Is thin film a viable alternative to the mounted solar systems?

Rahul Budhwar, Chief Executive Officer, Flisom explains the potential of thin film

The evolution of solar technology has been a slow but important journey. While many people see solar power as a modern phenomenon, the first R&D milestone came in 1839 when Alexandre Becquerel observed the photovoltaic effect. Using knowledge from Einstein and other scientists, Bell Laboratories then produced the first modern photovoltaic panel in 1954. Today, I believe we are witnessing the next momentous breakthrough in the sector, the development of solar film technology as a viable alternative to traditional rigid solar panels.

The term "solar film technology" refers to solar products that use a much thinner level of photovoltaic material than mono-crystalline or multi-crystalline solar panels. Thin film solar cells consist of layers of active materials about 10 nm thick or less compared with 200- to 300-nm layers for crystalline-silicon cells used in mounted solar panels.

Solar film technology, and the excitement that follows it, isn't new. It has taken decades to get the technology from the stage of promising research to the first manufacturing plants producing early product.

The first technology developed was amorphous Silicon (a-Si), a non-crystalline form of silicon. The technology is most commonly used in devices that require very little power (e.g. pocket calculators) because of low conversion efficiency.

The most widely used solar thin film technology today is Cadmium Telluride (CdTe) photovoltaic modules. Cheaper to manufacture, this technology is based on the use of Cadmium Telluride, a thin micro-crystalline semiconductor layer designed to absorb and convert sunlight into electricity.

However, the most exciting and significant technological development is Copper Indium Gallium Selenide (CIGS) which represents the highest-efficiency alternative for large-scale, commercial solar cells. Silicon solar panels have history on their side but the future lies in CIGS solar films.

Historically, the challenge with CIGS technology hasn't been the science. Researchers across the world have been able to show impressive levels of efficiency. Our important and internationally well-known research partner Empa (Swiss Federal Laboratories of Material Science and Technology) has achieved a world-record efficiency of 20.4% with a flexible CIGS solar cell on a Polyimide substrate. The challenge for the industry has been taking laboratory success to industrial scale production to successfully commercialise the technology. This is where we believe we have reached a defining moment.

Over the last ten years, Flisom has developed a line of proprietary manufacturing equipment and components. We now have a "˜roll to roll' manufacturing process that allows production from cell to solar module in one single factory. The system allows us to use fewer and better materials across less manufacturing steps, as well as giving us better process controls over the whole value chain. The process means we can now efficiently bring CIGS thin-film solar cells to market.

Why is this so important? The properties of CIGS solar films enable new applications, which need flexibility, light weight, thinness and durability. These benefits open up a whole new world of applications from automotive sun roofs, to solar powered watches and building facades. CIGS films can offer better aesthetics, better low light performance and quite importantly, a new degree of customization compared to traditional crystalline-silicon solar panels. Quite simply, the technology can bring solar power to many new industries which was not possible before with traditional solar panels.

Flisom is pioneering the use of CIGS based flexible solar power in these new industries. In the aerospace sector, for example, we are working with a customer to develop a high-altitude long endurance, lightweight and efficient solar power application. The weight of our customised solar film for the client is under 200gms/m2 with possible power density of 780W/kg. This actually represents an over 50x power to weight ratio of regular solar panels.

The technology has the potential to support the environmental evolution of the automotive sector and aid the adoption of electric vehicles. Solar power for vehicles can offer a longer range for electric cars, power for electronics and help manufacturers meet increasing standards for lower emissions. The lightness of the films offer the highest power to weight ratio and the flexibility and thinness of the film 30 µm will ensure negligible drag and help its easy integration onto the vehicles' surfaces. The absence of glass or other material that can crack or break from vibration also guarantees durability and sustained performance. Furthermore, thin films offer far superior aesthetics for vehicles, integrating well with the dark shades of car sunroofs.

Incorporating the solar modules into the car's electric system can be easily done using a charge controller, which will stabilize the voltage of the module to allow the battery to be charged with the generated green energy. Depending on the number of solar panels installed and the orientation, multiple charge controllers might be required to achieve the highest energy generation. This approach will work for both electric and combustion vehicles. In both cases the range of the vehicle will be increased as fuel/power consumption will be reduced by the amount of the generated solar energy.

Another major consumer of power is buildings and therefore it is important that advances in solar power technology offer more solar applications for this sector. Unfortunately, the heavy rigid solar panels limit solar applications to rooftops of buildings. Lightweight, and ultra-thin, flexible CIGS solar panels can be applied on all surfaces of the buildings including a far wider range of roofs and most façade elements. With innovative installation methods like adhesives, the panels can be bonded on Aluminum, EPDM, TPO or bituminous roofs, offering flexible lightweight solar installations. I believe that flexible solar technology truly has the potential to shape the future of building integrated solar energy generation.

Flexible solar technology can revolutionise the solar power sector and enable many new applications across the sectors that most need them. Because of product development cycles, there will of course be a certain gestation period for many of these sectors and products (such as aerospace and automotive) but they will become major multi-billion dollar solar markets in the coming years.

The potential for growth of the solar film sector is exponential. The global thin film solar cell market was valued at $11,421 million in 2016, which is conservatively projected to grow at a CAGR of 19.4% from 2017 to 2023, to reach $39,512 million by 2023. These figures most likely don't consider the recent advances in the production and manufacturing of flexible solar technology, so the market opportunity has the potential to be much higher.

Flexible and thin solar films truly have the potential to revolutionise how solar power can be used in different applications not possible before, and we are working towards turning that dream into a reality.