Bright future

Bright future, Chemistry, Solar Panels
Winter 2017
Materials chemist Cheng Lu and his mentor, U of T chemistry professor Cynthia­ Goh, are helping advance­ the solar panel industry thanks to the creative­ use of photocatalysis in surface coatings.

Through his company Phantin, Cheng Lu, pictured here at a solar farm in Jiangsu province in China, has developed a nanomaterials-based,  self-cleaning, hydrophilic coating for solar panels. The coating prevents grime build up, which reduces solar panel efficiency by up to 50 percent.

Through his company Phantin, Cheng Lu, pictured here at a solar farm in Jiangsu province in China, has developed a nanomaterials-based, self-cleaning, hydrophilic coating for solar panels. The coating prevents grime build up, which reduces solar panel efficiency by up to 50 percent. Photo credit: Joney Huai 

The city of Suzhou in Jiangsu province in China lies about 100 kilometres northwest from Shanghai, China’s largest economic and trading centre. One of the most affluent cities in China, Suzhou has long been a destination for Sinophiles, who are drawn to its classic Ming and Qing dynasty gardens as well as attractions like the 12th century Humble Administrator’s Garden, a UNESCO World Heritage Site featuring elegant pavilions and bridges amidst a maze of connected pools and islands. 

Also known for its quality silks, jade sculpture and pearl jewelry, Suzhou, in more recent years, has become known for a less tourist-friendly feature — its air pollution. It is something that bothered Cheng Lu of Toronto when he visited Suzhou several years ago. “When I was young in China, everything was great: the air, the water, the bluest sky,” recalls Lu, a research associate at the University of Toronto who works in the labs of Chemistry and Materials Science and Engineering professor Cynthia Goh. Now, says Lu, who did his undergrad degree at Suzhou University before moving to Canada for graduate work, “the sky is grey, it’s no longer blue.” 

The grey skies indicated something worse than a mere aesthetic incongruity. The Jiangsu Province Air Monitoring Commission records air pollution levels in various parts of Suzhou several times per day, with real-time results available online in the form of an Air Quality Index (AQI). The AQI consistently shows a PM2.5 level (a measure of the amount of airborne particulate matter with a diameter of 2.5 micrometres or less, created primarily by coal combustion) of between 139 and 174. The AQI site rates the lower end “unhealthy for sensitive groups;” on the higher end, it’s unhealthy for everyone. China officially labels AQI levels from 151 to 200 as “moderately polluted,” recommending that individuals with breathing problems or heart conditions reduce outdoor exercise. 

Lu, who on his trip visited not only Suzhou but other urban centres like Shanghai and Nanjing, suffered physically from the high pollution levels. “I had a runny nose and my eyes were watering. When I tried to speak, my voice was harsh,” he recalls. To Lu, the dramatic increase in pollution throughout much of China “is sad. The people suffer a lot. I thought, ‘I’m a chemist. I work in materials. What can I do about this?’ That’s how I came to work with Prof. Goh.”  

Following a PhD in chemistry at Western University in London, Ont. Lu focused his research in the field of green chemistry, specifically on the use of photocatalysis to absorb solar energy and convert it to chemical energy for mitigating various types of pollutants. One of the first projects that Lu undertook after joining Goh’s lab in 2011 was the development of nanomaterials-based coatings that could photocatalytically destroy bacteria or other pathogens on their surfaces. In strong light, these surfaces would essentially disinfect themselves. At the time, says Lu, this area of research was a “new field.”

Lu’s discovery of the self-cleaning coating, he realized, would be a potential boon for hospitals, where bacteria accumulate on surfaces like door handles and taps, exacerbating the transmission of serious disease. In 2012, one year after joining Goh’s lab, Lu won a $100,000 Rising Star in Global Health Program grant from Grand Challenges Canada, a federal government-funded organization that supports ideas that impact global health. The funding enabled Lu to undertake preliminary testing at a hospital in China. Results were positive; the Phantin coating indeed killed surface bacteria.

Lu’s next challenge, says Goh, was figuring out “how to enhance his discovery, optimize it and get it to be useful in actual situations.” In this regard, Lu was particularly fortunate to have joined the lab that he did. Goh is a physical chemist who for years has championed the translation of scientific discovery into commercial ventures through entrepreneurship. Not only has her lab spun off three new companies since 2000 but she has also promoted training in entrepreneurship to university students through a series of courses, workshops and speaker series. She’s also the founder of the Impact Centre, one of nine campus-linked accelerators at U of T that run under the umbrella of the Banting and Best Centre for Innovation & Entrepreneurship. 

With the support of Goh as a co-founder, Lu started the company Phantin, an abbreviation of Photo Anti Infections. The company was incubated through the Impact Centre’s Techno program, an intensive four-week entrepreneurship training boot camp.  “Without the Techno program, I don’t think I would have started the company myself,” says Lu. “I would possibly have just joined other companies, instead of working independently. The Techno group provided networks and the chance to speak to different individuals, from business people to those in government.” 

A worker checks the Phantin coating developed  by Cheng Lu at a solar facility in Toronto.

A worker checks the Phantin coating developed by Cheng Lu at a solar facility in Toronto. Photo credit: Cheng Lu 

Through these discussions and with further mentorship from Goh herself, Lu gradually came to the realization that the coating was a potential solution to problems beyond those experienced in hospitals. Besides the anti-bacterial property, the coating was self-cleaning and exhibited hydrophilic properties. This potentially addressed two simple but fundamental problems with many transparent surfaces, says Goh. “When you look at surfaces, what’s the biggest contaminant? Organics.” As organic molecules from the air deposit on a transparent surface, they create a fine layer of grime that impedes the transmission of light. On top of that, the grime layer makes it easier for water vapour to condense onto the surface, forming fog.

Lu’s coating addressed both problems; its self-cleaning properties destroy the molecules that form grime, while the hydrophilic property prevents fog formation. Goh and Lu began envisioning potential anti-fog solutions for swimmers’ goggles and the inside of vehicle windows. Ever willing to put her innovations to the test in realistic situations, Goh coated her own car’s side view car mirrors with Lu’s material. Sure enough, it prevented both dust and rain droplets from adhering to the surface. “It makes it easier to see,” Goh says. This, the pair soon realized, opened up an entirely new potential market for the Phantin coating: solar panels. The timing couldn’t be more perfect. The market for solar energy is expanding due to increasing demand and government incentives and wind and solar photovoltaic energy are the fastest growing sources of electricity in the country. According to Natural Resources Canada, in 2014 the total installed solar capacity in Canada was about 1.8 gigawatts while the Canadian Solar Industries Association estimates that the solar market in Canada will produce 6.3 gigawatts of power by 2020.

One of the major problems with solar panels is that they get dusty. If solar panels aren’t regularly cleaned — a significant expense, as well as a time-consuming endeavour — then, after about six months, the reduction in efficiency can be more than 50 percent in some desert areas, says Lu. His coating seemed the perfect solution. However, improvements were needed. Initially, says Goh, the coating “actually had a pretty poor adherence to the surface and could be easily removed.”

Lu’s coating contains titanium dioxide (TiO2) and silicon dioxide (SiO2), both of which are commonly used in a wide range of industrial and cosmetic applications, from paints to toothpaste. (Lu won’t reveal what other chemicals are used, as he is patenting his innovation.) In the Phantin coating, TiO2 exists in the form of nanoparticles about 15 to 20 nanometres in size; this format is what gives the substance its photocatalytic properties, says Lu. As a nanomaterial, the coating also has a unique bump pattern that, Lu says, is “self-assembled.” These tiny bumps help make the coating hydrophilic. In his research, Lu focused on increasing the mechanical stability of the coatings in order to increase durability. He also altered the formulation to enhance the hydrophilic and anti-electrostatic properties for stronger rain- and dust-repelling qualities. 

Through his entrepreneurship training, Lu realized that if he were to make the coating an integral part of the growing solar energy sector, he would need business partners who would be willing to experiment with the coating. He found just such a partner in Morgan Solar of Toronto. Morgan Solar has created next-generation solar panels that utilize a Concentrated Photovoltaic (CPV) module. This CPV module concentrates sunlight in a planar direction, enabling an ultra-thin module that generates industry-leading energy yields at low cost. The problem is, says Lu, is that the surface isn’t flat, which means the dust accumulation is actually worse than for traditional solar panels. Lu and the company worked on the problem together, undertaking field-testing in California by coating the solar modules. The results have been remarkable. The dust was causing a 50 percent efficiency loss in Morgan Solar panels; Lu’s coating reduced that to 15 percent.

Last spring, Lu’s innovation was recognized as one of four U of T Inventions of the Year. The award honours university scientists’ unique research and their potential for global impact and commercial appeal.

Lu’s coating does more than decrease inefficiencies by preventing dust from gathering. Thanks to the unique optical properties of the nanoparticles, the coating actually increases light transmission, so more light is absorbed by the solar panel to convert into energy. This is because of the refractive index of the coating, Lu says. If the refractive index of the coating is higher than the glass, it reduces the amount of light flowing through. The opposite is true when the refractive index is lower, thus increasing light absorption by the underlying panels. Lab results, says Lu, indicate the amount of light being absorbed with the coating is about four percent higher than without it. The best field studies to date show an average increase of just over two percent. While this seems like a small number, the impact on the overall market is “very big,” Lu says.

Multiplying that by Canada’s total installed capacity of 1.8 gigawatts would increase the amount of electricity produced by around 150 million kilowatt-hours per year, corresponding “to $15 million in market value,” Lu says. 

As a new company, Phantin is at the point where significantly larger amounts of money will be needed to move to the next stages of scaling up and marketing and Goh and Lu are in discussion with potential private investors. They are also adjusting the formulation of the coating to ensure it works in different environments. Some parts of China, for example, where the Phantin coating is being tested are extremely humid. “We just did tests in places that were super humid and it wasn’t very good,” says Goh. “So we have to change some things to handle that.” 
Lu adds that solar panel operators in China are undertaking numerous tests with the coating, necessitating travel to the country at least twice a year, possibly more in the near future. Despite China’s notorious air pollution problems, the country is amenable to solar power. “The Chinese government is definitely pushing in this direction,” says Lu. 

At this point, Lu’s plans include scaling up and marketing Phantin in 2017. Three years from now, he predicts, Phantin will be an established company with its own core technologies that expand and adapt to the changing demands of the solar industry sector. “I think how important this technology is and it makes me realize how bright the future is going to be.” 

The world’s energy future, Lu adds, lies with solar power. “I really want to push people to go to solar instead of the coal or fossil fuel energy we are using right now. It’s getting cheaper to produce solar energy. We just need to increase the efficiency of the solar panels so the whole world accepts it more. Solar energy is the future of energy.”