Innovative Energy Storage Solutions: Harnessing Photo Switches for Efficient Heating

Harnessing solar energy for heating through molecular photoswitch technology offers potential solutions for winter energy storage. These light-sensitive compounds can store energy harvested in summer for later use. By circulating a specialized liquid with photoswitches in solar thermal systems, energy can be effectively stored and released as heat on demand. Ongoing research aims to enhance their stability and energy absorption, while also addressing cost challenges. This innovative approach could transform renewable energy utilization and municipal heating strategies in the future.

Harnessing Solar Energy for Heating: The Future of Photoswitch Technology

While relying solely on solar energy for heating can be challenging during the winter months due to limited sunlight, the innovative development of molecular photoswitches holds promise. These advanced compounds could facilitate the storage of energy harvested in summer for use throughout the colder months.

Currently, effective technology for storing solar energy over extended periods is not readily available. However, photoswitches have the potential to revolutionize this aspect of renewable energy.

The initial discovery of photoswitches dates back over a century. Yet, their true capabilities are only now being recognized. These minuscule light-sensitive molecules, measuring only a few nanometers, react to sunlight by altering their structure and properties. Researchers aim to harness these transformations for improved energy storage solutions.

Winter Heating Using Stored Solar Power

Looking ahead, photoswitches could play a vital role in solar thermal systems, which are already installed on some rooftops. Presently, these systems circulate water that is heated by solar energy, but unfortunately, the warm water cannot be stored for long durations. This is precisely where photoswitches enter the equation.

Instead of water, a specialized liquid containing photoswitches would circulate through these solar modules. “Ideally, we would have a liquid solution that is pumped onto the roof to absorb energy,” explains photochemist Christoph Kerzig from Johannes Gutenberg University Mainz. The energy-laden photoswitches could then be stored in a basement until needed in winter.

The Mechanism of Energy Storage in Photoswitches

When exposed to sunlight, the molecular structure of photoswitches undergoes deformation, altering the chemical bonds within them. This transformation requires significant energy input, such as from sunlight. The photoswitches can remain in this altered state for weeks or months, enabling long-term energy storage. A minor stimulus from a catalyst or an electrical impulse can revert the molecule to its original structure, releasing the stored energy as heat.

This stored solar energy can be accessed on demand, similar to a heat pad, and has already been validated in laboratory settings. Research conducted by Hermann Wegner’s team at Justus Liebig University in Gießen demonstrates the feasibility of this heating mechanism.

Enhancing Solar Energy Utilization with Dyes

Despite their potential, photoswitches face challenges in practical applications. Two primary concerns are currently at the forefront of scientific discussions: the need for photoswitches to maintain stability over time while effectively absorbing energy. So far, available molecules tend to excel in only one of these areas. “In the future, we aim for them to achieve both simultaneously,” states Till Zähringer from Johannes Gutenberg University Mainz. To address this, researchers are experimenting with additional dyes.

These dyes enable photoswitches to capture a broader spectrum of sunlight. “By incorporating the dye, we can now also store visible energy,” says Christoph Kerzig. Historically, only a limited range of sunlight, specifically ultraviolet light, could be utilized. The integration of dyes has resulted in the ability to store six times more energy, according to recent findings from the Mainz research team. However, the current iteration of photoswitches can only undergo a few storage cycles, indicating the need for further stability improvements for practical applications.

The Promise of Photoswitches

The principle behind photoswitches mirrors the natural process of photosynthesis in plants, where energy is stored by pigments. However, while natural systems utilize only a fraction of available light, photoswitches are designed to be much more efficient.

“Our goal is to achieve 100 percent efficiency,” says Kerzig. If successful, photoswitches could harness the entire sunlight spectrum. “The sun’s energy has the potential to address all our energy challenges if we can improve our methods for utilizing and storing it, particularly through chemical bonds with photoswitches,” he adds.

Across Germany, municipalities and energy providers are actively developing municipal heating strategies that could benefit from these advancements.

Challenges in Cost and Stability

At present, the production of photoswitches remains prohibitively expensive. A small pilot facility could cost millions of euros. “To scale this technology to kilograms or tons, we are still far from the target. Costs must come down significantly,” notes Till Zähringer. Interestingly, other technologies, such as lithium-ion batteries, once faced similar cost barriers and are now ubiquitous in smartphones.

The size of the storage systems using photoswitches also poses a question. “The required storage size will depend on storage density,” explains Wegner, who envisions that these systems could fit into many basements in the future.

Currently, research into photoswitches is still in its infancy, particularly regarding their stability for extended energy storage. However, a research team in Barcelona is already testing this storage solution with small rooftop modules, aiming to effectively store summer energy for winter heating.

This topic was featured in the knowledge magazine Impuls on January 13, 2025, at 4:05 PM on SWR Kultur.

Related Articles