Hybrid Solar Panel Device Stores Energy Like a Battery

In the ongoing energy transition, solar energy is crucial, but it still faces hurdles like intermittency and energy demand fluctuations. Traditional photovoltaic (PV) systems struggle with these issues due to overheating, which lowers efficiency and durability. While batteries have been the go-to solution for energy storage, they often rely on unsustainable materials. A research team led by professor Kasper Moth-Poulsen from Universitat Politècnica de Catalunya – BarcelonaTech (UPC) has developed a new hybrid device that could change all that.

MOST-PV hybrid device. Credit: Paulius Baronas/UPC

The innovation combines standard silicon-based solar cells with a molecular solar thermal energy storage system (MOST), marking the first time these technologies have been integrated into one device. The hybrid system allows the solar panel to generate electricity while storing energy for later use. It also provides cooling to the PV cells, helping prevent efficiency losses due to heat.

How the MOST system works

The MOST system uses organic molecules that capture high-energy photons from sunlight, storing the energy in chemical form. These molecules also act as an optical filter, preventing excess heat from reaching the PV cells by blocking certain wavelengths of light, effectively cooling the system. The stored energy can later be released when needed, making it an attractive alternative to conventional batteries.

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A key advantage of MOST is its reliance on abundant elements like carbon, hydrogen, oxygen, and nitrogen, offering a more sustainable solution than materials often used in batteries.

Researcher Helen Hölzel working at the MOST lab at UPC. Credit: Paulius Baronas/UPC

Challenges with traditional battery materials

While batteries are widely used for energy storage, many of them depend on materials that raise environmental and sustainability concerns. Lithium-ion batteries, for example, require rare metals like cobalt, lithium, and nickel, which are not only limited in supply but also involve mining processes that can be environmentally damaging and ethically problematic. The extraction of these materials often results in significant ecological disruption and has raised concerns over labor practices in mining regions. Additionally, recycling these batteries is challenging, leading to potential waste management issues. In contrast, the MOST system offers a more sustainable alternative by using readily available and more environmentally friendly elements such as carbon, hydrogen, oxygen, and nitrogen.

Addressing overheating challenges

Overheating is a significant issue in photovoltaic systems, where the cells absorb not only the visible light that generates electricity but also excess heat from the infrared spectrum. This heat buildup can reduce the system's overall efficiency, as higher temperatures increase electrical resistance within the solar cells, leading to lower energy output. In addition, overheating can degrade the materials used in PV systems over time, shortening their operational lifespan. By integrating the MOST system, this new hybrid device acts as an optical filter, selectively blocking the wavelengths that contribute to heating while still allowing the energy needed for electricity generation. As a result, the system can cool the PV cells, preventing the temperature spikes that typically hinder performance.

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Efficiency gains

In laboratory tests, the device demonstrated an energy storage efficiency of 2.3%—a record for molecular thermal solar systems. Additionally, by lowering the temperature of PV cells by up to 8°C, the system reduced energy losses and increased efficiency by 12.6%. Overall, the device achieves a solar energy utilization efficiency of up to 14.9%, outperforming conventional systems operating independently.

This new technology not only promises to boost the efficiency of solar power but also aligns with global efforts to reduce reliance on fossil fuels and unsustainable energy storage methods.

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The research was conducted under the ERC PHOTHERM and EU FET-PROACT MOST projects, funded by the European Union. Other participating institutions include the University of Cambridge, Chalmers University of Technology in Sweden, and the Institute of Materials Science of Barcelona. The results of the research has been published in the journal Joule.

From left to right, researchers Paulius Baronas, Kasper Moth-Poulsen, Helen Hölzel and Lorette Fernandez at UPC's MOST laboratory. Credit: Paulius Baronas/UPC