Project Idea: solar energy Photo Voltaic Cell
Apart from researches, solar energy is the best source available to us as an alternate source of energy. Various researches suggest that a 1.5 kilovolt PV system would keep around 110,000 pound co2 out of our atmosphere. This much electricity is produced by burning 60,000 pounds of coal. If we somehow do this the atmosphere would be free from pollution and greenhouse effect.
Think just that if we somehow manage to utilize the solar energy. We go outside to the sunny day and take the amount energy we want and then get back to work. The technology which is developed and using so far is the use of photo voltaic cell. Which is very elegant yet sophisticated?
Theory for photovoltaic module
Light from the sun consists of photons and each photon is associated with energy with them equivalent to have. As explained by the Maxwell Planck law
PV uses that to and converts it into electricity. The majority of the module use wafer of crystalline silicon and cadmium telluride. The load carrying or structural can be the front or the back layer. The cell membrane must be protected from any kind of physical and chemical damage caused by the moisture and other chemicals. Most solar modules are rigid but semi flexible is also available which depends on thin film of cells. In order to get continuous flow of current, electrical connections are made in series or in parallel for the desired voltage. The current carrying conductive wire that take off the current from the solar module can have silver, copper, or other non- magnetic transition metal.
To connect externally popular connectors are available like MC3 or MC4, to make sure easy weather proof connection to the rest of the system. Some of the recent solar module designs include lenses and mirrors as concentrators on the array of smaller cells, maximizing thus the output current per square meter. The gallium arsenide thus becomes cost effective. So by now we are quite familiar with the construction of the PV but what about the efficiency?
How much is PV efficient?
Well, currently the best achieved by PV is around 21.5% in new commercial products. The most efficient solar module have the power density of upto 175 w/m^2. The main reason is, most of the solar module does not cover the whole range of sunlight which includes – ultraviolet, infrared, and low diffused light. However when the monochromatic light is incident on the particular cell which is tuned in with the falling light frequency may provide higher efficiency. With this idea new PV is designed with a light splitter and panel of different cells. The sunlight falls on the splitter (kind of a prism), light deviates according to their respective frequencies on the tuned cells. This system has been projected to be capable of raising the efficiency to 50%. Now that’s something amazing, right?
The researchers of London Imperial college has shown too, that efficiency can be improved more by studding the light receiving semiconductor surface with the aluminum nano-cylinders. The science behind this is simple. The scattered light by doing so travels longer path and more photons are trapped by the semiconductors hence more electricity conversion. Previously instead of aluminum, silver and gold were used by that was not cost effective.
There is one more terminology here – ‘Micro inverted’ solar panel. These coverts the DC(Direct Current) generated by the solar panel to Ac(Alternating current).The output from several inverters sometimes fed to electrical grid. Micro inverter works completely independent so each panel contributes its maximum possible output with the available sunlight. These are wired in parallel than the normal panel which is wired in series. The output is determined with that arrangement is determined by the lowest panel and this is called the “Christmas Light Effect”
Types of solar modules
Crystalline silicon modules – Two years back, crystalline silicon accounted for more than ninety percent Photo-voltaic worldwide. Which shows most of the solar modules are manufactured of the solar cells made of the poly-crystalline and mono-crystalline silicon.
Thin Film Modules – The third generation or 3g solar module comes with advanced thin –film cell. They produce relatively higher efficiency conversion compared to other solar technologies with low cost. Thanks to Jacob S. Gibbs and Brinsley Coleberd for developing such technologies.
Rigid thin-film modules –The cell and the module are manufactured in the same production line. On a glass substrate or superstrate the cell is created with the proper positions. The process is called “monolithic integration”. The substrate or superstrate is then perfectly packed from front and back with another sheet of the glass. The main cell technologies in rigid thin film category are CdTe, or a-Si, or a-Si+uc-Si tandem,or CIGS (or variant). Amorphous silicon has a sunlight conversion rate between 6-12%.
Flexible thin-film modules – The flexible thin film modules are also produced in the same production line like the rigid thin film module by depositing the necessary photo active layers on the flexible substrate. For polyester or polyimide film monolithic integration can be
incorporated as these are insulator in nature. On the other hand if the substrate is conductor then the electrical connection is made with the necessary technique. The cells are fabricated into modules by laminating them to a transparent colorless fluoro polymer on the front side. Suitable polymer for bonding is incorporated on the other side of the module. Presently only amorphous silicon triple junction is available for the flexible module.
The main advantage of flexible thin film solar modules is that they can be used as a portable device for energy. They are very resistance to breakage unlike regular crystalline cells. They can though be broken by bending them into a sharp angle. They are also lighter than the rigid standard solar panels per square foot. It is expected that by 2019 flexible thin film PV market experience a CAGR of over 35%.
Smart solar modules – last but not the least is the smart solar module. Many companies have initiated embedding electronics into photovoltaic modules. This ensures maximum power point tracking (MPPT) per module individually. The fault can be detected and monitoring is possible at module level in this. To optimize the solar power harvest, technology like DC to DC power conversion is used which
are also called as power optimizer. Such electronic technology ensures shading effect, which means that when light falls on some part of the panel but shades on the other part due to hindrance on the path of the light then one part shows the zero output current but other does not. This is corrected by using such electronics technology, where the entire module falls to zero in that case.
So this was all about Photo-voltaics. I hope this idea would be helpful in making your Engineering projects. Its your time to think something related to this, add some technical possibilities to make it yours and help researchers. In case you have any query regarding the article or want to know some more technicalities, please don’t hesitate to ask. We would love to reply you to the most possible way we can. Stay tuned with us for other Project Ideas and Engineering Projects.