The use of solar energy is increasing every day, but photovoltaic (PV) cells convert only a fraction of the solar energy into electricity; most of it is lost as heat. A solution in the form of a PV sheet is a nature-inspired hybrid system that uses biomimetic transpiration to cool PV cells. This innovative concept lowers the operating temperature by 26°C, improves electrical efficiency and adapts to different ambient temperatures. The innovation was recently published in Nature,.
Researchers have developed an innovative ‘PV sheet’ system that cools solar cells through biomimetic transpiration. This multi-energy system also produces heat and clean water. Tests showed that the PV sheet outperformed standard solar cells in terms of energy conversion efficiency.
Remarkably enough, the PV sheet can also use salt water as a coolant, which offers a sustainable solution in regions where fresh water is scarce. In addition to the cooling capacity, the PV sheet simultaneously generates electricity, heat and clean water, greatly increasing the usefulness of solar energy. With its potential to effectively address thermal management, power generation and water scarcity, the PV sheet is an important step in the sustainable and efficient use of solar energy.
BT layer
At the heart of this breakthrough technology is a biomimetic transpiration layer (BT layer), ingeniously formed from bamboo fibers and hydrogel cells. The BT layer passively moves water from a separate tank to a solar cell, lowering the operating temperature of the cell. This reduction in temperature improves energy conversion efficiency, generating more electricity from the same amount of sunlight.
From wasted heat to useful energy
The PV sheet not only cools the solar cells, but puts the excess heat to work. Instead of being lost as waste, the heat produces water and thermal energy, turning the PV sheet into a multi-energy system. This innovative approach to energy generation significantly increases the efficiency of solar energy and represents a major leap forward in the sustainable use of solar energy.
Testing with the PV sheet showed an energy conversion efficiency of 15.0% and a fill factor of 0.77, outperforming standalone PV cells. These results show how the innovative cooling mechanism of the PV sheet can improve the performance of solar energy systems.
Economic feasibility
The PV sheet not only performs well, but also makes economic sense. The additional components required for the PV sheet, including the BT layer and the water tank, have a cost structure of approximately $1.1/m². This is only 2% of the cost of conventional solar panels. The payback period for these additional components is estimated at less than half a year.
In addition, the PV sheet concept can be scaled up to larger collectors. The simplicity of the system also makes it attractive, as it does not require expensive porous materials, pumps or control units, making it suitable for multi-generation and thermal management applications for PV cells.
A solution to water scarcity
Another notable feature of the PV sheet is the ability to use saline as a coolant. This means that the system can function in areas with freshwater scarcity. It also has the potential to generate an additional 1.1 L/h/m² of fresh water when irradiated by the sun, which could significantly improve water supply in arid areas.
This property also makes the PV sheet particularly suitable for hot and dry climates, where it outperforms traditional PV systems. The better transpiration performance in such conditions could make the PV sheet an important player in the transition to renewable energy in these regions.
From the Nature.com article: a) Typical internal structure of a true leaf. The vascular bundles ensure an even distribution of liquid water over the entire leaf surface. Effective cooling of perspiration protects the photosynthetic process. b) Internal structure of the bioinspired transpiration structure. Hydrophilic fiber bundles and hydrogel cells are used to mimic the vascular bundles and sponge cells. c) Exploded view of the transpiration structure. The biomimetic transpiration layer (BT) is made up of bamboo fiber bundles and wrapped hydrogel cells. The root of the fiber bundles is soaked in bulk water. d) Scheme and working principle of the PV sheet transpiration structure. Water flows from the root to the hydrogel cells, driven by capillary and osmotic processes. The water molecules in the molecular network then evaporate, dissipating PV heat. e) Photo of the prototype of a single PV sheet.
2023-09-03 13:05:00
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