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The reflective film has arrived
Recently, Solar Capital of Germany stated that from June 2022 to May 2023, it used white solar reflective film in three photovoltaic power plants in Greece. The photovoltaic power station is a single axis tracking Photovoltaic system with an inclination of 25 degrees and a height of 1.5 meters from the ground. One year’s data shows that the photovoltaic power generation increased by more than 6.4% with the array using white solar reflective film.
In fact, as early as 2017, Taizhou Longji conducted empirical power station monitoring on different ground launch materials, studied the power generation performance of double-sided components in different reflective environments, and tested their attenuation after 1 year of exposure to sunlight to further evaluate the performance of double-sided components when working outdoors. Research has found that using reflective film generates 22.1% more electricity compared to conventional components (the lowest point of the component is 2m above the ground).
In 2021, the solar reflective film produced by Chinese company Zhejiang Hailide Company achieved its first application in overseas photovoltaic power station projects, supporting a 500 MW photovoltaic power station in the Saudi Arabian Oman region, and is expected to continue to receive a total of 100 million yuan in Oman orders in 2023 and 2024.
The Origin of Reflective Film
In fact, as early as 2017, when the combination of double-sided components and tracking brackets gradually gained attention, Chinese companies began exploring the power generation gain of double-sided components.
Previous studies have compared the back gain of double-sided power generation on snow, cement, yellow sand, mud, white gravel, grassland, and water surfaces to simulate various installations such as snow, roofs, deserts, ground photovoltaic, and water photovoltaic.
As the market share and double-sided rate of double-sided components continue to increase, how to make the back side generate more electricity has become a new topic. It is precisely this demand that various reflective designs that can improve reflectivity have begun to emerge. In the Taizhou Longji Experimental Power Station, a comparison was made between cement ground and aluminum foil bonded with asphalt. Although the power generation gain of aluminum foil exceeded 20%, it was not widely promoted due to its high cost.
Afterwards, the PVC reflective film launched by Zhejiang Hailide Company has been proven to have a power generation gain of over 10%, an expected service life of 3-5 years, and significantly reduced costs, successfully entering the most environmentally demanding Middle Eastern desert market.
Reflective film, increasing power generation so effortlessly
There are many ways to increase power generation, and the most influential one is to improve Solar-cell efficiency. From polycrystalline to single crystal, from PERC to HJT/TOPCon, are all products of this route and are also the “right path” for the progress of photovoltaic power generation technology.
However, almost any improvement in photoelectric conversion efficiency is a milestone breakthrough, and it may also be a revolution in battery design philosophy, which is destined to always be a ‘path of righteousness’. Therefore, technical personnel who are not engaged in battery technology research will focus on the second path: increasing the light intake of photovoltaic modules to allow more sunlight to reach the surface of the battery.
Under this concept, the most typical one is focused photovoltaics, but the excessive amount of incoming light generated by focusing leads to other technical difficulties. Since then, the industry has made various breakthroughs in improving the light transmittance of glass (high transmittance photovoltaic glass, anti reflection film), the transmittance of packaging film (sacrificing the aging performance of packaging film), increasing the reflection light of white film, adding reverse power generation to double glass modules/transparent backplates, tracking brackets, conversion films, and other products.
It can be said that all the current Technology roadmap of photovoltaic are developed around these two directions. For large desert photovoltaic power plants, double-sided and tracking have become the mainstream of additional issuance, and the utilization of ground reflected light has become a focus of system design.
Reflective film is a product that can reflect more ground sunlight onto the back of photovoltaic modules when laid on the ground. As long as it can overcome the exposure to sunlight, high temperature, dryness, and extreme cold in desert areas, and has a lifespan of more than 2 years, it can generate the benefits of any flash sale technology.
According to relevant reports, using reflective film technology can increase power generation by about 10%. According to the current conversion rate of single crystal PERC (23%), it is equivalent to increasing the battery efficiency by 10% by 23%, that is, 23%+2.3%=25.3%.
It should be noted that even the crystalline silicon heterojunction battery created by Longji has a conversion efficiency of 26.81%, which was only referred to as the “2681 concept product” at this year’s SNEC and Munich exhibitions in Germany. The cost of heterojunction technology is considered the biggest factor losing to the TOPCon route in the past two years.
If only a reflective film is applied, the effect achieved can surpass the use of heterojunctions and TOPCon, making it so easy!
Future research on reflective film
Photovoltaic desertification control has become a new hot topic in global photovoltaics, and sand, Ge, and Huangfeng Guangda bases will be the focus of China’s new energy development in the coming years. In these regions, double-sided and tracking are the optimal configurations, while reflective film is a better bonus for the optimal configuration.
But reflective film also has its inherent flaws:
One is the need for larger placement intervals to generate more reflected light for use in deserts, which can affect the land occupation rate;
The second is the need for aging resistance and the ability to withstand natural weather conditions such as high temperatures, exposure to sunlight, extreme cold, sandstorms, and strong winds in desert areas;
Thirdly, after a period of use, the surface of the reflective film may be covered with sand and dust, and the reflective effect will be severely weakened. How to achieve no dust accumulation and less dust accumulation in terms of laying and product design?
The fourth is how to reduce the impact on the soil and other environments of photovoltaic power plants without affecting desertification control and vegetation.
These may all be factors that affect the promotion of reflective film applications. However, simply using a simple layer of reflective film can achieve an increase of over 10% and a net improvement of 2.3% in battery efficiency, which is worth paying attention to.