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By Susha Cheriyedath, M.Sc.Aug 28 2019.jpg)
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Image Credits: Korrapath/shutterstock.com
Solar panels are one of the most reliable and durable energy harvesting technologies available today. Research and development in the industry have helped create solar cells that are more and more resistant to weather damage. Waterproof solar panels help us produce our power even during rainy or stormy weather. These kinds of solar cells can even be washed and still work and generate power as they would normally do.
Earlier, solar panels used to be delicate and get dislodged at high wind speeds and stormy weather and get damaged due to water exposure. However, with the advent of robust, waterproof solar panels that can survive even hurricanes, they are tested and certified to withstand wind speeds of about 140 mile-per-hour (MPH). In addition, the glass and aluminum casings that hold these solar panels are also waterproof.
According to the National Renewable Energy Laboratory (NREL), out of the 50,000 solar systems installed between the years 2009 and 2013, only 0.1% of the systems were affected by damaged modules every year. Waterproof solar panels are tested by manufacturers for their capability to withstand hurricanes and hail storms. The new robust panels are equipped to withstand impacts from severe weather events that are capable of shattering car windows and causing dents in vehicles and roofs of homes.
Research at RIKEN
Waterproof photovoltaic cells were developed by RIKEN, a Japanese research center, and the University of Tokyo. These solar cells are ultra-thin and are coated with a waterproof film on both sides. The key advantage of these solar cells is they can be compressed, stretched, or washed and they would still function normally and generate power at almost the same efficiency as before.
These solar cells are made of a material called PNTz4T and are super thin and flexible. Both sides of the waterproof solar cells were coated with 1-micron-thick layers of an acrylic elastomer called parylene that acts as a barrier to water and air exposure while allowing light to reach the cells and enabling power generation. Waterproof solar cells can be sewn into washable clothing to analyze various parameters and spot early indicators of medical problems.
Waterproof Solar Cells in Wearables
Wearable devices require a steady supply of power in the range of several milliwatts. Energy-harvesting textiles, apart from efficiently gathering energy, should also be highly stretchable and should be able to withstand exposure to both air and water. Producing a solar cell that satisfies all of these features proved very challenging in the past because the flexible and ultra-thin materials that were stretchable were often permeable and could be easily damaged by water, oxygen, or even water vapor.
Also, in the past, the main challenge with photovoltaics employed in the textile industry was the lack of stability and robustness to withstand long-term exposure to water or compression or a combination of the two. Thanks to the efforts of several initiatives and organizations, we now have more durable, waterproof solar panels that are cost-effective and long-lasting. These waterproof solar cells can resist deformation and hence open up an array of new applications of solar cells in wearables.
These panels generated power at an efficiency of 7.9% which translates to 7.86 mW of power generated per cm2. There was only a slight decrease in efficiency after soaking them in water for 2h and they retained 80% of the initial efficiency after compression by almost half while being soaked in water. Waterproof photovoltaic cells could power heat and motion sensors that can monitor body temperature and heartbeats and give warnings about health issues at an early stage when they are more treatable. The elastomers used in these solar cells are easily, commercially available and future research could try using other elastomers to further boost performance.
Sources and Further Reading
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