'Sweet spot' helps solar device store more energy, thrive in heat

A recent study indicates that an emerging solar technology performs better at higher temperatures, a finding that could impact the development of renewable energy storage.

“Instead of fighting against the sun’s heat, our research shows we can harness it,” said lead author Dr. Dowon Bae. 

“It flips the conventional wisdom on its head and gives us a new way to design solar storage systems that thrive in hot conditions.”

The research shows that specific “solar-plus-storage” devices exhibit improved performance with rising temperatures, with an optimal operating window identified at approximately 45°C (113°F).

This behavior is contrary to that of conventional solar panels, which lose efficiency as they get hotter.

Using PEC flow cells

The study from Loughborough University examined photoelectrochemical (PEC) flow cells. These devices are designed to both capture sunlight and store the resulting energy in a single unit. 

“PEC technology is considered promising for integrating a photovoltaic (PV) or PEC device with a secondary battery, such as a redox flow battery system, to convert and store the absorbed sunlight,” remarked the researchers in a new study.

In standard solar technology, which primarily uses silicon-based photovoltaic (PV) panels, heat is a persistent problem. As a conventional panel gets hotter, its internal electrical resistance increases.

This thermal agitation causes electrons to lose energy as heat rather than contributing to the electrical current, leading to a noticeable drop in voltage and overall efficiency. For every degree Celsius above the standard test condition of 25°C, a typical solar panel can lose between 0.3% and 0.5% of its peak power output.

The new research demonstrates that for PEC flow cells, the opposite can be true. While the solar capture component is still subject to thermal effects, the energy storage component benefits from the heat. The study found that elevated temperatures act as a catalyst for the device’s internal electrochemical reactions.

The heat energizes the liquid electrolyte, leading to faster ion movement and improved conductivity. This reduces the system’s internal resistance to charging, allowing it to store the generated solar energy more rapidly and efficiently.

Implications for future design

By identifying a performance “sweet spot,” engineers can now design systems that are meant to run hot, rather than spending resources to keep them cool.

“So, instead of fighting against the heat, engineers can now use it to their advantage, creating more efficient solar energy storage solutions,” noted Dr Bae.

“By understanding and harnessing this hidden effect, we can ultimately make integrated solar technology a more viable option for powering our world.”

A benefit is a potential reduction in cost. Active cooling systems, such as fans or fluid circulation, add to the complexity, initial capital cost, and ongoing maintenance expenses of a solar installation. Eliminating their need would make integrated solar-plus-storage solutions more affordable.

“The study is an important step toward making integrated solar capture and storage a practical reality—where a solar charging device not only generates electricity but also stores it, making renewable power more reliable and accessible,” concluded the press release.