A global player in solar energy

There has been a rapid increase in large scale solar projects in Tamil Nadu in recent years. In the last five years, the cumulative installed capacity has increased four-fold to 4.4 GW by March 2021. Adding to this capacity is the state’s reasonably high insolation levels and an estimated 279GW of solar capacity. Another factor is the sharp fall in solar energy prices and consequent cost competitiveness. For example, auction searched solar bids dropped from ₹10.95 in 2010 to ₹1.99 by 2020. Additionally, in response to the ambitious national goals and to promote sector specific development, Tamil Nadu released the 2019 Solar Policy, which aims at 9GW. Solar installation by 2023

types of technologies

To meet this target, the current capacity would need to be more than doubled. To do so, Tamil Nadu must keep up with the market trends and incorporate innovations in the sector to improve the efficiency and long-term reliability of solar power plants. ‘First-generation’ solar cells use mono-crystalline and multi-crystalline silicon wafers. While the first is made from a single crystal (of high purity) of silicon, the latter is made by combining several pieces. The efficiency of mono-crystalline panels is about 24%, while it is about 20% for multi-crystalline panels. 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 cost more than multi-crystalline panels, the gap is narrowing and will soon achieve parity. This will result in mono panels being preferred over multiple ones due to their higher efficiency, higher energy yield and lower cost of energy.

New technologies incorporating crystalline silicon focus on bifurcated solar cells capable of harvesting energy from either side of the panel. Bifacials can increase power output by 10-20%. Within this, passive emitter and rear contact technology is predicted to gain popularity. However, price parity for large-scale deployment has yet to be achieved. Later developed thin film technologies are classified as ‘second generation’ of solar PV. They are manufactured by depositing single or multiple layers of PV material onto a substrate, usually plastic or glass. In addition to being used in solar farms and roofs, thin films with their low thickness, light weight, and flexibility are also used on electronic equipment and vehicles, electric street lights and traffic signals. Mainstream thin films use semiconductor chemistries such as cadmium telluride with a module efficiencies of about 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 classified as ‘third generation’ and include technologies such as perovskite, nanocrystals and dye-sensitized solar cells. Perovskites have seen rapid progress 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 high capacity potential. Nanocrystals and dye-sensitized solar cells are variants of thin film technology. These are in the initial stage for large scale commercial deployment.

There is also interest in the use of graphene quantum-dots for solar PV. Graphene is made up of a single layer of carbon atoms that are bonded together to form hexagons. Solar cells made of graphene are of interest because of their high theoretical efficiency of 60% and its super capacitive nature. Quantum-dot PVs utilize semiconductor nanocrystals exhibiting quantum mechanical properties capable of a high efficiency of approximately 66%. However, both of these are in the early stages of research.

Significant progress has also been made in developing solutions that better integrate solar PV into the grid. These include weather forecasting and power generation prediction systems; operation monitoring and control systems; and scheduling and optimization systems. Additionally, automated systems have been developed for smooth resolution of output fluctuations. These techniques should be considered.

policy support

Policy support is essential for rapid adoption of new technologies. A portion of the budget for renewable energy targets should be set aside specifically for new technologies. Grants and subsidies may also be provided for their adoption. This can reduce the high initial cost of such technologies and help establish a market. Efforts should be made to bridge the gaps in research, development and manufacturing capabilities in the solar sector through sector-specific investments and incentives. There should also be greater industry-academic collaboration and funding opportunities for startups. A comprehensive sector-specific skills program for workers is also required. All these efforts will help Tamil Nadu to become a global player in the solar energy sector.

Vaishakh Suresh Kumar (vaisakh.kumar@wri.org) and Kajol (kajol@wri.org) are researchers from the World Resources Institute.