Solar Energy

Efficiency limits of next-generation hybrid photovoltaic-thermal solar technology

Published

3 years ago

February 14, 2021

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Efficiency limits of next-generation hybrid photovoltaic-thermal solar technology

Solar energy is one of the most abundant renewable energy sources, and effective solar technologies have great potential to alleviate the grand challenges of rising global energy demands, while reducing associated emissions. Solar energy is capable of satisfying the electrical and thermal-energy needs of diverse end-users by means of photovoltaic (PV) and solar thermal (ST) technologies, respectively.

Recently, hybrid photovoltaic-thermal (PVT) concepts have been proposed that synergistically combine the benefits of PV and ST technologies, and are capable of generating both electricity and useful heat simultaneously from the same area and component.

Spectral splitting is an emerging approach for designing high-performance PVT solar collectors, which employ advanced designs with optical filters that direct different parts of the solar spectrum either to the PV cells for electricity generation or to a thermal absorber for heat generation.

Nevertheless, the ultimate efficiency limits of spectral-splitting PVT (SSPVT) collectors depending on the application and end-user demands, along with the optimal collector designs, PV cell and optical filter materials that can enable us to approach these limits have remained unclear, with a lack of consensus in the field, motivating a closer examination of these aspects of SSPVT technology.

In a new paper published in Light Science and Application, Christos N. Markides and Gan Huang from Imperial College London in the UK, in collaboration with Kai Wang from Zhejiang University in China, report a comprehensive framework for predicting the performance of such collectors, which is then used to identify their efficiency limits, and to provide detailed guidance for selecting optimal PV materials and optimal spectral-splitting filters capable of delivering a combined thermal and electrical performance that approaches the efficiency limits of this technology.

“We found that the relative value of thermal energy to that of electricity has a significant influence on the total effective efficiency limits, the optimal PV cell material and the optimal spectral-splitting filter of SSPVT collectors.”

“”CIGS solar cells are considered particularly promising for SSPVT collector applications owing to their adjustable bandgap energy. The optimal lower- and upper-bounds of the spectral-splitting filter depend strongly on the PV material” they added.

“”Detailed maps in our research can assist designers in selecting appropriate solar-cell materials and spectral-splitting optical filters, depending on the conditions and application, in order to achieve optimal overall performance accounting for both energy vectors (electricity and heat) generated by these systems.” the scientists stated.

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Solar Energy

Project receives funding for advanced solar-thermal research

Published

4 days ago

April 12, 2024

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Project receives funding for advanced solar-thermal research

by Sophie Jenkins

London, UK (SPX) Apr 12, 2024

The University of Surrey, leading a collaboration with the University of Bristol and Northumbria University, has received a GBP 1.1 million grant from the Engineering and Physical Sciences Research Council (EPSRC) to develop solar-thermal devices. These devices aim to revolutionize the way we heat homes and generate power, differing from traditional solar cells by converting sunlight into heat for energy production.

The research focuses on creating surfaces that selectively absorb sunlight and emit heat through near-infrared radiation. This project leverages the combined expertise of the institutions in photonics, advanced materials, applied electromagnetics, and nanofabrication to address a global need for efficient solar energy utilization.

Professor Marian Florescu, Principal Investigator from Surrey, highlighted the importance of the project: “The sun provides an immense amount of energy daily, much more than we currently harness. By advancing these solar-absorbing surfaces, we aim to transform solar energy use into a sustainable powerhouse for our increasing energy needs.”

Goals of the project include developing high-temperature solar absorbers, enhancing the efficiency of solar-absorbing structures, and improving the management of heat generated from sunlight. Prototypes will be constructed to demonstrate these technologies.

Professor Marin Cryan, Co-Principal Investigator from the University of Bristol, explained their focus on thermionic solar cell technology, which uses concentrated sunlight to initiate electron emission for high-efficiency solar cells.

Dr. Daniel Ho, Co-Principal Investigator from Northumbria University, added: “Our university leads in thermophotovoltaic research, utilizing advanced thermal analysis techniques. We’re excited to contribute to groundbreaking developments in renewable energy.”

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Solar Energy

Improving Solar and Wind Power Integration in the U.S. Grid

Published

5 days ago

April 11, 2024

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Improving Solar and Wind Power Integration in the U.S. Grid

by Clarence Oxford

Los Angeles CA (SPX) Apr 11, 2024

The Midcontinent Independent System Operator manages a high-voltage electricity network spanning from Manitoba to Louisiana, serving 45 million users. This vast operation requires maintaining a balance between the energy generated and the demand across its regions.

The traditional reliance on coal and natural gas power plants is changing. For example, wind farms in Iowa now generate over 64% of the state’s electricity, and recent initiatives like the Alliant Energy Solar Farm at Iowa State University represent the shift towards renewable energy sources. These sources, however, introduce variability and uncertainty into grid management.

Zhaoyu Wang, a Northrop Grumman associate professor of electrical and computer engineering at Iowa State, emphasized, The power system seeks certainty which is challenging with unpredictable natural resources like sun and wind.

Wang is leading the MODERNISE project, aimed at modernizing grid operations. The U.S. Department of Energy has earmarked a $3 million grant over three years for this initiative, with an additional $1.1 million coming from project collaborators including Argonne National Laboratory and Siemens Corp.

The project, titled Modernizing Operation and Decision-Making Tools Enabling Resource Management in Stochastic Environment, involves developing computational tools that allow for better integration and management of renewable energy sources into the grid.

Jennifer M. Granholm, U.S. Secretary of Energy, supported this initiative stating that effective integration of renewable resources is essential for deploying clean energy. The project is part of a larger $34 million investment by the DOE to develop technologies that enhance grid reliability and efficiency.

By aggregating smaller renewable energy resources into larger operational blocks, MODERNISE aims to improve grid stability and predictability. Bai Cui, project co-leader and assistant professor at Iowa State, explained that this approach allows operators to manage grid operations more effectively by understanding and handling the uncertainties of renewable supply sources.

This initiative promises to make grid operations more adaptable and efficient, critical for accommodating the increasing reliance on renewable energy.

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Solar Energy

Quantum Material Achieves Up to 190% Efficiency in Solar Cells

Published

5 days ago

April 11, 2024

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Quantum Material Achieves Up to 190% Efficiency in Solar Cells

by Clarence Oxford

Los Angeles CA (SPX) Apr 11, 2024

Researchers from Lehigh University have developed a material that significantly enhances the efficiency of solar panels.

A prototype incorporating this material as the active layer in a solar cell displays an average photovoltaic absorption rate of 80%, a high rate of photoexcited carrier generation, and an external quantum efficiency (EQE) reaching up to 190%. This figure surpasses the theoretical Shockley-Queisser efficiency limit for silicon-based materials, advancing the field of quantum materials for photovoltaics.

This work signifies a major advance in sustainable energy solutions, according to Chinedu Ekuma, professor of physics at Lehigh. He and Lehigh doctoral student Srihari Kastuar recently published their findings in the journal Science Advances. Ekuma highlighted the innovative approaches that could soon redefine solar energy efficiency and accessibility.

The material’s significant efficiency improvement is largely due to its unique intermediate band states, which are energy levels within the material’s electronic structure that are ideally positioned for solar energy conversion.

These states have energy levels in the optimal subband gaps-energy ranges capable of efficiently absorbing sunlight and producing charge carriers-between 0.78 and 1.26 electron volts.

Moreover, the material excels in absorbing high levels in the infrared and visible regions of the electromagnetic spectrum.

In traditional solar cells, the maximum EQE is 100%, which corresponds to the generation and collection of one electron for each photon absorbed. However, newer materials and configurations can generate and collect more than one electron per high-energy photon, achieving an EQE over 100%.

Multiple Exciton Generation (MEG) materials, though not yet widely commercialized, show immense potential for enhancing solar power system efficiency. The Lehigh-developed material utilizes intermediate band states to capture photon energy typically lost in traditional cells, including energy lost through reflection and heat production.

The research team created this novel material using van der Waals gaps, atomically small spaces between layered two-dimensional materials, to confine molecules or ions. Specifically, they inserted zerovalent copper atoms between layers of germanium selenide (GeSe) and tin sulfide (SnS).

Ekuma developed the prototype based on extensive computer modeling that indicated the system’s theoretical potential. Its rapid response and enhanced efficiency strongly indicate the potential of Cu-intercalated GeSe/SnS as a quantum material for advanced photovoltaic applications, offering a path for efficiency improvements in solar energy conversion, he stated.

While the integration of this quantum material into existing solar energy systems requires further research, the techniques used to create these materials are already highly advanced, with scientists mastering precise methods for inserting atoms, ions, and molecules.

Research Report:Chemically Tuned Intermediate Band States in Atomically Thin CuxGeSe/SnS Quantum Material for Photovoltaic Applications