A convective cooling approach keeps solar system temperatures down. A group of researchers from Portland State University have developed a method of raising the energy yield from solar plants around 5% while reducing degradation of the panel by more than 0.3% per year.
This remarkable increase has been developed using a convective cooling approach. Put simply, this means that the solar system is cooled through accounting for wind direction, speed and the inclination of the module. This technique is the first of its kind to scale the enhancements to an array level, which provides optimism for future commercial success.
The paper, published in Nature Research, suggested that the proposed method would augment, rather than abandon current PV panel designs, which is welcome news for all within the industry. This practical adoption element is an important ability of the technology, allowing array-level optimisation to receive more focus when considering the design of a PV system.
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Conclusion of the Portland State University study
Although progress is being made on increasing solar PV efficiency and maximizing power produced, challenges remain in decreasing PV panel operating temperatures. This study experimentally demonstrates the achievable enhancements in solar PV efficiency if PV arrays are designed to take advantage of convective cooling. A 30–45% increase in convective heat transfer coefficient was observed when the incoming flow direction shifts 180° to face the rear surface of the PV panels. This increase corresponds to a 5–9 °C decrease in PV module temperature. While changing the inclination angle of solar panels to optimize for convective cooling may be impractical or undesirable, this parametric study highlights the significant impact wakes, turbulence and sub-panel velocity have on panel operating conditions, through altering the convective heat transfer.
The current approach can be considered as a passive cooling mechanism that leads to the increase of conversion efficiency and reduces the irreversible damage to the PV-cell materials. The increase in connectivity reduces the reduction in open circuit voltage, fill factor and power output for PV cells. Compared to past studies that used active cooling systems, the current approach is considered as a promising alternative for the solar energy community. Following solar industry rules, solar panels last about 25–30 years, and degradation rates below 1% are common throughout the industry. With our approach, the degradation will be below 0.7% per year meaning that the solar panel will still be operating at approximately 85% of their efficiency.
The importance of these factors opens a pathway for future work to examine other parameters that may be easily optimized, such as panel row spacing, height of panel from the ground, and other structures or layouts that enhance flow channeling through the farm. In related applications, roof mounted arrays are often more adversely impacted by temperature, so questions arise around the possibilities of convection enhancement through parameters such as roof offset height. Further, this study stresses the importance of wind direction on PV energy yield, and provides values to be used in solar farm modeling systems that will lead to improvement of the existing models.
The convection enhancement strategies discussed herein began the conversation in the forced convection regime. However, it is important that future studies examine enhancements that may be possible using only natural convection since many solar sites are without large incoming velocities for much of the hotter months. Although this study examined forced convection relevant to higher wind sites, the same methodology could be applied in the regime of natural convection, and demonstrates that small changes at the low end of inflow speeds could offer substantial temperature benefits. Further, any high-potential layout changes will have to be weighed against added material, land, or installation costs and future work should examine the tradeoffs therein.