Solar cells are manufactured using various technologies. Some, on one hand are highly efficient but very expensive to set up manufacturing units; other technologies, although less efficient are cheaper in scaled productions. Several Solar Cell manufacturing echniques have been adopted suitable for operating environments depending on dust content, humidity, operating temperatures, direct/diffused solar radiation incident on the cells etc. Chart shown below is a summarized representation of various cell manufacturing technologies that are deployed in manufacturing of cells that can be used in varied applications ranging from rooftop power generation to powering satellites. Click on these technologies to read more about them.
Efficiency of Solar Cells
Generally, Crystalline Silicon Solar cells have been ranked higher in efficiencies than any other technology. Crystalline Silicon Cells have been recorded with efficiencies as high as 25-30%. Whereas thin films have only 7-13% efficiencies.
Efficiency comparison of various solar cell technologies is available in a study conducted by NREL.
Technology Suitability for India
|Parameter||Crystalline Silicon Solar Cell Technology||Thin Film Solar Cell Technology|
|c-Si has been well established for around 30 years, Thus having proven credentials for a time period equal to the entire operational life of a power plant.||Being a new technology, it lacks proven track record and hence performance of the system cannot be guaranteed over the lifetime of operation of the power plant. This makes the system prone to heavier scrutiny from banks.|
|In India, large tracts of land are readily available (at cheap rates when compared with project costs), nullifying lesser land requirement advantage offered by c-Si.||Thin film technologies typically require more land than c-Si based systems due to their lower power density. So to avoid increase in total project costs thin films are favored.|
|The project cost can be constituted to the modules and the balance of systems cost. Module Cost attributes to about 60% of the project cost. c-Si modules are about 25% to 40% more expensive per Wp when compared with thin film. Considering BoS costs, c-Si holds the advantage. However in the Indian context, the BoS costs play a subdued role in choice of technology due to lower labour, project management, civil and construction costs.||Thin Film Modules are cheaper but the BoS for thin film systems are 9% higher than c-Si technology. The cost savings from module offsets the additional BoS cost requirement for thin film, thus making the overall project cost of thin film based systems lower than that of c-Si systems or in the worst case, comparable.|
|Alternate financing mechanisms are available for projects which import modules from foreign countries. Most solar projects under JNNSM are based on c-Si technology and are bound to have local content requirement as per Phase I Batch II Guidelines.||Ex-Im, OPIC, EDC etc. offer attractive financing options at lower interest rates for import of modules from USA and Canada respectively. This route may be taken by thin film technologies alone.|
|India falls under sub-tropical regions of earth where average temperature is around 25-30 degree Celsius. The degree to which the performance of cells drop is measured through a factor known as temperature coefficient. c-Si modules show considerable performance losses at higher temperatures.||Thin film modules produce 5% more electricity per unit of installed capacity in high temperature regions due to their lesser negative temperature coefficient and better performance under diffused light conditions. Thus thin film might be more suitable to Indian climatic conditions.|
|As per guidelines under Phase 1, Batch 2 of JNNSM scheme, all power plants using c-Si based technology are required to procure their cells and modules from local manufacturers. This could lead to a shortage of supply or out-dated, inefficient modules.||However, thin film modules are exempt from this regulation meaning that they can be procured from any provider outside India – thus ensuring technological superiority as well as bringing in the added experience of foreign project integrators.|
Tracking systems help improve the output of a power plant by up to 10%. These systems are more suitable for projects employing c-Si technology than thin film technology. But most Indian Project developers and System integrators do not go for tracking because of:
|Thin film based systems generate electricity even under lower or diffused light conditions. Peak performance is thus independent on the presence of tracking systems.|