Large-scale solar projects in Tamil Nadu have seen rapid growth in recent years. In the past five years, the cumulative installed capacity witnessed a four-fold increase to 4.4 GW, as of March 2021. Aiding this capacity addition is the State’s reasonably high insolation levels and matching solar potential, estimated at 279GW. The sharp decline in the prices for solar and resulting cost competitiveness is another factor. For instance, auction discovered solar bids reduced significantly, from ₹10.95 in 2010 to ₹1.99 by 2020. Additionally, in response to the ambitious national targets and to spur sector specific development, Tamil Nadu released the Solar Policy of 2019, aiming for 9GW of solar installations by 2023.
Types of technologies
To meet this target, the current capacity would need to be more than doubled. To do this, Tamil Nadu must keep up with market trends and incorporate innovations in the sector to improve efficiency and long-term reliability of solar power plants. ‘First-generation’ solar cells use mono-crystalline and multi-crystalline silicon wafers. While the former is made from a single crystal of silicon (of higher purity), the latter is made by combining several fragments. The efficiency of mono-crystalline panels is about 24%, while for multi-crystalline panels it is about 20%. Crystalline silicon technologies are one of the oldest in the market and occupy 95% of the global photovoltaic (PV) market. Mono-crystalline cells are dominant today. Although mono-crystalline panels are priced higher than multi-crystalline ones, the difference is diminishing and will soon attain parity. This would result in mono panels being preferred over multi due to their higher efficiency, greater energy yield and lower cost of energy.
Newer technologies incorporating crystalline silicon focus on bifacial solar cells, capable of harvesting energy from both sides of the panel. Bifacials can augment the power output by 10-20%. Within this, the Passive Emitter and Rear Contact technology is predicted to gain popularity. However, it is yet to achieve price parity for large-scale deployment. The thin film technologies developed later are classified as the ‘second generation’ of solar PVs. They are manufactured by depositing single or multiple layers of PV material on a substrate, typically plastic or glass. In addition to being used in solar farms and rooftops, thin films with their low thickness, light weight and flexibility are also placed on electronic devices and vehicles, power streetlights and traffic signals. Mainstream thin films utilise semiconductor chemistries like Cadmium Telluride with module efficiencies of around 19%. Other technologies include Amorphous Silicon and Copper Indium Gallium Di-Selenide. However, the efficiency of thin films is lower than that of crystalline silicon. This has affected their popularity and market share.
New and upcoming solar cells are grouped as ‘third generation’ and contain technologies such as perovskite, nanocrystal and dye-sensitised solar cells. Perovskites have seen rapid advances in recent years, achieving cell efficiency of 18%. They have the highest potential to replace silicon and disrupt the solar PV market, due to factors such as ease of manufacture, low production costs and potential for higher efficiencies. Nanocrystal and dye-sensitised solar cells are variants of the thin film technology. These are in early stages for large-scale commercial deployment.
There is also interest in the use of Graphene Quantum-dots for solar PVs. Graphene is made of a single layer of carbon atoms bonded together as hexagons. Solar cells made of graphene are of interest due to high theoretical efficiency of 60% and its super capacitating nature. Quantum-dot PVs use semiconductor nano crystals exhibiting quantum mechanical properties capable of high efficiency of about 66%. However, both these are in the early stages of research.
Considerable advances have also been made in developing solutions that better integrate solar PVs into the grid. These include weather forecasting and power output prediction systems; operation monitoring and control systems; and scheduling and optimisation systems. Additionally, automatic systems have been developed for the smooth resolution of output fluctuations. These technologies must be considered.
Policy support
Policy support is essential to fast-track adoption of new technologies. A portion of the budget for renewable energy targets should be set aside exclusively for new technologies. Grants and subsidies can also be provided for their adoption. This can mitigate the higher initial costs of such technologies and help establish the market. Efforts must be taken to address gaps in research, development, and manufacturing capabilities in the solar sector through sector-specific investment and incentives. There must also be greater industry-academia collaborations and funding opportunities for startups. A comprehensive sector-specific skilling programme is also required for workers. All these efforts would help Tamil Nadu become a global player in the solar power sector.
Vaisakh Suresh Kumar (vaisakh.kumar@wri.org) and Kajol (kajol@wri.org ) are researchers at the World Resources Institute
