“We Expect TOPCON To Be The Leader For The Next 5-7 years”, S Vasanthi, Websol Energy

S Vasanthi is a true solar veteran, thanks to her long association with one of the earliest solar manufacturers in India, Websol Energy System Limited. As the Chief Technical officer and director she has been instrumental in visualizing the company’s 1.8GW solar PV cells and 550 MW Module manufacturing capacity expansion at its Falta plant in West Bengal. Her team has improved solar cell efficiency from 10% to 23% plus. She has mentored a number of solar professionals who are heading Indian Solar cells and Modules manufacturing plants in India.
She was conferred the Technomentor Award 2010 by India Semiconductor Association SaurEnergy caught up with the M.Tech (Energy Studies) from IIT Delhi and M.Sc (Physics) IIT Mumbai expert to understand her views on the sector.

From a solar technology professional’s perspective, what are the decisive changes you want to highlight from your career so far?

I am in the solar industry since 1994. Over the past two decades there has been a multi fold transformation in this industry. When I started solar was getting popular mainly in Germany, Italy, Japan and the US. It was considered more suitable for small off-grid applications. In Germany, Japan there was more focus on roof top applications.

In the 1990s solar PV price was in the range of 6$/Wp. From there the industry came down to around 3.5$/Wp. From 2010-11, prices started dropping at a much faster rate due to oversupply from China and now it is around 0.25$/Wp. It has thus become more competitive than the conventional sources of energy.

Along with price drop came technological advancement, with solar cell efficiencies improving from 11% to 19% and now with further advancement in technology since 2020, efficiencies are improving every year. Mono PERC has achieved efficiencies of 23%+, TOPCON is seeing 25.5% +, HJT is 26%+.

At the same time cell sizes have seen dramatic changes starting from 4” to 5”. Then came 156 x 156mm size. This has now increased to 182 x 182mm and 210x210mm. There is possibility of further increase to 230x230mm in the future.

Industry has also seen decrease in wafer thickness. We started with above 300 micron wafer thickness in the beginning of 2000, which saw a continuous reduction to now 150 micron thickness or lower. Slicing using blades migrated to wire saw cutting using slurry and then further advanced to diamond saw cutting all with the aim to improve quality and reducing kerf loss so as to reduce wastage and hence cost per wafer.

Quality of silicon which started with 7N purity which was inferior to semiconductor grade wafers has now moved to 9N or 11N  purity. This improvement in wafer quality has led to a remarkable improvement in cell efficiencies as well.

As India seeks to increase solar manufacturing manifold over the coming few years, do you believe the move is well timed? Could more have been done earlier?

Definitely, more should have been done earlier. We are at least 5 years behind if not ten years. Every industry takes some years to mature. Our taxi time is over and we are ready to take off.  In the next two years there will be massive capacity additions for cell and module manufacturing.

What is still missing is the availability of critical raw materials for the manufacturing for cell and module. We still have to import all the wafers, metallization paste and specialty gases for cell manufacturing as well as many of the raw materials for module manufacturing.

What is also missing is the road and rail infrastructure for transportation of raw materials and finished goods within the country.

Another big vacuum is the absence of equipment suppliers for both cell and module manufacturing. We are fully dependent on imports from Germany and China for the same.

Same is the story regarding R&D activities in the cell and module manufacturing, where spending is very minimal. A lot more research institute and industry participation is required.

Can Indian manufacturing be competitive globally? Especially as we go further back the supply chain into cells, wafers and even polysilicon?

Indian manufacturing will become more and more competitive when all the promised capacity additions will start operating. Larger supplies and more competition will drive prices down. However to reach international levels, we will need to overcome the problems of :

• High fund cost
• Non availability of critical raw materials like wafer, paste, speciality gases
• High power cost
• Lack of trained manpower

For wafer and Polysilicon manufacturing, we will need:

• High quality, low cost power
• Access to technology
• High investment
• Economies of scale (6 -10 GW Scale)

Today, we are seeing a lot more talk around TOPCON, HJT technologies, even thin film for solar. Which ones do you see dominating in the coming decade? Is there anything else on the horizon that could surprise?

Since 2020 Mono Perc became a stable technology, which TOPCON was still under R&D as there were yield and efficiency problems which still needed to be sorted out. By beginning 2023, TOPCON has now become a stable process with high yield and efficiency. Hence everyone is moving to TOPCON technology.

HJT has been there for a long time, but the capex and opex costs are still high, which is 2X and 3X of the TOPCON costs, hence not a favorite of the Industry. Companies who want to distinguish themselves from others are into HJT, but we expect TOPCON to be the leader for the next 5-7 years.

The R&D roadmap for many companies is to introduce new concepts on TOPCON so that efficiencies can be increased at each step without making obsolete the machines that have been installed and running. Multi bus bars, Back contact technology are some interesting concepts that will be added to increase efficiencies by 1% + in absolute terms.

Another landmark jump in solar technology would happen if perovskite would be integrated with crystalline silicon technology as a tandem structure. Efficiencies of 29% + are being expected.

Thin film solar has progressed relatively slowly until recently. What do you think about the prospects for that?

Thin film solar using CdTe (First Solar) has been successful so far. However, sustainability in the long run is difficult because cadmium is a very toxic substance. Amorphous silicon thin film modules has not been successful as a technology and is also not competitive compared to crystalline silicon.

We have seen major government initiatives like PMKUSUM that sought to spread the use of solar struggle. Now, the Jal Jeevan Mission actually used more solar than PMKUSUM till date. What’s going right here versus PMKUSUM?

The High level of Technology integration from project planning to execution, central , state government and local community  participation & use of solar energy in water pumping in Jal Jeevan Mission creates Job opportunities and market for solar products  like solar submersible pumps , Solar Panels and other material need for water pumping and storage. Total Rs 3.5 Lakhs crores has been allocated for this project from 2019-24 .

At present total installed capacity under PMKUSUM Component A is 160MW against sanctioned 4.8GW , for B &C 2.29 lakhs pumps were installed against 32.4 lakhs pumps. Component A (Off grid) scheme achieved good response Rajasthan, Himachal Pradesh, Haryana and Madhya Pradesh while the rest of states need to address various issues like project funding and land identification processes. More than 2 lakhs farmers response is good in Punjab , Maharashtra, HP,UP and Rajasthan for Component B and C .

Polycrystalline modules seem all but over. Or are they? Do you see any potential to extend their lifecycle at a manufacturing level?

Yes, polycrystalline silicon can be considered as over. It may be alive for a few more months, after which mono-crystalline will take over completely. It was a successful technology so far, however it has limitations of efficiency. Any new structures like PERC do not give high efficiencies as they do with mono-crystalline silicon. Hence all production capacities for multi crystalline has been made obsolete and new lines for mono PERC and TOPCON are being added. At the same time wafer manufacturers have stopped production of multi wafers and have shifted to crystal pullers for mono wafer manufacturing.

Gujarat is dominating as far as solar manufacturing goes. What can other states do to get a share too?

So far most of the manufacturing was happening in Gujarat. Government incentives, proximity to two big ports which makes import of raw materials as well as export of finished goods very convenient. Also Rajasthan and Gujarat are the top markets for solar installations, hence proximity of market is an important advantage.

Additionally, many raw material suppliers like glass, backsheet etc. have their manufacturing facility in Gujarat. All these factors made Gujarat an attractive destination for setting up facilities.

Now, Orissa, Madhya Pradesh and few other states are also giving incentives, have port facility and developing market to attract new entrants to establish their facility in their state.

How states can attract manufacturing to be set up in their states is by giving financial incentives, land and electricity at low cost, develop market in their state and also establish training institutes suitable for this industry.

As a technologist yourself, is there an aspect of solar manufacturing where you see fresh entrants slipping up? What about the risk of obsolescence in this sector?

In this sector technology will not become obsolete overnight. Even if a disruptive technology comes up, it will take a minimum of 3-5 years for adoption. This is because solar products have to guarantee a life of 25 – 30 years. Any accelerated testing cannot outright guarantee such a long life. There will be early adopters who will put the technology in the market, while majority will wait and watch for at least 5 years to ensure that there are no surprises and that the technology can be successful in the long term.

Since the capex costs are high, in this sector it is mostly technological advancement. This means few changes are few additions to the process steps are done in order to improve efficiency and increase power output. This ensures that old machines do not become obsolete.

Fresh entrants take time to adopt to the technology, and hence they usually start with the technology which is expected to become popular in the next 2-3 years.

What are the key technology developments that excite you personally in the sector currently?

I have a preference for back contacts, where all contacts are taken to the back side. This will help increase efficiency as no shading loss from the front surface will help gain efficiency significantly.

Another interesting area is perovskite cell in tandem with crystalline silicon technology.  Perovskite technology by itself is still in R&D stage. Though efficiencies of above 25% have been achieved in the labs, stability of the cell is still an issue. Scientists are trying to integrate this technology with crystalline silicon so that additional efficiency due to this structure can be obtained and overall cell efficiency can touch 30%.

What do you see as the next big milestone for solar worldwide? Could it be Commercial scale efficiency of 30% plus, or 100% recycling of panels, or perhaps a further drop in prices below a specific level ?

I am seeing the next big thing in solar to be replacing silver contacts with solder plated or silver plated copper. Also reducing wafer thickness to about 100 microns from the present 150 microns. These steps will go a big way in reducing prices by another 30% or more.

100% Recycling of panels will become an absolute necessity in another 10 years’ time when most of the panels installed about 10 -15 years back would get scrapped. It may not be a pressing requirement now, however research in this direction should progress in parallel.

Could a drop in energy storage costs provide the next big fillip to solar? What is the best case scenario for solar’s share of capacity and generation by 2040?

At present solar installed capacity is 67GW and by 2030 government target is 292 GW , it is about 16% of total electricity, by 2030 it will come about 29% and by 2040 it will be 40% plus so we will reach net zero target by 2070 . Reduction in Energy storage cost will further boost solar sector and help rural areas economy where grid electricity is concerns.