L&T ECC has commissioned a total of 445 MWp of solar photovoltaic (PV)-based power plants, of which 131 MWp of capacity is based on thin-film technology. Milan Kumar, head, engineering services, L&T ECC, talks about the pros and cons of the technology and their experience so far…
What factors do you consider before choosing a technology for a project?
Selecting the appropriate PV module technology for a project depends on a combination of factors like the project location and specifications of the different PV module technologies. The strengths of a crystalline module are its high efficiency, robustness, lower degradation rates, rapidly falling cost and non-toxicity. Its challenges are the higher temperature coefficient of power and higher efficiency drops at diffused irradiance conditions. The plus points of thin-film technology are lower temperature-related power losses and better response to diffuse irradiance. Lesser available area and higher land cost call for highest module efficiency for attaining the maximum installed capacity. Due to this, crystalline modules are preferred over thin-film ones. For areas with higher diffuse radiation or high temperature, thin-film modules are preferred as they support higher generation per installed capacity.
Compare thin-film technology with its counterpart in India in terms of cost, climatic conditions, performance, operations and maintenance?
In terms of performance or energy generated per installed capacity, thin-film outperforms crystalline modules, thanks to its lower temperature-related power losses and lesser drastic efficiency drop in low-light conditions. The crystalline module on trackers is another technology that is gaining popularity. The combination results in an average 18 per cent enhancement in the annual energy generated per installed capacity, with an additional cost of nearly 10-12 per cent. On the other hand, thin-film modules deliver up to 4-5 per cent higher annual energy generated per installed capacity at 30 per cent higher cost of modules. (It should be noted that modules contribute about 60 per cent of the total cost of a plant and mounting structures constitute 5-10 per cent.)
The cost of thin-film modules at the moment is about 25-30 per cent higher compared to monocrystalline and polycrystalline technologies. The cost of installation is also higher in the case of thin-film modules as more modules have to be installed for a project of the same capacity due to lower module efficiency. This also results in higher balance-of-system costs. This also reflects on operations and maintenance expenses, where higher number of modules and a larger plant area result in higher cleaning and maintenance costs. One of the current concerns regarding the technology is its durability and performance degradation with time. Since thin-film technology is relatively new with respect to crystalline silicon, it needs to prove itself on field for over 25 years of operation. Thus, the onus of proving their field performance for over 25 years of operation is as much on the present day commercial crystalline modules as on thin-film ones.
What has been your client feedback on the performance of various technologies?
Thin-film technology has been the better performing technology (4-6 per cent more energy is being generated through this as compared to crystalline technology). Also, thin-film modules face lower degradation and are less prone to defects, except glass breakages. Two key issues that clients are worried about is the availability of thin-film modules of the same rating over 25 years towards replacement and limited number of original equipment manufacturers in the market. Clients at the moment prefer the crystalline technology with tracker combination, which is delivering about 15 per cent more energy at 5-10 per cent less cost compared to fixed-tilt plants with thin-film technology.
What is the outlook for thin film in India?
The current efficiency levels of the module are comparable to commercial polycrystalline modules. Providing better performance in high temperature and low irradiance conditions, the thin-film technology can gain a competitive edge on energy generation. Reduction in the quantity of photoactive material per watt-peak had once made thin-film more economical than crystalline silicon. In recent times, however, falling costs of crystalline technology, aided by market competition and the presence of numerous competitors, are posing a major challenge for thin-film modules.
For thin-film technology to compete in the Indian market, costs have to come down as the market currently is driven by the lowest cost per megawatt-peak. In a tropical country like India, improvement in efficiencies can result in the lowest levellised cost of energy, thus making it a technology of choice in the future.