Solar Panels are sold by hundreds of companies around the world ranging from small to very large and comes in various shapes and sizes as well.Besides this solar panels are also made of very different materials for example silicon solar panels and thin film solar panels.So comparing solar panels and choosing a solar panel is a very difficult process if you want the best solar panel according to your need.The most efficiency solar panels are needed in cases where the land area or rooftop area is at a premium.Note a typical 200-250 watt solar panel requires an area of 60×38 inches which means an area of around 2000 square inches.1 megawatt of solar panels would require an area of between 5-10 acres of land depending on the efficiency of the solar panels.However this can be reduced by using solar trackers which can increase the output of solar panels though they to increase the area requirement slightly.Also the area also depends on the location of the place since a place recieving high sunlight for example California would require lesser area for generating the same amount of electricity compared to London (upto 30% fewer solar panels).Note solar panels with higher efficiency have a higher price tag associated with them since they require higher cost to manufacture.The most efficiency solar panels which are used in spacecraft and have a efficiency of around 35-40% may cost upto 100 times more than the normal silicon solar panel.
Multijunction Solar Cell Concept
The basic principle on which solar cells work is Photovoltaic ie. they convert the photons from the sunlight into usable electricity. However, in this process neither is all the light absorbed nor does all the photons get converted into electricity. High energy blue light photons do not have all of their energy converted into electricity, some is wasted as heat & low energy red light photons are not absorbed at all. Sunlight is made up of a broad spectrum and depending upon these various wavelengths, photons of light also have different energy levels.Hence, to minimize this wastage & to enhance the efficiency of solar cells, scientists came up with the concept of multijunction solar cells.