Solar glass is part of the building-integrated photovoltaics category and is designed to replace conventional building materials in parts such as roofs, skylights, facades, and windows to efficiently generate power.

The main difference between solar glass technologies and traditional solar photovoltaics (PV) is that the newer panels are built into the structure rather than being added on top, which provides an incentive for users concerned about balancing aesthetics and functionality.

Spurred on by the commitments of multiple countries to achieve their net-zero emission targets and the march of technological advancement, solar glass capacity is growing. China is leading the way, with over 11,000 solar glass-related enterprises in the country and a solar glass capacity of 25,360 t/d at the end of 2019.

Currently there are two types of solar glass, the first ones are thin-film modules that have been around for a while and come orange in colour, as they are made of amorphous silicone, which makes them only up to 20% transparent.

The second type is PV glass, which appears black and can be up to 50% transparent can be used in balconies, skylights, or in facades, alternated with standard windows. 

A third type of solar glass technology made of organic polymer PV is being developed by companies such as England-based cleantech Polysolar and promises to operate in as little as 10% sunlight, depending on the angle of positioning.

The rise of solar glass

Over November and December 2020, quotes for PV glass rose to reach the price of $6.64/㎡ according to market research company PV InfoLink, with some small-scale suppliers even quoting prices of $7.72/㎡.

Over the past ten years, the number of PV patent filings, among which are solar glass, have risen by roughly 200% across Europe. According to Duncan Nevett, a partner at intellectual property law firm Reddie & Grose, many more applications are being filed each month .

“That’s not all glass, but as it seems like the solution lies in organic solar cells or polymer solar cells, that’s an area we’ve seen an increase in patenting activity,” Nevett says.

Chinese market brands such as Xinyi Solar, Flat Group, Caihong Group, CNBM, and CSG Holdings seem to be the companies leading the race to take solar glass into mass production and commercialisation.

The explosion in Chinese patents and activity could be explained by the Chinese government’s initiative known as ‘Made in China 2025’. As part of it, the government has identified 10 technology areas that it wishes to promote activity and growth in for domestic companies, which features PV and solar glass in particular. 

Nevett explains: “They intend not simply to be the manufacturer for themselves, but for the world, and in line with that we have seen significantly increased patent activity from Chinese companies.

“Clearly growth there will be very proportional to the growth across the world, if they grow then I suspect the output globally will be largely affected as well.”

Looking ahead, he points out that it’s not likely that there will be just one company to reach that breakthrough point with solar glass, but it’s probably going to be a combination of innovations that come through from different companies.

“In fact, what happens often is that they’ve each acquired their patents to whatever piece of the puzzle they’ve got, they bring it to the table and then they collaborate in some form of licencing agreement to allow them to use each others’.

“Normally it’s a race, the race that we’re witnessing involves everybody piling up what they have, then they get to that point trying to talk to each other about who’s entitled to what, and that’s where the fun begins,” Nevett says.

What’s holding solar glass back?

The impact of Covid-19 has resulted in some solar glass projects not meeting capacity expectations and China’s downstream enterprises have become overwhelmed, especially by the spiralling glass price solar industry. 

For example, solar company Flat recently announced that it expects solar glass shortages of around 15% in 2021 since the supply-demand balance will not be achieved earlier than 2022.

In addition to pandemic-related delays and supply issues, it seems like solar glass is not there yet in a technical sense as manufacturers cannot yet ensure efficiency of the technology, which would then attract further investment and drive its price down to a commercially attractive point.

Nevett explains: “The technical challenge in commercialising such a product is balancing these three key areas – making it highly transparent, highly efficient, and highly resistant to degradation. And I think that’s why the technology’s not been adopted, because the innovation hasn’t quite gotten us to that point.”

Like many technologies, panels went from technically possible but not economically viable to their current position. But for solar glass to move forward, these technical challenges still need to be solved. 

“And then having solved them it will be about getting to the point where it can be manufactured and where someone can say: ‘There’s a business case to do this, that will pay for itself’ or it will improve the environment,” Nevett says.

Eased regulations and the future of solar glass

With solar installations increasing around the world and the rising popularity of the green buildings concept, the market demand for solar glass is unlikely to fade away soon, especially if backed by government initiatives and incentives.

For instance, last November in China, six solar firms asked the government for fewer restraints on glass production expansion. 

The Chinese Government is consequently looking to loosen the existing restrictions on new investments in additional PV glass production capacity, as announced by the Ministry of Industry and Information Technology.  

A welcome amendment will be that all new projects intending to add glass capacity will not have to submit capacity replacement plans, which have until now required new planned output to replace an equivalent amount of decommissioned capacity. 

The new regulatory framework will now enable the Chinese Government to remove obstacles for new investment in the solar glass sector and help reduce PV glass bottlenecks.

When it comes to the UK and its role in solar glass development, Nevett believes that while the country might not compete with China because of its heavy reliance on wind energy as part of the emission transition, the UK can still play a crucial part in the technical advancement of solar glass.

“I have been at UK energy conferences where there has been a prominent presence of UK companies in the solar field. In fact, many of those partner with manufacturers from China, and a lot of the design, innovation, research, and development is done by companies within the UK itself.”