical energy simultaneously. They call it solar thermal photo voltaic.
Solar pvts are basically manufactured with crystal silicon cells which generates electricity but little heat. These two researchers designed and tested amorphous silicon cells in a PVT system. The study demonstrated ten percent more solar electric output and increased heat generation due to higher operating temperature. This experiment opened up an entire use of amorphous silicon and make highly economic PVT possible. The dual purpose of PVT is very useful in cold countries to be used at home. It can be used to heat up the house and generate electricity.
The amorphous silicon has several advantages in contrast to crystal silicon. It needs less material, cost less in manufacturing and provides greater return on investment. It also shows that amorphous silicon solar cells can be manufactured into thicker cells if they are operated at greater temperatures in PVT system.