Quantum Dots Turn Windows Into Solar Generators

By Sunny Lewis

LOS ALAMOS, New Mexico, February 27, 2018 (Maximpact.com News) – Imagine double-pane solar windows that generate electricity with great efficiency and create shade and insulation at the same time. These windows can turn entire skyscrapers into solar energy generators.

And these windows have become a reality! After years of research, scientists at Los Alamos National Laboratory are now creating just such solar windows.

This new window architecture utilizes two different layers of low-cost quantum dots tuned to absorb different parts of the solar spectrum.

Los Alamos Center for Advanced Solar Photophysics researchers hold a large prototype solar window. From left: Jaehoon Lim, Kaifeng Wu, Victor Klimov, Hongbo Li. Photo courtesy Los Alamos National Laboratory) Public domain

Los Alamos Center for Advanced Solar Photophysics researchers hold a large prototype solar window. From left: Jaehoon Lim, Kaifeng Wu, Victor Klimov, Hongbo Li. Photo courtesy Los Alamos National Laboratory) Public domain

The scientists at the Center for Advanced Solar Photophysics at Los Alamos National Laboratory are seeking to transform everyday windows into solar collectors by harnessing the unique properties of quantum dots. They suggest the new technology will lower the cost of solar electricity.

Victor Klimov, lead researcher and director of the Center, said, “The approach complements existing photovoltaic technology by adding high-efficiency sunlight collectors to existing solar panels or integrating them as semitransparent windows into a building’s architecture.”

Quantum dots are tiny manufactured crystals, so small they can’t be seen with a typical microscope. Although they’re 10,000 times smaller than a human hair, quantum dots are actually powerful devices.

Each quantum dot is actually a tiny semiconductor, which means it can convert incoming energy.

It’s their size that gives quantum dots the unique ability to convert light into nearly any color in the visible spectrum with very high efficiency.

To transform a double-paned window into a luminescent sunlight collector, the Los Alamos team deposits a layer of highly emissive manganese-doped quantum dots onto the surface of the front glass pane and a layer of copper indium selenide quantum dots onto the surface of the back pane.

Light absorbed by the quantum dots activates these impurities. The front layer absorbs the blue and ultraviolet portions of the solar spectrum, while the rest of the spectrum is picked up by the bottom layer.

Following absorption, the dot re-emits a photon at a longer wavelength, and then the re-emitted light is guided by total internal reflection to the glass edges of the window.

There, solar cells integrated into the window frame collect the light and convert it to electricity.

The key to this advance is “solar-spectrum splitting,” which allows researchers to process separately higher–energy and lower-energy solar photons. The higher-energy photons can generate a higher photovoltage, which can boost the overall power output.

Windows that can collect solar energy like this, called photovoltaic windows, are the next frontier in renewable energy technologies. They have the potential to greatly increase the surface of buildings suitable for energy generation without impacting their aesthetics, a crucial aspect, especially in metropolitan areas.

Luminescent solar concentrator photovoltaic windows do not require anything to be applied onto their surface and since the photovoltaic cells are hidden in the window frames, they blend invisibly into the built environment.

Los Alamos has been on the development track towards solar windows for several years. Back in 2015, the Los Alamos team developed the colorless, non-toxic quantum dots that enable solar windows.

The building-integrated photovoltaic devices are now packaged as a luminescent solar concentrator or sunlight harvesting technology that can turn any window into a daytime power source.

“In these devices, a fraction of light transmitted through the window is absorbed by nanosized particles (semiconductor quantum dots) dispersed in a glass window, re-emitted at the infrared wavelength invisible to the human eye, and wave-guided to a solar cell at the edge of the window,” Klimov said in 2015.

“Using this design,” he said, “a nearly transparent window becomes an electrical generator, one that can power your room’s air conditioner on a hot day or a heater on a cold one.”

The University of Minnesota invented the process for creating silicon nanoparticles about a dozen years ago and holds a number of patents on this technology, which provided the starting point for quantum dot solar window technology.

University of Minnesota is one of five universities that are members of the Center for Advanced Solar Photophysics at Los Alamos National Lab, which is funded by the U.S. Department of Energy, Office of Science.

In early 2017, researchers at the University of Minnesota and University of Milano-Bicocca in Italy brought the dream of windows that can efficiently collect solar energy closer to reality with their high tech silicon nanoparticles.

Sergio Brovelli, an expert in LSC fabrication and lead researcher on the Italian team, concluded then, “Quantum dot solar window technology, of which we had demonstrated the feasibility just one year ago, now becomes a reality that can be transferred to the industry in the short to medium term, allowing us to convert not only rooftops, as we do now, but the whole body of urban buildings, including windows, into solar energy generators.”

While the price of solar photovoltaic cells recently has fallen and their efficiency has gone up, challenges remain around siting vast arrays of solar-electric panels and finding ways to integrate them into buildings and other applications.

These challenges prompted a joint research team from Los Alamos National Laboratory and the University of Milano-Bicocca to try a fresh approach to solar power. Working with quantum dots, the team achieved a breakthrough in solar-concentrating technology that can turn windows into electric generators and revolutionize the way we think about where and how we generate energy.

Featured image: Solar cells integrated into the window frames collect the light and convert it to electricity. (Photo courtesy Los Alamos National Laboratory) Public domain


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India, World Bank Empower Sunshine Nations

India, World Bank Empower_Sunshine Nations

India One, a 1 megawatt solar thermal power plant in Rajasthan, India is due for completion in 2016. It uses 770 newly developed 60m2 parabolic dishes and features thermal storage for continuous operation. The plant will generate enough heat and power for a campus of 25,000 people and is a milestone for clean power generation in India. (Photo by Brahma Kumaris) Creative Commons license via Flickr

By Sunny Lewis

NEW DELHI, India, July 13, 2016 (Maximpact.com News) – Solar power prospects are brightening with a new global focus on renewable energy to avert climate change. A burst of financial power was added at the end of June as the World Bank Group signed an agreement with the International Solar Alliance (ISA) – 121 countries led by sunny India – with the goal of mobilizing US$1 trillion in investments by 2030.

 The ISA was launched at the UN Climate Change Conference (COP21) in Paris on November 30, 2015 by Prime Minister Modi and French President Francois Hollande. Most of the sunshine countries lie between the tropics of Cancer and Capricorn, including Mexico, Peru, Chile, Argentina, Paraguay, Brazil, Australia, New Zealand and China. The United States and European Union also are involved.

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World Bank Group President Jim Yong Kim, left, meets with Prime Minister of India Narendra Modi before attending the General Assembly of the United Nations in New York City, September 25, 2015. (Photo by Dominic Chavez / World Bank) Creative Commons license via Flickr

On a two-day trip to New Delhi at the end of June, World Bank Group President Jim Yong Kim established the Bank as a financial partner for the ISA and pledged to collaborate on expanding the use of solar energy in India.

After meeting with Indian Prime Minister Narendra Modi, World Bank Group chief Kim said with a smile, “One of the reasons that I always appreciate my meetings with the Prime Minister is that he always pushes us to move faster and faster – to keep pace with him. We promised that we would do so, and in particular talked about supporting his government’s pace on expanding renewable energy sources.

The Prime Minister emphasized the importance of adequate climate change financing for countries like India which are “consciously choosing to follow an environmentally sustainable path.

India’s plans to virtually triple the share of renewable energy by 2030 will both transform the country’s energy supply and have far-reaching global implications in the fight against climate change,” the banker said.

The International Energy Agency calculates that India is set to contribute more than any other country to the projected rise in global energy demand. Steep rises in power production and consumption are expected to accompany India’s economic growth.

 “Prime Minister Modi’s personal commitment toward renewable energy, particularly solar, is the driving force behind these investments,” said Kim. “The World Bank Group will do all it can to help India meet its ambitious targets, especially around scaling up solar energy.”

Kim said he envisions the ISA as using its global development network, global knowledge and financing capacity to promote the use of solar energy throughout the world.

 India’s Ministry of New and Renewable Energy identified the initial joint projects to actualize the new agreement as:

  • Developing a roadmap to mobilize financing.
  • Developing financing instruments including credit enhancement, reduce hedging. costs/currency risk, bond raising in locally denominated currencies etc. which support solar energy development and deployment.
  • Supporting ISA’s plans for solar energy through technical assistance and knowledge transfer.
  • Working on mobilization of concessional financing through existing or, if needed, new trust funds.
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Solar panels on the rooftop of the Reserve Bank of India in Jaipur. (Photo by Kirti Solar Limited) Posted for media use by India PRwire

In addition, India will receive a loan of more than US$1 billion dollars to support expanding solar power through investments in solar generation.

 Projects now under development include solar rooftop technology, infrastructure for solar parks, bringing innovative solar and hybrid technologies to market, and transmission lines for sun-rich Indian states.

As part of our $1 billion dollar solar commitment to India, today we signed an agreement with the Government of India for a $625 million dollar grid connected rooftop solar program,” said Kim.

The project will finance installation of at least 400 megawatts of solar photovoltaic installations.

These investments for India will together become the Bank’s largest financing of solar projects for any country in the world. The banker said. “India has become a global leader in implementing the promises made in Paris for COP21 and the global efforts to tackle climate change.”

 India’s pledge to the Paris summit offered to bring 40 percent of its electricity generation capacity, not actual production, from non-fossil sources – renewable, large hydro, and nuclear – by the year 2030.

India has capacity of 4GW and the Modi Government has set a target of adding 100 GW of solar power by 2022.

In January, Modi and Hollande jointly laid the foundation stone of the International Solar Alliance headquarters and inaugurated the interim Secretariat of the ISA in National Institute of Solar Energy in Gwal Pahari in the Gurgaon District of Haryana state in northern India.

At that ceremony, the Indian Renewable Energy Development Agency and the Solar Energy Corporation of India (SECI) each announced a contribution of US$1 million to the ISA.

Prime Minister Modi has described the ISA as “the sunrise of new hope, not just for clean energy but for villages and homes still in darkness, for mornings and evening filled with a clear view of the glory of the Sun.


 Featured image: Solar Panels | by Jeremy Levine Design flickr.com