New device can help solar panels capture more sunlight

Solar panels will play an important role in future renewable energy production, but they work best when sunlight hits them directly. This can be a problem when the sunlight is scattered by clouds or when the sun rises all day long.

Many solar panels actively turn towards the sun to capture as much energy as possible. This makes them more expensive and complicated to build and maintain than those that remain stationary.

But moving solar panels may not be necessary in the future, as a technical researcher has designed a device that can capture 90% of the light that falls on it — regardless of angle or frequency — and concentrate it three times brighter.

The Research was published in Microsystems and nanoengineering

“It’s a completely passive system — it doesn’t require energy to track the source or have moving parts,” said first author Dr. Nina Vaidya, who completed the research as a doctoral student at Standford University, USA, and is now an assistant. professor of aerospace engineering at the University of Southampton, UK.

“Without an optical focus that moves positions or the need for tracking systems, focusing light becomes much easier.”

AGILE – Axial Grade Index Lens

The device is called AGILE, which stands for axial graded index lens, and it looks like an inverted glass pyramid with the tip cut off.

It works a bit like a how one magnifying glass sunlight can focus on a smaller, brighter point on a sunny day. But the focal point of a magnifying glass moves with the sun, which isn’t useful if you want to focus sunlight on a specific area of ​​a photovoltaic cell throughout the day.

With AGILE, light enters the wide, square top from all angles and is directed downwards to focus on the same position at the bottom – creating a brighter spot on the narrow base that sits atop a photovoltaic cell.

“We wanted to create something that takes light and focuses it on the same position even if the source changes direction,” explains Vaidya. “We don’t want to have to keep moving our detector or solar cell, or have the system keep looking at the source.

Senior author Olav Solgaard, a Stanford electrical engineering professor and Vaidya’s doctoral advisor, says, “An ideal AGILE at the very front has the same refractive index as the sky and gradually gets higher — the light bends into a perfectly smooth curve.

“But in practice you will not have that ideal AGILE.”

Instead, the prototype AGILE is made of what is known as a graded index material, which consists of several layers of glass and polymers that bend light to varying degrees. These layers change the direction of the incoming light incrementally until it comes almost vertically to the exit.

Bringing AGILE from theory to reality

One of the biggest challenges in creating the AGILE prototype was finding and making the right commercially available materials that transmit, transmit and increasingly bend a broad spectrum of light toward the output – all while being compatible with each other. to be .

Nina Vaidya measures the experimental performance of optical concentrators under a solar simulator that acts as an artificial sun
Nina Vaidya measures the experimental performance of optical concentrators under a solar simulator that acts as an artificial sun. Credit: Nina Vaidya

For example, if one glass expands at a different rate in response to heat than another, the entire device could burst. The materials also had to be robust enough to be machined to shape and remain durable.

The sides of the prototypes are also mirrored to bounce light going in the wrong direction back to the base.

These AGILE devices can be installed in a layer on top solar panelsreplacing the existing encapsulation protecting solar panels, and would create even more space for cooling and circuitry to run between the narrowing pyramids of the individual devices.

“It has been very rewarding to use these new materials, these new manufacturing techniques and this new AGILE concept to create better solar concentrators,” concludes Vaidya.

“Abundant and affordable clean energy is an essential part of tackling the pressing climate and sustainability challenges, and we need to catalyze engineering solutions to make that happen.”

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