Windows of opportunity to harness solar energy in infrastructure

The development of low-cost, semi-transparent solar cells provides a number of opportunities to harness energy through infrastructure forms, including windows, walls and roofs. But what is standing in the way of progress?

With Tesla’s Elon Musk and now, British billionaire Sanjeev Gupta – through the GFG Alliance – making significant investments in South Australia’s renewable energy sector, all eyes are on Australia.

Tesla has already delivered the world’s largest lithium-ion battery system (100-megawatt/129-megawatt-hour) to the state, while Gupta announced plans to up the ante and build a 120-megawatt/140-megawatt-hour storage battery in South Australia.

While billionaires are putting South Australia’s renewable energy sector in the global spotlight, Australian researchers are exploring other renewable energy sources posing unique opportunities for the country’s energy future.

At the end of 2017, the Australian Renewable Energy Agency (ARENA) announced $29.2 million in funding for 20 research projects to propel the development of solar photovoltaic (PV) – or solar cell – technology.

The funding supports early stage research to reduce the cost and improve the efficiency of solar PV technology. Many of the projects under the fund focus on silicon cells, as the vast majority of solar panels worldwide are made using silicon, according to ARENA.

However, some of the projects will aim to develop solar cells using different materials, such as organic photovoltaics and perovskites, which would cost less to manufacture, are printable, sustainable and can be made semi-transparent.

Associate Professor of Materials Science & Engineering at Monash University and Director of the Monash Energy Materials and Systems Institute, Dr. Jacek Jasieniak is one of the ARENA funding recipients exploring the development of highly efficient and extremely thin, semi-transparent solar cells made from perovskites.

“About 10 years ago, it was discovered that perovskite materials were suitable for the fabrication of efficient and low cost solar cells,” Dr. Jasieniak says. He says solar cells, in general, are a multi-layered structure, and what makes perovskites special is that they not only convert light to electricity efficiently but are also amendable to printing – akin to newspaper printing, where the cells can be deposited layer by layer with specialised “electronic inks”.

“Traditional solar panels are rigid and heavy – how do we go beyond that to something that’s lighter and more amenable to large rooftops and also different types of applications?” he says. “I’m interested in developing new types of solar technology that can be printed but also embedded into different types of form factors.”

Those form factors include windows, which, with the use of semi-transparent solar perovskites technology, can be used to capture solar energy.

“In commercial buildings, the windows are typically glazed to cut out sunlight to a value of over 50 per cent because there are requirements about how bright, for example, office spaces can be. This raises a simple question: instead of wasting that light, can we use it in a more effective way, such as, to generate electricity?” Dr. Jasieniak asks.

“Traditional solar cells are opaque because they lose efficiency if you attempt to make them sufficiently thin to enable semi-transparency in the visible region of the electromagnetic spectrum.

“In contrast, by controlling the thickness/thinness of the perovskite solar cell, such devices can be made semi-transparent, while also remaining very efficient. The technological concept is simple, and it has to be simple for it to work on a large scale.”

The integration of solar power generation modules into a building or in place of ordinary building materials – also called building-integrated photovoltaics (BIPV) – expands beyond windows to building walls and even roofs.

Historical hurdles

While the opportunity to explore the use of perovskites, and subsequent BIPV forms, is gaining traction, Dr. Jasieniak says the development of semi-transparent solar cell technology has historically been overshadowed by the technology comprising traditional solar panels today.

“Crystalline silicon solar cells – the dominant technology today – came out in 1950s from Bell Labs. In 1969 a different kind of silicon came out – amorphous silicon. It was the same type of material in crystalline silicon cells, but it didn’t have an ordered crystal structure, which enabled it to be fabricated at relative low-temperature, be more flexible, absorb more light, but also be made sufficiently thin to be semi-transparent. These were very exciting developments and, at that time, it was seen as something that could revolutionise the world,” Dr. Jasieniak explains.

“The ability to make amorphous silicon semi-transparent led significant research into such technologies, however they ultimately ran into challenges around low efficiency and poor stability.

“The historical lack of alternative high efficiency and stable solar cell technologies that could be made semi-transparent has prevented the broader market around solar windows from being developed. This is in stark contrast to crystalline silicon, which has been demonstrated as a scalable technology and has become the fastest growing source of deployed electricity generation across energy markets.

“While there have been a few potential suitable semi-transparent solar cells proposed, such as dye-sensitised solar cells, the most commercially promising was realised in 2006 by Heliatek, which used organic materials as the backbone of their technology”.

Dr. Jasieniak says that the company has been developing and scaling up the technology for many years now, with gradual progress in efficiency and stability, but there are few available products today, which suggests commercialisation hurdles still exist.

Perovskites are a fundamentally different type of technology in that they are very efficient compared to all other materials suitable for semi-transparent solar cell applications. “The question that we are answering now is how do we take these perovskite materials and integrate them into a semi-transparent solar cell structure that is simple, stable, efficient and scalable?” he asks.

Scaling up

BIPV will transition the solar cell market from a scenario where solar panels are installed onto roofs into roofs that are installed with solar panels. Semi-transparent windows will have a similar transition. According to Dr. Jasieniak, BIPV represents just one per cent of the entire market for solar technology in world.

“Only 1 per cent of all solar cells are integrated into a building and that, to me, represents a massive opportunity. Ultimately, we’re building a whole range of infrastructure without considering the potential value-add, such as the introduction of energy-generation.”

Improving commercial viability of the technology is where Dr. Jasieniak aims to take his research and where he sees there’s enormous opportunity for perovskite solar cells as an alternative to existing commercial products.

“There is an opportunity take a more design-led way of thinking about that problem,” he says. “Silicon solar cells are commercial – the technology is integrated into a module that’s a viable product. We need to integrate that thinking into the market with perovskites and make it into a product. But, how to integrate that is the question.”

For the production of the ultra-thin, semi-transparent perovskite solar cells, he says stability is the element that needs to be overcome in its design, which is also where his research comes into the picture.

“It needs to be made stable and scalable. It also needs to pass through regulatory tests for solar cells – but also for windows,” Dr. Jasieniak says.

“The final part of it is toxicity. The material currently being used possesses lead. The amount it uses is not very much from a regulatory perspective, but they do contain lead,” he says. “There is this question of whether that lead is a problem or not, and that will determine how they are manufactured or implemented.”

Dr. Jasieniak says the next iteration would be to translate to a lead-based product that is stable. “Then, we would move away from lead to something that’s less toxic, which would be the next generation of the technology,” he adds.

“The BIPV area is the natural next step for solar technology. It’s a complement to the glass industry here and also to companies working on different levels within the infrastructure sector.”

As part of the ARENA project, Dr. Jasieniak is working with two industry partners – GrearCell Solar and CSR Viridian – to start investigating a prototype design and real-world trials around stable, semi-transparent perovskite solar cells.

Dr. Jasieniak says now is a pivotal time for the Australian infrastructure sector to shine a light on BIPV and semi-transparent solar technology, such as perovskites, in the grander scheme of infrastructure planning and delivery.

“We see these big infrastructure projects being announced – billion-dollar projects – but I rarely see the collaboration between multiple sectors looking at infrastructure challenges through different lenses,” he says, “An example of this is using major construction projects and coupling them to specific targets such as sustainable energy generation, zero-carbon emissions, or improved electricity distribution, which would effectively continue the development of our learning curves across both an infrastructure industry and an energy sector problem.”

He says these are issues that affect multiple industries that haven’t been addressed on the same footing. “Take the big infrastructure project out there already – what are the energy saving opportunities that could be taken up? There’s certainly opportunity there and that could be taken through a holistic approach.” An example, Dr. Jasieniak says, could be a case of looking at the noise-reducing walls that line a motorway as a power-harvesting asset via solar cells.

“Australia is a country where there is a lot of opportunities, and historically, we’ve been very strong at solar research. But, we need to translate research that’s been done into real-world outcomes and for that to happen we need to support the mechanisms that foster those industry and research advancements.”