News from China Hydrogel Significantly Increases the Yield of Solar Modules

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Solar panels are sensitive devices that spend their lives "outdoors". If leaves or bird droppings fall on them, this can lead to so-called hotspots. These localized overheating points reduce performance. Chinese researchers have now declared war on them.

Jerry Yan, Professor of Energy and Buildings, and his team at Hong Kong Polytechnic University (PolyU) have developed a new hydrogel coating for solar modules that they claim can reduce hotspot temperatures by 16 percent and increase energy yield by up to 13 percent.

Teflon Works on Panels Too

One of the materials used is commonly known by its trade name: Teflon. It turns out that polytetrafluoroethylene is useful not only as a non-stick coating for frying pans but also as the top layer on solar panels, where it keeps dust away and controls water evaporation. However, the hydrogel invention by the PolyU researchers consists of a total of three layers. A water-absorbent material called polyacrylamide is enhanced by the addition of a thickening agent called hydroxyethylcellulose. "We also weave cotton threads in a leaf-like pattern to transport water to the hottest areas, ensuring a uniform and long-lasting cooling effect," said Professor Yan to Chinese journalists. The Teflon material is then applied as the top layer.

Hydrogel Increases Efficiency and Long-Term Stability

With this invention, the team addresses a well-known "pain point" in the photovoltaic industry: not only fallen debris but also shadows can lead to hot spots. The new coating could be particularly useful for solar panels on or integrated into buildings, the researchers write in a paper published in the scientific journal "Advanced Energy Materials."When the new hydrogel is applied to "rooftop and building-integrated photovoltaic systems (BIPV)," it could "reduce nearly half of the performance losses caused by hot spots," according to the website of PolyU in Hong Kong. Especially in supplying buildings with solar power, both the efficiency and long-term stability of the panels could be enhanced.

Our hydrogel cooling technology provides an effective solution to the hot spot problem in solar modules without the need to change the existing design of their circuits.

Jerry Yan on the PolyU website

After extensive outdoor testing and the publication of their research findings, the researchers have now begun negotiations with companies to bring their innovation to market readiness. A key factor is how quickly the costs of the hydrogel coating can be recouped:

• Applying the gel increases the price of solar panels by an average of 10.7 percent, Jerry Yan said in interviews with Chinese media. However, the increase in energy efficiency and longer lifespan of the panels lead to significant savings after a few years.
• In regions with abundant and intense sunlight, such as Singapore or southern China, the payback period can be reached within four and a half years. 
• In areas where the sun is somewhat less strong and electricity prices are lower, such as in the Chinese coastal city of Tianjin, it could take "11.1 years," the professor stated with the typical precision of scientists.

Halving Energy Losses Due to Hot Spots

The PolyU team has collaborated with colleagues at Tianjin University and Hebei University of Technology. In their jointly published paper, they speak of the "transformative potential" of their invention, stating that a reduction of around 50 percent in energy losses due to hot spots on a "global scale" could significantly enhance the profitability of residential solar panels. There are many possibilities for future applications.